WO2026027770A1

WO2026027770A1 - Method and composition for increasing plant nutrition

Info

Publication number: WO2026027770A1
Application number: PCT/EP2025/072257
Authority: WO
Inventors: Jean-Marc Sanchez; Tarryn GOBLE; Kris AUDENAERT; Geert HAESAERT; Silke DEKETELAERE; Jolien VENNEMAN; Danny VEREECKE
Original assignee: Universiteit Gent; Danstar Ferment AG
Current assignee: Universiteit Gent; Danstar Ferment AG
Priority date: 2024-08-02
Filing date: 2025-08-01
Publication date: 2026-02-05
Anticipated expiration: 2027-02-02

Abstract

The present invention provides a method and a composition for increasing nitrogen fixation of at least one strain of a nitrogen fixing bacteria or acquisition of nitrogen for a plant in need thereof.

Description

METHOD AND COMPOSITION FOR INCREASING PLANT NUTRITION TECHNOLOGICAL FIELD The present disclosure relates to methods and compositions for increasing the nitrogen fixation capacity of nitrogen fixing bacteria strain resulting in measurable plant benefits such as an increase in nitrogen content, growth, yield, tolerance to biotic and abiotic stressors and general plant health. BACKGROUND Nitrogen is a critical limiting element for plant growth and production. It is a major component of chlorophyll, the most important pigment needed for photosynthesis, as well as amino acids, the key building blocks of proteins. It is also found in other important biomolecules, such as ATP and nucleic acids. Even though it is one of the most abundant elements (predominately in the form of nitrogen gas (N₂) in the Earth’s atmosphere), plants can only utilize reduced forms of this element. Plants acquire these forms of “combined” nitrogen by: 1) the addition of ammonia and/or nitrate fertilizer or manure to soil, 2) the release of these compounds during organic matter decomposition, 3) the conversion of atmospheric nitrogen into the compounds by natural processes, such as lightning, and 4) biological nitrogen fixation. In order to utilize the N2, the N2 must be combined with hydrogen, which combination is known as nitrogen fixation. One area of interest is to improve nitrogen fixation because often, simply applying a single strain of nitrogen fixing bacteria does not lead to the anticipated crop yield increases. Accordingly, there is a need to provide new technologies to increase the amount of fixed nitrogen produced by microorganisms in order to reduce fertilizer and pesticide usage, increase plant health and improve food quality and safety. Indeed, the identification of co- inoculants that are compatible with rhizobial bacteria and that can enhance the nitrogen fixation capacity of rhizobial bacteria would be desirable. BRIEF SUMMARY OF THE INVENTION The present disclosure provides a method and composition for increasing the nitrogen fixation capacity of nitrogen fixing bacteria (i.e. a rhizobial bacteria) via co-inoculation of at least one strain of a nitrogen fixing bacteria together with at least one strain of Serendipita sp. The present invention provides a method for increasing nitrogen fixation of at least one symbiotic nitrogen fixing bacteria strain in association with a host plant, said method comprising contacting the host plant or a germplasm thereof with at least one Serendipita sp. strain, wherein the at least one Serendipita sp. strain causes the at least one nitrogen fixing bacteria strain to fix nitrogen at a higher rate compared to the nitrogen fixation rate of the at least one nitrogen fixing bacteria strain in the absence of the at least one Serendipita sp. strain. The invention further provides a method for enhancing at least one growth parameter of a plant, the method comprising co-inoculating a plant or a germplasm thereof with at least one strain of Serendipita sp. and at least one symbiotic nitrogen fixing bacteria strain, wherein the co-inoculated plant or a plant grown from the co-inoculated germplasm exhibits at least one enhanced growth parameter relative to a plant of the same taxon that has not been co-inoculated with the at least one strain of Serendipita sp. strain. The growth parameter may be a number and/or mass of nodules of a plant and/or a concentration and/or amount of a nutrient in a plant. The nutrient may be nitrogen, phosphorus or potassium. The invention also provides the use of at least one Serendipita sp. strain for increasing nitrogen fixation of at least one symbiotic nitrogen fixing bacteria strain in association with a host plant or a germplasm thereof. Said use may comprise contacting the host plant or a germplasm with the least one Serendipita sp. strain and at least one nitrogen fixing bacteria strain wherein contacting the host plant or the germplasm with at least one Serendipita sp. strain causes the at least one nitrogen fixing bacteria strain to fix nitrogen at a higher rate compared to the nitrogen fixation rate of the at least one nitrogen fixing bacteria strain in the absence of the at least one Serendipita sp. strain. Also provided by the present invention is an inoculant composition for increasing nitrogen fixation in a host plant, wherein the inoculant composition comprises at least one strain of Serendipita sp. strain and at least one symbiotic nitrogen fixing bacteria strain. In any of the methods, uses or inoculant compositions of the present invention, the at least one nitrogen fixing bacteria strain may be a strain of Bradyrhizobium, Rhizobium, Mesorhizobium, Ensifer, Azorhizobium, Sinorhizobium, Azorhizobium, Frankia, Burkholderia, Cupriavidus, or a combination thereof. The at least one nitrogen fixing bacteria strain may be a strain of B. japonicum, B. elkanii, B. diazoefficiens, R. leguminosarum biovar viciae, R. tropici, M. ciceri, E. meliloti, or a combination thereof. The at least one nitrogen fixing bacteria strain may be B. japonicum, B. elkanii, B. diazoefficiens or combinations thereof. The at least one strain of B. japonicum may be B. japonicum USDA 110, B. japonicum USDA 136, B. japonicum 442, B. japonicum SEMIA 5079 or combinations thereof. The at least one strain of B. japonicum may be B. japonicum USDA 110 and B. japonicum USDA 136. The at least one nitrogen fixing bacteria strain may be R. leguminosarum biovar viciae. In one embodiment, the at least one nitrogen fixing bacteria strain is B. diazoefficiens SEMIA 5080. In a further embodiment, the at least one nitrogen fixing bacteria strain is B. elkanii SEMIA 587, B. elkanii U-1301, B. elkanii SEMIA 5019, B. elkanii U-1302 or a combination thereof. In another embodiment, the at least one nitrogen fixing bacteria strain is a combination of B. japonicum SEMIA 5079 and B. diazoefficiens SEMIA 5080. In a further embodiment, the at least one nitrogen fixing bacteria strain is a combination of B. japonicum SEMIA 5079 and B. diazoefficiens SEMIA 5080. In a further embodiment, the at least one nitrogen fixing bacteria strain is a combination of B. japonicum USDA 110 and B. japonicum USDA 442. In a further embodiment, the at least one nitrogen fixing bacteria strain is a combination of a combination of B. elkanii SEMIA 587 and B. elkanii SEMIA 5019. In another embodiment, the at least one nitrogen fixing bacteria strain is R. leguminosarum biovar viciae. In any of the methods, uses or inoculant compositions of the present invention, the at least one Serendipita sp. strain may be a strain of S. indica or S. williamsii. In any of the methods, uses or inoculant compositions of the present invention, the at least one Serendipita sp. strain may be Serendipita sp. isolate 46 as deposited on 28 February 2024 by Universiteit Gent, Sint-Pietersnieuwstraat 25, 9000 Gent, Belgium, according to the Budapest Treaty under accession number 280224-01 with the International Depository Authority of Canada (IDAC), 1015 Arlington Street, Winnipeg, Manitoba, R3E 3R2, Canada. In any of the methods, uses or inoculant compositions of the present invention the host plant may be soybean, pea, lentil, fava bean, common bean, chickpea, peanut, lupins, alfalfa, clover, lucerne, sorghum, sugarcane, wheat, corn, potato, sweet potato or rice. In any of the methods, uses or inoculant compositions of the present invention, the ratio of the total CFU of the at least one Serendipita sp. strain to the at least one nitrogen fixing bacteria strain may be: (a) 1:1 to 1:20; 1:1 to 1:15; 1:1 to 1:10; 1:1 to 1:9; 1:1 to 1:8; 1:1 to 1:7; 1:1 to 1:6; 1:1 to 1:5; 1:1 to 1:4; 1:1 to 1:3; or 1:1 to 1:2; (b) 1:1 to 20:1; 1:1 to 15:1; 1:1 to 10:1; 1:1 to 9:1; 1:1 to 8:1; 1:1 to 7:1; 1:1 to 6:1; 1:1 to 5:1; 1:1 to 4:1; 1:1 to 3:1; or 1:1 to 2:1; (c) 1:1; 1:1.25; 1:1.50; 1:1.75; 1:2; 1:3; 1:4; or 1:5; (d) 1:25 to 1:10000; 1:50 to 1:10000; 1:75 to 1:10000; 1:100 to 1:10000; 1:200 to 1:10000; 1:300 to 1:10000; 1:400 to 1:10000; 1:500 to 1:10000; 1:600 to 1:10000; 1:700 to 1:10000; 1:800 to 1:10000; or 1:900 to 1:10000; (e) 1:100 to 1:200; 1:200 to 1:300; 1:300 to 1:400; 1:400 to 1:500; 1:500 to 1:600; 1:600 to 1:700; 1:700 to 1:800; 1:800 to 1:900; 1:900 to 1:1000; 1:1000 to 1:1100; 1:1100 to 1:1200; 1:1200 to 1:1300; 1:1300 to 1:1400; 1:1400 to 1500; 1:1500 to 1:1600; 1:1600 to 1:1700; 1:1700 to 1:1800; 1:1800 to 1:1900; 1:1900 to 1:2000; 1:2000 to 1:2100; 1:2100 to 1:2200; 1:2200 to 1:23000; 1:2300 to 1:2400; 1:2400 to 1:2500; 1:2500 to 1:2600; 1:2600 to 1:2700; 1:2700 to 1:2800; 1:2800 to 1:2900; 1:2900 to 1:3000; 1:3000 to 1:3100; 1:3100 to 1:3200; 1:3200 to 1:3300; 1:3300 to 1:3400; 1:3400 to 1:3500; 1:3500 to 1:3600; 1:3600 to 1:3700; 1:3700 to 1:3800; 1:3800 to 1:3900; 1:3900 to 1:4000; 1:4000 to 1:4100; 1:4100 to 1:4200; 1:4200 to 1:4300; 1:4300 to 1:4400; 1:4400 to 1:4500; 1:4500 to 1:4600; 1:4600 to 1:4700; 1:4700 to 1:4800; 1:4800 to 1:4900; 1:4900 to 1:5000; 1:5000 to 1:5100; 1:5100 to 1:5200; 1:5200 to 1:5300; 1:5300 to 1:5400; 1:5400 to 1:5500; 1:5500 to 1:5600; 1:5600 to 1:5700; 1:5700 to 1:5800; 1:5800 to 1:5900; 1:5900 to 1:6000; 1:6000 to 1:6100; 1:6100 to 1:6200; 1:6200 to 1:6300; 1:6300 to 1:6400; 1:6400 to 1:6500; 1:6500 to 1:6600; 1:6600 to 1:6700; 1:6700 to 1:6800; 1:6800 to 1:6900; 1:6900 to 1:7000; 1:7000 to 1:7100; 1:7100 to 1:7200; 1:7200 to 1:7300; 1:7300 to 1:7400; 1:7400 to 1: 7500; 1:7500 to 1:7600; 1:7600 to 1:7700; 1:7700 to 1:7800; 1:7800 to 1:7900; 1:7900 to 1:8000; 1:8000 to 1:8100; 1:8100 to 1:8200; 1:8200 to 1:8300; 1:8300 to 1:8400; 1:8400 to 1:8500; 1:8500 to 1:8600; 1:8600 to 1:8700; 1:8700 to 1:8800; 1:8800 to 1:8900; 1:8900 to 9000; 1:9000 to 9100; 1:9100 to 9200; 1:9200 to 9300; 1:9300 to 9400; 1:9400 to 9500; 1:9500 to 9600; 1:9600 to 9700; 1:9700 to 9800; 1:9800 to 9900; or 1:9900 to 1:10000; (f) 1:500 to 1:9000; or (g) 