Occurrence and Distribution of Plant-Parasitic Nematodes on Muscadine Grapes in Georgia and North Carolina

Muscadine grape, Vitis rotundifolia, is native to the southeastern United States, but Georgia (GA) and North Carolina (NC) are the largest North American producers. Plant-parasitic nematodes (PPNs) have become a significant factor affecting the health, quality, production, and maintenance of bunch grapes (V. labrusca, V. vinifera), but little is known about muscadine PPNs. A systematic survey was conducted of PPNs infesting eight and 11 muscadine grape vineyards in GA and NC in August and October 2018, respectively. The most frequently detected PPNs across all samples from both states were Helicotylenchus (90%), Mesocriconema (72%), and Xiphinema (58%). However, 5 Hemicycliophora and 710 Scutellonema nematodes/100 cm 3 of soil were found only in GA, whereas only 1 Belonolaimus nematode/100 cm 3 of soil was found only in NC. Ordination of the nematode communities from the samples collected in GA and NC yielded groupings that aligned with the state of origin. Multivariate tests for group membership indicated that several genera were statistically associated with either NC or GA muscadines, and the PPN communities distinctly differed between states. Because muscadine grapes do not have established nematode thresholds, it is not known whether these nematode species are negatively impacting mature grapes.