Pérez Melisa P, Sauka Diego H, Onco María I, Berretta Marcelo F, Benintende Graciela B
Instituto de Microbiología y Zoología Agrícola INTA, CC No 25 (1712) Castelar, Buenos Aires, Argentina.
Instituto de Microbiología y Zoología Agrícola INTA, CC No 25 (1712) Castelar, Buenos Aires, Argentina.
Rev Argent Microbiol. 2017 Jul-Sep;49(3):264-272. doi: 10.1016/j.ram.2016.12.010. Epub 2017 May 9.
Preliminary bioassays with whole cultures (WC) of 124 Bacillus thuringiensis strains were performed with neonate larvae of Anthonomus grandis, a major cotton pest in Argentina and other regions of the Americas. Three exotic and four native strains were selected for causing more than 50% mortality. All of them were β-exotoxin producers. The native strains shared similar morphology of parasporal crystals, similar protein pattern and identical insecticidal gene profiles. These features resembled Lepidoptera-toxic strains. Furthermore, these strains showed a Rep-PCR pattern identical to lepidoptericidal strain HD-1, suggesting that these strains may belong to serovar kurstaki. However, some differences were observed in the plasmid profiles and in the production of β-exotoxin. To determine the culture fractions where the insecticidal metabolites were present, bioassays including resuspended spore-crystal pellets, filtered supernatants (FS) were compared with those of WC. Both fractions tested showed some level of insecticidal activity. The results may suggest that the main toxic factors can be found in FS and could be directly correlated with the presence of β-exotoxin. Based on the bioassays with FS and autoclaved FS, the participation of thermolabile virulence factors such as Cry1I in toxicity is neither discarded. In the selected strains, β-exotoxin would be the major associated virulence factor; therefore, their use in biological control of A. grandis should be restricted. Nevertheless, these strains could be the source of genes (e.g., cry1Ia) to produce transgenic cotton plants resistant to this pest.
用124株苏云金芽孢杆菌的全培养物（WC）对美洲棉铃象甲（Anthonomus grandis）的初孵幼虫进行了初步生物测定，美洲棉铃象甲是阿根廷和美洲其他地区的主要棉花害虫。选择了3株外来菌株和4株本地菌株，它们导致的死亡率超过50%。所有这些菌株都是β-外毒素产生菌。本地菌株的伴孢晶体形态相似、蛋白质图谱相似且杀虫基因谱相同。这些特征类似于对鳞翅目有毒的菌株。此外，这些菌株显示出与杀鳞翅目菌株HD-1相同的Rep-PCR图谱，表明这些菌株可能属于库斯塔克血清型。然而，在质粒图谱和β-外毒素的产生方面观察到了一些差异。为了确定存在杀虫代谢物的培养物组分，将包括重悬的芽孢-晶体颗粒、过滤上清液（FS）的生物测定结果与全培养物的结果进行了比较。测试的这两个组分都显示出一定水平的杀虫活性。结果可能表明主要的毒性因子可以在过滤上清液中找到，并且可能与β-外毒素的存在直接相关。基于对过滤上清液和高压灭菌过滤上清液的生物测定，不排除热不稳定毒力因子如Cry1I在毒性方面的作用。在所选择的菌株中，β-外毒素可能是主要的相关毒力因子；因此，它们在美洲棉铃象甲生物防治中的应用应受到限制。然而，这些菌株可能是产生抗这种害虫的转基因棉花植物的基因（例如cry1Ia）来源。
