Inheritance and stability of resistance to Bacillus thuringiensis formulations in field population of diamondback moth, Plutella xylostella

Levels, genetic traits and stability of resistance to Bacillus thuringiensis of the Bang Bua Tong (BS) population of the diamondback moth Plutella xylostella collected in Thailand were investigated. The BS population exhibited 668 and 66.5-fold resistance to formulations derived from B. thuringiensis subsp. kurstaki (Toarow CT®), and B. thuringiensis subsp. aizawai (XenTari®), respectively. In order to determine the genetic traits of resistance to B. thuringiensis subsp. kurstaki, two reciprocal crosses and backcross were conducted using a Japanese susceptible (S) population, BS population. Analysis of dose-mortality relationship of the S population, BS population, F1 progenies of the two reciprocal crosses and backcross progenies suggested that resistance to B. thuringiensis subsp. kurstaki in the moth might be controlled by some incompletely recessive autosomal alleles. Resistance to B. thuringiensis subsp. kurstaki and aizawai in the moth have remained at high levels despite rearing in the absence of B. thuringiensis selection.