PINEAPPLE MEALYBUG WILT ASSOCIATED VIRUS AND MEALYBUG WILT OF PINEAPPLE

The long-term goals of our research on MWP are to understand the interactions between viruses, vectors and host plants, and to use this information to develop strategies to manage this important disease. Our recent work shows that pineapple mealybug wilt associated virus (PMWaV) is a complex of closteroviruses. We have produced specific monoclonal antibodies against two distinct PMWaVs. A reverse transcription-polymerase chain reaction assay was developed to detect and distinguish these two viruses. The entire genome of PMWaV-2 was cloned and its sequence determined. The genome contains 10 open reading frames and is typical of the monopartite closteroviruses. PMWaV-1 has also been cloned and ten kilobases have been sequenced. The two PMWaVs are distinct and share less than 50% nucleic acid homology with each other based on available sequences. Both PMWaVs can be acquired and transmitted by mealybugs (Dysmicoccus spp.). We have shown in transmission experiments that the presence of PMWaV-2 and mealybug exposure are necessary for the induction of MWP. Mealybug feeding on pineapple plants in the absence of the PMWaVs, or the presence of the PMWaVs in the absence of mealybug feeding, does not induce MWP symptoms. Meristem propagation through tissue culture has been shown to produce PMWaV-free plant material. Constructs of selected PMWaV-2 genes are being introduced into pineapple to develop MWP-resistant transgenic plants by inducing gene-silencing mechanisms.