Genetic and QTL Mapping of Fusarium Wilt Race 1 Resistance in Cotton.

Fusarium oxysporum f.sp. vasinfectum (FOV) Atk. Sny & Hans causes a vascular wilt disease that significantly reduces yield in cotton (Gossypium spp.). Host-plant resistance can be highly effective in limiting FOV-induced yield loss. We conducted genetic and QTL analyses of FOV race 1 resistance by applying available molecular markers to F₂ and recombinant inbred line (RIL) interspecific mapping populations generated from the crosses Pima-S7 (G. barbadense L.) x cv Acala NemX (G. hirsutum L.) and Upland TM-1 (G. hirsutum) x Pima 3-79 (G. barbadense), respectively. Parents and populations were evaluated for disease severity based on foliar symptoms, and stem and root vascular staining, in three greenhouse artificial inoculation-tests and in one field test. QTL mapping and a set of 24 SSR markers indicated gene interactions and inheritance from nine cotton chromosomes, with major QTLs detected on five chromosomes (C06, C08, C011, C016, and C019). The FOV1 locus, previously identified in Pima-S7 x NemX using AFLP markers, was mapped to chromosome 16 and co-located with the Fov1-C016 QTL in the TM-1 x Pima 3-79 RIL. We conclude that this QTL has a significant role in conferring FOV race 1 resistance in different cotton backgrounds and should be a primary target for cotton breeding. Moreover, the set of 24 SSR markers may have utility for breeding FOV resistance into elite cultivars by marker-assisted selection.