Selection for Meloidogyne incognita virulence against resistance genes from tomato and pepper and specificity of the virulence/resistance determinants

Experiments were designed to analyze the relationships between the root-knot nematode Meloidogyne incognita and resistant tomato and pepper genotypes. From a natural avirulent isolate, near-isogenic nematode lineages were selected with virulence either against the tomato Mi resistance gene or the pepper Me3 resistance gene. Despite the drastic selection pressure used, nematodes appeared unable to overcome the pepper Mel gene, therefore suggesting some differences in the resistance conferred by Mel and Me3 in this species. Nematodes virulent on Mi-resistant tomatoes were not able to reproduce on Mel-resistant nor on Me3-resistant peppers, and nematodes virulent on Me3-resistant peppers were not able to reproduce on Mi-resistant tomatoes nor on Mel-resistant peppers. These results clearly demonstrate the specificity of M. incognita virulence against resistance genes from both tomato and pepper, and indirectly suggest that gene-for-gene relationships could occur between these two solanaceous crops and the nematode.