Browsing by Author "Jin, Y."
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Item Identification and mapping of a leaf rust resistance gene in barley line Q21861(Genome, 1997) Steffenson, Brian; Borovkova, I.G.; Jin, Y.; Kilian, A.; Blake, T.K.; Kleinhofs, A.Barley line Q21861 possesses an incompletely dominant gene (RphQ) for resistance to leaf rust caused by Puccinia hordei. To investigate the allelic and linkage relations between RphQ and other known Rph genes, F2 populations from crosses between Q21861 and donors of Rph1 to Rph14 (except for Rph8) were evaluated for leaf rust reaction at the seedling stage. Results indicate that RphQ is either allelic with or closely linked to the Rph2 locus. A doubled haploid population derived from a cross between Q21861 and SM89010 (a leaf rust susceptible line) was used for molecular mapping of the resistance locus. Bulked segregant analysis was used to identify markers linked to RphQ, using random amplified polymorphic DNAs (RAPDs), restriction fragment length polymorphisms (RFLPs), and sequence tagged sites (STSs). Of 600 decamer primers screened, amplified fragments generated by 9 primers were found to be linked to the RphQ locus; however, only 4 of them were within 10 cM of the target. The RphQ locus was mapped to the centromeric region of chromosome 7, with a linkage distance of 3.5 cM from the RFLP marker CDO749. Rrn2, an RFLP clone from the ribosomal RNA intergenic spacer region, was found to be very closely linked with RphQ, based on bulked segregant analysis. An STS marker, ITS1, derived from Rrn2, was also closely linked (1.6 cM) to RphQ.Item Molecular mapping of the leaf rust resistance gene Rph5 in barley(Crop Science, 2003) Steffenson, Brian; Mammadov, J.A.; Zwonitzer, J.C.; Biyashev, R.M.; Griffey, C.A.; Jin, Y.; Saghai Maroof, M.A.Leaf rust caused by Puccinia hordei G. Otth is an important disease of barley (Hordeum vulgare L.) in many regions of the world. Yield losses up to 32% have been reported in susceptible cultivars. The Rph5 gene confers resistance to the most prevalent races (8 and 30) of barley leaf rust in the USA. Therefore, the molecular mapping of Rph5 is of great interest. The objectives of this study were to map Rph5 and identify closely linked molecular markers. Genetic studies were performed by analysis of 93 and 91 [F.sub.2] plants derived from the crosses `Bowman' (rph5) x `Magnif 102' (Rph5) and `Moore' (rph5) x Virginia 92-42-46 (Rph5), respectively. Bulk segregent analysis (BSA) using amplified fragment length polymorphism (AFLP), restriction fragment length polymorphism (RFLP), and simple sequence repeat (SSR) markers was conducted. Linkage analysis positioned the Rph5 locus to the extreme telomeric region of the short arm of barley chromosome 3H at 0.2 centimorgans (cM) proximal to RFLP marker VT1 and 0.5 cM distal from RFLP marker C970 in the Bowman x Magnif 102 population. Map positions and the relative order of the markers were confirmed in the Moore x Virginia 92-42-46 population. RFLP analysis of the near isogenic line (NIL) Magnif 102/*8Bowman, the susceptible recurrent parent Bowman, and RpH5 donor Magnif 102, confirmed the close linkage of the markers VT1, BCD907, and CD0549 to Rph5. Results from this study will be useful for marker-assisted selection and gene pyramiding in programs breeding for leaf rust resistance and provide the basis for physical mapping and further cloning activities.Item Puccinia coronata var. hordei var. nov. morphology and pathogenicity(Mycologia, 1999) Steffenson, Brian; Jin, Y.A new variety of Puccinia coronata causing a disease on barley and other gramineous species is described. The fungus is different from other reported forms of P coronata in both morphology and pathogenicity. Its most prominent characters are the elongated teliospore appendages with dichotomous branching and wide pathogenicity on species in the tribe Triticeae, particularly the genus Hordeum. The name of P coronata var. hordei is proposed for the rust fungus. The common name 'crown rust of barley' is proposed for the disease of barley caused by this rust fungus. Results of inoculation indicated that P coronata var. hordei is pathogenic on species of Aegilops, Agropyron, Elymus, Elytrigia, Leymus, Pascopyrum, Psathyrostachys, Secale, and Triticum in the tribe Triticeae, and some species of Brachypodium, Bromus, Festuca, and Lolium in the tribe Poeae, and Phalaris in the tribe Aveneae. In the northern Great Plains of the USA, the following native and introduced gramineous species were found naturally infected by P coronata var. hordei: Bromus tectorum, Elymus canadensis, E. trachycaulus, E. virginicus, Elytrigia intermedia, E. repens, Hordeum jubatum, H. vulgare, Leymus angustus, L. cinerius, L. dahuricus, L. racemosus, Pascopyrum smithii, Psathyrostachys juncea, and Secale cer- eale.