A METHOD TO MEASURE GENETIC-DISTANCE BETWEEN ALLOGAMOUS POPULATIONS OF ALFALFA (MEDICAGO-SATIVA) USING RAPD MOLECULAR MARKERS

Alfalfa (Medicago sativa L.) is a forage legume of world-wide importan ce whose both allogamous and autotetraploid nature maximizes the genet ic diversity within natural and cultivated populations. This genetic d iversity makes difficult the discrimination between two related popula tions. We analyzed this, genetic diversity by screening DNA from indiv idual plants of eight cultivated and natural populations of M. sativa and M. falcata using the RAPD method. A high level of genetic variatio n was found within and between populations. Using five primers, 64 int ense bands were scored as present or absent across all populations. Mo st of the loci were revealed to be highly polymorphic whereas very few population-specific polymorphisms were identified. From these observa tions, we adopted a method based on the Roger's genetic distance betwe en populations using the observed frequency of bands to discriminate p opulations pairwise. Except for one case, the between-population dista nces were all significantly different from zero. We have also determin ed the minimal number of bands and individuals required to test for th e significance of between-population distances.