Abstract
Rhizoctonia solani, Fusarium solani, F. oxysporum and Macrophomina phaseolina were found to be associated with root rot and 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 damping-off and root rot/wilt diseases. R. solani isolates 2 and 5, F. solani isolate 8, F. oxysporum isolate 12 and M. phaseolina isolate 14 were the more virulent ones in the pathogenicity tests. Biocontrol agents (Trichoderma viride, Bacillus megaterium) and chemical inducers (salicylic acid and hydrogen peroxide) individually or in combination were examined for biological control of damping-off and root rot/wilt and growth promotion of faba bean plants in vitro and in vivo. Both antagonistic biocontrol agents and chemical inducers either individually or in combination inhibited growth of the tested pathogenic fungi.Biocontrol agents combined with chemical inducers recorded the highest inhibited growth especially in case SA + T. viride and SA+ B. megaterium. Under green house and field conditions, all treatments significantly reduced damping-off and root rot/ wilt severity and increased survival of plants. Also, these treatments increased fresh and dry weights of the survived plants in pots compared with control. The combination of biocontrol agents and chemical inducers were more effective than using them individually and SA+ T. viride was the best treatment in this respect. Under field conditions, all these treatments significantly increased growth parameters (plant height and No. of branches plant-1) and yield components (No. of pods and seedsplant-1, weight of 100 seeds and total yield feddan-1 and protein content in both seasons (2010-2011 and 2011-2012). Faba bean seeds soaked in SA+ T. viride and SA+ B. megaterium were recorded the highest growth parameters and yield components. Generally, the combination of biocontrol agents and chemical inducers recoded the best results for controlling damping-off and root rot/wilt diseases in greenhouse and field with addition improved plant growth and increased yield components in the field.
Highlights
Faba bean (Vicia fabe L.) is used as an important human food in developing countries and as an animal feed, mainly for pigs, horses, poultry and pigeons in industrialized countries
These isolates were identified as Rhizoctonia solani (5 isolates), Fusarium solani (4 isolates), F. oxysporum (4 isolates), Macrophomina phaseolina (4 isolates) as well as 3 isolates not identified
Results presented in Table (1) reveal that all tested isolates could infect the roots of faba bean and cause damping-off, root rot and wilt symptoms reduce the survived plants
Summary
Faba bean (Vicia fabe L.) is used as an important human food in developing countries and as an animal feed, mainly for pigs, horses, poultry and pigeons in industrialized countries. Feeding value of faba bean is high and this legume has been considered as a meat extender or substitute due to its high protein content (20-41%) (Chaven et al, 1989). Root rot and wilt diseases caused by several soil borne fungal pathogens are widespread and serious in many crops cultivated in different soil types. Faba bean is subjected to attack by many pathogenic organisms wherever the crop is grown.
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