scholarly journals Genetic and Biochemical Approach for Characterization of Resistance to Bacillus thuringiensis Toxin Cry1Ac in a Field Population of the Diamondback Moth, Plutella xylostella

2000 ◽  
Vol 66 (4) ◽  
pp. 1509-1516 ◽  
Author(s):  
Ali H. Sayyed ◽  
Robert Haward ◽  
Salvador Herrero ◽  
Juan Ferré ◽  
Denis J. Wright
Keyword(s):  
Bacillus Thuringiensis ◽  
Plutella Xylostella ◽  
Diamondback Moth ◽  
Resistance Mechanism ◽  
Membrane Vesicles ◽  
Cross Resistance ◽  
Binding Studies ◽  
Susceptible Population ◽  
Biochemical Approach

ABSTRACT Four subpopulations of a Plutella xylostella (L.) strain from Malaysia (F4 to F8) were selected with Bacillus thuringiensis subsp.kurstaki HD-1, Bacillus thuringiensis subsp. aizawai, Cry1Ab, and Cry1Ac, respectively, while a fifth subpopulation was left as unselected (UNSEL-MEL). Bioassays at F9 found that selection with Cry1Ac, Cry1Ab, B. thuringiensissubsp. kurstaki, and B. thuringiensis subsp. aizawai gave resistance ratios of >95, 10, 7, and 3, respectively, compared with UNSEL-MEL (>10,500, 500, >100, and 26, respectively, compared with a susceptible population, ROTH). Resistance to Cry1Ac, Cry1Ab, B. thuringiensis subsp. kurstaki, andB. thuringiensis subsp. aizawai in UNSEL-MEL declined significantly by F9. The Cry1Ac-selected population showed very little cross-resistance to Cry1Ab, B. thuringiensis subsp. kurstaki, andB. thuringiensis subsp. aizawai(5-, 1-, and 4-fold compared with UNSEL-MEL), whereas the Cry1Ab-,B. thuringiensis subsp. kurstaki-, and B. thuringiensis subsp.aizawai-selected populations showed high cross-resistance to Cry1Ac (60-, 100-, and 70-fold). The Cry1Ac-selected population was reselected (F9 to F13) to give a resistance ratio of >2,400 compared with UNSEL-MEL. Binding studies with125I-labeled Cry1Ab and Cry1Ac revealed complete lack of binding to brush border membrane vesicles prepared from Cry1Ac-selected larvae (F15). Binding was also reduced, although less drastically, in the revertant population, which indicates that a modification in the common binding site of these two toxins was involved in the resistance mechanism in the original population. Reciprocal genetic crosses between Cry1Ac-reselected and ROTH insects indicated that resistance was autosomal and showed incomplete dominance. At the highest dose of Cry1Ac tested, resistance was recessive while at the lowest dose it was almost completely dominant. The F2 progeny from a backcross of F1 progeny with ROTH was tested with a concentration of Cry1Ac which would kill 100% of ROTH moths. Eight of the 12 families tested had 60 to 90% mortality, which indicated that more than one allele on separate loci was responsible for resistance to Cry1Ac.

scholarly journals Common, but Complex, Mode of Resistance of Plutella xylostella to Bacillus thuringiensis Toxins Cry1Ab and Cry1Ac

2005 ◽  
Vol 71 (11) ◽  
pp. 6863-6869 ◽  
Author(s):  
Ali H. Sayyed ◽  
Roxani Gatsi ◽  
M. Sales Ibiza-Palacios ◽  
Baltasar Escriche ◽  
Denis J. Wright ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Resistance Genes ◽  
Plutella Xylostella ◽  
Specific Binding ◽  
Management Strategies ◽  
Cross Resistance ◽  
Single Pair ◽  
Dominant Trait ◽  
Binding Studies ◽  
Susceptible Population