1:600 to 1:8500. In any of the methods, uses or inoculant compositions of the present invention, the at least one Serendipita sp. strain may cause the at least one nitrogen fixing bacteria strain to increase nitrogen fixation by at least 5% compared the nitrogen fixation rate of the at least one nitrogen fixing bacteria strain associated with the host plant in the absence of the at least one Serendipita sp. strain. BRIEF DESCRIPTION OF THE FIGURES Having thus generally described the nature of the invention, reference will now be made to the accompanying drawings, showing by way of illustration, a preferred embodiment thereof, and in which: Figure 1 illustrates the concentration of ureide (mg/L) in the stem of sampled soybean plants measured by ureide method and results was significantly different for all the treatments (F_2.32=172.63, p<0.001). The untreated control had the lowest concentration of ureide in the stems (2.4 mg N/L), the B. elkanii SEMIA 587 and SEMIA 5019 applied alone had 41.1 mg N/L in the stem and the co-inoculation of B. elkanii SEMIA 587 and SEMIA 5019 with Serendipita sp. isolate 46 had the highest concentrations of ureide in the stems with 53.5 mg N/L. Means followed by the same letter do not significantly differ from each other according to Tukey’s post hoc test (α = 0.05). Figure 2 illustrates the average dry weight of nodules produced per plant was significantly different between all the treatments (F_2.31=51.21, p<0.001). The dry weight of nodules for the untreated control was 0.01 g/plant while the B. elkanii SEMIA 587 and SEMIA 5019 applied alone had nodules that weighed 0.11 g/plant and the co-inoculation of B. elkanii SEMIA 587 and SEMIA 5019 with Serendipita sp isolate 46 had nodules that weighed 0.14 g/plant. Means followed by the same letter do not significantly differ from each other according to Tukey’s post hoc test (α = 0.05). Figure 3 illustrates the soybean plants (100%) in the co-inoculation of B. elkanii SEMIA 587 and SEMIA 5019 with Serendipita sp isolate 46 were in a more advanced crop stage (R3) at 37 days as compared with B. elkanii SEMIA 587 and SEMIA 5019 applied alone (which had 90% of the plants in R3 stage and 10% of the plants in an R2 stage) or the untreated control (which had 72.7% in R3 stage; 27.3% in R2 stage). Figure 4 illustrates the average dry weight of nodules produced per plant was significantly different between all the treatments (F_2.63=93.03; p<0.001). The dry weight of nodules for the untreated control was 0 g/plant while the B. japonicum USDA 110 and USDA 442 applied alone had nodules that weighed 0.04 g/plant and the co-application inoculation of B. japonicum USDA 110 and USDA 442 with Serendipita sp isolate 46 had nodules that weighed 0.053 g/plant. Means followed by the same letter do not significantly differ from each other according to Tukey’s post hoc test (α = 0.05). Figure 5 illustrates the number of nodules produced per plant inoculated with R. leguminosarum biovar viciae and co-inoculated with R. leguminosarum biovar viciae and Serendipita sp isolate 46. Means followed by the same letter do not significantly differ from each other according to Fisher LSD post hoc test (α = 0.05). Figure 6 illustrates a significant increase in P (phosphorus) and K (potassium) concentrations in pea plants co-inoculated with R. leguminosarum biovar viciae and Serendipita sp isolate 46. Means followed by the same letter do not significantly differ from each other according to Fisher LSD post hoc test (α = 0.05). DETAILED DESCRIPTION The present disclosure concerns the use of a strain of Serendipita sp. to increase the nitrogen fixation of nitrogen fixing bacteria strains when, but not limited to, the nitrogen fixing bacteria strains are already associated with a plant or in soil or whether the nitrogen fixing bacteria strains are added as part of a combination with the Serendipita sp. strain (e.g. as an inoculant to a plant). As described in more details in the Examples, when at least one strain of Serendipita sp. is combined with at least one strain of nitrogen fixing bacteria, the observed nitrogen fixation rate of the nitrogen fixing bacteria strain is higher compared to the nitrogen fixation rate of the nitrogen fixing bacteria strain in the absence of the at least one Serendipita sp. strain. Therefore, the combination can be used as field treatments (such as, furrow application, drench application or spraying) to increase plant nutrition or the concentration of nitrogen in plants. As nitrogen is an essential nutrient for plants, the combination of strains disclosed herein (e.g. at least one strain of a nitrogen fixing bacteria and at least one strain of Serendipita sp.) can provide for additional amount of nitrogen in any plant. Furthermore, the Serendipita sp. strain disclosed herein can contribute to an increased concentration of nitrogen in any plant once added to the soil surrounding plants, through the activity with any nitrogen fixing bacteria already associated with plants. In other embodiments, the at least one strain of Serendipita sp. is added in combination with at least one strain of nitrogen fixing bacteria and this combination is added to the soil surrounding plants to increase the nitrogen fixation of the at least one strain of nitrogen fixing bacteria and the existing strains of nitrogen fixing bacteria already associated with the plants. In other embodiments, the combination (i.e. the at least one strain of Serendipita sp. and the at least one strain of nitrogen fixing bacteria) can be used as a seed treatment or coating or any other application (such as furrow application, drench application or spraying) resulting in measurable plant benefits such as an increase in nitrogen content, growth, nodule number, yield, tolerance to biotic and abiotic stressors and general plant health. As described in the Examples, it has been observed that the combination of at least one strain of Serendipita sp. and at least one strain of nitrogen fixing bacteria allows for a higher nitrogen fixation capacity of the at least one strain of nitrogen fixing bacteria. Enhancing nitrogen fixation in plants can indeed have significant benefits for sustainable agriculture and can result in reducing the reliance on chemical fertilizers for crop production and mitigating greenhouse gas emissions, including nitrous oxide (N₂O). In an embodiment, the present disclosure provides a method to increase the concentration or amount of nitrogen in a plant by enhancing or increasing the nitrogen fixation capacity of the at least one strain of nitrogen fixing bacteria. This method involves contacting at least one strain of Serendipita sp. with soil, a seed or a plant in need thereof, wherein the at least one strain of Serendipita sp. interact with strains of nitrogen fixing bacteria in the soil or associated with the plant resulting in increased nitrogen fixation rates compared to the nitrogen fixation rates of nitrogen fixing bacteria strains in the absence of the at least one strain of Serendipita sp. In another embodiment, the present invention provides a method to increase the nitrogen fixation of at least one strain of a nitrogen fixing bacteria. The method involves contacting at least one strain of a nitrogen fixing bacteria with at least one strain of Serendipita sp., wherein when contacting the at least one strain of a nitrogen fixing bacteria with at least one strain of Serendipita sp. causes the at least one strain of a nitrogen fixing bacteria to fix nitrogen at a higher rate compared to the nitrogen fixing rate of the at least one strain of a nitrogen fixing bacteria in the absence of the at least one strain of Serendipita sp. In an embodiment, the present disclosure provides for an inoculant for increasing nitrogen fixation of at least one strain of a nitrogen fixing bacteria. The inoculant of the present disclosure comprises at least one strain of Serendipita sp. and the at least one strain of nitrogen fixing bacteria. In an embodiment, the present disclosure further provides a method for enhancing at least one growth parameter of a plant. The method involves co-inoculating a plant or a germplasm with at least one strain of Serendipita sp. strain and at least one strain of a nitrogen fixing bacteria strain, wherein the co-inoculated plant or a plant grown from the co-inoculated germplasm exhibits at least one enhanced growth parameter relative to a plant of the same taxon that has not been co-inoculated with the at least one strain of Serendipita sp. strain. The growth parameter may be a number and/or mass of nodules of a plant and/or a concentration and/or amount of a nutrient in a plant. The nutrient may be nitrogen, phosphorous or potassium. In the context of the present disclosure, the term “nitrogen fixation” concerns the conversion of diatomic nitrogen (N2) into nitrogen-containing organic or inorganic molecules that can be utilized by living organisms in their metabolic processes. In other words, it provides nitrogen in a form capable of being used in metabolism by living organisms such as plants. More particularly, nitrogen fixation is the biological process by which certain types of bacteria, such as rhizobia in legume root nodules or free-living soil bacteria, convert atmospheric nitrogen (N2) into a form that plants can use, typically ammonium (NH4+) or nitrate (NO3-). This process occurs primarily in the soil or within specialized plant structures like root nodules. The nitrogen fixed by bacteria becomes available for uptake by plants, contributing to their nitrogen nutrition. When plants absorb nitrogen from the soil, whether through nitrogen fixation by bacteria, uptake of nitrogen compounds from the soil, or application of nitrogen-containing fertilizers, the nitrogen is assimilated into plant tissues. This assimilated nitrogen plays essential roles in various plant processes, including photosynthesis, protein synthesis, and overall growth and development. An increase in nitrogen in plant tissues indicates that the plant has successfully absorbed and utilized nitrogen for its metabolic functions and growth. While nitrogen fixation by bacteria contributes to the availability of nitrogen for plant uptake, an increase in nitrogen in plant tissues reflects the successful incorporation and utilization of nitrogen by the plant for its physiological processes. In the context of the present disclosure, the term “associated with” when referring to nitrogen fixing bacteria in relation to plants means that the nitrogen fixing bacteria are forming a symbiotic association with a host plant. When nitrogen fixing bacteria are “in association with” host plants, they form root nodules and engage in a mutually beneficial relationship with the host plants. Nitrogen fixing bacteria can also live freely in the soil or in the soil in the vicinity of a host plant. The present disclosure further concerns methods of increasing nitrogen fixation or increase the concentration of nitrogen in a plant, comprising exposing or contacting soil, a seed or a plant with at least one strain of Serendipita sp. or contacting at least one strain of Serendipita sp. and at least one strain of nitrogen fixing bacteria, wherein the at least one strain of nitrogen fixing bacteria produces at least about 1%, 2%, 3%, 4% or 5% or more of nitrogen in the plant, as compared to the plant in the absence of the at least one strain of Serendipita sp. More particularly, the increase in nitrogen concentration in a plant is at least about 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 15%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30% or at least more than 30%. In some embodiments, the increase in nitrogen concentration in a plant can be a least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95% or more than 100%. In some embodiments, the combination of the present disclosure (i.e. at least one strain of Serendipita sp. and at least one strain of nitrogen fixing bacteria) allows the at least one strain of nitrogen fixing bacteria to produce at least 1% or more of nitrogen in a plant (e.g. 