Biocontrol of faba bean black root rot caused by <i>Fusarium solani</i> using seed dressing and soil application of <i>Trichoderma harzianum</i>

Abstract

Black root rot of faba bean is one of the most destructive diseases that causes up to 100% yield loss on farmers’ fields under severe conditions. As use of chemical fungicides for control of the disease is neither efficient nor economical, alternative options such as biological control need to be exploited. The antagonistic fungus <em>Trichoderma harzianum</em> was used as seed dressing or soil application treatment in combination with three varieties <em>viz</em>. Kasa (susceptible), Wolki (moderately resistant) and Wayu (resistant) in two consecutive cropping seasons in a sick plot. Each variety was sown with and without <em>T. harzianum</em>. There were a total of six treatments. The experimental design was randomized complete block design with three replications in a 2 x 3 factorial arrangement. Results showed that in the first year highly significant variations in the percentage of dead plants at harvesting stage were observed only due to varietal differences for soil treatment (<em>P</em> = 0.0001) and seed dressing (<em>P</em>< 0.0001) respectively. Percentage of dead plants of variety wayu was 26.1% and 30.8% in soil application and seed dressing treatments respectively. Similarly, 92.1% and 95.2% dead plants were observed for the susceptible variety Kassa in soil application and seed dressing treatments respectively. In the second year there was a significant interaction between varieties and <em>Trichoderma</em> treatments (<em>P</em>=0.0047, F=8.66, df= 2) with variety Wayu showing the least percentage of dead plants (56.58%) significantly differing from Kassa (93.86%) and Wolki (77.08%) in the soil treatments. It is concluded that use of <em>T. harzianum</em> in combination with a resistant variety such as Wayu is effective to reduce the incidence of faba bean root rot caused by <em>Fusarium solani</em>. Future research should focus on studying the effects of combining different <em>Trichoderma</em> spp. on the disease as integrated with resistant varieties.