Biological Control of Bean Damping-off Caused by Sclerotium rolfsii

The role of four bioagents, i.e. Bacillus subtilis, Pseudomonas fluorescens, yeast (Saccharomyces cerevisiae) and Trichoderma viride, in controlling damping-off disease of bean (Phaseolus vulgaris L.) caused by Sclerotium rolfsii was evaluated under greenhouse and field conditions. The greenhouse experiment indicated that all the tested bioagents significantly reduced the incidence of the disease compared to control treatment. The most effective treatments were B. subtilis, T. viride and P. fluorescens which reduced disease incidence by more than 83.7 and 74.5% for pre- and post-emergence damping-off, respectively, while increased the plant survival by 90.3, 86.1 and 87.6%, respectively, compared to 26.3% in untreated plants. These treatments also increased the dry and fresh weights of bean shoot and root as well as resulted in considerable increases in the activities of peroxidase, polyphenoloxidase and chitinase by 260.0, 109.0 and 218.3%, respectively. Under field conditions, all the tested bioagents significantly reduced disease incidence with considerable increases in plant survival and higher seed yield during the two seasons (February of 2009 and 2010) of study. During the first season, B. subtilis T. viride, S. cerevisiae and P. fluorescens were found to be the most effective bioagents which reduced the disease incidence with more than 61.3 and 41.3% than the control for pre- and postemergence damping-off, respectively. The corresponding percentages of survived plants were 78.2, 79.0, 75.2 and 76.8%, respectively, viz. 38.5% for the control. On the other hand, the most effective treatments for increasing seed yield were S. cerevisiae followed by P. fluorescens, being 894.95 and 748.1 kg/feddan viz. 269.2 kg/feddan for the control. The other two bioagents showed moderate effect. The same trend was obtained during the second season. It could be suggested that such bioagents might be promising as alternatives to synthetic fungicides for controlling bean damping-off caused by S. rolfsii.