Supplanting resistance of the Mi gene by root-knot nematode in industrial tomato in the Cerrado in Goias State of Brazil/Suplantacao de resistencia do gene Mi por nematoide-das-galhas em tomate industrial no Cerrado de Goias, Brasil

Problems with root-knot nematodes, caused by genus Meloidogyne, can be controlled through the introduction of resistance genes in commercial varieties of tomatoes. However, plants of the hybrid 'Heinz 9992 'for industrial processing, carrying the Mi gene, were reported with their roots severely infected in experimental cultivation in Goias State of Brazil with symptoms typical of galls caused by Meloidogyne spp. After dissecting the galls present in the root samples, the females of the nematodes were removed and afterwards, performed the analysis of the perineal pattern and the biochemical characterization by electrophoresis of isoenzymes, besides the pathogenicity test. The pathogen analyzed was identified as Meloidogyne incognita. The pathogenicity test confirmed the supplanting resistance of the tomato hybrid with the Mi gene by this virulent population of M. incognita. Key words: Solanum lycopersicum, Meloidogyne incognita, virulence, vegetables. Problemas causados pelos nematoides-das-galhas, pertencentes ao genero Meloidogyne podem ser controlados com a introducao de genes de resistencia em cultivares comerciais de tomateiro. No entanto, plantas do hibrido 'Heinz 9992' adequadas ao processamento industrial, portadoras do gene Mi, foram encontradas com suas raizes severamente infectadas, em um cultivo experimental no municipio de Morrinhos (GO) com sintomas tipicos de galhas causadas por Meloidogyne spp. Apos dissecar as galhas presentes nas amostras de raizes, as femeas do nematoide foram retiradas para a analise do padrao perineal e a caracterizacao bioquimica por eletroforese de isoenzimas, alem do teste de patogenicidade. O patogeno em estudo foi identificado como Meloidogyne incognita. O teste de patogenicidade confirmou que ocorreu a suplantacao de resistencia do hibrido de tomateiro, portador do gene Mi, por esta populacao virulenta de M. incognita. Palavras-chave: Solanum lycopersicum, Meloidogyne incognita, virulencia, hortalicas.