Biological control of tomato early blight in Pakistan using local rhizobacteria

• Published in: Pest management science Vol. 80; no. 3; pp. 1412 - 1422
• Main Authors: Riaz, Hafiz Muhammad, Chohan, Sobia, Yuen, Gary Y., Abid, Muhammad
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.03.2024; Wiley Subscription Services, Inc
• Subjects: Alternaria solani; Antagonism; Bacillus amyloliquefaciens; Bacillus cereus; Bacteria; Biological control; Blight; Catalase; Chitinase; Chitinases; Early blight; Foliage; Fungicides; Greenhouses; induced resistance; Inoculation; Leaves; Pakistan; Pathogens; Plant Diseases - microbiology; Priming; RNA, Ribosomal, 16S - genetics; rRNA 16S; Soil microorganisms; Solanum lycopersicum; Stenotrophomonas rhizophila; Strains (organisms); Tomatoes; Pakistan; priming; Alternaria solani; Bacillus cereus; induced resistance; antagonism; Stenotrophomonas rhizophila; Bacillus amyloliquefaciens
• ISSN: 1526-498X; 1526-4998
• DOI: 10.1002/ps.7872

BACKGROUND The biocontrol potential of soil microbes can reduce the extensive use of hazardous synthetic fungicides. This study was designed to find a strain of rhizobacteria indigenous to Pakistan with potential biocontrol against early blight of tomato caused by Alternaria solani and to characterize its biocontrol mechanisms. RESULTS Among 88 strains tested for antagonism against A. solani on agar media, S27, Dt10 and 423, identified by 16S rRNA sequencing as strains of Bacillus amyloliquefaciens, B. cereus and Stenotrophomonas rhizophila, respectively, were the most inhibitory. When applied to detached tomato leaflets in Petri dish assays, the strains reduced lesion development by over 30% compared to the control. In greenhouse pot trials, the bacterial strains reduced early blight severity by over 50%. In three field trials, all three strains applied to tomato foliage slowed early blight disease progress and reduced disease severity, with B. amyloliquefaciens S27 reducing the area under the disease progress curve by up to 70%. All three strains showed protease, catalase and oxidase activities in vitro, but none produced β‐1,3‐glucanase and only B. cereus Dt10 showed slight chitinase activity. In a greenhouse experiment in which the bacteria were applied to tomato foliage prior to pathogen inoculation, bacteria‐treated leaves had higher β‐1,3‐glucanase and chitinase levels than leaves inoculated only with the pathogen, indicating priming induction of response. CONCLUSION Three rhizobacteria strains have the potential to control early blight of tomato under Pakistan's growing conditions, with B. amyloliquefaciens S27 being the most promising candidate for commercial development. Antagonism and induction of the priming response may be mechanisms of biocontrol by the bacterial strains. © 2023 Society of Chemical Industry. Screened rhizosphere bacteria Stenotrophomonas rhizophila strain 423, Bacillus amyloliquefaciens strain S27 and Bacillus cereus strain Dt10 were found very effective in controlling Alternaria solani in all in vitro and in vivo experiments.