Fine mapping of the red plant gene R1 in upland cotton (Gossypium hirsutum)

Sub 16 is a substitution line with G. hirsutum cv. TM-1 genetic background except that the 16th chro-mosome (Chr. 16) is replaced by the corresponding homozygous chromosome of G. barbadense cv. 3-79, and T586 is a G. hirsutum multiple gene marker line with 8 dominant mutation genes. The R1 gene for anthocyanin pigmentation was tagged in Chr. 16 in T586. The objective of this research was to screen SSR markers tightly linked with R1 by using the F2 segregating population containing 1259 plants derived from the cross of Sub 16 and T586 and the backbone genetic linkage map from G. hir-sutum×G. barbadense BC1 newly updated by our laboratory. Genetic analysis suggested that the seg-regation ratio of red plants in the F2 population fit Mendelian 1:2:1 inheritance, confirming that the red plant trait was controlled by an incomplete dominance gene. Preliminary mapping of R1 was conducted using 237 randomLy selected F2 individuals and JoinMap v3.0 software. Then, a fine map of R1 was constructed using the F2 segregating population containing 1259 plants, and R1 was located between NAU4956 and NAU6752, with only 0.49 cM to the nearest maker loci (NAU6752). These results pro-vided a foundation for map-based cloning of R1 and further development of cotton cultivars with red fibers by transgenic technology.