Differences in distribution and community structure of plant-parasitic nematodes in pecan orchards between two ecoregions of Georgia

Authors: JAGDALE, GANPATI - University Of Georgia; BRENNEMAN, TIMOTHY - University Of Georgia; SEVERNS, PAUL - University Of Georgia; Shapiro Ilan, David

Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/28/2021
Publication Date: 9/7/2021
Citation: Jagdale, G., Brenneman, T.B., Severns, P.M., Shapiro Ilan, D.I. 2021. Differences in distribution and community structure of plant-parasitic nematodes in pecan orchards between two ecoregions of Georgia. Journal of Nematology. vol 53:e2021-75. https://doi.org/10.21307/jofnem-2021-075.
DOI: https://doi.org/10.21307/jofnem-2021-075

Interpretive Summary: Pecans are an economically important crop in Georgia and other states in the Southeastern USA. Productivity and profitability of pecans can be limited by various pests including plant-parasitic nematodes. Plant parasitic nematodes are small round worms that attack plants (mostly the roots). The population levels of plant parasitic nematodes can be influenced by environmental conditions such as soil characteristics. In Georgia, commercially grown pecans occur primarily in the Piedmont and Coastal Plain ecoregions. The Coastal Plain region tends to have lighter, well-drained sandy soils compared with the Piedmont that tends to have heavier clay-type soils. We conducted a survey to determine if the ecoregion (Coastal Plan versus Piedmont) differs in population levels of plant parasitic nematodes. Our results confirmed our hypothesis that the Coastal Plan, with its sandier soils, is more conducive to plant parasitic nematode populations than the Piedmont. These findings may have important implications for farmer expectations in nematode management. Farmers that grow pecans in Coastal Plan may need to implement more intensive nematode control programs than farmers planting in the Piedmont region.

Technical Abstract: In Georgia, commercially grown pecans occur primarily in the Piedmont and Coastal Plain ecoregions which are characterized by sandy-loam, sandy and/or clay soils. If well-drained, all these soils are suitable for pecan production, but the soil characteristics differ enough between ecoregions that the plant parasitic nematode (PPN) communities could differ substantially. We conducted a study of pecan PPN communities in Georgia to evaluate the potential for ecoregion differences. Eleven genera (Helicotylenchus spp., Hemicycliophora spp., Heterodera spp., Hoplolaimus spp., Meloidogyne spp., Mesocriconema spp., Pratylenchus spp., Paratylenchus spp., Paratrichodorus spp., Tylenchorhynchs spp., Xiphenema spp.) were recovered from pecan orchards in the Piedmont and Coastal Plain ecoregions. However, Non-Metric Multi-Dimensional Scaling (NMDS) ordination, Multi-Rank Permutation Procedure (MRPP) and Indicator Species Analyses indicated that the pecan PPN communities strongly differed between ecoregions and that different genera were strongly associated with single ecoregions. The maximum population densities of nine out of eleven PPN genera were comparatively higher in the Coastal Plain than in the Piedmont, suggesting that the well-drained and sandy soils in the Coastal Plain, and ill-drained red clay soils in the Piedmont, may be conducive and unfavorable for movement/ reproduction/ development of PPNs, respectively.