Thirty-nine genotypes of Hordeum spontaneum were selected from three geographically separated areas (southwestern, northern, and southeastern) of the Fertile Crescent. The lines were subject to AFLP (amplified fragment length polymorphism) analysis from which a similarity matrix was produced. A dendrogram of the data showed, with two exceptions, that the genotypes grouped together according to area of origin. This was confirmed by principal coordinate analysis in which the first principal coordinate separated the genotypes of the southwestern area from the other two areas, which in turn could be separated by the second principal coordinate. While genotypes from the same site of origin can exhibit very similar AFLP profiles, sharp genetic differences were detected between genotypes separated by relatively short distances. Thirty of the 39 genotypes were subjected to hydroculture salt tolerance tests. These were analysed for shoot Na+ content and carbon isotope composition (δ13C) after 4 weeks of treatment (100 mol∙m−3 NaCl). Shoot Na+ content and δ13C were highly correlated. Twelve AFLP markers were found to be associated with both shoot Na+ content and shoot δ13C and were also associated with site of origin ecogeographic data, particularly longitude. The most salt tolerant genotype came from Ilam in the southeastern area and the most salt sensitive genotype originated in the southwestern area. The 12 markers were partitioned into groups that showed significant associations within groups but no significant association between groups. In a multiple regression analysis, three AFLP markers, from separate groups, accounted for more than 60% of the variation for shoot Na+ content and δ13C. The results demonstrate the effectiveness of AFLP fingerprinting in genetic studies of complex traits at the wild species and (or) population level.

Segregation of 850 polymorphic AFLP (amplified fragment length polymorphism) fragments was followed in three different doubled haploid (DH) barley populations, Dicktoo x Morex (DM), Igri x Franka (IF) and Blenheim x E224/3 (BE), which had previously been used to construct linkage maps using other molecular markers. The final maps consisted of 310, 655 and 474 markers, of which 234, 194 and 376, respectively, were AFLPs. A comparison of profiles from the parental lines identified 51 similar-sized AFLPs segregating in both DM and IF populations, 20 in the DM and BE populations and 18 in the IF and BE populations. Eight segregated in all three. Analysis of the complete datasets for each of the populations using Joinmap V.2. indicated that in general terms each of the AFLPs which were polymorphic in more than one population mapped to the same genetic locus. The number of co-dominant markers segregating in a single population ranged from 6% for DM to 12.6% for IF. These results are discussed in the context of using AFLP in genetic linkage and diversity studies.

Wheat/Hordeum vulgare and wheat/H. chilense disomic chromosome addition lines have been used to locate genes influencing tolerance to salt to specific chromosomes of the H and Hd genomes of H. vulgare and H. chilense respectively. The addition lines were grown in hydroculture containing either 0 mol m3, 175 mol m3 or 200 mol m3 sodium chloride. Various growth and yield parameters were measured and comparisons were made both between species and between chromosomes. Nat vigour was found to have a major effect on tolerance to salt in the wheat/H. vulgare addition lines. Vigorous genotypes, in control conditions generally performed well in saline conditions. However, significant interactions between genotype and salt concentration were found and this indicated specific chromosomes with positive and negative effects. Genes with positive effects for salt tolerance were located to chromosomes 4H and 511 of H. vulgare and IH", 4H'' and 511ch of H. chilense. The genetic control of salt tolerance is discussed.

Amplified fragment length polymorphisms (AFLPs) produced with EcoRI and PstI both in combination with MseI restriction enzymes have been studied in the parents of four barley mapping populations. Averages of 15.9 and 18.7 polymorphic products per assay were produced for the EcoRI/MseI and PstI/MseI combinations, respectively. There was some evidence of interaction between cross combinations and restriction enzyme combinations, with PstI/MseI generating relatively more polymorphic products than EcoRI/MseI in the Blenheim x E224/3 cross combination, the least polymorphic of the four. Three hundred and ninety-eight AFLP products, using both restriction enzyme combinations, were generated in a doubled haploid population of 68 lines produced from the Blenheim x E224/3 cross. These were added to existing marker data for the cross to study the effects of incorporation of AFLPs produced by different restriction enzyme combinations upon genetic maps. Addition of the AFLP data resulted in greater genome coverage, both through linking previously separate groups and extensions to other groups. This increase in coverage appeared to result from AFLPs sampling some different regions of the genome compared to RAPDs and RFLPs, as the map distances spanned by the RAPD and RFLP linkage groups were similar with and without incorporation of AFLPs. There was also evidence that the EcoRI and PstI restriction enzymes sampled different regions of the genome. The revised maps were used in scanning for QTLs controlling a subset of 12 economically important traits measured in the cross. Overall, the QTLs accounted for an average of 53 per cent of the phenotypic variation for the characters. Positive and negative alleles were present in each parent for each character, apart from hot water extract corrected to 1.5 per cent nitrogen (HWEc). Several regions of the genome appeared to be involved in the control of several characters, notably chromosome 2, the denso locus on chromosome 3, the short arm of chromosome 5 and chromosome 7.Although there was considerable similarity to previous results of QTL mapping for the subset of characters, the greater genome coverage afforded by the inclusion of the AFLPs revealed some new QTL locations.Keywords: AFLPs, barley, genes, mapping, markers, QTL.Introduction this technology has been widely deployed in plants (Helentjaris & Burr, 1989). However, the RFLP AFLPS AND QUANTITATIVE TRAITS IN BARLEY 49& Vos, 1993). Two important aspects of a marker system's utility are: information content and multiplex ratio . Standard measures of diversity may be used to evaluate information content and the multiplex ratio is the number of loci simultaneously analysed per experiment. These two metrics have been used to compare RFLPs, AFLPs, SSRPs and RAPDs in common soybean and barley genotypes (Powell et a!., , 1995. Multiplex ratio and the diversity index were combined to provide an overall measure of marker utility defined as the Marker Index. To date, all comparative studies concur in identifying AFLP as an unique tec...

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