Antifungal metabolites from antagonistic fungi used to control tomato wilt fungus Fusarium oxysporum f. sp. lycopersici

Chaetomium elatum strain ChE01, Chaetomium lucknowense strain CLT01 and Emericella rugulosa strain ER01, which were isolated from soil in Thailand, effectively controlled the most virulent isolate of Fusarium oxysporum f. sp. lycopersici NKSC02 causing wilt of tomato (Lycopersicon esculentum var Sida). Two antifungal substances were purified: Chaetoglobosin-C from Ch. elatum and Ch. lucknowense and tajixanthone from E. rugulosa. Chaetoglobosin-C showed greater antifungal activity against F. oxysporum f. sp. lycopersici, with an effective dose (ED sub(50)) of 5.98 mu g/ml, compared with tajixanthone (ED sub(50) of 167 mu g/ml). These results suggest that the disease control mechanism of these antagonistic fungi involves antibiosis. The inoculating tomato seedlings var. Sida with conidia of F. oxysporum f.sp. lycopersici, mixed with either a solution of chaetoglobosin-C or tajixanthone showed no wilt symptom. The conidia of F. oxysporum f. sp. lycopersici treated with these two compounds appeared abnormal and lost pathogenicity.