scholarly journals Diversity of indigenous Bacillus thuringiensis isolates toxic to the diamondback moth, Plutella xylostella (L.) (Plutellidae: Lepidoptera)

2021 ◽  
Vol 31 (1) ◽  
Author(s):  
R. Naga Sri Navya ◽  
V. Balasubramani ◽  
M. Raveendran ◽  
M. Murugan ◽  
A. Lakshmanan
Keyword(s):  
Bacillus Thuringiensis ◽  
Plutella Xylostella ◽  
Diamondback Moth ◽  
Leaf Disc ◽  
Pcr Screening ◽  
Molecular Weights ◽  
Resistance Evolution ◽  
Sds Page ◽  
White Colour

Abstract Background Toxins from the Bacillus thuringiensis (Bt) bacterium are employed as an alternative to synthetic pesticides in pest management. The greatest threat to the long-term viability of Bt toxins is resistance evolution in the target pests. Genetic diversity and toxicity of Bt isolates were studied in this work in order to find Bt isolates with novel cry genes. Results In terms of colony morphology, among a total of 60 isolates, 51 isolates had off-white colour colonies with typical fried egg appearance, irregular shape, flat and undulate margin. Different crystal shapes, viz. spherical (88.13%), bipyramidal (49.15%), cuboidal (42.37%), rectangular, and crystals attached to spores (3.38%) were observed among Bt isolates. SDS-PAGE analysis of spore crystal mixture showed the presence of proteins with various molecular weights ranging from 124 to 26 kDa. PCR screening with cry1, cry2, cry9 and vip3A1 primers showed isolates with varied insecticidal gene combinations. Bt isolates containing cry1 genes were found to be abundant (30), followed by cry2 (9) and vip3A1 (9). Cry9 was absent in all the 60 isolates tested. Insecticidal activity of spore crystal mixtures ranged from 0 to 100% mortality. Furthermore, 12 isolates were found to be highly toxic against the larvae of diamondback moth, Plutella xylostella (L.) (Plutellidae: Lepidoptera) with 100% mortality, at 25 µg/ml in leaf disc bioassay. Conclusions The present work established the diversity of Bt isolates and confirmed the importance of continuous exploration of new Bt isolates for novel genes. Further, research needs to be carried out to unveil the hidden potential of these toxic isolates.

The effects of local selection versus dispersal on insecticide resistance patterns: longitudinal evidence from diamondback moth (Plutella xylostella (Lepidoptera: Plutellidae)) in Australia evolving resistance to pyrethroids

2008 ◽  
Vol 98 (2) ◽  
pp. 145-157 ◽  
Author(s):  
N.M. Endersby ◽  
P.M. Ridland ◽  
A.A. Hoffmann
Keyword(s):  
Gene Flow ◽  
Plutella Xylostella ◽  
Diamondback Moth ◽  
Management Strategies ◽  
Resistance Management ◽  
Synthetic Pyrethroids ◽  
Forage Crops ◽  
Microsatellite Variation ◽  
Resistance Evolution ◽  
Local Selection

AbstractWhen strong directional selection acts on a trait, the spatial distribution of phenotypes may reflect effects of selection, as well as the spread of favoured genotypes by gene flow. Here we investigate the relative impact of these factors by assessing resistance to synthetic pyrethroids in a 12-year study of diamondback moth, Plutella xylostella, from southern Australia. We estimated resistance levels in populations from brassicaceous weeds, canola, forage crops and vegetables. Differences in resistance among local populations sampled repeatedly were stable over several years. Levels were lowest in samples from weeds and highest in vegetables. Resistance in canola samples increased over time as insecticide use increased. There was no evidence that selection in one area influenced resistance in adjacent areas. Microsatellite variation from 13 populations showed a low level of genetic variation among populations, with an AMOVA indicating that population only accounted for 0.25% of the molecular variation. This compared to an estimate of 13.8% of variation accounted for by the resistance trait. Results suggest that local selection rather than gene flow of resistance alleles dictated variation in resistance across populations. Therefore, regional resistance management strategies may not limit resistance evolution.

Enhancement of δ-Endotoxin Activity by Toxin-Free Spore of Bacillus thuringiensis against the Diamondback Moth, Plutella xylostella

1994 ◽  
Vol 63 (1) ◽  
pp. 111-112 ◽  
Author(s):  
Minoru Miyasono ◽  
Shyuichiro Inagaki ◽  
Makiko Yamamoto ◽  
Katsuaki Ohba ◽  
Takeo Ishiguro ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Plutella Xylostella ◽  
Diamondback Moth ◽  
Endotoxin Activity ◽  
Free Spore

scholarly journals Insecticidal Effects of Organotin(IV) Compounds on Plutella Xylostella (L.) Larvae. II. Inhibitory Potencies Against Acetylcholinesterase and Evidence for Synergism in Tests With Bacillus Thuringiensis(BER.) and Malathion

1994 ◽  
Vol 1 (1) ◽  
pp. 1-17 ◽  
Author(s):  
Nazni W. Ahmad ◽  
Tay Siew Huang ◽  
S. Balabaskaran ◽  
K. M. Lo ◽  
V. G. Kumar Das
Keyword(s):  
Bacillus Thuringiensis ◽  
Plutella Xylostella ◽  
Resistant Strain ◽  
Synergistic Effects ◽  
Diamondback Moth ◽  
Ache Inhibition ◽  
Microbial Insecticide ◽  
In Vitro Inhibition ◽  
Sublethal Concentrations

Features of pesticide synergism and acetylcholinesterase (AChE) inhibition (in vitro) were studied using a selected range of organotin compounds against the early 4th instar larvae of a highly resistant strain of the diamondback moth (DBM), Plutella xylostella, a major universal pest of cruciferous vegetables.Fourteen triorganotin compounds were evaluated for their ability to enhance the toxicity of the microbial insecticide, Bacillus thuringiensis (BT) and of the commercial insecticide, Malathion to Plutella xylostella larvae. Supplemental synergism was observed with triphenyl- and tricyclopentyltin hydroxides in combinations with Bacillus thuringiensis. Increased synergism was observed with an increase in the number of cyclopentyl groups on tin in the mixed series, CypnPh3-n SnX, where X = OH, and 1-(1,2,4-triazolyl). The combination of (p-chlorophenyl)diphenyltin N,N-dimethyldithiocarbamate at LD10 and LD25 concentrations with sublethal concentrations of Malathion as well as of tricyclohexyltin methanesulphonate at the 0.01% (w/v) concentration with Malathion exerted strong synergistic effects (supplemental synergism) with toxicity index (T.I) values of 7.2, 19.8 and 10.1, respectively.Studies on the in vitro inhibition of acetylcholinesterase prepared from the DBM larvae showed that while most of the triorganotin Compounds tested were without effect on the enzyme, compounds containing the thiocarbamylacetate or the dithiocarbamylacetate moieties demonstrated appreciable levels of inhibition, being comparable in efficacy to commercial grades of Malathion and Methomyl.

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