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

Ganpati B. Jagdale,Timothy B. Brenneman,Paul M. Severns,David Shapiro-Ilan

doi:10.21307/jofnem-2021-075

Abstract

In Georgia, pecans are commercially grown in the Piedmont and Coastal Plain ecoregions which are characterized by sandy-loam, sandy, and/or clay soils. If well-drained, these soils are suitable for pecan production, but the soil characteristics differ enough between ecoregions in which the plant-parasitic nematode (PPN) communities could differ substantially. We studied PPN communities in pecan orchards to evaluate the potential for ecoregion differences. In total, 11 genera (Helicotylenchus, Hemicycliophora, Heterodera, Hoplolaimus, Meloidogyne, Mesocriconema, Pratylenchus, Paratylenchus, Paratrichodorus, Tylenchorhynchs, Xiphenema) were recovered from pecan orchards in the Piedmont and Coastal Plain ecoregions. However, Non-Metric Multi-Dimensional Scaling ordination, Multi-Rank Permutation Procedure, and Indicator Species Analyses indicated that the pecan PPN communities strongly differed between ecoregions and that different genera were strongly associated with different ecoregions. For 9 of the 11 PPN genera, the maximum counts occurred in Coastal Plain locations, suggesting that the well-drained sandy soils of the Coastal Plain and comparatively ill-drained red clay soils of the Piedmont may be conducive and unfavorable for movement/reproduction of PPNs, respectively.

Highlights

In Georgia, pecans are commercially grown in the Piedmont and Coastal Plain ecoregions which are characterized by sandy-loam, sandy, and/or clay soils
The distribution of 11 plant-parasitic nematode (PPN) genera in six and 22 pecan orchards varied among the four and 21 counties that located in Piedmont and Coastal Plain ecoregions, respectively (Table 1)
The percent frequencies of occurrence, abundances, and maximum population density of five major PPNs including Meloidogyne, Mesocriconema, Paratrichodoru, Helicotylenchus, and Xiphenema that occurred on pecans differed between the nematodes and counties that are located in two different ecoregions of Georgia (Table 2)

Summary

Introduction

In Georgia, pecans are commercially grown in the Piedmont and Coastal Plain ecoregions which are characterized by sandy-loam, sandy, and/or clay soils. If well-drained, these soils are suitable for pecan production, but the soil characteristics differ enough between ecoregions in which the plant-parasitic nematode (PPN) communities could differ substantially. 11 genera (Helicotylenchus, Hemicycliophora, Heterodera, Hoplolaimus, Meloidogyne, Mesocriconema, Pratylenchus, Paratylenchus, Paratrichodorus, Tylenchorhynchs, Xiphenema) were recovered from pecan orchards in the Piedmont and Coastal Plain ecoregions. Nematodes are among the most ubiquitous, abundant, and biologically diversified groups of invertebrate soil organisms. Based on their feeding behavior, nematodes can be grouped as bacterivores, fungivores, predatory, carnivores, and herbivores (plant-parasites). Incorporation of organic soil amendments and fertilizers, such as compost, can change soil

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