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30% or at least more than 30%, a least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90% or at least about 95% or more than 100%) compared to plant in the absence of the at least one strain of Serendipita sp. In an embodiment, the increase in nitrogen fixation of at least one strain of a nitrogen fixing bacteria can be at least about 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30% or at least more than 30%. In an embodiment, the increase in nitrogen fixation can be at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95% or more than 100% compared to the nitrogen fixation rates of nitrogen fixing bacteria strains in the absence of the at least one strain of Serendipita sp. The increase of nitrogen fixation and/or the production of 1% or more of the nitrogen in the plant are measured relative to control plants which have not been exposed to the Serendipita sp. of the present disclosure. All increases or decreases in bacteria are measured relative to control bacteria. All increases or decreases in plants are measured relative to control plants. The amount of nitrogen fixation that occurs in the plants described herein may be measured in several ways, for example by ureide method, N balance, N difference, C₂H₂ reduction assay, ¹⁵N natural abundance, ¹⁵N dilution or GlnLux. The present disclosure concerns amongst other the use of at least one strain of Serendipita sp. In an embodiment, the at least one strain of Serendipita sp. can be at least one strain of S.australiana, S. communis, S. evanescens, S. herbamans, S. inclusa, S.indica, S. interna, S. invisibilis, S. lyrica, S. occidentalis, S. orliensis, S. rarihospitum, S. restingae, S. sacchari, S. secunda, S. sigmaspora, S. talbotii, S. vermifera, S. warcupii, S. whamiae or S. williamsii. In an embodiment, the at least one strain of Serendipita sp. can be at least one strain of S. indica or S. williamsii. In another embodiment, the strain used in the context of the present disclosure is Serendipita sp. isolate 46 which has been deposited the 28^th February 2024 according to the Budapest Treaty under accession number 280224-01 with the International Depository Authority of Canada (IDAC), 1015 Arlington Street, Winnipeg, Manitoba, R3E 3R2, Canada. The Serendipita sp. isolate 46 was isolated from soils in Masaco, 14km from Kisangani (N: 0.58789; E: 25.25166) in the Democratic Republic of Congo. In addition to Serendipita sp. isolate 46, the present invention relates to any Serendipita sp. strain whether physically derived from the original deposit of strain isolate 46 or independently isolate, so long as they retain at least one of the identifying characteristics of the deposited Serendipita sp. isolate 46 strain. Such Serendipita sp. strains of the invention include any progeny of strain isolate 46, including mutants of said strain. Mutant strains of Serendipita sp. isolate 46 may be obtained by any methods well-known in the art. For example, such mutants are obtainable by applying a mutagenic chemical agent, such as N-methyl-nitrosoguanidine, X-ray or UV radiation. Subsequent to said treatment a screening for mutant strains showing the desired characteristics may be performed. Thus, the term mutant is meant to designate a Serendipita sp. strain obtained by direct mutant selection but also includes Serendipita sp. strains that have been further mutagenized or otherwise manipulated (e.g., via the introduction of a plasmid). Accordingly, embodiments include both naturally occurring and artificially induced mutants. In particular, the Serendipita sp. strains of the invention are characterized in that they are capable of retaining at least one of the identifying characteristics. A Serendipita sp. strain isolate 46 of the invention is one having the following morphological characteristics: - The spore diameter after growth on PDA for 4 weeks at 30°C is 11 µM; - The colony surface area after growth on PDA for 7 days is 35 cm²; - The colony surface area after growth on MYP for 7 days is 20 cm²; - The mycelium grows submerged in agar with no to only limited formation of aerial hyphae; - In liquid medium such as PDB the isolate grows conglomerated in small globose balls; - The young mycelium is white to hyaline without indentations; - The old mycelium is rather granulated and irregularly inflated (moniliform); and - The spores (chlamydospores) are pear shaped (see former name: pririformospora). The at least one strain of Serendipita sp. of the present disclosure can be seen as a helper strain that allows increasing the nitrogen fixation rate of any at least one strain of nitrogen fixing bacteria compared to the nitrogen fixation rates of nitrogen fixing bacteria strains in the absence of the at least one strain of Serendipita sp. Further, the combination of these at least two strains generates an increased concentration of nitrogen in a plant which concentration of nitrogen is greater than compared to the concentration of nitrogen of the at least one strain of nitrogen fixing bacteria in the absence of the at least one strain of Serendipita sp. In an embodiment, the at least one strain of nitrogen fixing bacteria is a rhizobial microorganism. As defined in the context of the present invention, a rhizobial microorganism may include any microorganism that is capable of fixing nitrogen after becoming established in a root nodule of a leguminous plant. More particularly, the nitrogen fixing bacteria of the present invention enter into a symbiotic relationship with certain plants. In exchange for sugars and other nutrients supplied by the host plant, symbiotic nitrogen-fixing bacteria convert atmospheric nitrogen into ammonium (a form usable by the host plant) and pass it to the plant. The at least one strain of nitrogen fixing bacteria can be from one genus of bacteria, two genera of bacteria, three genera of bacteria, four genera of bacteria, five genera of bacteria, six genera of bacteria, seven genera of bacteria, eight genera of bacteria, nine genera of bacteria, ten genera of bacteria or more than ten genera of bacteria. The at least one strain of nitrogen fixing bacteria can be from one species of bacteria, two species of bacteria, three species of bacteria, four species of bacteria, five species of bacteria, six species of bacteria, seven species of bacteria, eight species of bacteria, nine species of bacteria, ten species of bacteria or more than ten species of bacteria. In the context of the present invention, the nitrogen fixing bacteria is not a free-living nitrogen-fixing bacterium that exists independently of a plant in the soil and that is capable of converting atmospheric nitrogen (N₂) into ammonia (NH₃) through the process of biological nitrogen fixation without forming a symbiotic relationship with a host plant. In an embodiment, the at least one strain of nitrogen fixing bacteria is of the genus Bradyrhizobium, Rhizobium, Mesorhizobium, Ensifer, Azorhizobium, Sinorhizobium, Azorhizobium, Frankia, Burkholderia, Ralstonia, Cupriavidus, Azotobacter, Azospirillum, Paenibacillus, Herbaspirillum, Acetobacter, Delftia, Rhodospirillum, Clostridium, Klebsiella, Pseudomonas, Gluconacetobacter, Beijerinckia or combinations thereof. In another embodiment, the at least one strain of nitrogen fixing bacteria is of the genus Bradyrhizobium, Rhizobium, Mesorhizobium, Sinorhizobium, or combinations thereof. In an embodiment, the at least one strain of nitrogen fixing bacteria is of the genus Rhizobium, Bradyrhizobium, Mesorhizobium, Sinorhizobium or Azorhizobium. In an embodiment, the at least one strain of nitrogen fixing bacteria is Bradyrhizobium japonicum, Bradyrhizobium elkanii, Bradyrhizobium diazoefficiens, Bradyrhizobium canariense, Rhizobium leguminosarum, Rhizobium tropici, Mesorhizobium ciceri, Ensifer meliloti (formerly Rhizobium meliloti and Sinorhizobium meliloti), Rhizobium fredii, Rhizobium leguminosarum biovar viciae, Mesorhizobium loti, Rhizobium leguminosarum biovar trifolii, Rhizobium legumninosarum biovar phaseoli, or combinations thereof. In an embodiment, the strain is a strain of B. japonicum, B. elkanii, B. diazoefficiens, R. leguminosarum biovar viciae or combinations thereof. In an embodiment, the strain is B. japonicum USDA 110, B. japonicum USDA 442, B. japonicum USDA 136 or B. japonicum SEMIA 5079, or combinations thereof. In an embodiment, the strains B. japonicum USDA 110 and B. japonicum USDA 442 are used in combination. In an embodiment, the strain is a strain of B. elkanii. In an embodiment, the strain is B. elkanii SEMIA 587, B. elkanii U- 1301, B. elkanii SEMIA 5019, B. elkanii U-1302, or combinations thereof. In an embodiment, the strains B. elkanii SEMIA 587 and B. elkanii SEMIA 5019 are used in combination. In an embodiment, the strain is a strain of B. diazoefficiens. In an embodiment, the strain is B. diazoefficiens SEMIA 5080. In an embodiment, the strains B. japonicum SEMIA 5079 and B. diazoefficiens SEMIA 5080 are used in combination. In an embodiment, the strain is a strain of R. leguminosarum biovar viciae as, for example, a R. leguminosarum biovar