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Key message: Novel wheat-rye 6RS small fragment translocation lines with powdery mildew resistance were developed, and the resistance gene PmW6RS was physically mapped onto 6RS-0.58–0.66-bin corresponding to 18.38 Mb in Weining rye. Rye (Secale cereale L., RR) contains valuable genes for wheat improvement. However, most of the rye resistance genes have not been successfully used in wheat cultivars. Identification of new rye resistance genes and transfer of these genes to wheat by developing small fragment translocation lines will make these genes more usable for wheat breeding. In this study, a broad-spectrum powdery mildew resistance gene PmW6RS was localized on rye chromosome arm 6RS using a new set of wheat-rye disomic and telosomic addition lines. To further study and use PmW6RS, 164 wheat-rye 6RS translocation lines were developed by 60Coγ-ray irradiation. Seedling and adult stage powdery mildew resistance analysis showed that 106 of the translocation lines were resistant. A physical map of 6RS was constructed using the 6RS translocation and deletion lines, and PmW6RS was localized in the 6RS-0.58–0.66-bin, flanked by markers X6RS-3 and X6RS-10 corresponding to the physical interval of 50.23–68.61 Mb in Weining rye genome. A total of 23 resistance-related genes were annotated. Nine markers co-segregate with the 6RS-0.58–0.66-bin, which can be used to rapidly trace the 6RS fragment carrying PmW6RS. Small fragment translocation lines with powdery mildew resistance were backcrossed with wheat cultivars, and 39 agronomically acceptable homozygous 6RS small fragment translocation lines were obtained. In conclusion, this study not only provides novel gene source and germplasms for wheat resistance breeding, but also laid a solid foundation for cloning of PmW6RS. [ABSTRACT FROM AUTHOR]

Key message: A wheat-rye 4R chromosome disomic addition line with resistances to powdery mildew, stripe rust, sharp eyespot and high kernel number per spike was developed and characterized by molecular cytogenetic method as novel resistant germplasm.Abstract: Rye (Secale cereale L.), a close relative of common wheat, is an important and valuable gene donor with multiple disease resistance for wheat improvement. However, resistance genes derived from rye have successively lost resistance to pathogens due to the coevolution of pathogen virulence and host resistance. Development and identification of new effective resistance gene sources from rye therefore are of special importance and urgency. In the present study, a wheat-rye line WR35 was produced through distant hybridization, embryo rescue culture, chromosome doubling and backcrossing. WR35 was then proven to be a new wheat-rye 4R disomic addition line using sequential GISH (genomic in situ hybridization), mc-FISH (multicolor fluorescence in situ hybridization) and ND-FISH (non-denaturing FISH) with multiple probes, mc-GISH (multicolor GISH), rye chromosome arm-specific marker analysis and SLAF-seq (specific-locus amplified fragment sequencing) analysis. At the adult stage, WR35 exhibited high levels of resistance to the powdery mildew (Blumeria graminis f. sp. tritici, Bgt) and stripe rust (Puccinia striiformis f. sp. tritici, Pst) pathogens prevalent in China, and a highly virulent isolate of Rhizoctonia cerealis, the cause of wheat sharp eyespot. At the seedling stage, it was highly resistant to 22 of 23 Bgt isolates and four Pst races. Based on its disease responses to different pathogen isolates, WR35 may possess resistance gene(s) for powdery mildew, stripe rust and sharp eyespot, which differed from the known resistance genes from rye. In addition, WR35 was cytologically stable and produced high kernel number per spike. Therefore, WR35 with multi-disease resistances and desirable agronomic traits should serve as a promising bridging parent for wheat chromosome engineering breeding. [ABSTRACT FROM AUTHOR]

