Antagonistic effects of trichoderma spp. Against damping off disease of haricot bean (phaseolus vulgaris l.), jimma zone, southwestern Ethiopia

Abstract

Rhizoctonia and Fusarium spp. are the common causative agents of the damping off disease of haricot bean (Phaseolus vulgaris L.). Trichoderma species are among the most important antagonists of plant pathogenic fungi. The antagonistic effects of two potential Trichoderma spp. (local and standard) were evaluated against damping off disease of haricot bean caused by Rhizoctonia and Fusarium spp. under in-vitro and greenhouse conditions. This study was carried out with the major objective of evaluating antagonistic effects of two Trichoderma isolates against damping off fungi isolated from diseased crops. Haricot bean fungal pathogens were isolated from 120 (30 each) apparently diseased faba bean, haricot bean, tomato and potato crops. Potato Dextrose Agar was used for fungal isolation following standard procedures. A total of 279 fungal pathogens were isolated from the four different types of diseased crops, out of which 215 (77.06%) isolates were identified to the genus level. Fifty three local Trichoderma isolates were investigated for their antagonistic properties against the test pathogens by dual culture techniques. The results showed that all of the isolates of Trichoderma inhibited the growth of the fungal pathogens with percentage of radial growth inhibition values ranging from 26.57 to 67.03%. In greenhouse experiment, Trichoderma isolates JUTr012+ standard fungus (T. harzianum) significantly (p<0.05) reduced the damping off disease incidence under greenhouse condition. Under greenhouse experiment, the highest number of leaves (25.30 leaves plant-1 ), number of branch (9.67 plant-1 ) and root fresh weight (17.52 g plant-1 ) were recorded due to inoculation with isolates JUTr012+ T. harzianum compared to the control. Moreover, shoot height (58.59 cm plant-1 ), root length (53 cm plant-1 ), nodule number (206.89 plant-1 ), nodule dry weight (0.59 g plant-1 ), shoot fresh weight (89.53 g plant-1 ), shoot dry weight (9.01 g plant-1 ), number of pod (28.33 plant-1 ), and seed weight (38.78 g plant-1 ), were significantly(p<0.05) increased in the presence of bio-control agents (JUTr012+ T. harzianum) compared to the control. The results of this study indicate that the possible use of Trichoderma spp. as a supplementary fungal disease (damping off) management option. Further studies under field conditions and other tests are also required to qualify the bio-control agents as potential inoculum in low inputs sustainable agriculture