Performance dos nematoides herbívoros meloidogyne incognita e meloidogyne javanica parasitando plantas sob estresse hidríco

Abstract

Plant parasitic nematodes are microorganisms that infect various agricultural crops, causing low productivity in plantations and significant economic losses. The root-knot nematode, of the genus Meloidogyne, is dispersed throughout the world, being considered the most important among phytoparasitic nematodes. The damage caused by these herbivoresis due to the attack of the plant roots, thus causing the formation of galls that hinder the absorption and translocation of water and nutrients by the root system. Using knowledge about the existence of two hypotheses that explain the process of plant choice by herbivorous organisms, we try to understand whether the process of parasitism in plants, caused by root-knot nematodes, follows any of these hypotheses. The first, the plant vigor hypothesis, establishes that herbivores should exhibit better performance when they feed on vigorously growing plant individuals, that is, plants with an abundance of resources for their growth. The second is the plant stress hypothesis, which postulates that plants under physiological stress would be less able to produce defenses, as they would invest energy and resources mainly in maintaining homeostasis. Thus, this work has the general objective of testing whether the induction of water stress in host plants decreases the performance of root-knot nematodes of the species M. javanica and M. incognita, which would be of potential applicability in the management and control of these parasites. For this, tomato plants(S. lycopersicum) were inoculated with nematodes and treatments, control and waterstress were established when receiving amounts of water equivalent to 60% and 30% of field capacity, respectively. After 40 days of experiment, data on development and reproduction (egg mass, total eggs and eggs per egg mass)of nematodes and hatching parameters of the F1 generation were collected. It was observed that water stress in the plants was not enough to significantly affect egg mass production in any of the studied Meloidogyne species. However, the performance of the species M. javanica parasitizing plants subjected to water stress was affected, as the total number of eggs, the proportion of eggs per mass and hatching of juveniles was significantly reduced, in addition to the delay in hatching time. On the other hand, the performance of M. incognita was similar when parasitizing healthy and stressed plants. Our work demonstrated that different species can present different behaviors under the same stressful conditions, but that for certain species of Meloidogyne, the induction of stressful conditions in the host plants, aswas the case of water stress, can be used as a promising and efficient management alternative.