Interactions Between B And Q Biotypes Of Bemisia Tabaci And Their Relevance To The Evolution And Management Of Insecticide Resistance

1. Using a variety of B and Q strains, courtship and mating behaviour was observed by video to determine the extent to which reproductive isolation between biotypes is due to pre-zygotic mechanisms leading to the failure of insects to produce diploid, female offspring. This observational work was complemented by experiments in which whiteflies were offered a choice of potential mates. It was confirmed that strong hostile and rejections of female are critical pre-zygotic mechanism in preventing the introgression between B and Q biotypes. Main results are as the below: The observation of sexual behaviours between B and Q biotypes showed no visible differences. However, Q biotype significantly spent less time in the durations of pre-copulation (P=0.002<0.01). Q biotype female showed more rejections in responding to male's contact than B biotype female but without significant difference. There were no significant differences between inter- and intra-biotype combinations in the experiments of no-choice and choice testing, insects paired with similar success and within a similar time of period. The phenomenon of Q males being more active in pairing than B males was observed in the treatments of 1Q♀1Q♂1 B♂and 1B♀1 Q♂1 B♂, but differences were not significant. The study on courtship and mating behaviours revealed that barriers to interbreeding between B and Q biotypes existed strongly but were not complete since Q males successfully mated with B females in the parallel body orientation of 1 Q♂1B♀1 B♂and 1B♀1 Q♂1 B. This will lead to assortative mating between these two biotypes but could allow some genetic introgressions of hybrid progenies are viable. The experiment performed by cutting off the antennae for both biotypes suggests that removal of antennae had little or no effect on the success of pairing or mating. Consistently all inter biotype pairs failed to mate. It therefore appeared that antennal contact is not essential for successful courtship, and does not account for the failure of inter-biotype combinations to mate successfully.