Sources and inheritance of resistance to anthracnose in Vitis

A method of artificial inoculation of young grape seedlings with anthracnose (Elsinoe ampelina (d By) Shear) was tested and found less reliable than several years of vineyard observations during the warm, humid summer months. Individual seedlings from crosses and selfs were rated for severity of anthracnose and compared with those of parents and grandparents. A trigenic hypothesis is proposed that explains the ratios of resistant to susceptible seedlings observed in segregating progenies. It involves two dominant genes for susceptibility (An1 and An2) and a single dominant gene conditioning resistance (An3), with independent inheritance of the three genes. A classification of cultivars according to level of resistance is presented, with genotypes proposed for each of those used as parents. Sources of resistance are primarily native species from humid areas of the United States or derivatives from them.