Identification of SCAR markers linked to the Foc gene governing resistance to Fusarium oxysporum f. sp. cucumerinum in cucumber cv. SMR-18

Fusarium wilt, caused by Fusarium oxysporum f. sp. cucumerinum (FOC) is an important soil-borne disease of cucumber in several parts of the world. In this study, we employed amplified fragment length polymorphic (AFLP) markers along with bulked segregant analysis (BSA), in order to identify structural markers linked to the Foc gene that governs resistance to FOC races 1, 2 and 3 in the resistant cv. SMR-18. From the four AFLP markers originally identified at the BSA level, only one (E12M50 134 + T ) maintained a linkage in coupling phase against the F 2 mapping population. AFLP-mediated sequencing was employed in order to ensure the identification and sequencing of the truly linked AFLP fragment. This AFLP marker mapped at a distance of 6.0 cM from the Foc resistance locus and was successfully converted into two sequence-characterized amplified region (SCAR) co-dominant markers. SCAR marker SCE12M50 B produced a single fragment linked to Foc and behaved as a dominant marker, while SCE12M50 A amplified one strong fragment linked to Foc in parallel with a second faint fragment. The SCE12M50 B fragment physically maps on chromosome 2 and lies 1.64 Mb (7,0 cM) away from the microsatellite marker SSR03084, which is closely linked to Ccu locus that controls resistance to scab, caused by Cladosporium cucumerinum in cv. SMR-18.