viciae strain from LALFIX Liquid Pea and Lentil, Lallemand Inc. In an embodiment, the strain is a strain of Mesorhizobium ciceri as, for example, a strain of Mesorhizobium Mesorhizobium ciceri from LALFIX Chickpea, Lallemand Inc. In an embodiment, the strain is a strain of Sinorhizobium meliloti as, for example, strains of Sinorhizobium meliloti U-137 and U-143 from NITRASEC alfalfa (peat) (Lage y Cia S.A.). In an embodiment, the strain is a strain of Rhizobium leguminosarum biovar trifolii as, for example, the strain Rhizobium leguminosarum biovar trifolii U-204 from NITRASEC Trifolium repens / Trifolium pratense (peat), the strain Rhizobium leguminosarum biovar trifolii U-206 from NITRASEC Trifolium alexandrium (peat) or the strain Rhizobium leguminosarum biovar trifolii U-276 from NITRASEC Trifolium vesiculosum (peat) (Lage y Cia S.A.). In an embodiment, the strain is a strain of Mesorhizobium loti as, for example, the strain of Mesorhizobium loti U-510 from NITRASEC Lotus corniculatus or Lotus glaber (peat) (Lage y Cia S.A.). In an embodiment, the strain is a strain of Bradyrhizobium sp. as, for example the strains Bradyrhizobium sp. U-612 or U-620 from NITRASEC Ornithopus compressus (Lage y Cia S.A.). In an embodiment, the strain is a strain of Bradyrhizobium loti as, for example the strain Bradyrhizobium loti U-1401 from NITRASEC Lotus uliginosus (Lage y Cia S.A.). In an embodiment, the strain is a strain of Rhizobium tropici as, for example, a strain of Rhizobium tropici from LALFIX Peat Dry Beans, Lallemand Inc. In an embodiment, the strain is a strain of Rhizobium leguminosarum as, for example, a strain of Rhizobium leguminosarum from Agribacter® Pea, Lallemand Inc. As set out above, the present invention contemplates co-inoculating a plant with at least one strain of nitrogen fixing bacteria and at least one strain of Serendipita sp. As referred to herein, “co-inoculating” or “contacting” should be understood to include any method or process wherein a plant (including a seed) is brought into contact with at least one strain of nitrogen fixing bacteria and at least one strain of Serendipita sp. In some embodiments, co-inoculation may comprise the at least one strain of nitrogen fixing bacteria and/or at least one strain of Serendipita sp. being applied to a plant seed. In some embodiments, co-inoculation may comprise the at least one strain of nitrogen fixing bacteria and/or at least one strain of Serendipita sp. being applied to soil in which a plant is growing. In some embodiments, co-inoculation may comprise at least one strain of nitrogen fixing bacteria and/or at least one strain of Serendipita sp. being applied to root and/or shoot tissue of a leguminous plant. In some embodiments, “co-inoculating” may also comprise where at least one strain of nitrogen fixing bacteria and/or at least one strain of Serendipita sp. is pre-existing in the environment (e.g. soil or aerial roots) into which a plant is grown. For example, in an embodiment, co-inoculation may comprise application of at least one strain of Serendipita sp. to a plant or soil and wherein a natural or pre-existing at least one strain of nitrogen fixing bacteria is in association with said plant. As used herein the term “inoculant” or “co-inoculant” or “inoculant composition” or “composition” comprises an effective amount or quantity (e.g. as measured in CFU) of the at least one strain of Serendipita sp. alone or an effective amount or quantity (e.g. as measured in CFU) of at least one strain of Serendipita sp in combination with at least one strain of nitrogen fixing bacteria. The “‘inoculant” or “co-inoculant” or “inoculant composition” or “composition” may be intended for inoculation or contacting with a single plant or the environment where a single plant is present (such as to the soil in a pot). In a further embodiment, the “inoculant” of the present disclosure comprises a ratio of the quantity of the at least one strain of Serendipita sp. to the quantity of at least one strain of nitrogen fixing bacteria. In embodiments where at least one strain of nitrogen fixing bacteria and/or at least one strain of Serendipita sp. is pre-existing in the environment (e.g. soil or aerial roots) into which a plant is grown, the ratio refers to the ratio in the environment after inoculation. The ratio of the at least one strain of Serendipita sp. and the at least one strain of nitrogen fixing bacteria may determined by measuring the total number of colony forming units (CFU) for each strain. In an embodiment, the ratio of the at least one strain of Serendipita sp. and the at least one strain of nitrogen fixing bacteria is between about: 1:1 to 1:20; 1:1 to 1:15; 1:1 to 1:10; 1:1 to 1:9; 1:1 to 1:8; 1:1 to 1:7; 1:1 to 1:6; 1:1 to 1:5; 1:1 to 1:4; 1:1 to 1:3; or 1:1 to 1:2. In an embodiment, the ratio of the at least one strain of Serendipita sp. and the at least one strain of nitrogen fixing bacteria is between about: 1:25 to 1:10000; 1:50 to 1:10000; 1:75 to 1:10000; 1:100 to 1:10000; 1:200 to 1:10000; 1:300 to 1:10000; 1:400 to 1:10000; 1:500 to 1:10000; 1:600 to 1:10000; 1:700 to 1:10000; 1:800 to 1:10000; or 1:900 to 1:10000. In an embodiment, the ratio of the at least one strain of Serendipita sp. and the at least one strain of nitrogen fixing bacteria is between about: 1:1 to 20:1; 1:1 to 15:1; 1:1 to 10:1; 1:1 to 9:1; 1:1 to 8:1; 1:1 to 7:1; 1:1 to 6:1; 1:1 to 5:1; 1:1 to 4:1; 1:1 to 3:1 or 1:1 to 2:1. In an embodiment, the ratio of the at least one strain of Serendipita sp. and the at least one strain of nitrogen fixing bacteria is about: 1:1; 1:1.25; 1:1.50; 1:1.75; 1:2; 1:3; 1:4; 1:5; 1:6; 1:7; 1:8; 1:9; or 1:10. In an embodiment, the ratio of the at least one strain of Serendipita sp. and the at least one strain of nitrogen fixing bacteria is about: 1:3; 1:4; or 1:5. In an embodiment, the ratio of the at least one strain of Serendipita sp. and the at least one strain of nitrogen fixing bacteria is about: 1:100 to 1:200; 1:200 to 1:300; 1:300 to 1:400; 1:400 to 1:500; 1:500 to 1:600; 1:600 to 1:700; 1:700 to 1:800; 1:800 to 1:900; 1:900 to 1:1000; 1:1000 to 1:1100; 1:1100 to 1:1200; 1:1200 to 1:1300; 1:1300 to 1:1400; 1:1400 to 1500; 1:1500 to 1:1600; 1:1600 to 1:1700; 1:1700 to 1:1800; 1:1800 to 1:1900; 1:1900 to 1:2000; 1:2000 to 1:2100; 1:2100 to 1:2200; 1:2200 to 1:23000; 1:2300 to 1:2400; 1:2400 to 1:2500; 1:2500 to 1:2600; 1:2600 to 1:2700; 1:2700 to 1:2800; 1:2800 to 1:2900; 1:2900 to 1:3000; 1:3000 to 1:3100; 1:3100 to 1:3200; 1:3200 to 1:3300; 1:3300 to 1:3400; 1:3400 to 1:3500; 1:3500 to 1:3600; 1:3600 to 1:3700; 1:3700 to 1:3800; 1:3800 to 1:3900; 1:3900 to 1:4000; 1:4000 to 1:4100; 1:4100 to 1:4200; 1:4200 to 1:4300; 1:4300 to 1:4400; 1:4400 to 1:4500; 1:4500 to 1:4600; 1:4600 to 1:4700; 1:4700 to 1:4800; 1:4800 to 1:4900; 1:4900 to 1:5000; 1:5000 to 1:5100; 1:5100 to 1:5200; 1:5200 to 1:5300; 1:5300 to 1:5400; 1:5400 to 1:5500; 1:5500 to 1:5600; 1:5600 to 1:5700; 1:5700 to 1:5800; 1:5800 to 1:5900; 1:5900 to 1:6000; 1:6000 to 1:6100; 1:6100 to 1:6200; 1:6200 to 1:6300; 1:6300 to 1:6400; 1:6400 to 1:6500; 1:6500 to 1:6600; 1:6600 to 1:6700; 1:6700 to 1:6800; 1:6800 to 1:6900; 1:6900 to 1:7000; 1:7000 to 1:7100; 1:7100 to 1:7200; 1:7200 to 1:7300; 1:7300 to 1:7400; 1:7400 to 1: 7500; 1:7500 to 1:7600; 1:7600 to 1:7700; 1:7700 to 1:7800; 1:7800 to 1:7900; 1:7900 to 1:8000; 1:8000 to 1:8100; 1:8100 to 1:8200; 1:8200 to 1:8300; 1:8300 to 1:8400; 1:8400 to 1:8500; 1:8500 to 1:8600; 1:8600 to 1:8700; 1:8700 to 1:8800; 1:8800 to 1:8900; 1:8900 to 9000; 1:9000 to 9100; 1:9100 to 9200; 1:9200 to 9300; 1:9300 to 9400; 1:9400 to 9500; 1:9500 to 9600; 1:9600 to 9700; 1:9700 to 9800; 1:9800 to 9900; or 1:9900 to 1:10000. In an embodiment, the ratio of the at least one strain of Serendipita sp. and the at least one strain of nitrogen fixing bacteria is between about 1:500 to 1:9000. In an embodiment, the ratio of the at least one strain of Serendipita sp. and the at least one strain of nitrogen fixing bacteria is between about 1:600 to 1:8500. In other embodiments, the inoculant can further comprise a solution or a dry composition comprising at least two, three, four, five, six, seven or more than seven strains of a nitrogen fixing bacteria which can be all combined in different ratios or proportions. The inoculant or inoculant composition comprising at least one strain of Serendipita sp. or the combination of at least one strain of Serendipita sp. and at least one strain of a nitrogen fixing bacteria, as described in the present disclosure, can take the form of a coating applied to the surface of a seed or may be in liquid, powder or granule form. More particularly, the inoculant compositions include seed coatings used in commercial agriculture. Additionally, the inoculant compositions can be sprayed onto the aerial parts of plants or applied to the roots by adding it into furrows where plant seeds are planted. Other application methods include watering it into the soil or dipping the roots in a suspension of the inoculant composition. Furthermore, the inoculant composition can be dehydrated in a manner that preserves cell viability, allowing it to effectively and artificially inoculate and colonize host plants. The at least one strain of Serendipita sp. may be present in the inoculation compositions at a concentration of between 10² to 10¹² CFU/ml. If the inoculant composition also contains at least one strain of nitrogen fixing bacteria in combination of an at least one strain of Serendipita sp., the at least one strain of nitrogen fixing bacteria can be present in the composition at a concentration of between 10² to 10¹² CFU/ml. The inoculant compositions comprising the at least one strain of Serendipita sp. or at least one strain of Serendipita sp. and at least one strain of a nitrogen fixing bacteria described herein may be coated onto the surface of a seed. The seed coating can be prepared by mixing the microorganism population (e.g. at least one strain of Serendipita sp. or at least one strain of Serendipita sp. and at least one strain of a nitrogen fixing bacteria) with a porous, inert carrier which are well known in the art. In another embodiment, the inoculant compositions can be inserted directly into the furrows into which the seed is planted or sprayed onto the plants or applied by dipping the roots into a suspension of the composition. An effective amount of the composition can be used to populate the sub-soil region adjacent to the roots of the plant with microorganism population or populate the leaves of the plant with microorganism population. In general, an effective amount