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Key message : A stripe rust resistance gene YrZH22 was mapped by combined BSR-Seq and comparative genomics analyses to a 5.92 centimorgan (cM) genetic interval spanning a 4 Mb physical genomic region on wheat chromosome 4BL1. Abstract: Stripe rust, caused by Puccinia striiformis f. sp. tritici (PST), is one of the most destructive diseases of wheat and severely threatens wheat production worldwide. The widely grown Chinese wheat cultivar Zhoumai 22 is highly resistant to the current prevailing PST race CYR34 (V26). Genetic analysis of F and F recombinant inbred line (RIL) populations indicated that adult-plant stripe rust resistance in Zhoumai 22 is controlled by a single gene, temporarily designated YrZH22. By applying bulked segregant RNA-Seq (BSR-Seq), 7 SNP markers were developed and SNP mapping showed that YrZH22 is located between markers WGGB105 and WGGB112 on chromosome arm 4BL. The corresponding genomic regions of the Chinese Spring 4BL genome assembly and physical map of Aegilops tauschii 4DL were selected for comparative genomics analyses to develop nine new polymorphic markers that were used to construct a high-resolution genetic linkage map of YrZH22. YrZH22 was delimited in a 5.92 cM genetic interval between markers WGGB133 and WGGB146, corresponding to 4.1 Mb genomic interval in Chinese Spring 4BL and a 2.2 Mb orthologous genomic region in Ae. tauschii 4DL. The genetic linkage map of YrZH22 will be valuable for fine mapping and positional cloning of YrZH22, and can be used for marker-assisted selection in wheat breeding. [ABSTRACT FROM AUTHOR]

Photosynthesis of carbohydrates is the primary source of grain yield in wheat. Photosynthetic organs, especially flag leaves and awns play important roles in wheat growth and development. Genetic analysis of flag leaf posture, size and shape and presence/absence of awns was conducted using a set of 269 recombinant inbred lines (RILs) derived from Yanda1817 × Beinong6. Six agronomic traits comprising flag leaf angle (FLAN), flag leaf width (FLW), flag leaf length (FLL), the ratio of length/width of flag leaf (FLR), flag leaf area (FLA) and presence/absence of awns were evaluated in Shijiazhuang (2011, 2012 and 2013) and Beijing (2012). Using the available high-density single nucleotide polymorphism and simple sequence repeats (SSR) genetic linkage map, a total of 61 putative quantitative trait loci (QTL) for FLAN, FLW, FLL, FLR and FLA were detected on 16 of the 21 wheat chromosomes excluding 1D, 4B, 5D, 6A and 7A, with single QTL in different environments explaining 2.49-42.41 % of the phenotypic variation. Among the identified QTL, 17 were for FLAN, 11 for FLW, seven for FLL, 13 for FLR and 13 for FLA. Twenty-five (41 %) QTL were detected in at least two environments, while four QTL for FLW were detected in all environments. Thirty QTL were associated with higher number of flag leaf traits originated from Yanda1817 alleles, whereas the remaining 31 QTL were derived from Beinong6. In addition, pleiotropic effects were detected for QTL on chromosomes 2D, 3B, 4A, 4D, 5A, 5B, 6B, 6D and 7D that could serve as target regions for fine mapping and marker-assisted selection in wheat breeding programs. Genetic analysis revealed that the presence/absence of awns in the RIL population is controlled by the awn-inhibitor gene B1 linked to SSR marker Xgwm291 on the long arm of chromosome 5A. Our results also suggest that physiological traits FLL, FLW and FLA were significantly and positively correlated to spike length (SL), grain weight per spike and grain number per spike. FLR was significantly and positively related to SL but negatively related to grain width and grain thickness (GT). In addition, the awn trait was strongly and positively correlated to thousand grain weight, grain length and GT. [ABSTRACT FROM AUTHOR]

Key message: Spot blotch disease resistance gene Sb3 was mapped to a 0.15 centimorgan (cM) genetic interval spanning a 602 kb physical genomic region on chromosome 3BS. Abstract: Wheat spot blotch disease, caused by B. sorokiniana, is a devastating disease that can cause severe yield losses. Although inoculum levels can be reduced by planting disease-free seed, treatment of plants with fungicides and crop rotation, genetic resistance is likely to be a robust, economical and environmentally friendly tool in the control of spot blotch. The winter wheat line 621-7-1 confers immune resistance against B. sorokiniana. Genetic analysis indicates that the spot blotch resistance of 621-7-1 is controlled by a single dominant gene, provisionally designated Sb3. Bulked segregant analysis (BSA) and simple sequence repeat (SSR) mapping showed that Sb3 is located on chromosome arm 3BS linked with markers Xbarc133 and Xbarc147. Seven and twelve new polymorphic markers were developed from the Chinese Spring 3BS shotgun survey sequence contigs and 3BS reference sequences, respectively. Finally, Sb3 was mapped in a 0.15 cM genetic interval spanning a 602 kb physical genomic region of Chinese Spring chromosome 3BS. The genetic and physical maps of Sb3 provide a framework for map-based cloning and marker-assisted selection (MAS) of the spot blotch resistance. [ABSTRACT FROM AUTHOR]