Distribution and Abundance of Nematodes in Horticultural Production in Paraguay

Abstract

In Paraguay, there is no information describing the distribution and abundance of plant-parasitic nematodes and other free-living nematodes from vegetable farms. The objectives of this study were to determine the prevalence and abundance of plant-parasitic nematodes on vegetable farms, to evaluate the relationship between plant-parasitic nematodes and ecological diversity, and to evaluate the relationship between edaphic factors and nematode communities. Vegetable farms ( n = 217) across nine departments in Paraguay were included in this survey, and soil samples were collected between March and September 2021. More than 10 plant-parasitic nematode genera were identified in this survey and are presented as follows in decreasing order of prevalence: Helicotylenchus (0 to 2,000 nematodes/100 cm3 of soil), Meloidogyne (0 to 4,120), Criconemella (0 to 400), root-related genera in Tylenchidae (0 to 400), Pratylenchus (0 to 280), Tylenchorhynchus (0 to 200), Trichodorus (0 to 40), Rotylenchulus (0 to 1,800), Hoplolaimus (0 to 20), Xiphinema (0 to 80), Scutellonema (0 to 1,000), Criconema (0 to 24), and Hemicycliophora (0 to 20). Meloidogyne was the most abundant nematode on vegetable farms, highlighting the potential threat of this pathogen to horticultural production in Paraguay. Nematodes were separated into five trophic groups depending on their feeding habits. Diversity of trophic groups was estimated using Shannon's diversity index, which was inversely related to plant-parasitic nematodes. Additionally, the relationship between edaphic factors (physical-chemical soil properties) and nematode abundance was evaluated. Soil texture was significantly associated with nematode abundance. This study is a first step to aid local growers in developing sustainable and economic agricultural systems.