Inheritance of resistance and cross resistance pattern in indoxacarb‐resistant diamondback moth Plutella xylostella L.

Abstract Leaf‐dip assay of Plutella xylostella against indoxacarb showed that the concentration that produced 50% mortality (LC 50 ) of indoxacarb ranged from 20.1 to 11.9 ppm, with highest in Nasik and lowest levels in Coimbatore strains. In selection studies, the LC 50 of indoxacarb was 18.5 ppm at generation 1 (G1), which increased to 31.3‐fold (167.8 ppm) resistance after ten exposed generations (G10) as compared to unexposed. The LC 50 of quinalphos was 74.4 ppm, which increased to 10.0‐fold (631.5 ppm) resistance after G10. The LC 50 of cypermethrin resistant strain resulted in an 11.5‐fold increase in resistance after G10. In P. xylostella , heritability (h 2 ) after ten generations of selection was estimated at 0.4. The number of generations required for tenfold increase in LC 50 (1/R) were 6.7. The response to indoxacarb selection in P. xylostella was 0.2 and the selection differential was estimated as 0.4. The phenotypic standard deviation was 0.2. Reciprocal crosses between indoxacarb‐resistant and susceptible strains showed that the inheritance of indoxacarb resistance was autosomal. The degree of heritability (D LC ) (0.4, 0.4) indicated incomplete recessive inheritance of indoxacarb resistance.