Genetics of resistance to root-knot nematodes (Meloidogyne spp.) and breeding

Abstract

Genetic control of root-knot nematodes (RKNs) is an essential part of an integrated pest management as the use of resistant cultivars or rootstocks constitutes an easy, inexpensive, non-polluting method of control. This chapter presents the results achieved in understanding the genetic basis of coffee resistance to Meloidogyne spp. in Latin America, and in using genetic resistance in breeding programmes. The context of breeding for improving coffee resistance is firstly described. This is followed by an overview of works published on the identification of resistance sources among the genetic resources preserved in collections worldwide. The methods of resistance evaluation are discussed, and a standardized method is proposed in order to improve the reliability of resistance evaluation trials. The results obtained from studies on the genetics of resistance to RKNs are then given for the main species that parasitize coffee. So far, only one resistance gene has been identified and mapped in the coffee genome, the gene Mex-1 of resistance to M. exigua. The advent of large-scale molecular genomics will provide an access to previously inaccessible sources of genetic variation which could be exploited in breeding programmes. Strategies for using resistance sources are finally proposed in the context of coffee breeding.