is an amount sufficient to result in plants with the increase level of nitrogen concentration or in an increase in nitrogen fixation of at least one strain of a nitrogen fixing bacteria compared to plants or to the nitrogen fixation rates of nitrogen fixing bacteria strains not in contact with the at least one strain of Serendipita sp. Inoculant compositions of the present disclosure can be formulated using one or more agriculturally acceptable carrier(s) which can be a solid carrier or a liquid carrier. The agriculturally acceptable carrier can confer different properties such as stability or dispersability. For example, the inoculant compositions can include at least one member selected from the group consisting of a tackifier, an adhesion agent, a microbial stabilizer, a fungicide, an antibacterial agent, an herbicide, a nematicide, an insecticide, a plant growth regulator, a fertilizer, a desiccant, and a nutrient. Agriculturally acceptable carriers are well known in the art. Solid inoculant compositions can be produced by dispersing bacterial populations onto or within a suitably solid carrier. Examples of such carriers include mineral carriers, peat, wheat, bran, vermiculite, clay, talc, bentonite, diatomaceous earth, fuller’s earth, inorganic salts or pasteurized soil. When these formulations are employed as wettable powders, biologically compatible dispersing agents can be used. When the inoculant composition is in liquid form, such as solutions or suspensions, the inoculant composition of the present disclosure can be blended or suspended in water or in any aqueous solutions (such as, but not limited to, vegetable oils, glycerol, ethylene glycol, polyethylene glycol, propylene glycol or polypropylene glycol). The methods and the inoculant compositions of the present disclosure are suitable for any of a variety of plants, such as (a) cereal grain, cover, forage, oilseed, and soybean crops, such as: alfalfa, barley, canola, corn, millet, oats, rice, rye, sorghum, soybean, safflower, sunflower, triticale, wheat, buckwheat, mustards, brassicas, pea, lentil, fava bean, chickpea, peanut, lupins, alfalfa, sub clover, lucerne, medic, white clover, mung bean, siratro, serradella, Adzuki bean, birdsfoot trefoil, Biserrula, Burgundy bean, Centro, Caucasian Clover, common bean, Desmanthus, Desmodium, Fenugreek, Guar bean, Jointvetch, Kenyan white clover, Leucaena, Lotononis, Greater Lotus, Messina, Pinto peanut, Stylo, Sulla, Tagasaste, Tedera, or sugarcane; (b) berries and small fruits, such as: blackberry, blueberry, cranberry, currant, elderberry, gooseberry, huckleberry, kiwifruit, loganberry, raspberry, strawberry or grape (e.g., table and wine); (c) citrus fruits, such as: citrus hybrids, grapefruit, kumquat, lemon, lime, orange, pummelo, satsuma or mandarin; (d) cucurbit vegetables, such as: cucumber, cantaloupe, melon, gourd, pumpkin, squash (e.g., butternut, winter, zucchini) or watermelon; (e) flowers, cut flowers, bedding plants, foliage and potted plants, and ornamentals, such as: achillea, African violet, ageratum, aloe, alyssum, amaryllis, anemone, anthurium, aster, azalea, begonia, calceolaria, campanula, carnation, centaurea, cerastium, chrysanthemum, cineraria, coleus, cyclamen, daffodil, dahlia, daisy, delphinium, dianthus, dieffenbachia, dracaena, fern, freesia, fuchsia, gaillardia, gazania, geranium, gerbera, gladiolus, gloxinia, gypsophila, hedera, hibiscus, hyacinth, impatiens, iris, kalanchoe, liatris, lily, lobelia, marigold, matthiola, monarda, myrtle, New Guinea impatiens, nigella, pansy, pelargonium, petunia, phlox, poinsettia, poppy, primrose, ranunculus, rhododendron, rose, rudbeckia, salvia, sansevieria, sedum, senecio, sinningia, spathiphyllum, statice, sweet pea, tulip, verbena, vinca or zinnia; (f) fruiting vegetables, such as: eggplant, pepper (e.g., bell, sweet, and hot), okra, tomatillo or tomato; (g) herbs, spices, and mints, such as: aniseed, basil, caraway, chive, cilantro, dill, fennel, lavender, marjoram, mustard seed, oregano, parsley, rosemary, sage, savory, stevia or thyme; (h) hydroponic crops, such as: cucumber, eggplant, lettuce and other leafy greens, herbs and spices, microgreens, pepper, tomato, squash or strawberry; (i) leafy vegetables, such as arugula, celery, Belgian endive, fennel, lettuce (e.g., head and leaf), parsley, radicchio, rhubarb, spinach, Swiss chard or watercress; (j) Brassica (cole) leafy vegetables, such as: broccoli, Brussels sprouts, cabbage, cauliflower, Chinese cabbage, collards, kale, kohlrabi or mustard greens; other vegetables, such as, asparagus; (k) peanut pome fruits, such as: apple, pear or quince; (l) stone fruits, such as: apricot, cherry (e.g., sweet and tart), nectarine, peach, plum or prune (fresh); (m) tobacco trees, shrub seedlings, and shade house and outdoor nursery crops, such as: arborvitae, ash, azalea, beech, birch, boxwood, buckeye, cactus, cedar, cherry, chestnut, crabapple, crepe myrtle, deciduous trees (e.g., maple and oak), dogwood, fir, forest trees, fruit trees, hemlock, herbaceous ornamentals, juniper, larch, lilac, magnolia, ornamentals, ornamental grasses, ornamental palm, pine, rhododendron, shrubs, spruce, vine crops, walnut, woody ornamentals or yew; (n) tree nuts, such as: almond, beech nut, Brazil nut, butternut, cashew, chestnut, coconut, filbert, hickory nut, macadamia nut, pecan, pistachio or walnut root; (o) tuber and bulb vegetables, such as: beet (e.g., garden and sugar), carrot, cassava, celeriac, chicory, Chinese artichoke, chive, dasheen, garlic, ginger, ginseng, horseradish, Jerusalem artichoke, leek, onion, parsnip, potato, radish, rutabaga, salsify, shallot, sweet potato, turmeric, turnip, turnip-rooted chervil or yam; (p) turf, such as: turf grown for use as seed, sod, lawns, turf greens, sports fields or municipal turf; (q) miscellaneous crops, such as: avocado, banana, coffee, cotton, globe artichoke, hops, mushrooms, olive, other flowering plants and bedding plants, papaya, pineapple, pitaya (Dragonfruit), plantain or tea. In an embodiment, the methods and the inoculant compositions of the present disclosure are suitable for soybean, pea, lentil, fava bean, common bean, chickpea, peanut, alfalfa, lucerne, white clover, wheat, canola, corn, rice, sorghum, sugarcane, potato or sweet potato. The present invention contemplates a method for enhancing at least one growth parameter of a plant. In an embodiment, the growth parameter a length and/or mass is a shoot of a plant. In an embodiment, the growth parameter is a length and/or mass of a root of a plant. In an embodiment, the growth parameter is a number and/or mass of nodules of a plant. In an embodiment, the growth parameter is a number and/or mass of seed pods and/or seed produced by the leguminous plant. In an embodiment, the growth parameter is a concentration and/or amount of a nutrient in a plant. In some embodiments, the nutrient is selected from: boron, calcium, copper, magnesium, manganese, potassium, phosphorous, sodium, sulphur, nitrogen and/or zinc. The concentration and/or amount of the nutrient may be measured using any known method in the art to be suitable for the relevant nutrient. In some embodiments, the nutrient is nitrogen, potassium or phosphorous. The present invention provides a plant or a germplasm co-inoculated with at least one strain of Serendipita sp. and at least one strain of a nitrogen fixing bacteria. As used herein, the term “germplasm” refers to the genetic material of or from individual plants, groups of plants (eg, plant lines, cultivars and families) and clones derived from plants or groups of plants. The germplasm can be part of an organism or cell or can be isolated from an organism or cell. In general, germplasm provides genetic material with a specific molecular composition that is the criterion for the heritable quality of plants. As used herein, “germplasm” refers to cells of a particular plant; a tissue of a particular plant (eg, tissue from which new plants can grow); refers to the non-seed part of a particular plant (eg, leaves, stems, pollination and cells). The term “germplasm” as used herein is synonymous with “genetic material” and may be used to refer to seeds (or other plant material) from which a plant can propagate. In the context of the present disclosure the term “increasing” the nitrogen fixation rate of at least one strain of nitrogen fixing bacteria should be understood to include any improvement in nitrogen fixation rates in a nitrogen fixing bacteria compared to the nitrogen fixation rates of nitrogen fixing bacteria strains in the absence of the at least one strain of Serendipita sp. In the context of the present disclosure the term “enhancing” of at least one growth parameter should be understood to include any improvement in a growth parameter in a co-inoculated plant relative to a plant of the same taxon that has son been co-inoculated in accordance with the method of the present invention. The terms “comprising” or “to comprise” and their conjugations, as used herein, refer to a situation wherein said terms are used in their non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. It also encompasses the more limiting verb “to consist essentially of” and “to consist of”. Reference to an element by the indefinite article “a” or “an” does not exclude the possibility that more than one of the elements is present, unless the context clearly requires that there be one and only one of the elements. The indefinite article “a” or “an” thus usually means “at least one”. The following example serves to further describe and define the invention and is not intended to limit the invention in any way. EXAMPLES EXAMPLE 1: Determination of the effect of the co-inoculation of Serendipita sp. and Bradyrhizobium elkanii on nitrogen fixation The objective of this assay was to determine if the co-inoculation of at least one strain of Serendipita sp. with a combination of B. elkanii SEMIA 587 and SEMIA 5019 can increase the concentration of nitrogen in a plant and the total nodule dry weight. An original culture of Serendipita sp. isolate 46 was subcultured onto potato dextrose agar for 21 days in a 25°C incubator before extraction. The culture plates were then flooded with 20 ml sterile recovery solution (0.85% saline + 0.01% Tween 80) and then the surface was rubbed gently with a rubber policeman. The solution was then poured from the plate into a 50 ml Falcon tube through a sterile cheesecloth to filter out the mycelia. The chlamydospore concentration was then calculated using a haemocytometer and then adjusted to the desired concentration using 