Introgression of stem rust resistance genes SrTA10187 and SrTA10171 from Aegilops tauschii to wheat
Department of Plant Pathology, Kansas State University, Manhattan, KS, 66506, USA. Theoretical and Applied Genetics
(Impact Factor: 3.79).
07/2013; 126(10). DOI: 10.1007/s00122-013-2148-z
Aegilops tauschii, the diploid progenitor of the wheat D genome, is a readily accessible germplasm pool for wheat breeding as genes can be transferred to elite wheat cultivars through direct hybridization followed by backcrossing. Gene transfer and genetic mapping can be integrated by developing mapping populations during backcrossing. Using direct crossing, two genes for resistance to the African stem rust fungus race TTKSK (Ug99), were transferred from the Ae. tauschii accessions TA10187 and TA10171 to an elite hard winter wheat line, KS05HW14. BC2 mapping populations were created concurrently with developing advanced backcross lines carrying rust resistance. Bulked segregant analysis on the BC2 populations identified marker loci on 6DS and 7DS linked to stem rust resistance genes transferred from TA10187 and TA10171, respectively. Linkage maps were developed for both genes and closely linked markers reported in this study will be useful for selection and pyramiding with other Ug99-effective stem rust resistance genes. The Ae. tauschii-derived resistance genes were temporarily designated SrTA10187 and SrTA10171 and will serve as valuable resources for stem rust resistance breeding.
Available from: Awais Rasheed
- "Interest in Ae. tauschii introgressions stems from the observation that the diploid D genome progenitor possesses a higher genetic diversity compared to bread wheat cultivars and landraces (Reif et al. 2005 ). Ae. tauschii was used to introgress specifi c traits that include diverse resistance genes (Olson et al. 2013 ; Mandeep et al. 2010 ; Leonova et al. 2007 ; Miranda et al. 2006 ; Ma et al. 1993 ; Eastwood et al. 1994 ), bread-making quality (Li et al. 2012 ), pre-harvest sprouting tolerance (Gatford et al. 2002 ; Imtiaz et al. 2008 ), yield (Gororo et al. 2002 ) and also morphological characters (Watanabe et al. 2006 ) into breeding material and cultivars of bread wheat. Since the mid-twentieth century directed efforts at Ae tauschii introgressions into wheat has come from two avenues. "
Available from: Vijay Kumar Tiwari
- "tauschii [5,6] have been used to enrich the bread wheat genetic base. Extensive wheat genetic resources and marker systems [7-9] are transferable and can be used for mapping of alien introgressions , characterizing genetic diversity  and gene isolation [12,13] from the primary gene pool. "
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ABSTRACT: Monitoring alien introgressions in crop plants is difficult due to the lack of genetic and molecular mapping information on the wild crop relatives. The tertiary gene pool of wheat is a very important source of genetic variability for wheat improvement against biotic and abiotic stresses. By exploring the 5Mg short arm (5MgS) of Aegilops geniculata, we can apply chromosome genomics for the discovery of SNP markers and their use for monitoring alien introgressions in wheat (Triticum aestivum L).
The short arm of chromosome 5Mg of Aegilops geniculata Roth (syn. Aegilops ovata L.; 2n = 4x = 28, UgUgMgMg) was flow-sorted from a wheat line in which it is maintained as a telocentric chromosome. DNA of the sorted arm was amplified and sequenced using an Illumina Hiseq 2000 with ~45x coverage. The sequence data was used for SNP discovery against wheat homoeologous group-5 assemblies. A total of 2,178 unique, 5MgS-specific SNPs were discovered. Randomly selected samples of 59 5MgS-specific SNPs were tested (44 by KASPar assay and 15 by Sanger sequencing) and 84% were validated. Of the selected SNPs, 97% mapped to a chromosome 5Mg addition to wheat (the source of t5MgS), and 94% to 5Mg introgressed from a different accession of Ae. geniculata substituting for chromosome 5D of wheat. The validated SNPs also identified chromosome segments of 5MgS origin in a set of T5D-5Mg translocation lines; eight SNPs (25%) mapped to TA5601 [T5DL . 5DS-5MgS(0.75)] and three (8%) to TA5602 [T5DL . 5DS-5MgS (0.95)]. SNPs (gsnp_5ms83 and gsnp_5ms94), tagging chromosome T5DL . 5DS-5MgS(0.95) with the smallest introgression carrying resistance to leaf rust (Lr57) and stripe rust (Yr40), were validated in two released germplasm lines with Lr57 and Yr40 genes.
This approach should be widely applicable for the identification of species/genome-specific SNPs. The development of a large number of SNP markers will facilitate the precise introgression and monitoring of alien segments in crop breeding programs and further enable mapping and cloning novel genes from the wild relatives of crop plants.
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ABSTRACT: Recent advances in our understanding of the nature of resistance genes and rust fungus genomics are providing some insight into the basis of resistance and susceptibility to rust diseases in our cereal crops. Characterized rust resistance genes, for the most part, resemble other resistance genes that interact with effectors intracellularly, but some have unique features. Characterization of rust effectors is just beginning but genomic information and technical advances in rust functional genomics will accelerate their characterization. The ephemeral nature of resistance in past varieties has made the design of cultivars with durable resistance a major focus for geneticists and cereal breeders. This includes strategies for deploying race-specific resistance genes that prolong their effects and methods of predicting which will be difficult for the pathogen to defeat. Identification of resistance genes with race-nonspecific effects is another strategy where recent breakthroughs have been made. Routinely combining the numerous genes required for complex resistance, whether specific or nonspecific, in elite cultivars remains a primary constraint to realizing durable resistance in most programs.
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