Galhas de nematoides em hortaliças: estabelecimento, desenvolvimento, impactos nas características agronômicas e biocontrole

Abstract

Vegetable production is affected by nematodes, with Meloidogyne spp. (knot nematode), one of the main causes of losses in vegetable crops. This parasite is responsible for one of the most complex parasite/host relationships, due to the induction of feeding sites that function as a biological drain and the formation of galls with different shapes and sizes, being the main symptom of the infection. The present research presents in four articles how root-knot nematodes can affect the development of okra (Meloidogyne incognita), lettuce (M. javanica), parsley (M. incognita) and jiloeiro (M. incognita) crops, showing the impacts structural changes caused in the root anatomy by the induction of the giant cells that form the feeding site. In the cultures of okra and lettuce, there was no damage to their development caused by the root-knot nematode, while the inoculated cultures of parsley and eggplant had their development affected by this parasite. The galls were already detected after 18 DAI in the four cultures analyzed, being smaller in lettuce and parsley and larger in okra and eggplant, giant cells and the feeding site were also already noticed at that time, promoting the disorganization of the vascular system. Changes in the cell wall in relation to pectic and hemicellulosic compounds in the formation of giant cells were investigated in these cultures. In lettuce and eggplant crops, it was evaluated whether biological products using fungi (Trichoderma harzianum or Paecilomyces lilacinus, respectively) would be effective in controlling the root-knot nematodes M. javanica or M. incognita, respectively. In this study, T. harzianum was not effective in controlling the nematode in this lettuce cultivar, while the fungus P. lilacinus helped the eggplant to better withstand the parasitism and reduced the number of galls and nematodes. The results provide new perspectives for the understanding of nematode feeding in giant cells, especially in the face of changes in cell wall structure, as well as the pest biocontrol mechanism.