I9RLICt 12-4 A DISEASE Y ~RESISTANT - AND COLD HARDY PLUM SEEDLING IL(for use in breeding) CIRCULAR 230 SEPTEMBER 1976 AGRICULTURAL EXPERIMENT AUBURN UNIVERSITY R. Dennis Rouse, Director STATION Auburn, Alabama BRUCE 12-4 A Disease Resistant and Cold -ardy for Use in Breeding J. Plum Seedling D. NORTON* 12-4, a plum seedling developed by the Alabama Agricultural Experiment Station, is being released for use in breeding. It possesses an unusual combination of disease resistance, cold hardiness, tree longevity, and other characteristics useful in breeding programs. This seedling has consistently produced high yields of fruit each year in central Alabama. Chilling requirement of Bruce 12-4 is 700 hours of temperature below 45 0 F. ORIGIN Bruce 12-4 was selected from a cross of 'Bruce' (Prunus salicinia X P. munsoniana) X 'Methley' (P. salicinia X P. cerasifera). The cross was made in 1961 and the seedling was selected in 1963. It was evaluated under the number Bruce 12-4. DESCRIPTION Bruce 12-4 is highly resistant to bacterial canker (Pseudomonas syringae) and black knot (Dibotryon morbosum), tables 1 and 2. It has a moderate level of resistance to bacterial fruit spot and bacterial leaf spot (Xanthomonas pruni). Tree longevity is greater for Bruce 12-4 than for the standard 'Bruce.' Trees are similar to 'Bruce' (growth habit spreading with medium green foliage) except they are more vigorous and larger. Fruit of Bruce 12-4 have a vivid red (5 R 5/13)1 skin and a light orange (2.5 Y R 8/6) flesh, Table 3. The fruit, usually 1%/4 to 2 inches in diameter and cling, are of fair to poor quality that makes Bruce 12-4 less desirable than Crimson, Purple, and Homeside for home and roadside markets. Fruit have inadequate firmness and storage quality for handling, packing, and shipping to * Professor, Department of Horticulture. BRUCE SNickerson Color Fan, Maximum Chroma, 40 hues, Nickerson Color Company, Inc. [2] TABLE 1. DISEASE RESISTANCE OF PLUM VARIETIES IN EXPERIMENTAL PLANTINGS AT AUBURN, CAMP HILL, CLANTON, CULLMAN, FAIRHOPE, AND HEADLAND, 1965-74 Variety Bruce Bruce Diseaseindex' Bacterial Bacterial Bacterial Black knot fruit spot leaf spot canker 0 0 0 Brown rot 4 4 0.8 1.2 0 1 0.2 0 0 0 Crimson---- .__________---5 5 5 3 4.2 Methley----------------------------3 1.0 ----. 0 0 1 1 3 Homeside .-------- ____ 1 3 1.2 0 1 1 Ozark Premier -----------------Purple ----------------------0 0 0 0 3 0.6 3.6 5 5 0 3 5 Santa Rosa ------------------------21-40, 3 41-60, 4 = 61-80, and 5 1-20, 2 'Disease index: 0 = 0, 1 = 81-100 percent of fruit, leaves, and tree infected with bacterial canker, bacterial fruit spot, bacterial leaf spot, and black knot. DIsEASE INDEX RATINGS FOR BLACK KNOT, BACTERIAL CANKER, TABLE 2. BACTERIAL LEAF SPOT, AND BACTERIAL FRUIT SPOT OF PLUM VARIETIES IN FIVE GROWER ORCHARDS, 1974 12-4 -----------------------1 1 0 0 ----------------------- 0 Entry Number of trees Planted Living Disease index rating' Black Bacterial Bacterial Bacterial knot canker leaf spot fruit spot 0.3 0.0 0.0 0.0 0.08 0.00 0.0 0.0 -----------1,087 1,061 Crimson 0.0 0.0 Bruce 12-4 -----110 110 5.0 239 4.5 275 Methley_____________ Homeside---------278 251 0.7 0.4 1.3 180 0.7 375 Ozark Premier-_. Purple 775 774 0.0 0.0 Santa Rosa 150 124 0.0 5.0 'Disease index: 0 - 0, 1 = 1-20, 2 = 21-40, 3 = 81-100 percent of tree, fruit, and leaves infected canker, bacterial fruit spot, and bacterial leaf spot. 5.0 0.4 5.0 0.0 4.87 0.36 -------------------- 2.0 0.0 5.0 0.0 0.0 5.0 0.00 0.00 3.75 41-60, 4 61-80, and 5 with black rot, bacterial commercial markets, Table 4. Maturity date is approximately 3-4 flowers profusely, and days after 'Bruce.' The plant is self-fruitful., sets a heavy crop annually. Bruce 12-4 has produced high yields each year in experimental and grower plantings, even in years when other plums have frost and cold injury, Table 5. Although no data were re- fered suf- corded on cold damage to dormant buds, no evidence of cold injury was observed in grower or experimental plantings. Progeny tests show Bruce 12-4 to be an excellent seedling for breeding purposes, one that transmits its desirable characters in high frequency. AVAILABILITY Budwood may be secured from Joseph D. Norton, Department of Horticulture, Auburn