Nematode quantitative resistance conferred by the pepper genetic background presents additive effects and is stable against different isolates of [i]Meloidogyne incognita[/i]
Résumé
Root-knot nematodes (RKNs), [i]Meloidogyne[/i] spp., are a major disease problem in solanaceous crops worldwide, including pepper (Capsicum spp.). Genetic control provides an economically and environmentally sustainable protection alternative to soil fumigants. In pepper, resistance to the main RKN species ([i]M.incognita[/i],[i] M.javanica[/i] and [i]M.arenaria[/i]) is conferred by the major genes (R genes) Me1, Me3 and N. However, RKNs are able to develop virulence, thus endangering the efficiency of R genes. Quantitative resistance (QR) against [i]Meloidogyne[/i] spp. is expected to provide an alternative to R genes, or to be combined with R genes, to increase the resistance efficiency and durability in pepper. In order to explore the ability of QR to protect pepper against RKNs, five pepper inbred lines, differing in their QR level, were tested directly, or after combination with the Me1 and Me3 genes, for their resistance to a panel of[i] M.arenaria, M.javanica[/i] and [i]M.incognita[/i] isolates. The[i] M.arenaria[/i] and [i]M.javanica[/i] isolates showed low pathogenicity to pepper, unlike the [i]M.incognita[/i] isolates. The QR, controlled by the pepper genetic background, displayed a high resistance level with a broad spectrum of action, protecting pepper against Me3-virulent as well as avirulent [i]M.incognita[/i] isolates. The QR was also expressed when combined with the Me1 and Me3 genes, but presented additive genetic effects so that heterozygous F-1 hybrids proved less resistant than homozygous inbred lines. The discovery of this QR is expected to provide promising applications for preserving the efficiency and durability of nematode resistance.