Distribution, transmission, and interactions of pineapple mealybug wilt associated viruses in Hawai'i

One of the limiting factors in pineapple production is the occurrence of mealybug wilt of pineapple (MWP), a serious disease of pineapple worldwide. Two commercially-grown pineapple hybrids, PRI 73-114 and PRI 73-50, recently imported to Hawaii and 131 pineapple accessions grown in Hawaii are susceptible to pineapple mealybug wilt associated viruses, badnaviruses, and MWP. Four distinct pineapple mealybug wilt associated ampeloviruses (family Closteroviridae), and badnavirus-like (family Caulimoviridae ) sequences tentatively placed in four clades, A, B, C, and D, were detected with specific reverse transcription-polymerase chain reaction (RT-PCR) and clade-specific PCR assays, respectively. Highest virus incidences for PRI 73-114 were observed for plants with PMWaV-1 infection and in PRI 73-50 as single infections with PMWaV-3 or in combination with PMWaV-1. PMWaV-4 infections were detected in PRI 73-50 hybrid and in pineapple accessions. Pineapple badnavirus was detected in badnavirus-like clade C with highest incidence observed in PRI 73-114. PRI 73-50 plants infected with PMWaV-2 alone or mixed infections with other PMWaV variants were consistently observed to exhibit wilting symptoms.;Pineapple mealybug wilt associated virus-2 (PMWaV-2) was found to be acquired and transmitted by Dysmicoccus neobrevipes and Pseudococcus sp. D. neobrevipes transmitted PMWaV-2 in a semipersistent manner since it acquired PMWaV-2 within 36 hours, achieved 100% transmission of PMWaV-2 after 72-hrs acquisition access period (AAP) and retained the virus for less than 72 hours. D. neobrevipes remained viruliferous for up to 3 days after AAP when transferred daily to healthy plants over a 7-day period. Pseudococcus sp. was found to be a vector of PMWaV-2. Pseudococcus sp. required longer AAP and obtained lower transmission efficiency compared to D. neobrevipes. Only D. neobrevipes feeding caused the appearance of MWP symptoms in PRI 73-114 hybrids.;Specific detection and absolute quantitation of PMWaV-2 in pineapple plant tissues using quantitative RT-PCR (TagMan®) assays were achieved. Optimized primers and probe designs based on the PMWaV-2 CP sequence of the virus were efficient in the amplification and quantification of PMWa-2 infected plants. PMWaV-2 levels in pineapple varied depending on plant tissues sampled, presence or absence of MWP symptoms and mealybug feeding.