Root-knot nematodes (RKNs), Meloidogyne spp., are considered, worldwide, as one of the main pathogens of solanaceous crops, including pepper (Capsicum spp.). Restrictions on the use of standard nematicides have motivated the development and use of resistant cultivars and rootstocks. Three genes in pepper, called Me1, Me3 and N, confer resistance to the three main RKN species (Meloidogyne incognita, Meloidogyne javanica and Meloidogyne arenaria). However, their effectiveness seems to be limited because nematode populations that have overcome the resistance have been found, leading to a search for new sources of resistance and strategies to preserve their effectiveness. In two greenhouses and over a 7-month growing period, we evaluated the resistance to M. incognita and the agronomic behaviour as rootstocks of nine pepper (Capsicum annuum) accessions – HDA330 (Me1 carrier), Serrano Criollo de Morelos, (Me3 carrier), Yolo Wonder (partially resistant) and another six accessions of unknown resistance originating from cultivars well adapted to the local growing conditions. The resistance conferred by the Me1 gene was more robust than that conferred by Me3. Resistance to M. incognita was found in four new accessions: P13, CTL, CT5, and P14. In P13, the level of resistance was similar to that of HDA330. The resistant accessions showed better agronomic behaviour than the susceptible accessions, which was most noticeable towards the final of the growing period. Some accessions constitute a potential resource for use in the genetic breeding of RKN-resistant rootstocks.

No abstract

Root‐knot nematodes (RKNs), Meloidogyne 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 (M. incognita, M. javanica and M. arenaria) 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 Meloidogyne 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 M. arenaria, M. javanica and M. incognita isolates. The M. arenaria and M. javanica isolates showed low pathogenicity to pepper, unlike the M. incognita 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 M. incognita isolates. The QR was also expressed when combined with the Me1 and Me3 genes, but presented additive genetic effects so that heterozygous F1 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.

In pepper (Capsicum annuum), the major genes (R‐genes) Me1 and Me3 confer resistance against root‐knot nematodes (Meloidogyne spp.). The combination of R‐genes and quantitative resistance factors in the same genotype is considered a good breeding strategy for increasing the durability of R‐genes. To ascertain this hypothesis, five pepper inbred lines, differing in their quantitative resistance level, were combined with Me1 or Me3 genes in F1 hybrids. The resistance of inbred lines and F1 hybrids was evaluated in a greenhouse with soil naturally infected by M. incognita in two successive growing years. In both years, lines carrying Me3 were less infected by the nematode when combined with quantitative resistance. An increase in nematode infection was observed in the second growing year in lines carrying Me1 or Me3, independently of quantitative resistance. The infection level recorded in inbred lines without R‐genes was similar in both years. The effectiveness of quantitative resistance controlling M. incognita is confirmed in greenhouse conditions, although the durability of Me1 and Me3 when combined with quantitative resistance factors was not seen to increase.