CONSTRUCTION OF A BASIC GENETIC-MAP FOR ALFALFA USING RFLP, RAPD, ISOZYME AND MORPHOLOGICAL MARKERS

The genetic map for alfalfa presented here has eight linkage groups re presenting the haploid chromosome set of the Medicago species. The gen etic map was constructed by ordering the linkage values of 89 RFLP, RA PD, isozyme and morphological markers collected from a segregating pop ulation of 138 individuals. The segregating population is self-mated p rogeny of an F1 hybrid plant deriving from a cross between the diploid (2n = 2x = 16) yellow-flowered Medicago sativa ssp. quasifalcata and the diploid (2n = 2x = 16) blue-flowered M. sativa ssp. coerulea. The inheritance of many traits displayed distorted segregation, indicating the presence of lethal loci in the heterozygotic parent plants. In sp ite of the lack of uniform segregation, linkage groups could be assign ed and the order of the markers spanning >659 centimorgans could be un ambiguously determined. This value and the calculated haploid genome s ize for Medicago (1n = 1x = 1.0 x 10(9) bp) gives a ratio of <1500 kb per centimorgan.