Managing Root Rot in Beans with Natural Biocontrol Methods and Compost Tea

Jim Crocker
16th July, 2024

Managing Root Rot in Beans with Natural Biocontrol Methods and Compost Tea

This figure from the study visually documents the severe root rot symptoms, including black microsclerotia on the root and stem (b), on a Common bean (Phaseolus vulgaris) plant caused by the fungal pathogen Rhizoctonia solani (a), the target disease successfully managed in this study, as contrasted with a healthy control plant (c).

Image adapted from: Helmy et al. / CC BY (Source)

Key Findings

  • The study in Egypt found that combining vermicompost tea (VCT) with beneficial microbes can effectively manage root rot in common beans
  • Under greenhouse conditions, using 5-10% VCT with Serratia marcescens, Trichoderma harzianum, or effective microorganisms (EM1) provided up to 95% protection against the disease
  • In field trials, VCT combined with EM1 or Trichoderma harzianum reduced disease severity by over 64% and significantly increased bean pod weight by more than 130%
Common bean (Phaseolus vulgaris L.) is a crucial food crop and income source for small-holder farmers in Africa. However, its production is significantly threatened by fungal diseases such as root rot caused by Rhizoctonia solani. A recent study conducted by researchers at Ain Shams University aimed to evaluate an integrated approach using vermicompost tea (VCT) and antagonistic microbes to manage R. solani root rot effectively and sustainably in common beans[1]. The study began by isolating fourteen fungal strains from infected common bean plants collected across three Egyptian governorates. Rhizoctonia solani emerged as the most virulent isolate, with a 50% dominance. The researchers then assessed the antagonistic potential of VCT, along with Serratia sp. and Trichoderma sp., against this destructive pathogen. The combination of 10% VCT and biocontrol agent isolates showed significant inhibition of R. solani growth in vitro, prompting further testing in plants. Under greenhouse conditions, integrated applications of 5% or 10% VCT with Serratia marcescens, Trichoderma harzianum, or effective microorganisms (EM1) provided up to 95% protection against pre- and post-emergence damping-off caused by R. solani in common bean cultivar Giza 6. In field conditions, combining VCT with EM1 or Trichoderma harzianum significantly reduced disease severity by 65.6% and 64.34%, respectively, compared to untreated plants. These treatments also increased defense enzyme activity and improved growth parameters, including a 136.68% and 132.49% increase in pod weight per plant over control plants. The study's findings align with earlier research demonstrating the effectiveness of beneficial microbes in promoting plant growth and controlling pathogens. For instance, Bacillus subtilis V26, a local isolate from Tunisian soil, has shown significant potential as a biocontrol agent against potato black scurf caused by R. solani[2]. This bacterium not only suppressed disease incidence but also promoted plant growth under greenhouse conditions. Moreover, the use of beneficial endophytic bacteria has been recognized as a promising tool for promoting plant growth and biocontrol of pathogens[3]. These bacteria help plants acquire nutrients, enhance growth and development, and suppress pathogens, offering a sustainable alternative to synthetic chemicals that can cause soil infertility and environmental contamination. The current study by Ain Shams University builds on these findings by demonstrating that VCT-mediated delivery of synergistic microbial consortia can be a sustainable platform for managing soil-borne diseases. GC–MS profiling of Trichoderma harzianum, Serratia marcescens, and VCT extracts revealed unique compounds with confirmed biocontrol and plant growth-promoting activities. These compounds include cyclic pregnane, fatty acid methyl esters, linoleic acid derivatives, and free fatty acids like oleic, palmitic, and stearic acids. In conclusion, the integrated approach using VCT and antagonistic microbes offers a promising solution for managing R. solani root rot in common beans. By enhancing soil health and improving plant growth, this method can increase productivity and incomes for smallholder bean farmers. Further large-scale validation of this climate-resilient approach could pave the way for its adoption, securing food and nutrition security in the region.

AgricultureBiochemPlant Science

References

Main Study

1) Root Rot Management in Common Bean (Phaseolus vulgaris L.) Through Integrated Biocontrol Strategies using Metabolites from Trichoderma harzianum, Serratia marcescens, and Vermicompost Tea

Published 15th July, 2024

https://doi.org/10.1007/s00248-024-02400-4

Related Studies

2) Efficacy of Bacillus subtilis V26 as a biological control agent against Rhizoctonia solani on potato.

https://doi.org/10.1016/j.crvi.2015.09.005

3) Use of beneficial bacterial endophytes: A practical strategy to achieve sustainable agriculture.

https://doi.org/10.3934/microbiol.2022040


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