ABSTRACT A field collected population of Plutella xylostella (SERD4) was selected in the laboratory with Bacillus thuringiensis endotoxins Cry1Ac (Cry1Ac-SEL) and Cry1Ab (Cry1Ab-SEL). Both subpopulations showed similar phenotypes: high resistance to the Cry1A toxins and little cross-resistance to Cry1Ca or Cry1D. A previous analysis of the Cry1Ac-SEL showed incompletely dominant resistance to Cry1Ac with more than one factor, at least one of which was sex influenced. In the present study reciprocal mass crosses between Cry1Ab-SEL and a laboratory susceptible population (ROTH) provided evidence that Cry1Ab resistance was also inherited as incompletely dominant trait with more than one factor, and at least one of the factors was sex influenced. Analysis of single pair mating indicated that Cry1Ab-SEL was still heterogeneous for Cry1Ab resistance genes, showing genes with different degrees of dominance. Binding studies showed a large reduction of specific binding of Cry1Ab and Cry1Ac to midgut membrane vesicles of the Cry1Ab-SEL subpopulation. Cry1Ab-SEL was found to be more susceptible to trypsin-activated Cry1Ab toxin than protoxin, although no defect in toxin activation was found. Present and previous results indicate a common basis of resistance to both Cry1Ab and Cry1Ac in selected subpopulations and suggest that a similar set of resistance genes are responsible for resistance to Cry1Ab and Cry1Ac and are selected whichever toxin was used. The possibility of an incompletely dominant trait of resistant to these toxins should be taken into account when considering refuge resistance management strategies.

scholarly journals Susceptibility of a Field-Derived, Bacillus thuringiensis-Resistant Strain of Diamondback Moth to In Vitro-Activated Cry1Ac Toxin

2001 ◽  
Vol 67 (9) ◽  
pp. 4372-4373 ◽  
Author(s):  
Ali H. Sayyed ◽  
Roxani Gatsi ◽  
Thaleia Kouskoura ◽  
Denis J. Wright ◽  
Neil Crickmore
Keyword(s):  
Bacillus Thuringiensis ◽  
Plutella Xylostella ◽  
Resistant Strain ◽  
Diamondback Moth ◽  
Resistance Mechanism ◽  
Lethal Concentration ◽  
Susceptible Population ◽  
Resistant Population ◽  
Susceptible Populations

ABSTRACT Resistant and susceptible populations of the diamondback moth (Plutella xylostella) were tested with crystalline, solubilized, and partially and fully activated forms of theBacillus thuringiensis Cry1Ac δ-endotoxin. Fully activated toxin greatly reduced the resistance ratio (ratio of the 50% lethal concentration for the resistant population to that for the susceptible population) of the resistant population, suggesting that a defect in toxin activation is a major resistance mechanism.

scholarly journals Genetic and Biochemical Characterization of Field-Evolved Resistance to Bacillus thuringiensis Toxin Cry1Ac in the Diamondback Moth, Plutella xylostella

2004 ◽  
Vol 70 (12) ◽  
pp. 7010-7017 ◽  
Author(s):  
Ali H. Sayyed ◽  
Ben Raymond ◽  
M. Sales Ibiza-Palacios ◽  
Baltasar Escriche ◽  
Denis J. Wright
Keyword(s):  
Bacillus Thuringiensis ◽  
Resistance Genes ◽  
Plutella Xylostella ◽  
Biochemical Characterization ◽  
Diamondback Moth ◽  
Field Population ◽  
Laboratory Population ◽  
Binding Studies ◽  
Slow Increase ◽  
Evolution Of Resistance

