Genetic diversity of four esterase loci in natural populations of Hordeum spontaneum C. Koch from Jordan.

The diversity of four esterase loci was studied electrophoretically in 690 individual spikes representing 12 populations of wild barley (Hordeum spontaneum C. Koch.) collected from central, peripheral and marginal regions of its distribution in Jordan. A minimum of 6, 10, 5 and 5 alleles were observed at the Est-1, Est-2, Est-4 and Est-5 loci, respectively. Est-2 and Est-4 were the most diverse loci (Hc=0.53±0.05 and 0.46±0.07, respectively). Est-5 was intermediate (Hc=0.33+0.07) and Est-1 was the lowest (Hc=0.22±0.04). Polymorphism was highest in the central populations (He=0.52±0.04), followed by the peripheral (He=0.40±0.05) and the marginal (He=0.22±0.05) populations. Average allelic diversity between (Gst=0.49) and within (Hs=0.51) populations reflects a high allelic differentiation among these populations. Log-linear analyses revealed that four two-locus terms and two three-locus terms were significantly associated (P<0.05). Geographical distances between populations were not significantly correlated with Nei's genetic similarity index (r=0.16; P<0.19). It is postulated that diversifying selection is a major factor in the population genetic differentiation of these esterase loci.