LINKAGE MAPPING IN DIPLOID ALFALFA (MEDICAGO-SATIVA)

A genome map of cultivated alfalfa was constructed using segregating r estriction fragment length polymorphisms (RFLPs) and random amplified polymorphic DNAs (RAPDs) in a diploid backcross population generated f rom noninbred parents. Among the 153 loci scored in 87 progeny, four s egregation ratios were observed for codominant and dominant markers: 1 :1, 1:2:1, 1:1:1:1, and 3:1. Deviations from expected Mendelian ratios (p < 0.05) were observed for 34% of the loci studied. A genome map wa s assembled from two separate linkage maps, each constructed from a su bset of the segregation data. One linkage map was constructed from 46 RFLP and 40 RAPD markers segregating 1:1 from the F-1 parent of the ba ckcross and the other linkage map was constructed from 33 RFLP and 28 RAPD markers segregating 1:1 from the recurrent parent. Sixteen loci w ith alleles segregating 1:1 from both parents were used as locus bridg es to align individual linkage groups between the two maps. The combin ed use of RFLPs and RAPDs was an effective method for developing an al falfa genome map.