Comparative diversity analysis of RFLPs and isozymes within and among populations of Hordeum vulgare ssp. spontaneum.

DNA restriction fragment length polymorphisms (RFLPs) and isozyme variation were surveyed in 268 accessions of a wild barley (Hordeum vulgare ssp. spontaneum) sampled from diverse ecogeographical areas in Israel and Iran. A total of 24 markers was used: 7 well characterized isozyme loci and 15 DNA probes which detected 17 putative loci and included three classes of DNA sequences (single copy, low copy and repetitive) representing all 7 barley chromosomes. Survey results indicated that both RFLPs and isozymes are highly polymorphic both within and among populations of this wild barley. The number of alleles per locus and average level of diversity do not differ between isozymes and RFLPs. However, the relative amounts of within vs. between population components vary greatly between these two sets of molecular markers. Isozymes demonstrated a larger amount of within population diversity, whereas RFLPs resolved a higher proportion of between population differentiation. Furthermore, RFLPs detected more heterozygosity than did isozymes. Both classes of markers resolved large numbers of multilocus combinations, the majority of which were represented by only one individual in the total sample. Up to 30% of the loci differ among individuals within populations, and about 50% of the loci differ among plants in different populations. While many important aspects of population diversity as determined by RFLPs are significantly correlated with those of isozymes, such correlation values are generally low, indicating that only a small proportion of the genetic variation detected by one class of markers can be predicted by the other.