The potential of microsatellite markers for use in genetical studies in potato (Solanum tuberosum) was evaluated. Database searches revealed that microsatellite sequences were present in the non-coding regions of 24 potato genes. Twenty-two sets of primers were designed and products successfully amplified using 19 primer pairs. These were tested against a panel of 18 tetraploid potato cultivars. Four pairs of primers designed to amplify microsatellites from tomato were also used. Seven (including 2 of the tomato sequences) failed to reveal any variation in the accessions tested. Sixteen primer pairs did reveal polymorphism, detecting between 2 and 19 alleles at each locus. Of these, 3 gave rise to complex band patterns, suggesting that multiple polymorphic loci were being amplified using a single primer pair. Heterozygosity values ranged from 0.408 to 0.921. Phenetic analysis of the derived information allowed a dendrogram to be constructed depicting the relationships between the 18 potato cultivars. The potential of microsatellite markers for genetic analysis and satutory applications in potato is discussed in the context of these results. Furthermore, the potential of 'crossspecies amplification' is highlighted as an additional source of microsatellite markers for genetic research in potato.

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.

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.

Absence of dormancy and good malting quality are significant targets of many barley (Hordeum vulgare L.) breeding programs. Expression of dormancy is strongly affected by the environment, and malting quality assays are expensive. Both groups of characters would therefore be suitable for marker‐assisted selection. The objective of this study was to identify quantitative trait loci (QTL) controlling germination and malting quality characters in a cross between the spring barley genotypes ‘Blenheim’ and E224/3 as an initial step in the development of a marker‐assisted selection scheme. The characters were measured on a random sample of doubled haploid lines from the cross grown in replicated trials each year from 1989 to 1992. The QTL were revealed by regression analysis of the data with marker scores from 120 mapped polymorphic loci. The QTL controlling hot water extract were located on barley Chromosomes 2, 3, and 7. Milling energy was largely controlled by a factor on Chromosome 7, a region also associated with extract viscosity. The denso dwarfing gene on Chromosome 3 was associated with a reduction in grain N but this was found to be a dilution effect as the locus had previously been found to be associated with an increase in grain yield. The germination characters showed little relationship with each other, possibly reflecting different mechanisms of control.

Microsatellites are now firmly established as an informative marker system, with increasing popularity as a tool amongst molecular ecologists. We have developed a method of constructing an enriched microsatellite library for the tropical tree species Swietenia humilis Zucc. (Meliaceae). This method is based on a precloning enrichment of SSRs using synthetic oligonucleotide probes, bound to magnetic beads and hybridizing to complementary microsatellite core sequences in digested genomic DNA. Here we describe the isolation and characterization of 10 microsatellite loci that have been used to survey the genetic diversity within a natural population of S. humilis. A total of 97 alleles were identified with an average of 9.7 alleles over all loci. Very high levels of allelic polymorphism were detected at individual loci, with 23 alleles observed at the most variable. The mean observed heterozygosity was 0.415 (range 0.038‐0.815) exceeding levels of diversity detected in related species which used isozymes as the marker system. Subpopulation differentiation at a microgeographical scale was low (FST= 0.036) and the values of Nm, calculated from the allelic frequencies, were greater than 1 thus reflecting the extent of gene flow occurring between individual trees.

Microsatellites are now firmly established as an informative marker system, with increasing popularity as a tool amongst molecular ecologists. We have developed a method of constructing an enriched microsatellite library for the tropical tree species Swietenia humilis Zucc. (Meliaceae). This method is based on a precloning enrichment of SSRs using synthetic oligonucleotide probes, bound to magnetic beads and hybridizing to complementary microsatellite core sequences in digested genomic DNA. Here we describe the isolation and characterization of 10 microsatellite loci that have been used to survey the genetic diversity within a natural population of S. humilis. A total of 97 alleles were identified with an average of 9.7 alleles over all loci. Very high levels of allelic polymorphism were detected at individual loci, with 23 alleles observed at the most variable. The mean observed heterozygosity was 0.415 (range 0.038-0.815) exceeding levels of diversity detected in related species which used isozymes as the marker system. Subpopulation differentiation at a microgeographical scale was low (FST = 0.036) and the values of Nm, calculated from the allelic frequencies, were greater than 1 thus reflecting the extent of gene flow occurring between individual trees.

No abstract

Protoplast fusion allows the transfer of both mono- and polygenic traits between species that are sexually incompatible. This approach has particular relevance for potato, and somatic hybridisation has been used to introduce a range of disease resistance genes from sexually incompatible wild species into the cultivated potato gene pool. In addition, protoplast fusion allows the resynthesis of tetraploid genotypes from preselected diploid or dihaploid donor parents. A limiting factor for the efficient exploitation of this technology in potato breeding is the difficulty of unequivocally identifying nuclear hybrids (heterokaryons). In order to facilitate the identification of hybrids at an early stage following fusion, Randomly Amplified Polymorphic DNA markers (RAPDs) have been used to characterise molecularly both inter- and intra-specific somatic hybrids of potato. RAPD markers detect naturally occurring polymorphism in the donor genotypes and utilise short oligonucleotide primers of arbitrary nucleotide sequence in combination with the polymerase chain reaction (PCR). The exploitation of RAPDs in the characterisation of both somatic and sexual hybrids is discussed.