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<p>Downy mildew, caused by <i>Plasmopara viticola,</i> poses a significant threat to global viticulture. In this study, 14 microbial cultures, including 10 bacterial and four actinomycete species, were isolated from grape field soil. These species were screened for their ability to inhibit downy mildew under in vitro conditions. Two strains, identified through molecular characterization as <i>Bacillus amyloliquefaciens</i> strain RP4 and <i>Streptomyces rochei</i> strain RP7, showed inhibitory activity. This study aimed to develop and evaluate microbial formulations containing these strains as biocontrol agents against downy mildew. Under in vitro conditions, pure cultures of <i>B. amyloliquefaciens</i> RP4 and <i>S. rochei</i> RP7 grown on medium 6 achieved 54.2% and 50% inhibition of downy mildew growth, respectively. Field trials further demonstrated the inhibition of disease by 46.2% and 43.9% for the <i>B. amyloliquefaciens</i> RP4 and <i>S. rochei</i> RP7 extracts, respectively. Six formulations were developed and tested, with Formulation 6 (F6) showing the highest efficacy. F6 comprised 45% extracts of each microbial strain, 5% Emulsifier 6000, 4% Emulsifier 7000, and 1% glycerol. This formulation achieved 91.1% inhibition of downy mildew symptoms in laboratory tests. F6 also demonstrated high efficacy in the field by reducing disease incidence by 77.27% on leaves and 78.5% on bunches, closely matching the chemical control (Metalaxyl 8% + Mancozeb 64%), which achieved 80.8% and 82.2%, respectively (<i>p</i> =  &gt; 0.05). Formulation F6 reduced the disease severity index (DSI) by 80.5% on leaves and 83.5% on bunches (<i>p</i> =  &gt; 0.05). Hence, Formulation 6 is an eco-friendly alternative to chemical fungicides, highlighting its feasibility for integration into sustainable viticulture practices.</p>

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Development and evaluation of microbial formulations containing Bacillus amyloliquefaciens RP4 and Streptomyces rochei RP7 for the sustainable management of downy mildew in grapes

  • 期刊论文

  • 发表日期：

    2025年8月23日

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  • Rakesh Prakash,
  • Neetha Shivakumar

摘要

Downy mildew, caused by Plasmopara viticola, poses a significant threat to global viticulture. In this study, 14 microbial cultures, including 10 bacterial and four actinomycete species, were isolated from grape field soil. These species were screened for their ability to inhibit downy mildew under in vitro conditions. Two strains, identified through molecular characterization as Bacillus amyloliquefaciens strain RP4 and Streptomyces rochei strain RP7, showed inhibitory activity. This study aimed to develop and evaluate microbial formulations containing these strains as biocontrol agents against downy mildew. Under in vitro conditions, pure cultures of B. amyloliquefaciens RP4 and S. rochei RP7 grown on medium 6 achieved 54.2% and 50% inhibition of downy mildew growth, respectively. Field trials further demonstrated the inhibition of disease by 46.2% and 43.9% for the B. amyloliquefaciens RP4 and S. rochei RP7 extracts, respectively. Six formulations were developed and tested, with Formulation 6 (F6) showing the highest efficacy. F6 comprised 45% extracts of each microbial strain, 5% Emulsifier 6000, 4% Emulsifier 7000, and 1% glycerol. This formulation achieved 91.1% inhibition of downy mildew symptoms in laboratory tests. F6 also demonstrated high efficacy in the field by reducing disease incidence by 77.27% on leaves and 78.5% on bunches, closely matching the chemical control (Metalaxyl 8% + Mancozeb 64%), which achieved 80.8% and 82.2%, respectively (p =  > 0.05). Formulation F6 reduced the disease severity index (DSI) by 80.5% on leaves and 83.5% on bunches (p =  > 0.05). Hence, Formulation 6 is an eco-friendly alternative to chemical fungicides, highlighting its feasibility for integration into sustainable viticulture practices.