Breeding and genetics of resistance to fusarium wilt in melon

Abstract

Melon Fusarium wilt (MFW), caused by Fusarium oxysporum f. sp. melonis (Fom), and is an important soil-borne disease of melon worldwide. The four known races 0, 1, 2, and 1,2 of this pathogen can be distinguished by infection on appropriate cultivars. Effective control can be achieved only through host resistance. Two major genes, Fom-1 and Fom-2, control resistance to races 0 and 2, and 0 and 1, respectively; whereas partial polygenic resistance to race 1,2 has been described. Fom-2 gene has been cloned, and the information generated from the LRR region sequences allowed the development of useful functional markers. Also, several molecular markers linked to Fom-1 gene have been reported; nevertheless, their usefulness was variety-dependent. These markers were used for the positional cloning of this gene. More recently this gene was isolated by a map-based cloning strategy. The sequence analysis revealed that Fom-1 belongs to the TIR-NB-LRR type. Resistance to Fom race 1,2 is complex and appears to be under polygenic control. Partial resistance to this race was detected in a few Far Eastern melon accessions, except for the breeding line BIZ where near-complete resistance was described. To date, quantitative trait loci (QTLs) associated with resistance to race 1,2 have been reported only in the line Isabelle and two other breeding lines BIZ and 03MFR001795. This chapter summarizes findings reported in the literature on genetic resources of resistance, molecular markers and quantitative trait loci for resistance to Fom.