RESUMO
Characterization of nearly 1,000 cultivated potato accessions with simple sequence repeats (SSRs; also referred to as microsatellites) has allowed the identification of a reference set of SSR markers for accurate and efficient genotyping. In addition, 31 SSRs are reported here for a potato genetic map, including new map locations for 24 of them. A first criterion for this proposed reference set was ubiquity of the SSRs in the eight landrace cultivar groups of the potato, Solanum tuberosum. All SSRs tested in the present study displayed the same allele phenotypes and allele size range in the diverse germplasm set as in the advanced potato cultivar germplasm in which they were originally discovered. Thirteen of 13 SSR products from all cultivar groups are shown to cross-hybridize with the corresponding SSR product of the source cultivar to ascertain sequence homology. Other important SSR selection criteria are quality of amplification products, locus complexity, polymorphic index content, and well-dispersed location on a potato genetic map. Screening of 156 SSRs allowed the identification of a highly informative and user-friendly set comprising 18 SSR markers for use in characterization of potato genetic resources. In addition, we have identified true- and pseudo-multiplexing SSRs for even greater efficiency.
Assuntos
Genótipo , Repetições de Microssatélites/genética , Solanum tuberosum/genética , Alelos , Marcadores Genéticos , Polimorfismo Genético , Sequências Repetitivas de Ácido NucleicoRESUMO
The ancestor of barley (Hordeum vulgare subsp. spontaneum) may be a source of novel alleles for crop improvement. We developed a set of recombinant chromosome substitution lines (RCSLs) using an accession of H. vulgare subsp. spontaneum (Caesarea 26-24, from Israel) as the donor and Hordeum vulgare subsp. vulgare 'Harrington' (the North American malting quality standard) as the recurrent parent via two backcrosses to the recurrent parent, followed by six generations of selfing. Here we report (i) the genomic architecture of the RCSLs, as inferred by simple sequence repeat (SSR) markers, and (ii) the effects of H. vulgare subsp. spontaneum genome segment introgressions in terms of three classes of phenotypes: inflorescence yield components, malting quality traits, and domestication traits. Significant differences among the RCSLs were detected for all phenotypes measured. The phenotypic effects of the introgressions were assessed using association analysis, and these were referenced to quantitative trait loci (QTL) reported in the literature. Hordeum vulgare subsp. spontaneum, despite its overall inferior phenotype, contributed some favorable alleles for agronomic and malting quality traits. In most cases, the introgression of the ancestral genome resulted in a loss of desirable phenotypes in the cultivated parent. Although disappointing from a plant breeding perspective, this finding may prove to be a useful tool for gene discovery.
Assuntos
Cromossomos de Plantas/genética , Hordeum/genética , Alelos , Mapeamento Cromossômico , Cruzamentos Genéticos , Genoma de Planta , Genótipo , Hordeum/crescimento & desenvolvimento , Repetições de Microssatélites , Fenótipo , Característica Quantitativa Herdável , Recombinação GenéticaRESUMO
Gliricidia sepium provides a variety of products important for rural communities in tropical countries. Native populations in Meso-America currently form an important source of seed for distribution to farmers, but concerns centre on mechanisms which may lead to their genetic erosion, including anthropogenic dispersal and subsequent introgression from the related species, G. maculata. Populations of Gliricidia were examined genetically using approaches based on the polymerase chain reaction to test for interspecific hybridization and introgression between G. sepium and G. maculata. Analysis involved 13 RAPD and two RFLP-PCR markers which were identified to have species-diagnostic distributions. Data from both approaches corresponded and indicated three locations where multilocus genotypes were consistent with an hybrid origin. Data at one of these sites was consistent with introgression following hybridization. The hybrid origin of populations was supported by the intermediate geographical location of these sites to 'pure' populations of each species. Analysis of maternally inherited organellar DNA, which involved the detection of SSCPs in mitochondrial DNA amplification products, allowed further delineation of genetic structure among Gliricidia populations. Mitochondrial data indicated a high degree of organelle differentiation between sampled locations and identified G. sepium- and G. maculata-diagnostic haplotypes. This data supported the interpretation of genetic structure based on RAPDs and RFLP-PCR. In addition, cytonuclear analysis allowed the directionality of gene transfer during the formation of hybrid populations to be described. Despite evidence for the occurrence of interspecific hybridization and introgression in Gliricidia, important resource populations of G. sepium on the Pacific coast appear to have retained their genetic integrity. Implications in terms of the conservation and utilization of genetic resources within the genus are discussed.
Assuntos
Fabaceae/genética , Plantas Medicinais , Reação em Cadeia da Polimerase/métodos , Árvores/genética , Sequência de Bases , América Central , DNA Mitocondrial/genética , DNA de Plantas/genética , Fabaceae/classificação , Marcadores Genéticos , Variação Genética , Hibridização Genética , México , Dados de Sequência Molecular , Polimorfismo de Fragmento de Restrição , Polimorfismo Conformacional de Fita Simples , Técnica de Amplificação ao Acaso de DNA Polimórfico , Sitios de Sequências Rotuladas , Especificidade da Espécie , Árvores/classificaçãoRESUMO
Randomly amplified polymorphic DNA (RAPD), and a mitochondrial marker based on amplification of the V7 region of the mitochondrial small ribosomal RNA (srRNA) gene, were used to partition genetic variation within a single population of Gliricidia sepium sampled from Guatemala. Seventeen per cent of the variation detected with RAPDs was partitioned among subpopulations and indicated a greater level of discrimination than previously detected with isozymes. Cluster analysis indicated a direct relationship between this variation and the geographical distance between subpopulations. A polymorphism identified within the maternally inherited mitochondrial V7 srRNA product, which relied on digestion with restriction endonucleases, confirmed the genetic subdivision identified with RAPDs, and suggested a relatively limited role for seed in gene dispersal.