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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 (ED50) of 5.98 μg/ml, compared with tajixanthone (ED50 of 167 μg/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.
Key words: Bioactivity test, Chaetomium elatum, Chaetomium lucknowense, Emericella rugulosa, Fusarium oxysporum.