Incidence and Pathogenicity of Plant-Parasitic Nematodes Associated with Blueberry (Vaccinium spp.) Replant Disease in Georgia and North Carolina
Abstract
Blueberry replant disease (BRD) is an emerging threat to continued blueberry (Vaccinium spp.) production in Georgiaand North Carolina. Since high populations of ring nematode Mesocriconema ornatum were found to be associated with commerciallygrown blueberries in Georgia, we hypothesized that M. ornatum may be responsible for predisposing blueberry to BRD. We thereforetested the pathogenicity of M. ornatum on 10-wk-old Rabbiteye blueberries (Vaccinium virgatum) by inoculating with initial populations(Pi) of 0 (water control), 10, 100, 1,000. and 10,000 mixed stages of M. ornatum/pot under both greenhouse (25 ± 28C) andfield microplot conditions. Nematode soil population densities and reproduction rates were assessed 75, 150, 225, and 255, and 75,150, 225, and 375 d after inoculation (DAI) in both the greenhouse and field experiments, respectively. Plant growth parameterswere recorded in the greenhouse and field microplot experiments at 255 and 375 DAI, respectively. The highest M. ornatumpopulation density occurred with the highest Pi level, at 75 and 150 DAI under both greenhouse (P , 0.01) and field (P , 0.01)conditions. However, M. ornatum rate of reproduction increased significantly in pots receiving the lowest Pi level of 10 nematodes/plant compared with the pots receiving Pi levels of 100, 1,000, and 10,000 nematodes 75 DAI. Plant-parasitic nematode populationswere determined in commercial blueberry replant sites in Georgia and North Carolina during the 2010 growing season. Mesocriconemaornatum and Dolichodorus spp. were the predominant plant-parasitic nematodes in Georgia and North Carolina, respectively,with M. ornatum occurring in nearly half the blueberry fields sampled in Georgia. Other nematode genera detected in both statesincluded Tylenchorhynchus spp., Hoplolaimus spp., Hemicycliophora spp., and Xiphinema spp. Paratrichodorus spp. was also found only inGeorgia. In Georgia, our results indicate that blueberry is a host for M. ornatum and its relationship to BRD warrants furtherinvestigation.Downloads
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