Identification of a randomly amplified polymorphic DNA marker linked to the Fom 2 Fusarium wilt resistance gene in muskmelon MR-1

Resistance to Fusarium oxysporum f. sp. melonis race 1 (causal agent of Fusarium wilt) in Cucumis melo (muskmelon) is controlled by the dominant gene Fom 2. Bulked segregant and random amplified polymorphic DNA (RAPD) analyses were employed to identify genetic markers linked to race 1 Fusarium wilt resistance. DNA was isolated from pooled (bulked) susceptible or resistant plant tissue from an F2 population of a susceptible AY X resistant MR-1 cross that segregated for race 1 resistance. Bulks from resistant plants were composed of both homozygous and heterozygous individuals and also pure homozygous individuals, determined by analysis of F3 populations. After screening the DNA from bulked resistant and susceptible plants by PCR with 320 decamer primers, one primer, 5' CCC CTC GAA T 3', produced a 1.6-kb fragment in the resistant bulks that was absent from the susceptible bulks. Using this primer to screen individual F2 plants, the outcome of 92 of 94 individual host-pathogen interactions was correctly predicted. Nine susceptible and three resistant commercial cultivars also were screened with this primer. The 1.6-kb fragment was not amplified using DNA from any of these cultivars. This is the first report of a RAPD marker linked to resistance to Fusarium wilt in muskmelon