Abstract
Rhizoctonia solani and Fusarium solani are among the most important soilborne root pathogens affecting production of alfalfa (Medicago sativa L.) and potato (Solanum tuberosum L.) in Qassim region, Saudi Arabia. This study aimed to test 5 strains of Bacillus spp., isolated from Qassim soil for controlling R. solani and F. solani in greenhouse experiments. The efficacy of the 5 plant growth-promoting Rhizobacteria (PGPR), (Bacillus amyloliquefaciens sub sp. plantarum ME 8, Paenibacillus polymyxa ME6, Bacillus amyloliquefaciens sub sp. plantarum ME 106, Bacillus subtilis ME 105, and Bacillus amyloliquefaciens subsp. plantarum ME 3), on controlling R. solani and F. solani on alfalfa and potato were tested. Seeds of alfalfa, California-1 cultivar and Sponta potato variety microtubers were treated with PGPR powder and sown in R. solani or F. solani artificially infected soil in a greenhouse. Seed treatments with PGPR powders induced significant changes in percentage of seed germination and/or plant fresh and dry weights. R. solani was more, virulent on alfalfa than F. solani. Fresh weights and dry weights of alfalfa seedlings increased by up to 21% in response to seed treatments with Paenibacillus polymyxa ME6 or B. amyloliviefacaciens subsp. plantarum ME 106 when compared to seeds treated with the fungicide Rizolex or non-treated check. Similar results were found with Sponta potato variety. However the effect of PGPR isolates on the interactions between R. solani and F. Salami and potato were not highly distinctive as found with the alfalfa.