Molecular characterization of the sex determination locus in Carica papaya L

A genetic map of papaya (Carica papaya L.) was constructed using 54 F2 plants derived from cultivars Kapoho and SunUp. Fifteen hundred and thirteen AFLP markers, together with the papaya ring spot virus coat protein marker, morphological sex type, and fruit flesh color were mapped into 12 linkage groups at an LOD score of 5.0 and recombination frequency of 0.25. The number of markers per linkage group ranged from 27 to 414, and the length ranged from 86.2 to 865.2 cM. However, the large differences in length of the linkage group were not caused by translocation during meiosis. The 12 major linkage groups covered a total length of 3464.1 cM, with an average distance of 2.3 cM between adjacent markers. This map revealed that around the sex locus, the recombination was highly suppressed and the cytosines were highly methylated. More sex co-segregating markers were generated from AT rich selective nucleotide primers than GC rich primers, and the biggest marker cluster occurred around the sex locus. The sex co-segregating marker W 11 identified four positive clones, which could be starting points to clone the sex determination gene.