Evaluation of Virulence of Fusarium oxysporum f. sp. medicaginis and Fusarium Wilt Resistance in Alfalfa. Gary Emberger, Former Graduate Research Assistant, Department of Plant Pathology, North Carolina Agricultural Research Service, Raleigh 27650. Ronald E. Welty, Research Plant Pathologist, U.S. Department of Agriculture, Tobacco Research Laboratory, Oxford, NC 27565, and Professor, Department of Plant Pathology, North Carolina Agricultural Research Service, Raleigh 27650. Plant Dis. 67:94-98. Accepted for publication 30 May 1982. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1983. DOI: 10.1094/PD-67-94.

Isolates of Fusarium oxysporum f. sp. medicaginis from Minnesota, Pennsylvania, Maryland, and North Carolina did not differ in virulence to alfalfa (Medicago sativa cv. Narragansett). Conidia of four isolates from North Carolina were combined to inoculate wilt-resistant (Moapa, Liberty, and NCMP 2) and wilt-susceptible (Apalachee and Narragansett) cultivars of alfalfa in the field and greenhouse. Field and greenhouse results were highly correlated (P = 0.01). Wilt resistance in 10 cultivars and four breeding lines adapted to the southeastern United States was evaluated at two locations. Entries with the highest level of wilt resistance were germ plasms NCMP 9, NCMP 11, and NCMP 13 and cultivars Cimarron and Saranac AR; Apalachee was highly wilt-susceptible and the remaining entries were moderately wilt-resistant. The disease reaction of entries common to wilt nurseries in North Carolina and Minnesota were similar.

Keyword(s): disease losses.