Effect of Soil Actinomycetes on Growth of Carbendazim-resistance <I>Colletotrichum gloeosporioides</I> Causing Strawberry Anthracnose

Abstract

Sixty three isolates of Colletotrichum gloeosporiodes causing strawberry anthracnose were collected from Samoeng, Muang, Mae Rim and Mae Chame districts, Chiang Mai province. Thirty-one of isolates showed highly resistance (HR) to carbendazim fungicide phenotype, and another five and twenty-seven isolates showed weakly resistance (WR) and sensitive (S), respectively. Six isolates of actinomycetes, i.e; NSP1, NSP2, NSP3, NSP4, NSP5 and NSP6, collected from Suthep-Pui National Park, were tested for their antifungal activity against C. gloeosporioides Cg_MCL8 (representative of highly resistance group) by dual culture method. All of six actinomycetes isolates could inhibit the mycelial growth of the tested fungus in range 76.18-79.52%. Then, actinomycetes grown in culture media as cell suspensions and culture filtrate, were tested for inhibitory effect on conidial germination of pathogen by slide culture technique, and showed percentage in range of 52.38-67.16% and 51.10-61.69%, respectively. Moreover, both cell suspensions and culture filtrate treated could inhibit conidial germination with time in term of delay germination. The elongation of cell suspensions treated germ tube at 6 h were 117.66 µm in length, and 133.90 µm in culture filtrate treated, while control were 261.90 µm in length. Moreover, both cell suspensions and culture filtrate caused abnormality of spore germination.