Addis Ababa University, Institute of Biotechnology, Ethiopia.
University of Chile, Faculty of Medicine, Institute of Biomedical Sciences, Cellular and Molecular Biology Program, Santiago, Chile.
Microbiol Res. 2021 Sep;250:126802. doi: 10.1016/j.micres.2021.126802. Epub 2021 Jun 3.
Tuta absoluta (tomato leafminer) is one of the devastating agricultural pest that attack mainly tomatoes. The continuous use of chemical pesticides is not affordable and poses a collateral damage to human and environmental health. This requires integrated pest management to reduce chemical pesticides. B. thuringiensis is a cosmopolitan, antagonistic soil bacterium used to control agricultural pests. In this study, effective Bt strains were screened from different sample sources based on their lepidopteran specific cry genes and larvicidal efficacy against tomato leafminer, T. absoluta under laboratory conditions. Of the 182 bacterial isolates, 55 (30 %) of isolates harbored parasporal protein crystals. Out of these, 34 (62 %) isolates possess one or more lepidopteran specific cry genes: 20 % of isolates positive for cry2, 18.2 % for cry9, 3.6 % for cry1, 16.4 % for cry2 + cry9, 1.8 % for cry1 + cry9, and 1.8 % for cry1 + cry2 + cry9. However, 21 (38.2 %) isolates did not show any lepidopteran specific cry genes. Isolates positive for cry genes showed 36.7-75 % and 46.7-98.3 % mortality against second and third instar larvae of the T. absoluta at the concentration of 10 colony forming units (CFUs) ml. Cry1 and cry1 plus other cry gene positive isolates were relatively more pathogenic against T. absoluta. However, third instar larvae of the T. absoluta was more susceptible than second instar larvae. Two of the isolates, AAUF6 and AAUMF9 were effective and scored LT values of 2.3 and 2.7 days and LC values of 3.4 × 10 and 4.15 × 10 CFUs ml against the third instar larvae, respectively. The phylogenetic studies showed some congruence of groups with cry gene profiles and lethality level of isolates and very interestingly, we have detected a putative new phylogenetic group of Bt from Ethiopia.
烟青虫（番茄潜叶蛾）是一种主要攻击番茄的破坏性农业害虫。持续使用化学农药不仅价格昂贵，还会对人类和环境健康造成附带损害。因此，需要采用综合虫害管理来减少化学农药的使用。苏云金芽孢杆菌是一种分布广泛、具有拮抗作用的土壤细菌，可用于防治农业害虫。在本研究中，我们根据鳞翅目特异性 cry 基因和对番茄潜叶蛾（Tuta absoluta）的幼虫毒力，从不同的样本来源筛选出有效的 Bt 菌株。在 182 个细菌分离株中，有 55 个（30%）分离株携带伴孢晶体蛋白。其中，有 34 个（62%）分离株含有一个或多个鳞翅目特异性 cry 基因：20%的分离株为 cry2 阳性，18.2%的分离株为 cry9 阳性，3.6%的分离株为 cry1 阳性，16.4%的分离株为 cry2+cry9 阳性，1.8%的分离株为 cry1+cry9 阳性，1.8%的分离株为 cry1+cry2+cry9 阳性。然而，有 21 个（38.2%）分离株未显示任何鳞翅目特异性 cry 基因。cry 基因阳性的分离株在 10 个集落形成单位（CFU）ml 的浓度下对番茄潜叶蛾的 2 龄和 3 龄幼虫的死亡率分别为 36.7-75%和 46.7-98.3%。cry1 和 cry1 加其他 cry 基因阳性分离株对番茄潜叶蛾的致病力相对更强。然而，3 龄幼虫比 2 龄幼虫更易感染。其中，分离株 AAUF6 和 AAUMF9 的效果显著，对 3 龄幼虫的 LT 值分别为 2.3 天和 2.7 天，LC 值分别为 3.4×10 和 4.15×10 CFU ml。系统发育研究显示，cry 基因谱和分离株致死水平的某些分组具有一致性，非常有趣的是，我们从埃塞俄比亚检测到了一个可能的新的苏云金芽孢杆菌系统发育群。