0.85% sterile saline. The strains SEMIA 587 and SEMIA 5019 of B. elkanii were cultured separately in a YM (yeast mannitol) medium for 7 days at 28°C. For inoculation, well-grown shake cultures of both strains were mixed in an equivalent proportion and used. The final strain mixture was adjusted to a concentration of 10⁹ cells/ml. Square black pots (712ml, 3.5” diameter) were filled with moist pasteurized 50:45:5 sand:clay:peat substrate to 1 cm below top. Each pot received one pregerminated soybean seed (gladstone variety), which was treated, by in-furrow application, according to treatments in Table 1. After treatments were applied, seeds were covered with substrate. Pots were placed in a reach-in growth chamber set to 24-18°C, 14:10 light:dark cycle, and 65% overall humidity, and allowed to grow for approximately 40 days (stage R3 for harvest) until nodulation and ureide could be assessed in order to measure biological nitrogen fixation in plants. Pots were watered as needed with half-strength nitrogen free Hoaglands’ solution. At the end of the experiment, plants were harvested, and the following parameters were measured for treatment efficacy: nodule dry weight, stem ureide content (mg N/L) and percentage of soybean plants in growth stage at harvest. Plant roots from each treatment were also sampled and stained for presence/absence of Serendipita chlamydopores. Table 1: Treatments included in the assay Treatment Total Total Amount Repetitions amount of amount of added in Serendipita B. elkanii furrow sp. isolate SEMIA 587 46 and SEMIA 5019 1 Uninoculated Control NA NA 30 µL 12 0.85% saline 2 B. elkanii SEMIA 587 NA 2.3 x 10⁶ 15 µL of 12 and SEMIA 5019 CFU/pot (or culture of B. plant) elkanii+ 15 µL 0.85% saline 3 Serendipita sp. isolate 2.3 x 10⁶ 15 µL of 12 46 + B. elkanii SEMIA 2.75 x 10² CFU/pot (or culture of B. 587 and SEMIA 5019 CFU/pot (or plant) elkanii + 15 plant) µL Serendipita sp. isolate 46 After harvesting the plants, the concentration of nitrogen (mg/L) in the stem of sampled soybean plants was measured by ureide method (adapted for microplate from Goos et al., 2014). Samples were dried at 60°C for 2 days and ground to pass a 0.1mm screen. The extracted plant tissue (0.1g) was placed into a screw-cap test tube, with 10ml of water, the tubes were sealed and heated to 90°C for 30min in a water bath. They were then cooled to room temperature and shaked on a mechanical shaker for 30min followed by filtration into 15- ml plastic screw cap vials. Extracts were then stored in the refrigerator until analyses for nitrogen concentration. Seven standards were prepared (containing 0, 1, 5, 10, 15, 20 and 30mg N/L of allantoin) in water with the addition of 0.5M NaOH (2g in 100ml of water). The color developing reagent was prepared by mixing 100ml of water, 100ml of mixed acid reagent (96ml of phosphoric acid and 4ml of sulfuric acid), 6.2ml of a 2,3-butanedione monoxime solution (3.75g in 100ml of warm water) and 3.9mL of a thiosemicarbazide solution (0.375g in 100ml of warm water). An aliquot (0.3mL of standard or plant extract) was placed in a screw-top glass test tube and 0.3mL of 0.5M NaOH was added. The tubes were sealed, contents mixed, and placed in a 90°C water/dry bath for 30min. After cooling, 7mL of color development reagent were added. The tubes were sealed, the contents mixed, and placed again in the 90°C water/dry bath 1 hour. The bath was covered with an opaque cover to exclude light during color development. After 1 hour, the tubes were removed from the hot water bath and aliquoted into a microplate (200ul of each sample per well with 3 repetitions). Absorbance was determined at 525 nm using a plate reader. The standards were used to make a calibration curve with absorbance vs concentration. Samples were mapped against the calibration curve. The results shown in Figure 1 indicate that the concentration of ureide in the stem of sampled soybean plants was significantly different for all the treatments (F_2.32=172.63, p<0.001). The untreated control had the lowest concentration of ureide in the stems (2.59 mg N/L), this was followed by the B. elkanii SEMIA 587 and SEMIA 5019 strains applied alone (42.44 mg N/L) and the co-inoculation of B. elkanii SEMIA 587 and SEMIA 5019 with Serendipita sp. isolate 46 (54.97 mg N/L) had the highest concentrations of ureide in the stems. The co-inoculation of B. elkanii SEMIA 587 and SEMIA 5019 with Serendipita sp. isolate 46 increased the nitrogen fixation rate of the B. elkanii SEMIA 587 and SEMIA 5019 strains compared to the nitrogen fixation rates of the B. elkanii SEMIA 587 and SEMIA 5019 strains in the absence of the at least one strain of Serendipita sp. Harvested plants from all treatments were washed under running tap water to remove dust and soil attached to the roots and nodules. The roots and nodules were separated from the plants and air-dried overnight at room temperature. The dried nodules were weighted. The results shown in Figure 2 indicate that the average dry weight of nodules produced per plant was significantly different between all the treatments (F_2.31=51.21, p<0.001). The dry weight of nodules for the untreated control was 0.01 g/plant while the B. elkanii SEMIA 587 and SEMIA 5019 strains applied alone had nodules that weighed 0.11 g/plant and the co-inoculated of B. elkanii SEMIA 587 and SEMIA 5019 strains with Serendipita sp. isolate 46 had nodules that weighed 0.14 g/plant. According to literature, a strong correlation was observed between nodule dry weight and N₂ fixation, providing an easily available method to estimate differences in biological N fixation activity between treatments (Juliana Trindade Martins et al., 2022). Furthermore, as illustrated in Figure 3 soybean plants co-inoculated with B. elkanii SEMIA 587 and SEMIA 5019 in combination with Serendipita sp. isolate 46 were in a more advance stage of growth (R3) as compared with soybean plants inoculated only with B. elkanii SEMIA 587 and SEMIA 5019 strains (which had 90% of the plants in R3 stage and 10% of the plants in an R2 stage) or the untreated control (which had 72.7% in R3 stage; 27.3% in R2 stage). These results confirm that plant growth capacity is enhanced due to enhanced nitrogen levels within the plant. The presence of Serendipita sp. isolate 46 chlamydospores inside the roots of the harvested soybean plants was confirmed by microscopic analyses. EXAMPLE 2: Determination of the effect of the co-inoculation of Serendipita sp. and Bradyrhizobium japonicum strains USDA 110 and USDA 442 on nitrogen fixation The objective of this assay was to determine if the co-inoculation of at least one strain of Serendipita sp. with strains USDA 110 and USDA 442 of B. japonicum can increase the total nodule dry weight which is an indicator of an increase of the N fixation activity. An original culture of Serendipita sp. isolate 46 was subcultured onto potato dextrose agar for 21 days in a 25°C incubator before extraction. The culture plates were then flooded with 20 ml sterile recovery solution (0.85% saline + 0.01% Tween 80) and then the surface was rubbed gently with a rubber policeman. The solution was then poured from the plate into a 50 ml Falcon tube through a sterile cheesecloth to filter out the mycelia. The chlamydospore concentration was then calculated using a haemocytometer and then adjusted to the desired concentration using 0.85% sterile saline. The strains USDA 110 and USDA 442 of B. japonicum were cultured separately in a YM medium at 28 °C. For inoculation, well-grown shake cultures of both strains were mixed in an equivalent proportion and used. The final strain mixed culture was adjusted to a concentration of 10⁹ cells/ml. Square black pots (712ml, 3.5” diameter) were filled with moist pasteurized 50:45:5 sand:clay:peat substrate to 1 cm below top. Each pot received one pregerminated soybean seed (gladstone variety), which was treated, by in-furrow application, according to treatments in Table 2. After treatments were applied, seeds were covered with substrate. Pots were placed in a reach-in growth chamber set to 24-18°C, 14:10 light:dark cycle, and 65% overall humidity, and allowed to grow for appropriately 40 days when 80% of plants reached stage R3 until nodulation. Pots were watered as needed with half- strength nitrogen free Hoaglands’ solution. At the end of the experiment, plants were harvested and the nodule dry weight was measured. Table 2: Treatments included in the assay Treatment Total Total Repetitions amount of amount of Serendipita B. sp. isolate japonicum 46 strains USDA 110 and USDA 442 1 Uninoculated Control NA NA 10 2 B. japonicum strains NA 3.89E+07 10 USDA 110 and USDA CFU/pot (or 442 plant) Treatment Total Total Repetitions amount of amount of Serendipita B. sp. isolate japonicum 46 strains USDA 110 and USDA 442 3 Serendipita sp. isolate 5.81E+03 3.89E+07 10 46 + B. japonicum CFU/pot (or CFU/pot (or strains USDA 110 and plant) plant) USDA 442 Harvested plants from all treatments were washed under running tap water to remove dust and soil attached to the roots and nodules. The roots and nodules were separated from the plants and air-dried overnight at room temperature. The dried nodules were weighted. The results shown in Figure 4 indicate that the average dry weight of nodules produced per plant was significantly different between all the treatments (F_2.63=93.03; p<0.001). The co-inoculated with Serendipita sp isolate 46 with B. japonicum USDA 110 and USDA 442 were statistically different than the dry weight of nodules of the untreated control the ratio of the at least one strain of Serendipita sp. and the at least one strain of nitrogen fixing bacteria is plants and the plants inoculated with B. japonicum strains alone. The dry weight of nodules for the untreated control was 0 g/plant while the B. japonicum strains applied alone had nodules that weighed 0.04 g/plant and the co-inoculated of B. japonicum strains USDA 110 and USDA 442 and Serendipita sp isolate 46 had nodules that weighed 0.053 g/plant. According to literature, a strong correlation was observed between nodule dry weight and N₂ fixation, providing an easily available method to estimate differences in biological N fixation activity between treatments (Juliana Trindade Martins et al., 2022). EXAMPLE 3: Determination of the effect of the co-inoculation of Serendipita sp. and Rhizobium leguminosarum biovar viciae (LALFIX Liquid Pea and Lentil, Lallemand) on nitrogen fixation The objective of this assay was to determine if the co-inoculation of at least one strain of Serendipita sp. with R. leguminosarum biovar viciae (LALFIX Liquid Pea and Lentil) strain can increase the total nodule dry weight and nitrogen fixation. An original culture of Serendipita sp. isolate 46 was subcultured onto potato dextrose agar for 21 days in a 25°C incubator before extraction. The culture plates were then flooded with 20 ml sterile recovery solution (0.85% saline + 0.01% Tween 80) and then the surface was rubbed gently with a rubber policeman. The solution was then poured from the plate into a 50 ml Falcon tube through a sterile cheesecloth to filter out the mycelia. The chlamydospore concentration was then calculated using a haemocytometer and then adjusted to the desired concentration using 0.85% sterile saline. Table 3 outlined the treatment used in the study which was conducted on peas. R. leguminosarum biovar viciae was enumerated by plating. Table 3: Treatments included in the assay Treatment CFU/pot (or Field rate Amount Repetitions plant) (mL/ha or applied per spores/ha) pot* T1 Untreated N/A N/A N/A 17 Control T2 R. 4.01x10⁶ 1095 4.24 µL 19 leguminosarum biovar viciae (LALFIX Liquid Pea and Lentil) T3 R. 4.01x10⁶ + 1095 + 4.24 µL + 18 leguminosarum 5.98x10³ 5x10⁸ 0.194 mg biovar viciae (LALFIX Liquid Pea and Lentil) + Serendipita sp. isolate 46 *Field rate calculated to 15.2 cm diameter at the top of the pot. A growth assay was initiated where 15.2 cm pots (1.84 L) were filled with 50:50 washed sand: attapulgite clay (by volume) to about 2.5 cm from the top. A master mix for each treatment was prepared to ensure consistent applications between replicates. Furrows were dug (about 2.5 cm deep) along the entire length of the pot using a sterile spoon and a single pre-germinated seed per pot was placed in the center. Each treatment was applied at the appropriate rates (Table 3; ratio Serendipita: R. leguminosarum biovar viciae 1:671) along the entire length of the furrow, in order from T1-T3, with mixing in between each application. Pots were placed in growth chamber and the conditions were set to 24/22˚C, with a 16/8 h photoperiod and lighting set to 450 moles/m²/sec. Plants were maintained with 500 mL of 1/2X N-free Hoagland’s solution once per week and watered every 2-3 days as needed for the duration of the experiment. Plant growth stages were monitored weekly. Plants were harvested at the R2 growth stage (at least one flower open) and comparative photos were taken. Plants were gently removed from the pots and roots were washed to remove residual substrate. The shoots were scored and cut approximately 1 cm from the surface of the substrate. Nodulation kinetics were evaluated, all nodules were counted and collected per plant into a single tube to be dried for nodule biomass measurements. Both shoots and roots were dried for at least 48 hours at 60˚C and weighed to obtain dry biomass measurements. Data was analyzed using Minitab v.19.0 (2021). Data were assessed using regression analyses and general linear models with Fisher’s LSD post-hoc tests. Data were tested to meet assumptions of the test and transformed when necessary. The data was analyzed at a 95% confidence interval. The results shown in Figure 5 indicate a significant increase in nodule number when Serendipita sp isolate 46 is combined with R. leguminosarum biovar viciae (LALFIX Liquid Pea and Lentil). Also, it was observed that the co-inoculation of Serendipita sp isolate 46 with R. leguminosarum biovar viciae (LALFIX Liquid Pea and Lentil) has led to an increase in phosphorus (P) and in potassium (K) in pea plants (Figure 6). REFERENCES R. J. Goos, N. Abdraimova & B. E. Johnson (2015) Method for Determination of Ureides in Soybean Tissues, Communications in Soil Science and Plant Analysis, 46:4, 424-429. Juliana Trindade Martins et al. (2022) Biological N fixation activity in soybean can be estimated based on nodule dry weight and is increased by additional inoculation. Rhizosphere, 24: 1-6. * * * While the invention has been described in connection with specific embodiments thereof, it will be understood that the scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole. Embodiments Embodiment 1. A method for increasing nitrogen fixation of a nitrogen fixing bacteria in a host plant, said method comprising contacting the host plant or a germplasm with at least one Serendipita sp. strain and at least one nitrogen fixing bacteria strain wherein contacting the host plant or the germplasm with the at least one Serendipita sp. strain and the at least one nitrogen fixing bacteria strain causes the at least one nitrogen fixing bacteria strain to fix nitrogen at a higher rate compared to the nitrogen fixation rate of the at least one nitrogen fixing bacteria strain in the absence of the at least one Serendipita sp. strain. Embodiment 2. A method for enhancing at least one growth parameter of a plant, the method comprising co-inoculating a plant or a germplasm with at least one strain of Serendipita sp. strain and at least one strain of a nitrogen fixing bacteria strain, wherein the co-inoculated plant or a plant grown from the co-inoculated germplasm exhibits at least one enhanced growth parameter relative to a plant of the same taxon that has not been co-inoculated with the at least one strain of Serendipita sp. strain. Embodiment 3. The method of embodiment 2, wherein the growth parameter is: (a) a number and/or mass of nodules of a plant; and/or (b) a concentration and/or amount of a nutrient in a plant, optionally wherein the nutrient is nitrogen. Embodiment 4. Use of at least one Serendipita sp. strain for increasing nitrogen fixation of a nitrogen fixing bacteria in a host plant. Embodiment 5. The use of embodiment 4, wherein said use comprises contacting the host plant or a germplasm with the least one Serendipita sp. strain and at least one nitrogen fixing bacteria strain wherein contacting the host plant or the germplasm with at least one Serendipita sp. strain and the at least one nitrogen fixing bacteria strain causes the at least one nitrogen fixing bacteria strain to fix nitrogen at a higher rate compared to the nitrogen fixation rate of the at least one nitrogen fixing bacteria strain in the absence of the at least one Serendipita sp. strain. Embodiment 6. An inoculant composition for increasing nitrogen fixation in a host plant, wherein the inoculant composition comprises at least one strain of Serendipita sp. strain and at least one strain of a nitrogen fixing bacteria strain. Embodiment 7. The method of any one of embodiments 1 to 3, the use of claim 4 or 5, or the inoculant composition of claim 6, wherein the at least one nitrogen fixing bacteria strain is already associated with the host plant or in soil in the vicinity of the host plant. Embodiment 8. The method of any one of embodiments 1 to 3 and 7, the use of any one of claims 4, 5 and 7, or the inoculant composition of claim 6 or 7, wherein the at least one nitrogen fixing bacteria strain is a strain of Bradyrhizobium, Rhizobium, Mesorhizobium, Ensifer, Azobacter, Azospirillum, Azorhizobium, Paenibacillus, Herbaspirillum, Acetobacter, Delftia, Rhodospirillum, Sinorhizobium, Azotobacter, Beijerinckia, Clostridium, Klebsiella, Pseudomonas, Herbaspirillum, Glucanoacetobacter, Azorhizobium, Frankia, Burkholderia, Ralstonia, Cupriavidus, or a combination thereof. Embodiment 9. The method, use or inoculant composition of embodiment 8, wherein the at least one nitrogen fixing bacteria strain is a strain of B. japonicum, B. elkanii, B. diazoefficiens, R. leguminosarum, R. tropici, M. ciceri, E. meliloti, or a combination thereof, preferably wherein the at least one nitrogen fixing bacteria strain is B. japonicum, B. elkanii, B. diazoefficiens or combinations thereof, optionally wherein the at least one strain of B. japonicum is B. japonicum USDA 110, B. japonicum USDA 136, B. japonicum 442, B. japonicum SEMIA 5079 or combinations thereof, preferably wherein the at least one strain of B. japonicum is B. japonicum USDA 110 and B. japonicum USDA 136. Embodiment 10. The method, use or inoculant composition of embodiment 9, wherein the at least one nitrogen fixing bacteria strain is: (a) B. diazoefficiens SEMIA 5080; (b) B. elkanii SEMIA 587, B. elkanii U-1301, B. elkanii SEMIA 5019, B. elkanii U-1302 or a combination thereof; or (c) a combination of B. japonicum SEMIA 5079 and B. diazoefficiens SEMIA 5080. Embodiment 11. The method of any one of embodiments 1 to 3 and 7 to 10, the use of any one of claims 4, 5 and 7 to 10, or the inoculant composition of any one of embodiments 7 to 10, or the inoculant composition of any one of embodiments 7 to 10, wherein the at least one Serendipita sp. strain is a strain of S. indica or S. williamsii. Embodiment 12. The method of any one of embodiments 1 to 3 and 7 to 10, the use of any one of embodiments 4, 5 and 7 to 10, or the inoculant composition of any one of embodiments 7 to 10, wherein the at least one Serendipita sp. strain is Serendipita sp. isolate 46 which has been deposited on 28 February 2024 according to the Budapest Treaty under accession number 280224-01 with the International Depository Authority of Canada (IDAC). Embodiment 13. The method of any one of embodiments 1 to 3 and 7 to 12, the use of any one of embodiments 4, 5 and 7 to 12, or the inoculant composition of any one of claims 7 to 12, wherein the host plant is soybean, pea, lentil, fava bean, common bean, chickpea, peanut, lupins, alfalfa, clover, lucerne, sorghum, sugarcane, wheat, corn, potato, sweet potato or rice. Embodiment 14. The method of any one of embodiments 1 to 3 and 7 to 13, the use of any one of embodiments 4, 5 and 7 to 13, or the inoculant composition of any one of embodiments 7 to 13, wherein the ratio of the at least one Serendipita sp. strain to the at least one nitrogen fixing bacteria strain is: (a) 1:1 to 1:20; 1:1 to 1:15; 1:1 to 1:10; 1:1 to 1:9; 1:1 to 1:8; 1:1 to 1:7; 1:1 to 1:6; 1:1 to 1:5; 1:1 to 1:4; 1:1 to 1:3 or 1:1 to 1:2; (b) 1:1 to 20:1; 1:1 to 15:1; 1:1 to 10:1; 1:1 to 9:1; 1:1 to 8:1; 1:1 to 7:1; 1:1 to 6:1; 1:1 to 5:1; 1:1 to 4:1; 1:1 to 3:1 or 1:1 to 2:1; or (c) 1:1; 1:1.25; 1:1.50;1:1.75; 1:2; 1:3; 1:4 or 1:5. Embodiment 15. The method of any one of embodiments 1 to 3 and 7 to 14, the use of any one of embodiments 4, 5 and 7 to 14, or the inoculant composition of any one of embodiments 7 to 14, wherein the at least one Serendipita sp. strain causes the at least one nitrogen fixing bacteria strain to increase nitrogen fixation by at least 5% compared the nitrogen fixation rate of the at least one nitrogen fixing bacteria strain associated with the host plant in the absence of the at least one Serendipita sp. strain.

