Towards the deciphering of the genetic factors involved in durability of plant major resistance genes to root knot nematodes in pepper

Root-knot nematodes (RKNs), Meloidogyne spp., are extremely polyphagous plant parasites worldwide. Since the use of most chemical nematicides is being prohibited, genetic resistance is an efficient alternative way to protect crops against these pests. However, few resistance genes (Rgenes) are available and some nematode populations may become able to overcome them with time. Sustainable management of these valuable resources is thus a key point of R-gene durability. ln pepper (Capsicum annuum), Me3 is a dominant major R-gene, currently used in breeding programs, that controls M. arenaria, M. incognita and M. javanica, the three main RKNs species. It was introgressed in either a susceptible or a partially resistant (i.e., that shows reduced symptoms) genetic background in either homozygous or heterozygous allelic status. Doux Long des Landes (DLL) was used as susceptible recipient pepper line and Yolo Wonder (YW) as a partially resistant one. Challenging all these genotypes with a high inoculation pressure of an avirulent M. incognita isolate demonstrated that i) the efficiency of the R-gene in reducing the reproductive potential of RKNs is strongly affected by the plant genetic background, ii) the allelic status of the R-genes has no effect on nematode reproduction. These results highlight the primary importance of the choice of both the R-gene and the genetic background into which it is introgressed during the selection of new elite cultivars by plant breeders