Enrichment of a papaya high-density genetic map with AFLP markers.

A high-density genetic linkage map of papaya, previously developed using an F2 mapping population derived from the intraspecific cross AU9 x SunUp, was enriched with AFLP markers. The comprehensive genetic map presented here spans 945.2 cM and covers 9 major and 5 minor linkage groups containing 712 SSR, 277 AFLP, and 1 morphological markers. The average marker density for the 9 major linkage groups is 0.9 cM between adjacent markers, and the total number of gaps >5 cM was reduced from 48 to 27 in the current map. AFLPs generated by EcoRI/MseI primer combinations were distributed throughout the 14 linkage groups and resulted in several large locus order rearrangements within the 9 major linkage groups. Integration of AFLP markers provided tighter linkage association between loci, leading to a reduction in map distance on LGs 1, 2, and 4, which were inflated in the previous map, and correction of the marker order on LG8. Suppression of recombination in the male-specific Y region (MSY) of LG1 is further validated by the addition of 27 sex co-segregating AFLP markers. A large region of distorted segregation surrounding the MSY spans 54.4 cM and represents approximately 71% of the linkage group. This comprehensive high-density genetic map provides a framework for mapping quantitative trait loci and for fine mapping as well as for comparative genomic studies of crop plant development and evolution.