CLAIMS 1. A method for increasing nitrogen fixing bacteria strain in association with a host plant, said method comprising contacting the host plant or a germplasm thereof with at least one Serendipita sp. strain, wherein the at least one Serendipita sp. strain causes the at least one nitrogen fixing bacteria strain to fix nitrogen at a higher rate compared to the nitrogen fixation rate of the at least one nitrogen fixing bacteria strain in the absence of the at least one Serendipita sp. strain. 2. A method for enhancing at least one growth parameter of a plant, the method comprising co-inoculating a plant or a germplasm thereof with at least one strain of Serendipita sp. and at least one symbiotic nitrogen fixing bacteria strain, wherein the co- inoculated plant or a plant grown from the co-inoculated germplasm exhibits at least one enhanced growth parameter relative to a plant of the same taxon that has not been co- inoculated with the at least one strain of Serendipita sp. strain. 3. The method of claim 2, wherein the growth parameter is: (a) a number and/or mass of nodules of a plant; and/or (b) a concentration and/or amount of a nutrient in a plant, optionally wherein the nutrient is nitrogen, phosphorous or potassium. 4. Use of at least one Serendipita sp. strain for increasing nitrogen fixation of at least one symbiotic nitrogen fixing bacteria strain in association with a host plant or a germplasm thereof. 5. The use of claim 4, wherein said use comprises contacting the host plant or a germplasm with the least one Serendipita sp. strain and at least one nitrogen fixing bacteria strain wherein contacting the host plant or the germplasm with at least one Serendipita sp. strain causes the at least one nitrogen fixing bacteria strain to fix nitrogen at a higher rate compared to the nitrogen fixation rate of the at least one nitrogen fixing bacteria strain in the absence of the at least one Serendipita sp. strain.

Claims

6. An inoculant composition for increasing nitrogen fixation in a host plant, wherein the inoculant composition comprises at least one strain of Serendipita sp. strain and at least one symbiotic nitrogen fixing bacteria strain. 7. The method of any one of claims 1 to 3, the use of claim 4 or 5, or the inoculant composition of claim 6, wherein the at least one nitrogen fixing bacteria strain is a strain of Bradyrhizobium, Rhizobium, Mesorhizobium, Ensifer, Azorhizobium, Sinorhizobium, Azorhizobium, Frankia, Burkholderia, Cupriavidus, or a combination thereof. 8. The method, use or inoculant composition of claim 7, wherein the at least one nitrogen fixing bacteria strain is a strain of B. japonicum, B. elkanii, B. diazoefficiens, R. tropici, M. ciceri, E. meliloti, R. leguminosarum biovar viciae, or a combination thereof, preferably wherein the at least one nitrogen fixing bacteria strain is B. japonicum, B. elkanii, B. diazoefficiens, R. leguminosarum biovar viciae or combinations thereof. 9. The method, use or inoculant composition of claim 8, wherein the at least one strain of B. japonicum is B. japonicum USDA 110, B. japonicum USDA 136, B. japonicum USDA 442, B. japonicum SEMIA 5079 or combinations thereof, preferably wherein the at least one strain of B. japonicum is B. japonicum USDA 110 and B. japonicum USDA 136 10. The method, use or inoculant composition of claim 8 or 9, wherein the at least one nitrogen fixing bacteria strain is: (a) B. diazoefficiens SEMIA 5080; (b) B. elkanii SEMIA 587, B. elkanii U-1301, B. elkanii SEMIA 5019, B. elkanii U-1302 or a combination thereof; (c) a combination of B. japonicum SEMIA 5079 and B. diazoefficiens SEMIA 5080; (d) a combination of B. japonicum USDA 110 and B. japonicum USDA 442; (e) a combination of B. elkanii SEMIA 587 and B. elkanii SEMIA 5019; or (f) R. leguminosarum biovar viciae.

11. The method of any one of claims 1 to 3 and 7 to 10, the use of any one of claims 4, 5 and 7 to10, or the inoculant composition of any one of claims 6 to 10, wherein the at least one Serendipita sp. strain is a strain of S. indica or S. williamsii. 12. The method of any one of claims 1 to 3 and 7 to 10, the use of any one of claims 4, 5 and 7 to 10, or the inoculant composition of any one of claims 6 to 10, wherein the at least one Serendipita sp. strain is Serendipita sp. isolate 46 as deposited on 28 February 2024 according to the Budapest Treaty under accession number 280224-01 with the International Depository Authority of Canada (IDAC). 13. The method of any one of claims 1 to 3 and 7 to 12, the use of any one of claims 4, 5 and 7 to 12, or the inoculant composition of any one of claims 6 to 12, wherein the host plant is soybean, pea, lentil, fava bean, common bean, chickpea, peanut, lupins, alfalfa, clover, lucerne, sorghum, sugarcane, wheat, corn, potato, sweet potato or rice. 14. The method of any one of claims 1 to 3 and 7 to 13, the use of any one of claims 4, 5 and 7 to 13, or the inoculant composition of any one of claims 6 to 13, wherein the ratio of the total CFU of the at least one Serendipita sp. strain to the at least one nitrogen fixing bacteria strain is about: (a) 1:1 to 1:20; 1:1 to 1:15; 1:1 to 1:10; 1:1 to 1:9; 1:1 to 1:8; 1:1 to 1:7; 1:1 to 1:6; 1:1 to 1:5; 1:1 to 1:4; 1:1 to 1:3; or 1:1 to 1:2; (b) 1:1 to 20:1; 1:1 to 15:1; 1:1 to 10:1; 1:1 to 9:1; 1:1 to 8:1; 1:1 to 7:1; 1:1 to 6:1; 1:1 to 5:1; 1:1 to 4:1; 1:1 to 3:1; or 1:1 to 2:1; (c) 1:1; 1:1.25; 1:1.50; 1:1.75; 1:2; 1:3; 1:4; or 1:5; (d) 1:25 to 1:10000; 1:50 to 1:10000; 1:75 to 1:10000; 1:100 to 1:10000; 1:200 to 1:10000; 1:300 to 1:10000; 1:400 to 1:10000; 1:500 to 1:10000; 1:600 to 1:10000; 1:700 to 1:10000; 1:800 to 1:10000; or 1:900 to 1:10000; (e) 1:100 to 1:200; 1:200 to 1:300; 1:300 to 1:400; 1:400 to 1:500; 1:500 to 1:600; 1:600 to 1:700; 1:700 to 1:800; 1:800 to 1:900; 1:900 to 1:1000; 1:1000 to 1:1100; 1:1100 to 1:1200; 1:1200 to 1:1300; 1:1300 to 1:1400; 1:1400 to 1500; 1:1500 to 1:1600; 1:1600 to 1:1700; 1:1700 to 1:1800; 1:1800 to 1:1900; 1:1900 to 1:2000; 1:2000 to 1:2100; 1:2100 to 1:2200; 1:2200 to 1:23000; 1:2300 to 1:2400; 1:2400 to 1:2500; 1:2500 to 1:2600; 1:2600 to 1:2700; 1:2700 to 1:2800; 1:2800 to 1:2900; 1:2900 to 1:3000; 1:3000 to 1:3100; 1:3100 to 1:3200; 1:3200 to 1:3300; 1:3300 to 1:3400; 1:3400 to 1:3500; 1:3500 to 1:3600; 1:3600 to 1:3700; 1:3700 to 1:3800; 1:3800 to 1:3900; 1:3900 to 1:4000; 1:4000 to 1:4100; 1:4100 to 1:4200; 1:4200 to 1:4300; 1:4300 to 1:4400; 1:4400 to 1:4500; 1:4500 to 1:4600; 1:4600 to 1:4700; 1:4700 to 1:4800; 1:4800 to 1:4900; 1:4900 to 1:5000; 1:5000 to 1:5100; 1:5100 to 1:5200; 1:5200 to 1:5300; 1:5300 to 1:5400; 1:5400 to 1:5500; 1:5500 to 1:5600; 1:5600 to 1:5700; 1:5700 to 1:5800; 1:5800 to 1:5900; 1:5900 to 1:6000; 1:6000 to 1:6100; 1:6100 to 1:6200; 1:6200 to 1:6300; 1:6300 to 1:6400; 1:6400 to 1:6500; 1:6500 to 1:6600; 1:6600 to 1:6700; 1:6700 to 1:6800; 1:6800 to 1:6900; 1:6900 to 1:7000; 1:7000 to 1:7100; 1:7100 to 1:7200; 1:7200 to 1:7300; 1:7300 to 1:7400; 1:7400 to 1: 7500; 1:7500 to 1:7600; 1:7600 to 1:7700; 1:7700 to 1:7800; 1:7800 to 1:7900; 1:7900 to 1:8000; 1:8000 to 1:8100; 1:8100 to 1:8200; 1:8200 to 1:8300; 1:8300 to 1:8400; 1:8400 to 1:8500; 1:8500 to 1:8600; 1:8600 to 1:8700; 1:8700 to 1:8800; 1:8800 to 1:8900; 1:8900 to 9000; 1:9000 to 9100; 1:9100 to 9200; 1:9200 to 9300; 1:9300 to 9400; 1:9400 to 9500; 1:9500 to 9600; 1:9600 to 9700; 1:9700 to 9800; 1:9800 to 9900; or 1:9900 to 1:10000; (f) 1:500 to 1:9000; or (g) 1:600 to 1:8500. 15. The method of any one of claims 1 to 3 and 7 to 14, the use of any one of claims 4, 5 and 7 to 14, or the inoculant composition of any one of claims 6 to 14, wherein the at least one Serendipita sp. strain causes the at least one nitrogen fixing bacteria strain associated with the host plant to increase nitrogen fixation by at least 5% compared to the nitrogen fixation rate of the at least one nitrogen fixing bacteria strain associated with the host plant in the absence of the at least one Serendipita sp. strain.

ABSTRACT The present invention provides a method and a composition for increasing nitrogen fixation of at least one strain of a nitrogen fixing bacteria or acquisition of nitrogen for a plant in need thereof.