Progress 10/01/02 to 09/30/05
Outputs
PMWaV-3 was identified and characterized. Six contiguous open reading frames including the helicase, RNA-dependent RNA polymerase, small hydrophobic protein, heat-shock protein 70 homolog, p61, coat protein and p23 regions have been sequenced. Phylogenetic analyses have shown PMWaV-3 to be a distinct virus and not a strain of PMWaV-1 or PMWaV-2. Also, PMWaV-3 is more closely related to PMWaV-1, and grapevine leafroll associated virus-4, (GLRaV-4), GLRaV-5, GLRaV-6, and GLRaV-9 than to PMWaV-2 and GLRaV-3. PMWaV-3 is present on Maui and Oahu in several hybrids (Sether et al., 2005. Plant Disease). The highest incidence of PMWaV-3 is in a newly imported hybrid to Oahu from Costa Rica. The PMWaV-3 infections detected on Maui have, thus far, been present as mixed infections with the other characterized PMWaVs. PMWaV-3 can be acquired and transmitted by the pink and grey pineapple mealybugs. Similar to what is observed for PMWaV-1 infections, PMWaV-3 infection in the
presence of mealybug feeding does not result in mealybug wilt of pineapple (MWP) unless PMWaV-2 is present. All three PMWaVs are systemic and infected plants produce infected propagation material. Visible symptoms of the viral infections are not apparent and require the use of molecular and serological assays to identify infected plants. Yield is reduced by PMWaV-1 and PMWaV-2 even in the absence of MWP. The biological and genomic similarities of PMWaV-3 with the other PMWaVs suggest PMWaV-3 may also reduce yield.
Impacts
The Pineapple mealybug wilt associated viruses (PMWaVs) are a complex of mealybug transmitted ampeloviruses infecting pineapple. PMWaV-1 and PMWaV-3 are more closely related biologically and genomically to one another than to PMWaV-2. PMWaV-2 is involved in mealybug wilt of pineapple disease when infected plants are exposed to mealybugs. PMWaV-1 and PMWaV-3 do not appear to be necessary for MWP induction. PMWaV-1 and PMWaV-2 correlate with decreased fruit yields culminating from reduced sucker numbers in the ratoon, and may also contribute to early or delayed fruit production, complicating and increasing costs of fruit harvest. The most robust approach to alleviating the disease and yield problems associated with the PMWaVs, is to eliminate the presence of virus infected material. The use of screening assays for the PMWaVs combined with accelerated propagation methods that use chemical inducers to promote large numbers of slips from single, PMWaV-free plants, and
adequate mealybug control during this transition period, will reduce the incidences of the PMWaVs and the subsequent accompanying MWP and economic hardships. Achieving the ultimate goal of PMWaV-free pineapple production in the Hawaiian Islands will require continuous development and utilization of screening assays for existing and new PMWaVs and continued diligence in replanting only PMWaV-free material. If this approach can be followed, MWP which has plagued Hawaii for almost 10 decades may be a disease of the past in the next decade.
Publications
- Sether, D.M., Melzer, M.J., Busto, J.L., Zee, F. and Hu, J.S. 2005. Diversity and mealybug transmissibility of Pineapple mealybug wilt associated viruses found in pineapple. Plant Dis. 89:450-456.
