Microbial efficacy as biological agents for potato enrichment as well as bio-controls against wilt disease caused by Ralstonia solanacearum.

The research aims to study the effect of Pseudomonas fluorescens, Bacillus subtilis, P. aeruginosa and Trichoderma spp. to enrich the growth and yield of potato crop and induce the resistance toward brown rot disease caused by Ralstonia solanacearum. Pot experiments were arranged in a completely randomized block design with three replicates. The selected strains were applied singly at three different intervals (before, after and zero time of planting). Three different potato cultivars were planted in soil infested with two virulent strains of R. solanacearum race 3 biovar 2. The results indicated that the soil treated with tested biological agents significantly stimulated the plant height, fresh weight, number of branches, dry weight, tuber number and potato weight/plant, up to 75.0 cm, 96.0 g, 6.0, 25.0 g, 10.0, 103.0 g, respectively, compared with control (plant only). Treatment with bio-control agents gives protection to the infected plants, resulting to an increase in growth parameters and yield of potato cultivars compared to pathogen control (infected plant). Biological treatment of infected potato cultivars also reduced the incidence of wilt by 80.50-20.63% and increased the disease reduction by 19.5-79.37% compared with pathogen control. P. fluorescens and B. subtilis were the highest for their activities against infection, followed by P. aeruginosa and then Trichoderma spp. The data showed that with the application of all antagonists, cultivars were often more sensitive to wilt infection with R. solanacearum T6 than R. solanacearum W11 strain. It was observed that the promising time for introducing these antagonistic strains grown in pots was prior to planting, in order to protect the plants from wilt infection. We can conclude that the antagonistic advantage of these strains against R. solanacearum according to in vivo results, along with their high efficacy in terms of improved plant development, suggests that these strains could be useful for biological control of potato wilt.