Production of beauvericin by different races of Fusarium oxysporum F. sp. Melonis, the Fusarium wilt agent of muskmelon

Fourty-four strains of Fusarium oxysporum were isolated from plants of melon with Fusarium wilt symptoms. Among these strains, thirty-nine were characterized for their pathogenicity on melon. Thirty-seven strains belonged to known races of F. oxysporum f. sp. melonis, while two strains were non-pathogenic. Four strains belonged to race 0, seven to race 1, four to race 2, and twenty-two to race 1,2. Beauvericin was produced by thirty-six strains in a range from 1 to 310 ìg g-1. Eight isolates of race 1,2 did not produce the toxin. In addition, of the two non- pathogenic strains, only one strain produced the toxin (290 ìg g-1). The production of enniatin A1, enniatin B1, and enniatin B was also investigated. Enniatin B was the only enniatin detected, being produced by eleven strains belonging to all the races, with a range of production from traces to 60 ìg g-1. Finally, melon fruits belonging to two different cultivars (Cantalupo and Amarillo) were artificially inoculated with one strain of F. oxysporum f. sp. melonis (ITEM 3464). Beauvericin was detected in the fruit tissues of both cultivars at a level of 11.2 and 73.8 ìg g-1, respectively. These data suggest that the production of both the toxins is not related to the pathogenicity of F. oxysporum f. sp. melonis, nor to the differential specificity of the races. The results confirm that beauvericin is a common metabolite of phytopathogenic Fusarium species.