Survey on Bacillus Subtilis Isolates for Biological Control of Sunflower Root Rot Caused by Macrophomina Phaseolina (Tassi) Goid.

The most important bacteria for antagonistic activities against the wide range of plant pathogens are Bacilli. Along the same line، this research of surveyed the antagonistic effects of Bacillus subtilis against the sunflower charcoal rot. The antagonistic effects of 24 isolates of B. subtilis from the sunflower field against the charcoal rot، Macrophomina phaseolina (Tassi) Goid، were examined under laboratory conditions. The antagonistic effects of six of the isolates were also tested under greenhouse conditions as «soil application» with bacterial suspension in concentration 109 cell/ml. Interactions among the bacterial isolates، the pathogen and the host، were calculated for disease severity، fresh and dry weight plants as their growth factors. The bacterial isolates showed various antagonistic effects against the causal agent disease in vitro. Bs15 isolates with 66. 5 percent and Bs19 with 70. 4 and 69. 5 percent showed the most inhibition in the volatile metabolites، the non-volatile metabolites and the dual culture tests، respectively. Contrary to the laboratory results، however، in the greenhouse experiment، the Bs4 isolate had significantly decreased in the disease rate and significantly increased in the growth factors.