Pineapple mealybug wilt-associated viruses: Vectors, impacts, and dynamics.

摘要

Mealybug wilt of pineapple (MWP) is a devastating disease worldwide, the etiology of which is unknown. Two closteroviruses, Pineapple mealybug wilt associated virus-1 (PMWaV-1) and PMWaV-2, were identified in pineapple from Hawaii and around the world. Both viruses are transmitted by pink pineapple mealybugs, Dysmicoccus brevipes, and grey pineapple mealybugs, D. neobrevipes. PMWaV-2 was shown to be an integral factor in MWP etiology. Typical MWP symptoms developed in pineapple plants infected with PMWaV-2 that were exposed to mealybugs. MWP did not develop in PMWaV-1-free or PMWaV-l-infected plants that were exposed to mealybugs or in plants infected with PMWaV-1, PMWaV-2, or both viruses if kept mealybug-free. MWP resulted in a 35% reduction in yield when compared to yields of PMWaV-free plants. Yield reductions were dependent on time of MWP symptom development; the earlier the expression of symptoms the greater the impact on plant crop fruit yield. Both PMWaV-1 and PMWaV-2 suppressed yield in the ratoon crop. Spatial analysis of PMWaV-2 spread and MWP symptom expression in mealybug-inoculated pineapple plots showed patterns of aggregation within rows and within beds but not between beds. Initial occurrence of MWP symptomatic plants showed underdispersed which was consistent with the random occurrence of PMWaV-2 plants. After six months of mealybug exposure, patterns of both PMWaV-2 incidence and MWP were overdispersed. PMWaV-1 and PMWaV-2 were detected in MWP symptomatic and healthy looking pineapple samples from around the world but PMWaV-2 infection was correlated with 100% of the MWP symptomatic samples that were PNIWaV-1-free. PMWaV-2 infection occurs at a lower frequency than PMWaV-1 infection in the Hawaiian grown pineapple selections and several hybrids. Infections of at least one PMWaV were found in 73% of the pineapple accessions maintained at the USDA-ARS National Clonal Germplasm Repository in Hilo, HI. No plants commonly found growing near or in pineapple fields were identified as hosts for PMWaV-1 and no pineapple germplasm was immune to PMWaV-1. PMWaV-1 was eliminated through bud propagation from infected crowns.