FUNCTIONAL HAPLODIPLOIDY - A MECHANISM FOR THE SPREAD OF INSECTICIDE RESISTANCE IN AN IMPORTANT INTERNATIONAL INSECT PEST

The coffee berry borer, Hypothenemus hampei, is the most important ins ect pest of coffee worldwide and has an unusual life history that ensu res a high degree of inbreeding. Individual females lay a predominantl y female brood within individual coffee berries and because males are flightless there is almost entirely full sib mating. We investigated t he genetics associated with this interesting life history after the im portant discovery of resistance to the cyclodiene type insecticide end osulfan. Both the inheritance of the resistance phenotype and the resi stance-associated point mutation the the gamma-aminobutyric acid recep tor gene Rdl were examined. Consistent with haplodiploidy, males faile d to express and transmit paternally derived resistance alleles. Furth ermore, while cytological examination revealed that males are diploid, one set of chromosomes was condensed, and probably non-functional, in the somatic cells of all males examined. Moreover, although two sets of chromosomes were present in primary spermatocytes, the chromosomes failed to pair before the single meiotic division, and only one set wa s packaged in sperm. Thus, the coffee berry borer is ''functionally'' haplodiploid. Its genetics and life history may therefore represent an interesting intermediate step in the evolution of true haplodiploidy. The influence of this breeding system on the spread of insecticide re sistance is discussed.