Inhibitory potential of fungi isolated from several weeds in Matsue city against Colletotrichum orbiculare, the causal agent of anthracnose disease in cucurbit crops

Anthracnose disease, caused by Colletotrichum orbiculare, is a major disease of cucumber and other cucurbit crops worldwide. In this study, the culture and culture filtrates of symbiotic and parasitic fungi were isolated from several weeds in Matsue City (Shimane prefecture), and screened for their inhibitory potential against C. orbiculare. Symbiotic and parasitic fungi (20 isolates) were isolated from the stems of 7 weed samples (Cerastium glomeratum, Equisetum arvense, Lamium purpureum, Rumex acetosa, Taraxacum albidum, Trifolium incarnatum, and Vicia sativa subsp. nigra) collected from a field in 2020. Inhibition zone against C. orbiculare on the petri dish was observed for two isolates (301, and 504) using dual culture method. The direct effects of culture filtrate of the isolated symbiotic and parasitic fungi was determined by investigating the germination of C. orbiculare conidia. Sixteen of the 20 fungal culture filtrates inhibited C. orbiculare conidia germination by more than 50%, while germination in control was not inhibited. Nine of 16 culture filtrates inhibited more than 90% of C. orbiculare conidia germination. Additionally, three of the nine culture filtrates inhibited more than 100% of C. orbiculare conidia germination. These results strongly suggest that the inhibitory effects of symbiotic and parasitic fungi on plant pathogenic fungi may contribute to the development of new fungicides and new biological agent to control plant diseases caused by plant pathogens.