Controlling root rot and wilt diseases in faba bean (Vicia faba) using bio-filtrates and bio-stimulant substances

BACKGROUND: The effectiveness of certain bio-culture filtrates (Bacillus subtilis, Bacillus megaterium, Pseudomonas fluorescens, Pseudomonas aeruginosa, Trichoderma harzianum and Trichoderma viride) and some bio-stimulant substances (humic acid and chitosan) against Rhizoctonia solani (responsible for root rot) and Fusarium oxysporum (responsible for wilt in faba bean) was evaluated under laboratory and greenhouse conditions. Ten isolates of both R. solani and F. oxysporum were tested. RESULTS: Both tested pathogens caused harmful effects on the faba bean root structure, and the scanning with an electron microscope showed some hyphal growth. In vitro, all tested bio-filtrates and bio-stimulant substances inhibited the linear growth of both pathogens. Trichoderma filtrates led to the highest reduction, followed by humic acid. In the greenhouse, the lowest values of all disease assessments occurred under Trichoderma culture filtrate followed by Pseudomonas and Bacillus. Trichoderma filtrates were the most effective on catalase, peroxidase, and polyphenol oxidase, while the highest chitinase activity occurred under chitosan treatment. Except for the current plus 50% wp fungicide, all treatments increased chlorophyll a, b, and consequently, total chlorophyll, and humic acid were more effective. Moreover, bacterial culture filtrates were the most effective in increasing carotenoids content; Bacillus ones gave the highest values then Pseudomonas without significant differences between them. Moreover, there is a positive correlation coefficient between the plant resistance (healthy surviving plants) and the antioxidant enzyme activities. CONCLUSION: The use of Trichoderma vs. Bacillus as bio-culture filtrates or chitosan vs. humic acid as bio-stimulant substances surpassed, in general, the results of most parameters with foliar treatment by current plus 50% wp. The treatment with such materials could be considered as fungicide alternatives favoring Trichoderma or chitosan for controlling root-rot and wilt diseases and enhancing physiological activities in faba beans.