Circular 299 October 1989 Alabama Agricultural Experimnent Station Auburn University Lowell T. Frobish, Director Auburn University. Alabama P. salicina Methley AU-Amber P. Angustifolia (Starcher No. 1) Pedigree of AU-Amber plum. Information contained herein is available to all without regard to race, color, sex, or national origin. FIRST PRINTING 4M, OCTOBER 1989 AU-AMBER An Excellent Quality Plum for the Early Market J.D. NORTON, G.E. BOYHAN, D.A. SMITH, and B.R. ABRAHAMS' INTRODUCTION A NEW PLUM cultivar has been developed by the Alabama Agricultural Experiment Station for growing in areas where sufficient chilling of 650 hours of temperature below 45 °F occurs. The new cultivar-named AU-Amber-was selected from a cross of Methley and Starcher No. 1 (Prunus angustifolia) followed by backcrossing and sibbing of selected seedlings, as shown by the pedigree. The cross was made in 1965 and the seedling was tested as Methley 12-10. It has resistance or tolerance to bacterial canker, bacterial fruit spot, and plum leaf scald, prevalent diseases of plum, table 1. Such resistance is particularly important in the Southeast where prevalence of these diseases and susceptibility of commercial varieties had discouraged plum production. The new cultivar received resistance to bacterial and fungal diseases from Starcher No. 1. Excellent fruit quality was inherited from both parents. TABLE 1. DISEASE RESISTANCE OF PLUM VARIETIES IN EXPERIMENTAL PLANTINGS AT AUBURN AND HEADLAND, ALABAMA Disease index' Bacterial Bacterial Bacterial Black Brown Plum leaf fruit spot leaf spot canker knot rot scald 2 0 AU-Amber ...... 0 0 0 5 1 2 1 0 0 0 AU-Producer .... 0 0 0 0 2 1 AU-Roadside .... 4 4 0 0 0 0 Bruce........... 1 3 Crimson......... 0 0 0 0 12 1 3 1 Homeside......... 0 0 5 5 3 4 Methley......... 3 5 2 2 Morris.......... 1 2 2 5 4 1 1 1 3 Ozark Premier ... 0 3 5 Purple.......... 0 0 0 0 5 0 3 5 Santa Rosa ...... 5 5 'Disease index: 0 = 0, 1 = 1-10, 2 = 21-40, 3 = 41-60, 4 = 61-80, 5 = 81-100 percent of fruit, leaves, and trees infected. Ratings were taken in years when injury from disease was severe on susceptible cultivars. Cultivar 'Professor, Research Associate, Associate Professor, and Technician of Horticulture. CULTIVAR CHARACTERISTICS Trees of AU-Amber are vigorous and spreading with dark green leaves. In test orchards in Alabama and Georgia, the trees were vigorous and long lived. The plant is self-fruitful, flowers profusely, and sets a heavy crop. Maturity date is about 1 week before Methley, table 2. TABLE 2. MEAN QUALITY EVALUATIONS' OF CANNED PLUM VARIETIES Variety AU-Amber.......... AU-Producer ........ AU-Roadside ........ Crimson............. Giant Cherry........ Methley ............ Morris .................. Ozark Premier ...... Red June........... Sapa ............... Starking Delicious ... Color 8 8 8 8 5 8 8 7 6 10 8 Texture 8 8 8 8 6 8 8.0 7 8 8 7 Flavor 8 8 8 8 7 8 6 8 8 5 Overall quality 8.8 8.0 8.0 8.0 6.0 8.0 6.7 7.4 8.6 6.7 'Numerical scores as follows: 9 or 10 = highly acceptable, 7 or 8 = acceptable, 5 or 6 = barely acceptable, below 5 = unacceptable. Mean scores of an expert panel (3-4 panelists) were obtained on the canned plums after at least 6 weeks warm-storage. 