Microsatellite diversity at 18 loci was analysed in 94 individual plants of 10 wild barley, Hordeum spontaneum (C. Koch) Thell., populations sampled from Israel across a southward transect of increasing aridity. Allelic distribution in populations was not distributed randomly. Estimates of mean gene diversity were highest in stressful arid-hot environments. Sixty-four per cent of the genetic variation was partitioned within populations and 36% between populations. Associations between ecogeographical variables and gene diversity, H(e), were established in nine microsatellite loci. By employing principle component analysis we reduced the number of ecogeographical variables to three principal components including water factors, temperature and geography. At three loci, stepwise multiple regression analysis explained significantly the gene diversity by a single principal component (water factors). Based on these observations it is suggested that simple sequence repeats are not necessarily biologically neutral.

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The genetic diversity produced by the amplified fragment length polymorphism (AFLP) method was studied in 94 genotypes of wild barley, Hordeum spontaneum (C. Koch) Thell., originating from ten ecologically and geographically different locations in Israel. Eight primer pairs produced 204 discernible loci of which 189 (93%) were polymorphic. Each genotype had a unique banding profile and the genetic similarity coefficient varied between 0.74 and 0.98. The phenogram generated from these similarities by the UPGMA method did not group genotypes strictly according to their geographical origin, which pattern was also seen in the principal coordinate (PCO) plot. Genetic diversity was larger within (69%) than among (31%) populations. Associations between ecogeographical variables and the mean gene diversity were found at one primer pair. The results are discussed and compared with data obtained by the simple sequence repeat (SSR) method.

Populations of wild barley, Hordeum spontaneum (C. Koch), originating from 10 ecologically and geographically different sites in Israel, were assessed for genome size. Measurements were obtained by flow cytometry using propidium iodide staining. Genome sizes ranged from 9.35 to 9.81 pg. Variance analysis indicated a significant difference between populations. Genome sizes were positively correlated with mean January temperature. Our results corroborate previous findings of intraspecific variation in genome size from different plant species. The positive correlations between climate and genome size suggest that the latter is adaptive and determined by natural selection.

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Developing resistance to powdery mildew, Erysiphe graminis f.sp. hordei, is a major goal of many barley breeding programmes. Several resistance genes have been tagged or mapped with molecular markers. The mlo gene confers durable resistance towards all known isolates of the pathogen. In this study, RAPD markers and bulked segregant analysis were used to determine PCR-based markers linked to the mlolocus. Sixty doubled haploid hnes from a cross between an isogenic line of'Ingrid' carrying the mloW allele and a susceptible cv. 'Pokko' were used as plant material. Seven linked RAPD markers were found, the closest lying 1.6 cM away from the resistance gene. When eight barley varieties were assayed for the presence of this band, F4-980, it was found in the resistant varieties but not in the susceptible ones. The linked marker bands could be amplified from DNA-samples prepared by using three different methods, including a quick squash technique. PCR-based markers hnked to the resistance gene can be used as tools for selection in breeding programmes.

Populations of wild barley, Hordeum spontaneum (C. Koch), originating from 10 ecologically and geographically different sites in Israel, were assessed for genome size. Measurements were obtained by flow cytometry using propidium iodide staining. Genome sizes ranged from 9.35 to 9.81 pg. Variance analysis indicated a significant difference between populations. Genome sizes were positively correlated with mean January temperature. Our results corroborate previous findings of intraspecific variation in genome size from different plant species. The positive correlations between climate and genome size suggest that the latter is adaptive and determined by natural selection.