AN RFLP-BASED GENETIC-MAP OF PEARL-MILLET (PENNISETUM-GLAUCUM)

Analysis of a sample of diverse pearl millet genotypes with 200 genomi c DNA probes revealed this crop species to be extremely polymorphic. A mong these genotypes, 85% of probes detected polymorphism using only t wo restriction enzymes, with an average pair-wise polymorphism between all of the probe-enzyme combinations of 56%. Two crosses were employe d to construct an RFLP-based genetic map. In an intervarietal F-2 popu lation, derived from a single F-1 plant, 181 loci were placed on a lin kage map. The total length of this map, which comprised seven linkage groups, was 303 cM and the average map distance between loci was about 2 cM, although a few intervals in excess of 10 cM were present at the ends of a few linkage groups. Very few clones, including those which hybridized to more than one copy, detected more than one locus in the pearl millet genome. The analysis was complicated initially because 83 of the 181 loci mapped to a single linkage group. Analysis of a secon d cross identified a probable translocation breakpoint in the middle o f this large linkage group.