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Progress 10/01/03 to 09/30/04
Outputs
Pineapple mealybug wilt associated viruses (PMWaV) are Ampeloviruses that infect pineapple. The three viruses, PMWaV-1, PMWaV-2, and PMWaV-3, that have been characterized thus far, are all mealybug transmissible. The presence of PMWaV-2 and Dysmicoccus mealybug feeding results in the induction of mealybug wilt of pineapple (MWP), a devastating disease. PMWaV-1 and PMWaV-3 do not appear to be involved in MWP, however. Unfortunately, in the absence of mealybugs, plants infected by the viruses can appear healthy, thus making visual identification of infected plants impossible. Pineapple mealybug wilt associated virus-3 has recently been purified from a pineapple hybrid imported into Hawaii from Costa Rica and a polyclonal antibody, capable of labeling PMWaV-3 has been identified. Additional PMWaV-like virus particles have also been isolated from the same pineapple hybrid. These virions are not decorated by the PMWaV-1- and PMWaV-2-specific monoclonal antibodies we have
previously produced, nor are the particles decorated by PMWaV-specific polyclonal antibodies produced in Hawaii and Australia. Based on these results it appears an additional PMWaV is present in the new hybrid. A mealybug wilt of pineapple outbreak recently occurred in another newer hybrid being expanded in Hawaii. Dysmicoccus brevipes, the pink pineapple mealybug, were present on stems and the portions of the plants located under the plastic mulch. Several hundred symptomatic plants and neighboring asymptomatic plants were analyzed with PMWaV-specific serological and reverse transcription-polymerase chain reaction assays. These assays showed that some of the MWP-symptomatic plants were infected with PMWaV-2 but many were not. This suggests that an additional factor, possibly another PMWaV-2-type virus, is involved. Virus purification and additional analyses of these plants are underway.
Impacts
The PMWaVs are a complex of viruses. At least one of the PMWaVs, PMWaV-2, that has been characterized to date is involved in MWP when mealybugs are present. Recent findings indicate that an additional factor, such as another PMWaV-2 type virus, may also be capable of inducing mealybug wilt in the presence of mealybug feeding. In order to eliminate MWP in the Hawaiian Islands, new or emerging causal agents must be identified, thus efforts are being directed at carefully analyzing newly stricken plants that appear to be PMWaV-2-free. In addition to MWP, PMWaV-1, PMWaV-2, and potentially, PMWaV-3 reduce yield in the ratoon crops. Reduction and potential elimination of MWP in Hawaii and improved yields can be achieved by reducing the incidence of infected plants. Efforts to develop rapid and robust detection assays for all of these new PMWaVs and variants need to continue as they will provide the crucial tools for managing the existing PMWaVs in Hawaii and potentially
preventing new ones from being introduced and establishing.
Publications
- No publications reported this period
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Progress 10/01/02 to 09/30/03
Outputs
Pineapple mealybug wilt associated viruses (PMWaV) are Ampeloviruses that infect pineapple. Two of these viruses, PMWaV-1 and PMWaV-2, are mealybug transmissible and have been detected serologically throughout the world. A third mealybug-transmitted PMWaV, designated PMWaV-3, has been identified and partially sequenced. Specific reverse transcription-polymerase chain reaction assay has been developed for small-scale detection of this virus, but is not appropriate for mass screening. PMWaV-3 has been detected in several pineapple accessions maintained at the USDA National Clonal Germplasm Repository for pineapple in Hilo, HI and in several identical accessions maintained in Del Monte's Pineapple Research Institute-derived display garden. PMWaV-3 has not been found in six of the pineapple selections and hybrids that are currently in mass-production in Hawaii, but PMWaV-3 has been detected in 10% of the plants belonging to a new commercial hybrid currently being imported
to Hawaii. PMWaV-3 shares more sequence similarities to PMWaV-1 than PMWaV-2. PMWaV-3 does not appear to be directly involved in mealybug wilt of pineapple (MWP) symptom induction but the impact on yield is as yet unknown. PMWaV-3 is serologically distinct to the other characterized PMWaVs, thus purification of PMWaV-3 for antibody production is underway. In addition, a fourth putative PMWaV has been identified and variants of the PMWaV-1 have recently been identified.
Impacts
The PMWaVs are a complex of viruses. Development of rapid and robust detection assays for all of these viruses and variants is a crucial tool for management and elimination of these viruses from the planting material in Hawaii. An important part of the management of this complex is the prevention of additional PMWaVs from becoming established in the Hawaiian Islands. Thus, developing detection assays for as many of these viruses is essential. In addition, identification of the sequence characteristics of the PMWaVs serves as a vital basis for successful development of genetically engineered pineapple with broad PMWaV and MWP resistance. Although PMWaV-3 does not appear to be directly involved in MWP, all of the characterized PMWaVs significantly suppress yields. The Hawaiian pineapple industry must maximize yields to thrive in the pineapple production market worldwide.
Publications
- No publications reported this period
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