Key message: A new broad-spectrum powdery mildew resistance allele Pm2c was identified and mapped in Chinese wheat landrace Niaomai. Abstract: Chinese wheat landrace Niaomai showed resistance to 27 of 28 Chinese Blumeria graminis f. sp tritici ( Bgt) races. Genetic analysis of an F population and its derived F families from the cross Niaomai × Mingxian 169 and backcross population, Niaomai/2*Mingxian 169, indicated that the resistance of Niaomai to Bgt races was conferred by a single dominant resistance gene, temporarily designated PmNM. Molecular tagging showed that PmNM was located on chromosome 5DS and flanked by SSR markers Xcfd81 and Xcfd78 with the genetic distances of 0.1/0.4 cM and 4.9/7.5 cM, respectively. Niaomai showed a different array of responses compared to lines with Pm2a, Pm2b, PmD57- 5D, PmLX66, PmX3986- 2 and Pm48 genes, sharing the same Xcfd81 allele but differing from Xcfd78 allele for Pm2a and Pm2b lines. Allelism tests based on crosses of Niaomai with Ulka/8*Cc and KM2939 showed that PmNM is allelic to Pm2a and Pm2b. We concluded that PmNM is a new allele of Pm2, re-designated Pm2c. Pm2c could be transferred into wheat cultivars by marker-assisted selection to improve the powdery mildew resistance of breeding cultivars/lines. [ABSTRACT FROM AUTHOR]

Key message: An allele of Pm2 for wheat powdery mildew resistance was identified in a putative Agropyron cristatum -derived line and used in wheat breeding programs. Abstract: Powdery mildew (caused by Blumeria graminis f. sp. tritici, Bgt) is one of the most devastating wheat diseases worldwide. It is important to exploit varied sources of resistance from common wheat and its relatives in resistance breeding. KM2939, a Chinese breeding line, exhibits high resistance to powdery mildew at both the seedling and adult stages. It carries a single dominant powdery mildew resistance (Pm) allele of Pm2, designated Pm2b, the previous allelic designation Pm2 will be re-designated as Pm2a. Pm2b was mapped to chromosome arm 5DS and flanked by sequence characterized amplified region (SCAR) markers SCAR112 and SCAR203 with genetic distances of 0.5 and 1.3 cM, respectively. Sequence tagged site (STS) marker Mag6176 and simple sequence repeat (SSR) marker Cfd81 co-segregated with SCAR203. Pm2b differs in specificity from donors of Pm2a, Pm46 and PmLX66 on chromosome arm 5DS. Allelism tests indicated that Pm2b, Pm2a and PmLX66 are allelic. Therefore, Pm2b appears to be a new allele at the Pm2 locus. The closely linked markers were used to accelerate transfer of Pm2b to wheat cultivars in current production. [ABSTRACT FROM AUTHOR]

Key message: The present study identified some new important genomic regions and demonstrated the availability of conditional analysis in dissecting QTLs induced by environmental factors. Abstract: The high input and low use efficiency of nutrient fertilizers require knowledge of the genetic control of crop reaction to nutrient supplements. In this study, 14 morphological and 8 physiological traits of a set of 182 wheat ( Triticum aestivum L.) recombinant inbred lines (Xiaoyan 54 × Jing 411) were investigated in six environments to map quantitative trait loci (QTLs). The influence of nitrogen (N) and phosphorus (P) fertilization on QTL expression was studied by unconditional and conditional analysis. A total of 117 and 30 QTLs were detected by unconditional and conditional analysis, respectively, among which 21 were common for both methods. Thirty-four QTL clusters were identified. Eighteen conserved QTLs (15.4 % of the 117 QTLs) between years, but within nutritional treatment were found. The three major QTLs on chromosomes 2D, 4B and 6A were coincident with Rht8, Rht- B1b and TaGW2, respectively. The other two important intervals on chromosomes 4B and 7A for yield component traits were newly detected QTLs that warrant further study. By conditional analysis, spikelet number per spike was found to be induced by P fertilization mostly, whereas N fertilization had more effects on the expression of the QTLs for nitrogen concentration and utilization efficiency traits. QTLs that respond to N and P interactions were also detected. The results are helpful for understanding the genetic basis of N utilization efficiency in wheat under different N and P supplement environments and provide evidence for the availability of conditional analysis in dissecting QTLs induced by environmental factors. [ABSTRACT FROM AUTHOR]