USPP3780P - smalley - Google Patents

Description

Sept. 9, 1975 SMALLEY ETAL Plant Pat. 3,780

ELM TREE 2 Sheets-Sheet 1 Filed lay 31, 1974 Sept. 9, 1975 B. SMALLEY ETAL Plant Pat. 3,780

ELM mm Filed May 31, 1974 2 Shuts-Sheet 2 United States Patent Plant Pat. 3,780 Patented Sept. 9, 1975 3,780 ELM TREE Eugene B. Smalley, Cottage Grove, and Donald T. Lester, Madison, Wis, assignors toWiscons'in'Alurnni Research Foundation, Madison, Wis.

Fiied May 31, 1974, Ser. No. 474,903 Int. Cl. Aiilli /12 U.S. (ll. Plt.-5l 1 Claim The present invention relates to a new and distinct variety of elm tree which is primarily distinguished by its high resistance to Dutch elm disease caused by Ceratocystis ulmi (Buism.) C. Moreau. The tree also shows a high tolerance to Verticillium albo-azrnm Reincke and Berth, the causal agent of Verticilliurn wilt and has limited susceptibility to the blackleaf spot disease caused by Gnomonia ulmea (Schw.) Thum.

The tree is characterized by its rapid development in its early years to a densely foliated, upright form with a vase shaped crown and with a projected height at maturity of 18 to meters. Budbreak takes place in southern Wisconsin in early May, the normal time in that locality for budbreak in the native American el-m.

New growth on the developing, moderately-pubescent shoots is mineral green in color (R#31) tinged on the upper surface of morocco red (RS-#K) to brick red (R#5K). As leaves mature they change first to a glossy Varleys green (R#3l'm) and then to a mature forest green (R#29m). The mature leaves exposed to full sun are nearly elliptical, obtuse and equal at the base, acuminate at the tip, doubly serrate at the leaf margins. 8.010.0 cm. long and 4.5 to 5.5 cm. wide, with shade leaves or leaves on highly vigorous sprouts being slightly larger. Leaves become a vivid, semi-transparent, pale greenish yellow (R#d) to light greenish yellow (R#25 b) in fall with this overall color holding well for many days prior to leaf drop. This tree has been named Sapporo Autumn Gold because of this fall coloration characteristic. (Color standards indicated are from Ridgways color chart (Ridgway, R. 1912. Color standards and color nomenclature. Washington, DC. 53 plates.))

Apical dominance is moderately strong resulting in limited side branch development on shoots of the current season, and usually beginning to 60 cm. below the apex. Mature bark development progresses at a rate intermediate between the parents resulting in a smooth to lightly roughened bark whose weathered color ranges from dark to lightmouse gray (R#l5""b,k) to blackish brown (R#9"m) underlaid in exposed cracks and new bark with a wood brown (R#l7"') to Sanfords brown (R#11'k) color. The inner bark 'is also a Wood brown to Sanfords brown. Floral and seed characters are generally intermediate betweenthe two parents. The original tree began flowering intensely at 5 years of age, somewhat earlier than is normally expected for either parent species.

The accompanying drawing shows a specimen tree of the new variety, as depicted in black and white to show its general form and habit of growth, with additional views in color to show new growth and the autumn coloration for which the tree variety has been named.

Origin The Sapporo Autumn Gold elm is derived from openpollinated seed collected from a single Siberian elm, U. pumila L., growing in the Botanical Garden of Hokkaido University, Sapporo, Japan. The maternal parents location in the botanical garden, the physical traits of the progeny, and controlled hybridization experiments (see references 2 and 3 in E. B. Smalley et al., Hortscience, Vol. 8(6), December 1973, p. 514) leave little doubt that the tree is an F hybrid between U. pumila and U. japonz'ca (Rehd.) Sarg.

Asexual Reproduction The Sapporo Autumn Gold elm cultivar can be prop- 'agated from root cuttings allowed to sprout in the greenhouse in moist sphagnum peat. Hormone treated sprouts can be transplanted as rooted cuttings after approximately 20 days in a perlite-peat rooting medium under fine intermittent mist.

Determination of Resistance to Dutch Elm Disease As a broad approach to identifying hardy elms with low disease susceptibility elm seed imported from many parts of the world was grown for one year in the seedbed, transplanted into the field the second season, maintained under clean cultivation, and artificially inoculated with Ceratacystis ulmi in the third or fourth year. The inoculum contained approximately 10 spores/ml. and 'was a mixture of spores from 10l5 different Wisconsin isolates of the fungus. Trees were inoculated in one-year-old wood in the upper crown. The survivors of this procedure were then reinoculated at least two or more times in subsequent years. As a final test (called the seasonal susceptibility test), selected resistant clones having ornamentally desirable features were clonally propagated in large numbers, grown in randomized field plantings for one or two years, and different individuals of each clone inoculated at the intervals indicated in the table below. In this test,

SEASONAL SUSOEPTIBILITY OF SELECTED ELM CLONES T0 DUTCH ELM DISEASE Percent crown damage at final reading (7/5 and 6/72) A b 1971 dates of inoculation Clone Elm species 0 N0. 4/ 28 5/ 12 5/18 5/ 25 6/1 6/7 6/ 14 6/21 7/6 7/19 8/2 Ulmus Americana 185-1 0 23. 4 28. 1 29 69. 6 62. 1 70. 1 90. 1 100 40 0 185-2 0 0 2. 5 29. 8 82. 8 79 100 81 37 58. 3 0 185-3 48. 0 7 53. 3 80 97. 5 100 185-4 31. 7 100 185-5 100 160 100 37. 5 411-3 62. 6 60 100 100 100 95. 8 99. 2 97. 2 0. 7 412-1 66. 7 86. 2 91. 7 89. 6 88. 3 79. 73 100 100 100 88. 9 0. 5

Ul'm'us Pumila 44-11 0 0 0 0 7. 5 0 0 6 8 0 0 0 Ulmus Japom'ca 44-25 0 0 0 Elm clones all derived from trees previously symptomless following one or more inoculations with Wisconsin strains of C'emtocystis ulmz.

Mixed inoculum consisted of a conidial suspension prepared from isolates of O. ulmi from Wisconsin, Kansas, Massachusetts, Illinois, Nebraska, Minnesota, New York, Connecticut, and Maine.

0 Trees planted as vigorous rooted cnttin s in 1970 3 plants per clone per block, 25 randomized clones per block (with some clones occasionally missing, and 40 locks.

3 4 inoculum consisted of a mixed conidial suspension from What is claimed is: 10 different isolates of the fungus from different North 1. A new and distinct variety of elm tree as herein de- American locations. Observations on disease development scribed and illustrated primarily characterized by its high were then recorded periodically through the year followr si t n t Dut h elm disease ing inoculation. 5

The cultivar of this application, named Sapporo Autumn Gold, possessed superior resistance to C. ulmi as shown in the table above. ROBERT E. BAGWILL, Primary Examiner No references cited.

Images