The PRI Apple Breeding Program

Abstract

and initiated an intensive study of crosses between cultivated apples and crab-like forms. A summary of Crandall’s work, published in University of Illinois Bulletin 275 (Crandall, 1926), describes all the material in the program. Crandall, infl uenced by the rediscovery of Mendel, was attempting to determine inheritance patterns in Malus. Ironically, he did not work with characteristics that would enable him to identify single genes or evaluate his material for disease resistance. The voluminous data he collected and maintained at the University of Illinois has never been completely analyzed, although the designations reported in Bulletin 275 describing his species sources have become justly famous. The selection he labeled Malus fl oribunda 821 was the original source of the V f gene. Fortunately, his breeding material was maintained following his retirement in 1927, but remained unevaluated until L.F. Hough joined the department in 1942 as a graduate student and plant-breeding assistant. Spring 1943 was unusually cool and wet, resulting in a severe epidemic of scab that defoliated all susceptible unsprayed apples trees. Hough noted that one progeny, an F 2 of M. fl oribunda 821 × Rome Beauty, segregated at a ratio of 1 resistant : 1 susceptible, suggesting the involvement of a single gene, later termed V f . Hough published his results with the Proceedings of the American Society of Horticultural Science in his famous paper “A Survey of the Scab Resistance of the Foliage of Seedlings in Selected Apple Progenies” (Hough, 1944). The paper was brought to the attention of J.R. Shay, a young professor who joined the Purdue’s Department of Botany and Plant Pathology from Arkansas and who had received his PhD from the University of Wisconsin where a program on the pathogenicity of Venturia inaequalis had been under investigation. (In the l940s, considerable interest in the genetics of the ascomycetes had been engendered by the work of Beadle and Tatum in Neurospora.) Shay and Hough decided to collaborate on a scab-resistance breeding program with the objective to advance genetic resistance identifi ed by Hough into improved horticultural backgrounds and identifi cation of additional resistant Malus germplasm through testing of material in arboreta and other collections. The fi rst screened hybrid progenies were planted in the fi eld in 1947 and began fruiting at Illinois in l951. A formal cooperative program was established in 1945 between the agricultural experiment stations associated with Purdue University and the University of Illinois.