A Study of the Antifungal Effects of Trichoderm Strains on Four Root and Crown Pathogens of Cowpea

This research was conducted with the aim of isolating and identifying cowpea root and crown pathogens in Khuzestan province. In addition, the antifungal effectiveness of nine selected strains of five Trichoderma species was surveyed on four root and crown pathogens of cowpea.

Out of twenty strainsobtained, four of them were selected for further investigation including pathogenicity test and siderophore assay. The relative amount of the siderophore produced by nine selected strains from five Trichoderma speciesand pathogens was assayed by the chrome Azurol S method (CAS). The radial growth of the pathogen’s colonies in front of the Trichodermastrains was analyzed using a completely randomized design, with three replicates. The pathogenic strains of ITS region were amplified and sequenced. The obtained sequences were compared with the reference strains using BLASTn search and the maximum likelihood (ML) phylogenetic analysis.

In the present study, the following pathogens were identified: Rhizoctonia solani, Fusarium chlamydosporum, F. falciforme, and Macrophomina phaseolina. In CAS assay, all of the Trichoderma strains and pathogens produced the siderophore into growth media under iron starvation.Strains of T. koningiopsis SCUA-Arak-96 and T. pleuroticola SCUA-Isf-15 produced the minimum and maximum siderophore with 31% and 85%, respectively. In the dual culture test, most Trichoderma strains significantly reduced the growth of pathogenic fungi. The most antifungal effect was observed in T. virens SCUA-Ham-65 strain on F. chlamydosporum and F. falciforme pathogens, with 30% and 29% growth inhibitory, respectively.

The results of the present study showed thatR. solani, F. chlamydosporum, F. falciforme, and M. phaseolina were the most important pathogens of the cowpea causing root and crown rot in Khuzestan province. Trichoderma strains produced the siderophore which chelates minimal iron of environment. In addition, they inhibit the growth of the plant pathogens in vitro.