PLUM IMPROVEMENT IN THE UNITED STATES
Trees of plum species, including several native ones, are grown in all states except Alaska (Weinberger, 1975). However, one state, California, produces 90 percent of the marketed fruit. Commercial statistics are reported for only 4 other states — Michigan and the Pacific Northwest states of Oregon, Washington, and Idaho (USDA, 1977b).
French prune types (Prunus domestica L.) account for over 70 percent of the commercial tonnage and nearly all of this crop is produced in California for drying. About 20 percent of total production is from various Japanese plum cultivars, P. salicina Lindl., nearly all grown in California and sold on the fresh market. Several southern states contribute slightly to this production. The Pacific Northwest states and Michigan produce most of the remainder, chiefly 'Fellenberg' (Italian Prune) and 'Stanley', for fresh market, canning and freezing. Areas close to the Great Lakes in Pennsylvania, Ohio, and New York also contribute to the production of these prune types.
These main plum types are not well-adapted to most areas of the country. Low temperature and frost tolerance, particularly of the P. salicina cultivars, is inadequate for many northern areas. Most of the prairie states have insufficient rainfall and winter temperatures that are too severe. Brown rot (Monilinia spp), bacterial spot (Xanthomonas pruni [Smith] Dowson) and other leaf spot diseases, bacterial canker (Pseudomonas syringae van Hall), and black knot (Dibotryon morbosum [Schweinitz] Theissen et Sydow) plague plum growers in eastern and southern areas.
Early breeding programs, therefore, had the objective of extending adaptability of plums to more rigorous climates. Programs were initiated in Minnesota, South Dakota, and New York before 1900. The New York program searched within the P. domestica and P. salicina species for better adapted plums. 'Stanley', introduced in 1926, received commercial acceptance and the recent introductions, 'Iroquois', 'Mohawk', and 'Oneida' in 1966, and 'Seneca' in 1972, all prune types, are