Development of IRAP- and REMAP-derived SCAR markers for marker-assisted selection of the strip rust resistance gene Yr15 derived from wild emmer wheat

Stripe rust (Pucinia striformis f.sp. tritici) is one of the most important fungal diseases of wheat, found on all continents and in over 60 countries. Wild emmer wheat, Triticum dicoccoides, which is the tetraploid progenitor of durum wheat, is a valuable source of novel stripe rust resistance genes for wheat breeding. T. dicoccoides G25 accession carries Yr15, a gene on chromosome arm 1BS. Yr15 confers resistance to all known stripe rust isolates; it is also effective in introgressed durum and bread wheat. Retrotransposons generate polymorphic insertions, which can be scored as Mendelian markers with techniques including REMAP and IRAP. Six REMAP and IRAP-derived SCAR markers were developed using 1256 F2 plants derived from crosses of the susceptible T. durum accession D447 with its resistant BC3F9 and BC3F10 (B9 and B10) near isogenic lines, which carried Yr15 introgressed from G25. The nearest markers segregated 0.1 cM proximally and 1.1 cM distally to Yr15. These markers were also mapped and validated at the same position in another independent 500 F2 plants derived from crosses of B9 and B10 with the susceptible cultivar Langdon. SCAR270 and SCAR790, surrounding Yr15 at an interval of 1.2 cM, were found to be reliable and robust co-dominant markers in a wide range of wheat lines and cultivars with and without Yr15. These markers are useful tags in marker-assisted wheat breeding programs aiming to incorporate Yr15 into elite wheat lines and cultivars for durable and broad-spectrum resistance against stripe rust.Peer reviewe

Towards positional cloning of the stripe rust resistance gene YR15, derived from wild emmer wheat

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Application of CAPS markers for genomic studies in wild emmer wheat

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Evaluation of marker-assisted selection for the stripe rust resistance gene Yr15, introgressed from wild emmer wheat.

Stripe rust disease is caused by the fungus Puccinia striiformis f. sp. tritici and severely threatens wheat worldwide, repeatedly breaking resistance conferred by resistance genes and evolving more aggressive strains. Wild emmer wheat, Triticum dicoccoides, is an important source for novel stripe rust resistance (Yr) genes. Yr15, a major gene located on chromosome 1BS of T. dicoccoides, was previously reported to confer resistance to a broad spectrum of stripe rust isolates, at both seedling and adult plant stages. Introgressions of Yr15 into cultivated T. aestivum bread wheat and T. durum pasta wheat that began in the 1980s are widely used. In the present study, we aimed to validate SSR markers from the Yr15 region as efficient tools for marker-assisted selection (MAS) for introgression of Yr15 into wheat and to compare the outcome of gene introgression by MAS and by conventional phenotypic selection. Our findings establish the validity of MAS for introgression of Yr15 into wheat. We show that the size of the introgressed segment, defined by flanking markers, varies for both phenotypic selection and MAS. The genetic distance of the MAS marker from Yr15 and the number of backcross steps were the main factors affecting the length of the introgressed donor segments. Markers Xbarc8 and Xgwm493, which are the nearest flanking markers studied, were consistent and polymorphic in all 34 introgressions reported here and are therefore the most recommended markers for the introgression of Yr15 into wheat cultivars. Introgression directed by markers, rather than by phenotype, will facilitate simultaneous selection for multiple stripe rust resistant genes and will help to avoid escapees during the selection process

Evaluation of marker-assisted selection for the stripe rust resistance gene Yr15, introgressed from wild emmer wheat

Stripe rust disease is caused by the fungus Puccinia striiformis f. sp. tritici and severely threatens wheat worldwide, repeatedly breaking resistance conferred by resistance genes and evolving more aggressive strains. Wild emmer wheat, Triticum dicoccoides, is an important source for novel stripe rust resistance (Yr) genes. Yr15, a major gene located on chromosome 1BS of T. dicoccoides, was previously reported to confer resistance to a broad spectrum of stripe rust isolates, at both seedling and adult plant stages. Introgressions of Yr15 into cultivated T. aestivum bread wheat and T. durum pasta wheat that began in the 1980s are widely used. In the present study, we aimed to validate SSR markers from the Yr15 region as efficient tools for marker-assisted selection (MAS) for introgression of Yr15 into wheat and to compare the outcome of gene introgression by MAS and by conventional phenotypic selection. Our findings establish the validity of MAS for introgression of Yr15 into wheat. We show that the size of the introgressed segment, defined by flanking markers, varies for both phenotypic selection and MAS. The genetic distance of the MAS marker from Yr15 and the number of backcross steps were the main factors affecting the length of the introgressed donor segments. Markers Xbarc8 and Xgwm493, which are the nearest flanking markers studied, were consistent and polymorphic in all 34 introgressions reported here and are therefore the most recommended markers for the introgression of Yr15 into wheat cultivars. Introgression directed by markers, rather than by phenotype, will facilitate simultaneous selection for multiple stripe rust resistant genes and will help to avoid escapees during the selection process

Evaluation of marker-assisted selection for the stripe rust resistance gene Yr15, introgressed from wild emmer wheat

201

Evolution of the Yr15 region in the Poideae

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