No abstract

Orobanche cumana Wallr., an obligate root parasite of sunflower can cause severe damage to this crop. The genetic diversity obtained with random amplified polymorphic DNA (RAPD) and amplified fragment length polymorphism (AFLP) on two Orobanche populations were compared. Nei and Li distance matrices obtained with both methods among the two populations were correlated significantly according to Mantel's test and could partition the populations. The sampling variance of genetic distances within and among populations estimated using bootstrap procedure were not significantly different between the two techniques. The principal difference between the two techniques is that AFLP markers gave a higher degree of resolution for discriminating closely related germplasm than RAPD.

Three experimental breeding populations, created by pooling four to five natural populations of perennial ryegrass, were used to indicate the effect of sampling and pooling on the retention of genetic variation. Conservation of allelic multiplicity and genotypic frequencies was observed using allelic frequencies measured on six isozyme markers. We observed that by bulking four or five natural populations, represented respectively by 25 or 20 plants, in a large polycross design, the allelic and genotypic frequencies of the original mother-plants were conserved. There was no loss of rare alleles (0.01