Development and molecular cytogenetic identification of a new wheat-rye 4R chromosome disomic addition line with resistances to powdery mildew, stripe rust and sharp eyespot.

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. 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.

An D ，Ma P ，Zheng Q ，Fu S ，Li L ，Han F ，Han G ，Wang J ，Xu Y ，Jin Y ，Luo Q ，Zhang X ... -  《-》

Molecular Cytogenetic Identification of a New Wheat-Rye 6R Chromosome Disomic Addition Line with Powdery Mildew Resistance.

Rye (Secale cereale L.) possesses many valuable genes that can be used for improving disease resistance, yield and environment adaptation of wheat (Triticum aestivum L.). However, the documented resistance stocks derived from rye is faced severe challenge due to the variation of virulent isolates in the pathogen populations. Therefore, it is necessary to develop desirable germplasm and search for novel resistance gene sources against constantly accumulated variation of the virulent isolates. In the present study, a new wheat-rye line designated as WR49-1 was produced through distant hybridization and chromosome engineering protocols between common wheat cultivar Xiaoyan 6 and rye cultivar German White. Using sequential GISH (genomic in situ hybridization), mc-FISH (multicolor fluorescence in situ hybridization), mc-GISH (multicolor GISH) and EST (expressed sequence tag)-based marker analysis, WR49-1 was proved to be a new wheat-rye 6R disomic addition line. As expected, WR49-1 showed high levels of resistance to wheat powdery mildew (Blumeria graminis f. sp. tritici, Bgt) pathogens prevalent in China at the adult growth stage and 19 of 23 Bgt isolates tested at the seedling stage. According to its reaction pattern to different Bgt isolates, WR49-1 may possess new resistance gene(s) for powdery mildew, which differed from the documented powdery mildew gene, including Pm20 on chromosome arm 6RL of rye. Additionally, WR49-1 was cytologically stable, had improved agronomic characteristics and therefore could serve as an important bridge for wheat breeding and chromosome engineering.

An D ，Zheng Q ，Luo Q ，Ma P ，Zhang H ，Li L ，Han F ，Xu H ，Xu Y ，Zhang X ，Zhou Y ... -  《PLoS One》

Molecular cytogenetic characterization of a new wheat-rye 4R chromosome translocation line resistant to powdery mildew.

Rye is an important and valuable gene resource for wheat improvement. However, due to extensive growing of cultivars with disease resistance genes from short arm of rye chromosome 1R and coevolution of pathogen virulence and host resistance, these cultivars successively lost resistance to pathogens. Identification and deployment of new resistance gene sources in rye are, therefore, of especial importance and urgency. A new wheat-rye line, designated as WR41-1, was produced through distant hybridization and chromosome engineering protocols between common wheat cultivar Xiaoyan 6 and rye cultivar German White. It was proved to be a new wheat-rye T4BL·4RL and T7AS·4RS translocation line using sequential genomic in situ hybridization (GISH), multicolor fluorescence in situ hybridization (mc-FISH), and expressed sequence tag-simple sequence repeat (EST-SSR) marker analysis. WR41-1 showed high levels of resistance to powdery mildew (Blumeria graminis f. sp. tritici, Bgt) pathogens prevalent in China at the adult growth stage and 13 of 23 Bgt isolates tested at the seedling stage. According to its resistant pattern to 23 different Bgt isolates, WR41-1 may possess new gene(s) for resistance to powdery mildew, which differed from previously identified and known powdery mildew genes from rye (Pm7, Pm8, Pm17, and Pm20). In addition, WR41-1 was cytologically stable, had a desirable fertility, and is expected to be useful in wheat improvement.

An D ，Zheng Q ，Zhou Y ，Ma P ，Lv Z ，Li L ，Li B ，Luo Q ，Xu H ，Xu Y ... -  《-》

Identification and characterization of a new stripe rust resistance gene Yr83 on rye chromosome 6R in wheat.

A physical map of Secale cereale chromosome 6R was constructed using deletion mapping, and a new stripe rust resistance gene Yr83 was mapped to the deletion bin of FL 0.73-1.00 of 6RL. Rye (Secale cereale L., RR) possesses valuable genes for wheat improvement. In the current study, we report a resistance gene conferring stripe rust resistance effective from seedling to adult plant stages located on chromosome 6R. This chromosome was derived from triticale line T-701 and also carries highly effective resistance to the cereal cyst nematode species Heterodera avenae Woll. A wheat-rye 6R(6D) disomic substitution line exhibited high levels of seedling resistance to Australian pathotypes of the stripe rust (Puccinia striiformis f. sp. tritici; Pst) pathogen and showed an even greater resistance to the Chinese Pst pathotypes in the field. Ten chromosome 6R deletion lines and five wheat-rye 6R translocation lines were developed earlier in the attempt to transfer the nematode resistance gene to wheat and used herein to map the stripe rust resistance gene. These lines were subsequently characterized by sequential multicolor fluorescence in situ hybridization (mc-FISH), genomic in situ hybridization (GISH), mc-GISH, PCR-based landmark unique gene (PLUG), and chromosome 6R-specific length amplified fragment sequencing (SLAF-Seq) marker analyses to physically map the stripe rust resistance gene. The new stripe rust resistance locus was located in a chromosomal bin with fraction length (FL) 0.73-1.00 on 6RL and was named Yr83. A wheat-rye translocation line T6RL (#5) carrying the stripe rust resistance gene will be useful as a new germplasm in breeding for resistance.

Li J ，Dundas I ，Dong C ，Li G ，Trethowan R ，Yang Z ，Hoxha S ，Zhang P ... -  《-》

Molecular cytogenetic identification of a wheat-rye 1R addition line with multiple spikelets and resistance to powdery mildew.

Alien addition lines are important for transferring useful genes from alien species into common wheat. Rye is an important and valuable gene resource for improving wheat disease resistance, yield, and environment adaptation. A new wheat-rye addition line, N9436B, was developed from the progeny of the cross of common wheat (Triticum aestivum L., 2n = 6x = 42, AABBDD) cultivar Shaanmai 611 and rye (Secale cereal L., 2n = 2x = 14, RR) accession Austrian rye. We characterized this new line by cytology, genomic in situ hybridization (GISH), fluorescence in situ hybridization (FISH), molecular markers, and disease resistance screening. N9436B was stable in morphology and cytology, with a chromosome composition of 2n = 42 + 2t = 22II. GISH investigations showed that this line contained two rye chromosomes. GISH, FISH, and molecular maker identification suggested that the introduced R chromosome and the missing wheat chromosome arms were 1R chromosome and 2DL chromosome arm, respectively. N9436B exhibited 30-37 spikelets per spike and a high level of resistance to powdery mildew (Blumeria graminis f. sp. tritici, Bgt) isolate E09 at the seedling stage. N9436B was cytologically stable, had the trait of multiple spikelets, and was resistant to powdery mildew; this line should thus be useful in wheat improvement.

Yang W ，Wang C ，Chen C ，Wang Y ，Zhang H ，Liu X ，Ji W ... -  《-》