Pathogenicity of Bacillus thuringiensis isolated from two species of Acromyrmex (Hymenoptera, Formicidae)

Abstract

The control of Acromyrmex leaf-cutting ants is necessary due to the severe damage they cause to diverse crops. A possibility was to control them using the bacterium Bacillus thuringiensis (Bt) that characteristically produces insecticidal crystal proteins (ICPs). The ICPs have been effective in controlling lepidopterans, dipterans, and coleopterans, but their action against hymenopterans is unknown. This paper describes an attempt to isolate Bt from ants of two Acromyrmex species, to evaluate its pathogenicity towards these ants, and to test isolates by PCR. Bacterial isolates of Bt obtained from A. crassispinus and A. lundi have been assayed against A. lundi in the laboratory. The bioassays were carried out in BOD at 25°C, with a 12-hour photoperiod, until the seventh day after treatment. The Bt isolates obtained were submitted to total DNA extraction and tested by PCR with primers specific to cry genes. The results showed Bt presence in 40% of the assessed samples. The data from the in vivo assays showed a mortality rate higher than 50% in the target population, with the Bt HA48 isolate causing 100% of corrected mortality. The PCR results of Bt isolates showed a magnification of DNA fragments relative to cry1 genes in 22% of the isolates, and cry9 in 67%. Cry2, cry3, cry7, and cry8 genes were not detected in the tested samples, and 22% had no magnified DNA fragments corresponding to the assessed cry genes. The results are promising not only regarding allele identification in new isolates, but also fort the assays aimed at determining the Bt HA48 LC 50 's, which can eventually be applied in controlling of Acromyrmex leaf-cutting ants.Key words: bioassay, leaf-cutting ants, Bacillus thuringiensis. RESUMO Patogenicidade de Bacillus thuringiensis isolados de duas espécies deAcromyrmex (Hymenoptera, Formicidae)O controle das formigas-cortadeiras do gênero Acromyrmex é necessário em razão dos severos danos que causam a diversas culturas. Uma alternativa é a utilização da bactéria Bacillus thuringiensis (Bt), caracterizada pela produção de proteínas inseticidas eficazes para lepidópteros, dípteros e coleópteros, mas cuja ação é ainda desconhecida para himenópteros. O presente trabalho teve por objetivo isolar Bt a partir de formigas de duas espécies de Acromyrmex, avaliar sua patogenicidade a formigas-cortadeiras e testar por PCR.

Differential gene expression between adult queens and workers in the antLasius niger

“…2003). B. thuringiensis also attack ants (Pinto et al . 2003), but whether the bacterial toxins bind to ant membrane alanyl aminopeptidases has not yet been investigated.…”

An Overview of Integrated Management of Leaf-Cutting Ants (Hymenoptera: Formicidae) in Brazilian Forest Plantations

“…The isolates HA58 and HA48 of Bacillus thuringiensis caused mortality of Acromyrmex lundi at levels of 80% and 100%, respectively [95]. The pathogenicity of the nematodes Steinernema and Heterorhabditis was increased by the symbiotic bacteria, Xenorhabdus and Photorhabdus.…”

Bacillus and Biopesticides in Control of Phytonematodes

“…1.2), containing Cry proteins, encoded by the cry genes, with a wide division of classes and subclasses according to their insecticide activity (Höfte and Whiteley 1989), and presently classified according to the percent identity between Cry protein sequences Crickmore et al 1998;Crickmore 2014). These toxins present insecticidal activity to different insect orders, such as Lepidoptera, Coleoptera, Diptera, Hymenoptera, Hemiptera, Isoptera, Orthoptera, Siphonaptera, and Thisanoptera (Feitelson et al 1992;Aranda et al 1996;Cavados et al 2001;Castilhos-Fortes et al 2002;Pinto et al 2003;De Maagd et al 2001 in addition to nematodes (Marroquin et al 2000;Jouzani et al 2008). Currently, 735 Cry proteins, 38 Cyt proteins, and 122 Vip proteins have been described in the B. thuringiensis database (Crickmore 2014).…”