2 Overall ratings are the means of all the panelists' three quality ratings. Disease Resistance AU-Amber is highly resistant to bacterial canker (Pseudomonas syringae, Van hall), bacterial fruit spot [Xanthomonaspruni E. F. Smith), Dows], bacterial leaf spot (X. pruni), and plum leaf scald (Xylella fastidiosa), table 1. It is susceptible to black knot [Apisporina morbosa (Schw.) Ark.]. Fruit Quality Fruits of AU-Amber have dark red (shrimp red, HCC 34A)2 skin and yellow flesh (maize yellow HCC 21B) '. Fruit quality is excellent for fresh market, which makes AU-Amber adaptable for home, roadside, and local markets. Fruits were rated acceptable in canned fruit tests, table 2. Fruit have adequate firmness for handling, packing, and shipping to commercial markets, table 1. Yields The cultivar has been in trials as Methley 12-10 at two locations in the Alabama Agricultural Experiment Station System, at Byron, 2 Horticulture Color Chart; Royal Horticulture Society, London. 4 TABLE 3. YIELD OF FRUIT OF AU-AMBER AT AUBURN, ALABAMA, AND HEADLAND, ALABAMA Year 3.................... 4.................... 5.................... Auburn Lb. Fruit yield per tree Headland Lb. Average Lb. 60 120 130 46 116 127 124 53 118 129 92 6............... 60' 'Reduced crop from late frost injury. Georgia, and in grower trials. It compares favorably with other cultivars in yield. Production has been highest in central and southeast Alabama, table 3. Average yields of marketable fruit per tree were 24 pounds, 118 pounds, and 129 pounds, respectively, from 3-, 4-, and 5-year-old trees. Storage Fruits of AU-Amber store as well as Homeside, Purple, and Methley and better than Bruce and Ozark Premier, table 4. TABLE 4. PERCENT MARKETABLE PLUM FRUIT AFTER STORAGE AT 35 OF Variety AU-Amber ...... AU-Producer .... AU-Roadside .... Bruce........... Crimson ......... Homeside........ Methley ......... Morris ........ Ozark Premier ... Purple .......... Santa Rosa ...... 3 Pct. 100 95 20 100 95 95 100 90 100 100 6 Pct. 70 90 70 5 90 65 70 90 65 85 80 Weeks of storage 9 Pt.ct. 20 65 20 0 65 15 20 65 15 55 45 12 0 30 0 0 30 0 0 30 0 25 20 14 Pct. 0 15 0 0 15 0 0 15 0 8 5 Outstanding Characteristics Tree vigor and tolerance to plum leaf scald are the primary improvements of AU-Amber over Methley. Trees of AU-Amber are vigorous and show no evidence of plum leaf scald, whereas trees of Methley grow much slower and are susceptible to plum leaf scald. Tree vigor is a primary selective criterion in the Southeast, and the relationship of plum leaf scald to phony peach makes resistance important. Two other characteristics, ripening date and skin color at maturity, may be taken collectively as another important advantage of AUAmber. AU-Amber ripens 10 days earlier, has a shorter growing season by 10 days, and is more fully colored at any comparable stage of maturity than Methley, tables 5 and 6. TABLE 5. FRUIT CHARACTERISTICS OF PLUM VARIETIES Cutvr Cutvr Fruit set' 5 5 Flesh color yellow dark red Skin color dark red dark red Sie Sz Sae hp' Fao' lvr Frns imes freeness cling free semi-cling cling cling cling cling cling semi-cling semi-cling cling Stone Tetue Tetr AU-Amber...... AU-Producer .... 1 34-2 2-2 1 /-2 11 -i3 AU-Roadside.... Bruce............ Crimson.......... CN 5 5 5 5 dark red orange to red crimson red cream to purple dark red orange to red crimson red orange to 13 -2 Soluble solids Pct. 19.2 16.5 17.2 9.4 16.3 18.8 18.5 13.4 15.7 14.8 16.7 Homeside.......... light red 1-11/ dark red 5 dark red Methley........... to purple light red light red Morris............ 