Variability in isolates of Colletotrichum gloeosporioides causing anthracnose diseases of Stylosanthes species

Abstract

Field surveys for anthracnose disease in pastures and seed crops of Stylosanthes spp. detected a rapid spread of Type B disease in the wet coast region of northern Queensland in 1978, but no new pathogenic races of Type B were found. The recovery of a pathogenic isolate of Glomerella cingulata, the sexual stage of Colletotrichum gloeosporioides, from a Type B isolate suggests that G. cingulata may be a significant component in the life cycle of the disease and may be involved in the development of new pathogenic races of the fungus. With Type A disease, there was evidence of differential specialization of isolates on S. humilis cv. Paterson and S. scabra cv. Fitzr0y.A seed crop of S. hamata cv. Verano was severely damaged by Type A anthracnose, but isolates from the crop produced only slight damage on plants in glasshouse inoculation tests. Plants induced to flower and seed at 8 weeks of age in a controlled environment room were no more susceptible to the seed crop isolates than plants 2, 4 or 6 weeks old.