Características estruturais de galhas induzidas por Meloidogyne incognita em plantas de tomate e alface

Abstract

Vegetables are essential for both food supply and the economy in Brazil. Among the main challenges in horticultural production are root-knot nematodes of the genus Meloidogyne, which impair the root system, reduce productivity, and affect the commercial quality of crops. Among the most widely cultivated vegetables, lettuce (Lactuca sativa L.) and tomato (Solanum lycopersicum L.) stand out, presenting a wide diversity of cultivars with different levels of susceptibility or resistance to nematodes. Root-knot nematodes induce morphological, anatomical, and physiological changes in the roots, resulting in the formation of galls associated with the differentiation of giant cells, disorganization of vascular tissues, and high metabolic demand. In this context, the present study aims to understand the morphological, anatomical, and cellular development of resistant and susceptible cultivars of lettuce and tomato infected by Meloidogyne incognita, evaluating the degree of root infestation as well as the morphological and anatomical changes induced by galls, in order to contribute to the improvement of agricultural practices and the sustainable management of crops. Susceptibility to infection, observed in the lettuce cultivar Regina and the tomato cultivar Santa Clara, was evidenced by reduced development of both the aerial parts and the root system. In contrast, the resistant cultivars, lettuce Mimosa and tomato COMPACK, maintained satisfactory growth and productive capacity even after pathogen inoculation. Gall formation occurred as a result of hyperplasia and hypertrophy processes, associated with the establishment of giant cells, leading to disorganization of the vascular cylinder. The results demonstrate that the genetic resistance present in the Mimosa and COMPACK cultivars, although it does not prevent initial infection, is effective in restricting nematode development. Thus, despite structural alterations in root tissues, the reduced number of galls does not compromise plant development.