5 2-21/ red to 5 cream Ozark Premier.. purple dark red 5 cream Purple............ to purple 11/4-1 / dark red red 4 Santa Rosa ... to purple 'Rating index: 5 = excellent, 4 = good, 3 = fair, 2 = poor, and 1 2 /4-2/ 13/ -2 very poor. TABLE 6. BLOOM AND HARVEST DATES AND YIELD OF PLUM VARIETIES Auburn Headland Bloom date Harvest date Yield' Bloom date Harvest date Yield AU-Amber ...... 3-17 5-30 5 3-18 5-27 5 AU-Producer .... 3-20 6-27 5 3-21 6-24 5 AU-Roadside .... 3-22 7-4 5 3-22 6-29 5 2. . . . . . .. .. . Bruce 3-20 6-29 2 3-22 6-26 3 Crimson... ...... 3-22 7-14 5 3-22 5-7 5 Homeside ........ 3-20 7-5 5 3-20 7-1 5 3 Methley ......... 3-22 6-10 3 3-24 6-7 5 Morris .......... 3-22 6-17 5 3-22 6-14 5 Ozark Premier... 3-20 7-10 4 3-23 7-5 5 Purple .......... 3-24 7-20 5 3-28 7-15 5 4. . . . . . Santa Rosa 3-24 7-5 3 3-26 7-1 5 'Yield index: 0 = 0, 1 = very low, 2 = low, 3 = fair, 4 = good, and 5 = excellent. 2 Trees short lived due to ring spot virus. 3Trees short lived due to black knot and bacterial canker. 4 Trees short lived due to bacterial canker. Variety Another improvement of AU-Amber over Methley is increased tree longevity. In test orchards at two locations in Alabama and one in Georgia (Byron), trees of AU-Amber remained in extremely vigorous condition. AVAILABILITY OF TREES Trees of AU-Amber are available from wholesale and retail nurseries. A limited supply of budwood may be obtained from J. D. Norton, Department of Horticulture, Auburn University, Alabama 36849. ACKNOWLEDGMENTS The authors gratefully acknowledge the essential assistance of H. M. Bryce, E. V. Smith Research Center, Shorter, Alabama, and H. W. Ivey, Wiregrass Substation, Headland, Alabama, in evalua- tion and propagation of the material. The assistance of J. M. Thompson, Geneticist, USDA Tree Fruit and Nut Laboratory, Byron, Georgia, in evaluating the seedling and of growers in conducting trials with the material is deeply appreciated. I.ab- tna s Agtricultural Experiment Statio n System AUBURN UNIVERSITY With an agricultural research unit in every major soil area, Auburn University serves the needs of field crop, livestock, forestry, and horticultural producers in each region in 0 O 2 "_ ® Alabama. Every citizen of the State has a stake in this research program, sice any 7 g 62 14 10 13j1 1 ) advantage from new and more economical ways of produc- ing and handling farm products directly benefits the consuming public. 8 t 2 Research Unit Identification ® Main Agricultural Experiment Station, Auburn. E. V. Smith Research Center, Shorter. - Tennessee Valley Substation, Belle Mina Sand Mountain Substation, Crossville North Alabama Horticulture Substation, Cullman Upper Coastal Plain Substation, Winfield Forestry Unit, Fayette County Chilton Area Horticulture Substation, Clanton Forestry Unit, Coosa County Piedmont Substation, Camp Hill Plant Breeding Unit, Tallassee Forestry Unit, Autauga County Prattville Experiment Field. Prattville Black Belt Substation, Marion Junction The Turnipseed-Ikenberry Place, Union Springs Lower Coastal Plain Substation, Camden Forestry Unit, Barbour County Monroeville Experiment Field, Monroeville Wiregrass Substation, Headland Brewton Experiment Field, Brewton Solon Dixon Forestry Education Center, Covington and Escambia counties 20 Ornamental Horticulture Substation. Spring Hill 21 Gulf Coast Substation. Fairhope 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19