Production of beauvericin by different races of Fusarium oxysporum f. sp. melonis, the Fusarium wilt agent of muskmelon

Abstract

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 μg 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 μgg⁻¹). The production of enniatin A_1, enniatin B_1, 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 μgg⁻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 μgg⁻¹) respectively. These data suggest that the production of both the toxins is not related to the pathogenicity of E 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.