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<p>The development of insect resistance against <i>Bacillus thuringiensis</i> (<i>Bt</i>) threatens the economic and environmental benefits of <i>Bt</i> products. Identifying new <i>Bt</i> strains with novel toxins is necessary to overcome these challenges. The present investigation aimed to assess the genetic diversity of native <i>Bt</i> isolates and evaluate their insecticidal activity to identify the <i>Bt</i> isolates that exhibit a broad spectrum of insecticidal activity. The colonies of the investigated <i>Bt</i> isolates were found to appear in two forms, predominantly fried egg type followed by mucoid type. The crystal shape of <i>Bt</i> isolates varied from bipyramidal (50.00%), spherical (32.00%), cuboidal (14.00%), and rectangular (4.00%). SDS-PAGE analysis revealed that ~ 135&#xa0;kDa protein bands were observed predominantly in 25 isolates (50.00%) followed by ~ 65&#xa0;kDa protein bands in 7 isolates (14.00%). Toxin gene profiling of native <i>Bt</i> isolates was carried out by PCR analysis with gene-specific primers of major insecticidal genes. The PCR analysis revealed that out of 50 isolates analyzed, <i>cry1</i> gene alone was found in 18 isolates (36.00%), while seven isolates (14.00%) harboured <i>cry1</i> and <i>cry2</i> genes along with <i>vip3</i> gene. Toxicity evaluation of spore-crystal mixtures demonstrated that five <i>Bt</i> isolates (T405, T406, T407, T408, and T409) were found to cause complete larval mortality in all four lepidopteran species tested, viz. <i>Spodoptera litura, S. frugiperda, Plutella xylostella</i>, and <i>Helicoverpa armigera</i> at 25&#xa0;µg/mL (<i>p</i> &lt; 0.001). The present research revealed the diverse range of <i>Bt</i> isolates and substantiated the importance of incessantly exploring newer <i>Bt</i> isolates for novel insecticidal genes.</p>

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Screening of native Bacillus thuringiensis isolates for activity against four species of lepidopteran insect pests

  • 期刊论文

  • 发表日期：

    2025年4月29日

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  • Rajadurai Gothandaraman,
  • Balasubramani Venkatasamy,
  • Raghu Rajasekaran,
  • Kokiladevi Eswaran,
  • Mohankumar Subbarayalu

摘要

The development of insect resistance against Bacillus thuringiensis (Bt) threatens the economic and environmental benefits of Bt products. Identifying new Bt strains with novel toxins is necessary to overcome these challenges. The present investigation aimed to assess the genetic diversity of native Bt isolates and evaluate their insecticidal activity to identify the Bt isolates that exhibit a broad spectrum of insecticidal activity. The colonies of the investigated Bt isolates were found to appear in two forms, predominantly fried egg type followed by mucoid type. The crystal shape of Bt isolates varied from bipyramidal (50.00%), spherical (32.00%), cuboidal (14.00%), and rectangular (4.00%). SDS-PAGE analysis revealed that ~ 135 kDa protein bands were observed predominantly in 25 isolates (50.00%) followed by ~ 65 kDa protein bands in 7 isolates (14.00%). Toxin gene profiling of native Bt isolates was carried out by PCR analysis with gene-specific primers of major insecticidal genes. The PCR analysis revealed that out of 50 isolates analyzed, cry1 gene alone was found in 18 isolates (36.00%), while seven isolates (14.00%) harboured cry1 and cry2 genes along with vip3 gene. Toxicity evaluation of spore-crystal mixtures demonstrated that five Bt isolates (T405, T406, T407, T408, and T409) were found to cause complete larval mortality in all four lepidopteran species tested, viz. Spodoptera litura, S. frugiperda, Plutella xylostella, and Helicoverpa armigera at 25 µg/mL (p < 0.001). The present research revealed the diverse range of Bt isolates and substantiated the importance of incessantly exploring newer Bt isolates for novel insecticidal genes.