Genetic and physical mapping of new EST-derived SSRs on the A and B genome chromosomes of wheat |
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Authors: | A Gadaleta A Giancaspro S L Giove S Zacheo G Mangini R Simeone A Signorile A Blanco |
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Institution: | (1) Department of Agro-Forestry and Environmental Biology and Chemistry, University of Bari, Via Amendola 165/A, 70126 Bari, Italy |
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Abstract: | The availability of genetic maps and phenotypic data of segregating populations allows to localize and map agronomically important
genes, and to identify closely associated molecular markers to be used in marker-assisted selection and positional cloning.
The objective of the present work was to develop a durum wheat intervarietal genetic and physical map based on genomic microsatellite
or genomic simple sequence repeats (gSSR) markers and expressed sequence tag (EST)-derived microsatellite (EST-SSR) markers.
A set of 122 new EST-SSR loci amplified by 100 primer pairs was genetically mapped on the wheat A and B genome chromosomes.
The whole map also comprises 149 gSSR markers amplified by 120 primer pairs used as anchor chromosome loci, two morphological
markers (Black colour, Bla1, and spike glaucousness, Ws) and two seed storage protein loci (Gli-A2 and Gli-B2). The majority of SSR markers tested (182) was chromosome-specific. Out of 275 loci 241 loci assembled in 25 linkage groups
assigned to the chromosomes of the A and B genome and 34 remained unlinked. A higher percentage of markers (54.4%), localized
on the B genome chromosomes, in comparison to 45.6% distributed on the A genome. The whole map covered 1,605 cM. The B genome
accounted for 852.2 cM of genetic distance; the A genome basic map spanned 753.1 cM with a minimum length of 46.6 cM for chromosome
5A and a maximum of 156.2 cM for chromosome 3A and an average value of 114.5 cM. The primer sets that amplified two or more
loci mapped to homoeologous as well as to non-homoeologous sites. Out of 241 genetically mapped loci 213 (88.4%) were physically
mapped by using the nulli-tetrasomic, ditelosomic and a stock of 58 deletion lines dividing the A and B genome chromosomes
in 94 bins. No discrepancies concerning marker order were observed but the cytogenetic maps revealed in some cases small genetic
distance covered large physical regions. Putative function for mapped SSRs were assigned by searching against GenBank nonredundant
database using TBLASTX algorithms. |
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