Improving Biocontrol of Damping-off, Root Rot and/or Wilt Diseases of Faba Bean by Salicylic Acid and Hydrogen Peroxide

Rhizoctonia solani, Fusarium solani, F. oxysporum and Macrophomina phaseolina were found to be associated with root rot and/or wilt symptoms of faba bean plants collected from different fields in New Valley Governorate, Egypt. All the obtained isolates were able to attack faba bean plants (cv. Giza 40) causing dampingoff, root rot and wilt diseases. Pathogenicity test revealed that five isolates, i.e. two of R. solani (No. 2 and 5), one of F. solani (No. 8), one of F. oxysporum (No. 12) and one of M. phaseolina (No. 14), were the most virulent ones on faba bean plants. The bioagents Bacillus megaterium and Trichoderma viride as well as the inducer chemicals salicylic acid and hydrogen peroxide were examined, either individually or in combinations, for controlling damping-off, root rot and/or wilt diseases, in addition to their in vitro and in vivo effects as growth promotions on faba bean plants. All bioagents and inducer chemicals applied either individually or in
combinations, inhibited the growth of the tested pathogenic fungi. Bioagents combined with inducer chemicals recorded the highest inhibition, especially in case of SA + T. viride and SA + B. megaterium. Under greenhouse and field conditions, all treatments significantly reduced damping-off, root rot and/or wilt diseases and increased the survived plants. Also, in pots experiment, tested treatments increased fresh and dry weight of the survived plants compared to the control treatment. Moreover, combinations of the tested bioagents and inducer chemicals were more effective than using each of them individually. Treatment of SA + T. viride recorded the best results in this respect. Under field conditions, all tested treatments significantly increased growth parameters (plant height and No. of branches/plant) and yield components (No. of pods and seeds/ plant, weight of 100 seeds and total yield/feddan) and protein content in both growing seasons of 2010/11 and 2011/12. Faba bean seeds soaked in SA + T. viride and SA + B. megaterium recorded the highest growth parameters and yield components. Generally, the combination between the bioagents and inducer chemicals recoded the best results for controlling damping-off, root rot and wilt diseases under the greenhouse and the field conditions, in addition to improve plant growth and increase yield components, protein content in seeds under field conditions.