Cross-Resistance Among CryIV Toxins of Bacillus thuringiensis subsp. israelensis in Culex quinquefasciatus (Diptera: Culicidae)

1997 ◽  
Vol 90 (6) ◽  
pp. 1471-1477 ◽  
Author(s):  
Margaret C. Wirth ◽  
George P. Georghiou
Keyword(s):  
Bacillus Thuringiensis ◽  
Culex Quinquefasciatus ◽  
Cross Resistance ◽  
Bacillus Thuringiensis Subsp

Variable Cross-Resistance to Cry11B from Bacillus thuringiensis subsp. jegathesan in Culex quinquefasciatus (Diptera: Culicidae) Resistant to Single or Multiple Toxins of Bacillus thuringienisis subsp.israelensis

1998 ◽  
Vol 64 (11) ◽  
pp. 4174-4179 ◽  
Author(s):  
Margaret C. Wirth ◽  
Armelle Delécluse ◽  
Brian A. Federici ◽  
William E. Walton
Keyword(s):  
Bacillus Thuringiensis ◽  
Culex Quinquefasciatus ◽  
Complex Mixture ◽  
Cross Resistance ◽  
Variable Cross ◽  
Bacterial Strains ◽  
Bacillus Thuringiensis Subsp ◽  
Cry Toxin

ABSTRACT A novel mosquitocidal bacterium, Bacillus thuringiensissubsp. jegathesan, and one of its toxins, Cry11B, in a recombinant B. thuringiensis strain were evaluated for cross-resistance with strains of the mosquito Culex quinquefasciatus that are resistant to single and multiple toxins of Bacillus thuringiensis subsp. israelensis. The levels of cross-resistance (resistance ratios [RR]) at concentrations which caused 95% mortality (LC95) betweenB. thuringiensis subsp. jegathesan and the different B. thuringiensis subsp.israelensis-resistant mosquito strains were low, ranging from 2.3 to 5.1. However, the levels of cross-resistance to Cry11B were much higher and were directly related to the complexity of the B. thuringiensis subsp. israelensis Cry toxin mixtures used to select the resistant mosquito strains. The LC95 RR obtained with the mosquito strains were as follows: 53.1 againstCq4D, which was resistant to Cry11A; 80.7 againstCq4AB, which was resistant to Cry4A plus Cry4B; and 347 against Cq4ABD, which was resistant to Cry4A plus Cry4B plus Cry11A. Combining Cyt1A with Cry11B at a 1:3 ratio had little effect on suppressing Cry11A resistance in Cq4D but resulted in synergism factors of 4.8 and 11.2 against strainsCq4AB and Cq4ABD, respectively; this procedure eliminated cross-resistance in the former mosquito strain and reduced it markedly in the latter strain. The high levels of activity ofB. thuringiensis subsp. jegathesan and B. thuringiensis subsp. israelensis, both of which contain a complex mixture of Cry and Cyt proteins, against Cry4- and Cry11-resistant mosquitoes suggest that novel bacterial strains with multiple Cry and Cyt proteins may be useful in managing resistance to bacterial insecticides in mosquito populations.

scholarly journals Lack of Cross-Resistance to Cry19A from Bacillus thuringiensis subsp. jegathesan in Culex quinquefasciatus (Diptera: Culicidae) Resistant to Cry Toxins from Bacillus thuringiensis subsp.israelensis

2001 ◽  
Vol 67 (4) ◽  
pp. 1956-1958 ◽  
Author(s):  
Margaret C. Wirth ◽  
Armelle Delécluse ◽  
William E. Walton
Keyword(s):  
Bacillus Thuringiensis ◽  
Culex Quinquefasciatus ◽  
Cross Resistance ◽  
Cry Toxins ◽  
Bacillus Thuringiensis Subsp

ABSTRACT Culex quinquefasciatus mosquitoes with high levels of resistance to single or multiple toxins from Bacillus thuringiensis subsp. israelensis were tested for cross-resistance to the Bacillus thuringiensis subsp.jegathesan polypeptide Cry19A. No cross-resistance was detected in mosquitoes that had been selected with the Cry11A, Cry4A and Cry4B, or Cry4A, Cry4B, Cry11A, and CytA toxins. A low but statistically significant level of cross-resistance, three to fourfold, was detected in the colony selected with Cry4A, Cry4B, and Cry11A. This cross-resistance was similar to that previously detected with B. thuringiensis subsp.jegathesan in the same colony. These data help explain the toxicity of B. thuringiensis subsp.jegathesan against the resistant colonies and indicate that the Cry19A polypeptide might be useful in managing resistance and/or as a component of synthetic combinations of mosquitocidal toxins.

scholarly journals Cyt1Ab1 and Cyt2Ba1 from Bacillus thuringiensis subsp. medellin and B. thuringiensis subsp. israelensis Synergize Bacillus sphaericus against Aedes aegypti and Resistant Culex quinquefasciatus (Diptera: Culicidae)

2001 ◽  
Vol 67 (7) ◽  
pp. 3280-3284 ◽  
Author(s):  
Margaret C. Wirth ◽  
Armelle Del�cluse ◽  
William E. Walton
Keyword(s):  
Bacillus Thuringiensis ◽  
Aedes Aegypti ◽  
Insecticide Resistance ◽  
Culex Quinquefasciatus ◽  
Bacillus Sphaericus ◽  
Bacillus Thuringiensis Subsp

ABSTRACT The interaction of two cytolytic toxins, Cyt1Ab fromBacillus thuringiensis subsp. medellinand Cyt2Ba from Bacillus thuringiensis subsp.israelensis, with Bacillus sphaericus was evaluated against susceptible and resistant Culex quinquefasciatus and the nonsensitive species Aedes aegypti. Mixtures of B. sphaericus with either cytolytic toxin were synergistic, and B. sphaericusresistance in C. quinquefasciatus was suppressed from >17,000- to 2-fold with a 3:1 mixture of B. sphaericusand Cyt1Ab. This trait may prove useful for combating insecticide resistance and for improving the activity of microbial insecticides.

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