Effects of Some Isolates of Trichoderma spp. and Rhizobacteria in Control of the Causal Agent of Cantaloupe Fusarium Wilt

Regarding the importance of biological control of plant pathogens, the present research was aimed to find antagonists with inhibitory effects on the causal agent of Cantaloupe Fusarium wilt, Fusarium oxysporum f. sp. melonis (FOM). At first, the inhibitory effect of four isolates of Trichoderma (including Trichoderma harzianum Tr3, T. harzianum 2, T. longibrachiatum and T. asperellum Tr14) and 52 bacteria (isolated from rhizosphere of Sophora alopecuroides( against FOM was investigated in laboratory conditions. Based on the results, three isoaltes of Trichoderma and two bacterial isolates (B1 and B2) were selected and along with Bacillus subtilis MCC0067 were assayed in green house experiments. The antagonists were applied on seed and in the soil and their potential for control of Cantaloupe Fusarium wilt and plant growth promotion were evaluated. In dual culture assay, the growth inhibition percentage of Trichoderma isoaltes varied from 62 to 75% and of bacterial isoaltes varied from 46 to 60%. In greenhouse conditions, the antagonist isolates were not able to prevent the incidence of Fusarium wilt disease on cantaloupe; but they delayed the onset of the disease and reduced disease progression. In 40 days after planting, the disease severity in T. harzianum Tr3 and T. longibrachiatum treatments was significantly lower than the others. The antagonists had no significant effect on increasing root length but they triggered an increase in root volume. Their effect on other indices was different. In general, B2 and the isolates of T. harzianum Tr3 and T. longibrachiatum treatmens were the most effective treatments in increasing growth indices and in control of disease, respectively.