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Races of the Aster-Wilt Fusarium. G. M. Armstrong, Research Associate, Department of Plant Pathology, University of Georgia, College of Agriculture Experiment Stations, Georgia Station, Experiment, Georgia 30212; Joanne K. Armstrong, Research Associate, Department of Plant Pathology, University of Georgia, College of Agriculture Experiment Stations, Georgia Station, Experiment, Georgia 30212. Phytopathology 61:820-824. Accepted for publication 15 February 1971. DOI: 10.1094/Phyto-61-820.

Races of Fusarium oxysporum f. sp. callistephi were evident after inoculating staghorn sumac (Rhus typhina); 24 cultivars of China aster (Callistephus chinensis); and 12 of African marigold (Tagetes erecta) with nine different isolates from aster, and three isolates from wilting sumac. With aster as a common host, races 1 and 2 of F. oxysporum f. sp. callistephi were from aster, and race 3 was from sumac. Races 1 and 2 did not cause wilt of sumac, but race 3 from sumac caused wilt of sumac and aster, all causing similar symptoms of disease on aster. However, there was a time differential for symptom expression on aster, as race 3 from sumac caused much slower wilting of aster than races 1 and 2. Forty-three other formae speciales (ff. sp.) and races of F. oxysporum were nonpathogenic on aster and sumac. Races 1 and 3 of f. sp. callistephi were also nonpathogenic on a susceptible host of each of these other ff. sp. Only race 2 caused wilt of marigold. Since race 2 Hoffman preceded race 2 Olsen, the latter is invalid, and since its exact status is uncertain, it is proposed as race 4.