Detection of carboxylesterase and esterase activity in culturable gut bacterial flora isolated from diamondback moth, Plutella xylostella (Linnaeus), from India and its possible role in indoxacarb degradation

Diamondback moth (DBM), Plutella xylostella (Linnaeus), is a notorious pest of brassica crops worldwide and is resistant to all groups of insecticides. The insect system harbors diverse groups of microbiota, which in turn helps in enzymatic degradation of xenobiotic-like insecticides. The present study aimed to determine the diversity of gut microflora in DBM, quantify esterase activity and elucidate their possible role in degradation of indoxacarb. We screened 11 geographic populations of DBM in India and analyzed them for bacterial diversity. The culturable gut bacterial flora underwent molecular characterization with 16S rRNA. We obtained 25 bacterial isolates from larvae (n = 13) and adults (n = 12) of DBM. In larval gut isolates, gammaproteobacteria was the most abundant (76%), followed by bacilli (15.4%). Molecular characterization placed adult gut bacterial strains into three major classes based on abundance: gammaproteobacteria (66%), bacilli (16.7%) and flavobacteria (16.7%). Esterase activity from 19 gut bacterial isolates ranged from 0.072 to 2.32 µmol/min/mg protein. Esterase bands were observed in 15 bacterial strains and the banding pattern differed in Bacillus cereus KC985225 and Pantoea agglomerans KC985229. The bands were characterized as carboxylesterase with profenofos used as an inhibitor. Minimal media study showed that B. cereus degraded indoxacarb up to 20%, so it could use indoxacarb for metabolism and growth. Furthermore, esterase activity was greater with minimal media than control media: 1.87 versus 0.26 µmol/min/mg protein. Apart from the insect esterases, bacterial carboxylesterase may aid in the degradation of insecticides in DBM.(AU)

Potential of Metarhizium anisopliae (Metsch.) Sorokin (Ascomycetes, hypocreales) in the control of Bonagota salubricola (Meyrick) (Lepidoptera, Tortricidae) and its compatibility with chemical insecticides / Potencialidade de Metarhizium anisopliae (Metsch.) Sorokin (Ascomycetes, Hypocreales) no controle de Bonagota salubricola (Meyrick) (Lepidoptera, Tortricidae) e sua compatibilidade com inseticidas químicos

Several insects are harmful to apples grown in Brazil, especially the leafroller Bonagota salubricola (Lepidoptera, Tortricidae), usually controlled with chemical insecticides. The purpose of the present study was to investigate the use of Metarhizium anisopliae strains in the control of the apple leafroller, by assessing their virulence to B. salubricola larvae in bioassays with suspensions of 2 x 10(5) to 2 x 10(9) conidia/mL as well as their relationship with protease expression. The most effective strain underwent a compatibility test with chemical insecticides. The M. anisopliae E6 strain showed a good performance, with up to 88 percent mortality and a LT50 of 1.66 days. The virulence was positively correlated with a higher enzymatic activity. The E6 strain was compatible with tebufenozide, evidencing its potential to control B. salubricola.

Diversos insetos são nocivos à macieira no Brasil, destacando-se a lagarta-enroladeira Bonagota salubricola (Lepidoptera: Tortricidae), controlada com inseticidas químicos. Este trabalho objetivou avaliar linhagens de Metarhizium anisopliae passíveis de serem utilizadas no controle desta praga, determinando-se a virulência sobre larvas de B. salubricola em bioensaios com suspensões de 2 x 10(5) a 2 x 10(9) conídios/mL considerando-se mortalidade larval e pupal, bem como a sua relação com a expressão de proteases. A linhagem mais efetiva foi submetida a teste de compatibilidade com inseticidas químicos. A linhagem E6 de M. anisopliae destacou-se por proporcionar mortalidade de 88 por cento com TL50 de 1,66 dias; tal virulência relacionou-se positivamente com maior produção enzimática. Esta linhagem foi compatível com tebufenozide, evidenciado seu potencial no controle de B. salubricola.