Molecular and biological characterization of native Bacillus thuringiensis strains for controlling tomato leafminer (Tuta absoluta Meyrick) (Lepidoptera: Gelechiidae) in Colombia

Abstract

Twenty-eight soil samples were obtained from open fields and greenhouses used for tomato cultivation in various regions of Colombia. For functional characterization, 99 Bacillus thuringiensis (Bt) strains were isolated and characterized by abundance and morphology of microscopic crystals, SDS-PAGE of protein extracts and M-PCR analyses of genes of the cry1 family, as well as for their insecticidal activity against Tuta absoluta second instar larvae. Native Bt strains had amorphous (5%), bi-pyramidal (27%), square (8%), spherical (38%) and triangular (22%) crystal forms. Based on the presence of 1-4 different crystal forms, 18 different profiles were established. The SDS-PAGE analyses of protein extracts established ten different strain groups based on their protein band weight and potential biological activity. The M-PCR technique identified 35 native Bt strains based on the presence of the 6 genes cry1Aa, cry1Ab, cry1Ac, cry1B, cry1C and cry1D, whose frequency of occurrence was 76, 26, 21, 35, 32 and 8.8%, respectively. Thirteen different PCR profiles were found in native Bt strains. Several gene combinations tended to cooccur with elevated frequency, such as the pairs cry1Ac/ cry1C, cry1Ab/cry1Ac and cry1Ab/cry1B, for which Pearson correlation coefficients were 0.69, 0.52 and 0.54, respectively. Native strains ZBUJTL39 and ZCUJTL11 had up to three times higher biological activity against T. absoluta second instar larvae than the reference strain Bt var. kurstaki HD1, with an LD 50 of 2.4 lg/ml (P \ 0.05) for native Bt strain ZCUJTL11. This study suggests a high biodiversity of native Bt strains from tomato growing regions in Colombia, which has important implications for designing biological control strategies for T. absoluta.

Tomato leafminer [(Tuta absoluta Meyrick) (Lepidoptera: Gelechiidae)] and its current ecofriendly management strategies: A review

“…The pure protein crystals from five B. thuringiensis strains that were taken from dead or diseased larvae exhibited satisfactory efficacy against T. absoluta larvae (Medeiros et al, 2006). B. thuringiensis that was isolated from local soil show three folds toxicity against T. absoluta larvae compared to one of commercial B. thuringiensis in Algeria (Hernandez-Fernandez et al, 2010). Furthermore, four (B1, B2, B3, B4) Bacillus spp.…”

Potential of standard strains of Bacillus thuringiensis against the tomato pinworm, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

“…During the last few decades, tomato productivity has been increased worldwide. Heavy reliance on chemical pesticides provide ephemeral benefits, often with adverse side effects and not viable (Hernandez et al, 2011) and, in some instances, actually worsen farmer's overall pest problems, and this pest became resistance to pesticides (Sandeep et al, 2020a). Thus, the major challenge is to increase and sustain crop productivity with less use of pesticides.…”

“…thuringiensis strains are very effective against all larval stages of T. absoluta (Joel et al, 2011;Molla et al, 2011 andAzra et al, 2015). Cry proteins are highly specific and very effective against the tomato pinworm (Sandeep et al, 2020b and Dakshina and Gary, 2003) and narrow specific to lepidopterans (Hernandez et al, 2011 andMuhammad et al, 2019). Bt has been characterized as being highly specific against several insect orders including Lepidoptera, Diptera and Coleoptera (Xin Zhang et al, 2018).…”

Molecular Characterization of the cry Gene profile of Bacillus thuringiensis Isolated from a Caribbean Region of Colombia

“…In Central and South America, several infectious diseases which affect humans, animals and plants are transmitted by insect vectors from all orders (López-Pazos et al, 2009;Hernández-Fernández 2011;Pérez et al, 2016;WHO 2016;Camacho-Millán et al, 2017). Among them are Diptera such as mosquitoes of Ano pheles and Aedes genus involved in the transmission of malaria and dengue, respectively, which cause great impact in human heath (WHO 2016;Soares-da-Silva et al, 2017).…”

“…Among them are Diptera such as mosquitoes of Ano pheles and Aedes genus involved in the transmission of malaria and dengue, respectively, which cause great impact in human heath (WHO 2016;Soares-da-Silva et al, 2017). Among the insect vectors that cause great pests in agriculture in Latin America, are Lepidoptera such as Tuta absoluta which produces great loss in tomato production (Salazar and Araya, 2001;Hernández-Fernández, 2011) and Coleoptera such as Premnotrypes vorax and Anthonomus grandis that cause devastating pests for potato and cotton crops, respectively (López-Pazos et al, 2009;Pérez et al, 2016) . For these reasons it is very important in Latin America to seek more effective, sustainable and ecological methods to improve the campaigns to control and eradicate the various vectors of communicable diseases present…”