ABSTRACT The long-term usefulness of Bacillus thuringiensis Cry toxins, either in sprays or in transgenic crops, may be compromised by the evolution of resistance in target insects. Managing the evolution of resistance to B. thuringiensis toxins requires extensive knowledge about the mechanisms, genetics, and ecology of resistance genes. To date, laboratory-selected populations have provided information on the diverse genetics and mechanisms of resistance to B. thuringiensis, highly resistant field populations being rare. However, the selection pressures on field and laboratory populations are very different and may produce resistance genes with distinct characteristics. In order to better understand the genetics, biochemical mechanisms, and ecology of field-evolved resistance, a diamondback moth (Plutella xylostella) field population (Karak) which had been exposed to intensive spraying with B. thuringiensis subsp. kurstaki was collected from Malaysia. We detected a very high level of resistance to Cry1Ac; high levels of resistance to B. thuringiensis subsp. kurstaki Cry1Aa, Cry1Ab, and Cry1Fa; and a moderate level of resistance to Cry1Ca. The toxicity of Cry1Ja to the Karak population was not significantly different from that to a standard laboratory population (LAB-UK). Notable features of the Karak population were that field-selected resistance to B. thuringiensis subsp. kurstaki did not decline at all in unselected populations over 11 generations in laboratory microcosm experiments and that resistance to Cry1Ac declined only threefold over the same period. This finding may be due to a lack of fitness costs expressed by resistance strains, since such costs can be environmentally dependent and may not occur under ordinary laboratory culture conditions. Alternatively, resistance in the Karak population may have been near fixation, leading to a very slow increase in heterozygosity. Reciprocal genetic crosses between Karak and LAB-UK populations indicated that resistance was autosomal and recessive. At the highest dose of Cry1Ac tested, resistance was completely recessive, while at the lowest dose, it was incompletely dominant. A direct test of monogenic inheritance based on a backcross of F1 progeny with the Karak population suggested that resistance to Cry1Ac was controlled by a single locus. Binding studies with 125I-labeled Cry1Ab and Cry1Ac revealed greatly reduced binding to brush border membrane vesicles prepared from this field population.

scholarly journals Cloning and Characterization of the Crystal Protein-Encoding Gene of Bacillus thuringiensis subsp. yunnanensis

2002 ◽  
Vol 68 (1) ◽  
pp. 408-411 ◽  
Author(s):  
Periasamy Balasubramanian ◽  
R. Jayakumar ◽  
Prashant Shambharkar ◽  
N. Unnamalai ◽  
S. Karutha Pandian ◽  
...  
Keyword(s):  
Amino Acid ◽  
Bacillus Thuringiensis ◽  
Molecular Mass ◽  
Plutella Xylostella ◽  
Diamondback Moth ◽  
Long Tail ◽  
C Terminus ◽  
Protein Encoding ◽  
Encoding Gene

ABSTRACT Molecular cloning and characterization of a novel cry gene, cry32Aa, of Bacillus thuringiensis subsp. yunnanensis was carried out. The Cry32Aa protein was predicted to have a molecular mass of 139.2 kDa and was found to have an unusual 42-amino-acid-long tail at the C terminus. The cry32Aa gene was localized on the 103-MDa plasmid of the organism. Bioassays showed no toxicity against several moths and mosquitoes. However, it exhibited weak toxicity against larvae of the diamondback moth, Plutella xylostella.

scholarly journals Cross-Resistance and Stability of Resistance to Bacillus thuringiensis Toxin Cry1C in Diamondback Moth

2001 ◽  
Vol 67 (7) ◽  
pp. 3216-3219 ◽  
Author(s):  
Yong-Biao Liu ◽  
Bruce E. Tabashnik ◽  
Susan K. Meyer ◽  
Neil Crickmore
Keyword(s):  
Bacillus Thuringiensis ◽  
Plutella Xylostella ◽  
Resistant Strain ◽  
Diamondback Moth ◽  
Field Population ◽  
Cross Resistance ◽  
Bacillus Thuringiensis Toxin ◽  
Stability Of Resistance ◽  
Resistant Strains ◽  
Reported Data

ABSTRACT We tested toxins of Bacillus thuringiensis against larvae from susceptible, Cry1C-resistant, and Cry1A-resistant strains of diamondback moth (Plutella xylostella). The Cry1C-resistant strain, which was derived from a field population that had evolved resistance to B. thuringiensis subsp.kurstaki and B. thuringiensis subsp.aizawai, was selected repeatedly with Cry1C in the laboratory. The Cry1C-resistant strain had strong cross-resistance to Cry1Ab, Cry1Ac, and Cry1F, low to moderate cross-resistance to Cry1Aa and Cry9Ca, and no cross-resistance to Cry1Bb, Cry1Ja, and Cry2A. Resistance to Cry1C declined when selection was relaxed. Together with previously reported data, the new data on the cross-resistance of a Cry1C-resistant strain reported here suggest that resistance to Cry1A and Cry1C toxins confers little or no cross-resistance to Cry1Bb, Cry2Aa, or Cry9Ca. Therefore, these toxins might be useful in rotations or combinations with Cry1A and Cry1C toxins. Cry9Ca was much more potent than Cry1Bb or Cry2Aa and thus might be especially useful against diamondback moth.

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