Diversity and distribution of lepidopteran-specific toxin genes in Bacillus thuringiensis strains from Argentina

Abstract

A total of 268 Bacillus thuringiensis strains obtained from different sources of Argentina were analyzed to determine the diversity and distribution of the cry1, cry2, cry8, cry9 and vip3A genes encoding for lepidopteran-specific insecticidal proteins. Twin strains were excluded. Ten different profiles were detected among the 80 selected B. thuringiensis strains. Two of these profiles (cry1Aa, cry1Ac, cry1Ia, cry2Aa, cry2Ab and vip3Aa (35/80), and cry1Aa, cry1Ab, cry1Ac, cry1Ia, cry2Aa, cry2Ab and vip3Aa (25/80)) pooled 75% of the strains. The existence of this low diversity is rare, since in most of the studied collections a great diversity of insecticidal toxin gene profiles has been described. In addition, the most frequently detected profile was also most frequently derived from soil (70%), stored product dust (59%) and spider webs (50%). In contrast, the cry1Aa, cry1Ab, cry1Ac, cry1Ia, cry2Aa, cry2Ab and vip3Aa profiles were mainly detected in strains isolated from leaves (40%) and dead insect larvae (50%). Six of the identified insecticidal toxin gene profiles were discovered in strains isolated from stored product dust and leaves indicating higher diversity of profiles in these kinds of sources than in others. Some strains with high insecticidal activity against Epinotia aporema (Lepidoptera) larvae were identified, which is important to explore future microbial strategies for the control of this crop pest in the region.

Molecular characterization of lepidopteran-specific toxin genes in Bacillus thuringiensis strains from Thailand

“…5 Larvicidal activity of B. thuringiensis against S. litura larvae. Error bar indicates ± standard error for three experiments frequencies of gene combinations in our B. thuringiensis collection, as 19 gene profiles were observed which were higher than that reported in Argentina where 10 gene combination profiles were reported (Sauka and Benintende 2017). However, higher numbers of cry gene combination profiles (43 profiles) were reported for cry1 subclasses of B. thuringiensis from China (Wang et al 2003).…”

“…The SEM images showed bipyramidal and cuboidal crystal morphologies of B. thuringiensis 225-15, 349-4, 417-1, 831-2, and 834-1 that were similar to most of the B. thuringiensis samples in Argentina, of which 88.8% of isolates containing cry1 and cry2 genes exhibited bipyramidal and cuboidal crystals (Sauka and Benintende 2017). The inclusion morphologies of B. thuringiensis serovar kurstaki HD1 have been reported to be bipyramidal and cuboidal structures (Monnerat et al 2007;Patel et al 2012;Zorzetti et al 2017); however, some publications reported that this strain contained bipyramidal, cuboidal, and spherical structures (Azizoglu et al 2015;Yılmaz et al 2012).…”

“…Our results showed that cry1A was usually found with cry1B and cry2, with combination frequencies of 88.17% and 80.91%, respectively. High associations between cry1 and cry2 have been commonly (Rangeshwaran et al 2014;Sauka and Benintende 2017;Wang et al 2003).…”

“…Application of B. thuringiensis in microbial insecticides may be limited due to the narrow host range, low larvicidal activity to the targeted pests, and the resistance from insects after long-term exposure to a single toxin. Therefore, screening new effective isolates and screening for novel B. thuringiensis toxins have been performed continuously (Jain et al 2017;Reyaz et al 2017;Sauka and Benintende 2017). Since the presence of specific toxin genes correlates with the corresponding specific larvicidal activity, detection of specific toxin genes using polymerase chain reaction (PCR) were performed worldwide to screen and characterize the effective B. thuringiensis isolates (Sauka and Benintende 2017;Thammasittirong and Attathom 2008;Yu et al 2011).…”

Dispersión y mortalidad de larvas de Spodoptera frugiperda J. E. Smith (Lepidoptera: Noctuidae) en híbridos de maíz convencional y transgénico Bt

“…Estas plantas resistentes a insectos se obtienen a partir de modificaciones genéticas consistentes en la introducción de un gen que codifica la síntesis de toxinas proteicas pertenecientes a distintas cepas de B. thuringiensis (Siebert et al, 2008;Tabashnik et al, 2009;Casmuz et al, 2010;James, 2012). Las propiedades insecticidas de B. thuringiensis son atribuidas principalmente a la síntesis de cristales proteicos insecticidas (toxinas Cry) y a proteínas insecticidas vegetativas (toxinas Vip), las cuales son producidas por la bacteria durante la fase de esporulación o crecimiento vegetativo, respectivamente (Pigott et al, 2008;Palma et al, 2012;Sauka & Benintende, 2017). El ciclo de vida de B. thuringiensis se divide en cuatro fases.…”