University, Auburn, Alabama 86830. [31 TABLE 3. Variety FRUIT CHARACTERISTICS OF PLUM VARIETIES Fruit set 5' Flesh color orange to red Skin color orange to red vivid red Bruce Bruce -_____ --------------- 12-4--- Crimson ---------------------------- Methley____ 5 5 5 5 light orange. crimson red dark red cream cream cream Fruit diameter In. 134-2 14-2 11/2-134 1-11/4 214-2/2 2-214 Shape Flavor Firmness Stone freeness 31 31 Tetr etue Homeside--------_-. Premier ----Purple -------------Ozark Santa Rosa--------- 4 red crimson red dark red to purple orange to light red red to purple dark red to purple dark red to 5' 5 5 5 5 5 3 5 5 3 5 3 4 cling cling cling cling. cling Soluble solids Pct. 9.4 9.7 16.3 18.5 18.8 15.7 14.8 16.7 5 5 4 5 free semi cling 13/4-2 114-1/2 = 5 very poor. 5 5 cling 'Rating index: 5 = excellent, 4=good,83 fair, 2 = poor, and 1 TA13LE 4. PERCENT MARKETABLE PLUM FRUIT AFTER DIFFERENT STORAGE PEluODS AT 35'F. Variety Bru ce --------------------------------Bruce 3 Pct. 20 Marketable fruit by weeks of storage 6 9 12 Pct. 5 Pct. 0 0 14 Pct. 0 0 15 90 65 Crim son ---------------------------100 95 70 20 ethl ----------------------Hom eside------ _----------------90 65 15 65 15 Ozark Premier ----------- _---- 90 Purple-------------------------------100 85 55 Santa Rosa -----------------------100 80 45 12-4 ----------------------- 10 25 Pct. 0 0 30 M ep 0 0 0 0 25 20 0 0 8 5 TABLE 5. BLOOI HARVEST DATES AND YIELD OF PLUM VARIETIES, Two LOCATIONS Auburn_ Clanton Bloom Harvest Yield' Bloom Harvest date date date date index 3-17 7-3 6-29 2 Bruce'------------------------------- 3-20 Bruce 12-4 ------------------------ 7-6 3-21 7-1 5 3-18 Crim son----------------------------- 3-22 7-14 5 3-19 7-18 Homeside--------------------------- 3-20 7-5 5 3-10 7-10 Methley---------------------------- 3-22 6-10 3 3-20 6-14 3-20 7-10 4 3-18 7-15 Ozark Premier 5 3-23 7-22 -----------------3-24 7-20 Purple ------------- Variety Yield index 3 5 -----------------3-24 7-5 3 5 5 3 4 5 Santa Rosa}------------------------ 3-22 7-8 3 'Yield index: 0 = none, 1 = very low, 2 5 = excellent. 2Trees 8 low, 3 fair, 4 = good, and short lived due to ring spot virus. Trees short lived due to' black knot and bacterial canker. Trees short lived due to bacterial canker. ACKNOWLEDGMENTS The author gratefully acknowledges the essential assistance of H. M. Bryce, Main Station, Auburn, and C. C. Carlton and K. C. Short, Chilton Area Horticulture Substation, Clanton, in evaluation and propagation of material. Valuable assistance was rendered by J. E. Barrett and H. F. Yates (retired), Gulf Coast Substation, Fairhope; M. H. Hollingsworth, North Alabama Horticulture Substation, Cullman; E. L. Mayton (retired ), W. A. Griffey, and H. E. Burgess, Piedmont Substation, Camp Hill. The assistance of growers in conducting commercial trials with this line is deeply appreciated. [5] AUBURN UNIV[RSITY With an agriculhtral unit in every major soil area. Auburn serves the Universit research needs of field crop, livestock, for estry, and horticultural producers in _ Q I0 each region in Alabama. Every citizen of the State has a stake in this research program, e Q a O C 1 since any advantage from new and more economical xays of I 19 producing and handling farm products directly benefits the consuming public. (I) Research Unit Identification 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13 14. 15. 16. 17. 18. 19. 20. 21. Tennessee Valley Substation, Belle Mina. Sand Mountain Substation, Crossville. North Alabama Horticulture Substation, Cullman Upper Coastal Plain Substation, Winfield. Forestry Unit, Fayette County. Thorsby Foundation Seed Stocks Farm, Thorsby. Chilton Area Horticulture Substation, Clanton. Forestry Unit, Coosa County. Piedmont Substation, Camp Hill Plant Breeding Unit, Tollassee. Forestry Unit, Autauga County. Prattville Experiment Field, Prattville. Black Belt Substation, Marion Junction Tuskegee Experiment Field, Tuskegee. Lower Coastal Plain Substation, Camden. Forestry Unit, Barbour County. Monroeville Experiment Field, Monroeville Wiregrass Substation, Headland. Brewton Experiment Field, Brewton. Ornamental Horticulture Field Station, Spring Hill. Gulf Coast Substation, Fairhope. .XrImin tnhi ilj is an ((qual oippounnfily employeijcr.