Impact of applying certain bio-agents and plant extracts to control root and pod rot peanut pathogens

Abstract

The current study was performed to evaluate the efficacy of some bacterial and fungal bio-agents and certain plant extracts i.e. garlic, neem and mint against Fusarium spp., the causal agent of peanut root and pod rot diseases. In vitro tests clarified that Penibacillus polymyxa (BP) and Pseudomonas fluorecensce (PF2) achieved the highest inhibition percentage of the tested pathogenic fungi followed by Bacillus subtilis (BS1) and P. fluorecensce (PF1) while, P. fluorecensce (PF3) and Bacillus megaterium (BM2) came in the last order. Addition of suspensions of Bacillus (B1), P. fluorecensce (P11), inoculum of T. harzianum (T10) and combination of all bio-control agents (Mixture) to infected soil significantly increased yield of peanut plants (Giza 6 cv), such as fresh weight (gm /plant), dry weight (gm /plant), plant height (cm /plant), number of pods /pot and weight of pods /pot. Regarding plant extracts, garlic extract was the most effective plant extract in suppressing the mycelial growth of the pathogenic fungi than any other treatment. Mint extract showed the lowest effect on reduction of linear growth of the tested pathogens. Concerning root rot disease management, addition of bio-agents in vivo resulted in distinct disease reduction obtained by P. fluorecensce (PF2) and Mixture treatments followed by Penibacillus polymyxa (BP) and T. harzianum (T10), respectively. In the concern of pod rot disease, the mixture and T. harzianum (T10) treatments recorded the highest disease reduction as compared to control while, P. fluorecensce (PF2) and Penibacillus polymyxa (BP) came in the last order. Treated seeds of peanut (Giza 6 cv.) with certain plant extracts (garlic, neem and mint) at concentration of 30% significantly reduced the severity of root and pod rot diseases compared to control. Garlic extract gave the highest reduction of root and pod rot severities on peanut plants followed by neem extract then mint extract, respectively.