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Wheat Populations (wheat + population)

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Life Sciences	100%

Selected Abstracts

Genetic control over silica deposition in wheat awns

PHYSIOLOGIA PLANTARUM, Issue 1 2010
Zvi Peleg
Awns are long, stiff filamentous extensions of glumes in many grasses. In wheat, awns contribute up to 40% of the grain's photosynthetic assimilates, and assist in seed dispersal. Awns accumulate silica in epidermal hairs and papillae, and silica has been positively associated with yield and environmental stress tolerance. Here, the awns of a set of domesticated wheat genotypes and their direct progenitor, Triticum turgidum ssp. dicoccoides were characterized. In addition, the silica concentration in awns was genetically dissected in a tetraploid wheat population of recombinant inbred lines (RILs) derived from a cross between durum wheat (cv. Langdon) and wild emmer (accession G18-16). Scanning electron micrographs revealed a continuous silica layer under the cuticle. Extended silicification was identified in the epidermis cell wall and in sclerenchyma cells near the vascular bundles, but not in the stomata, suggesting that an active process directs the soluble silica away from the water evaporation stream. The number of silicified cells was linearly correlated to silica concentration in dry weight (DW), suggesting cellular control over silicification. Domesticated wheat awns contained up to 19% silica per DW, as compared with 7% in the wild accessions, suggesting selection pressure associated with the domestication process. Six quantitative trait loci (QTLs) for silica were identified in the awns, with a LOD score of 3.7,6.3, three of which overlapped genomic regions that contribute to high grain protein. Localization of silica in the awns and identification of QTLs help illuminate mechanisms associated with silica metabolism in wheat. [source]

Identification of novel QTL for resistance to crown rot in the doubled haploid wheat population ,W21MMT70' × ,Mendos'

PLANT BREEDING, Issue 6 2006
W. D. Bovill
Abstract Crown rot (causal agent Fusarium pseudograminearum) is a fungal disease of major significance to wheat cultivation in Australia. A doubled haploid wheat population was produced from a cross between line ,W21MMT70', which displays partial seedling and adult plant (field) resistance to crown rot, and ,Mendos', which is moderately susceptible in seedling tests but partially resistant in field trials. Bulked segregant analysis (BSA) based on seedling trial data did not reveal markers for crown rot resistance. A framework map was produced consisting of 128 microsatellite markers, four phenotypic markers, and one sequence tagged site marker. To this map 331 previously screened AFLP markers were then added. Three quantitative trait loci (QTL) were identified with composite interval mapping across all of the three seedling trials conducted. These QTL are located on chromosomes 2B, 2D and 5D. The 2D and 5D QTL are inherited from the line ,W21MMT70', whereas the 2B QTL is inherited from ,Mendos'. These loci are different from those associated with crown rot resistance in other wheat populations that have been examined, and may represent an opportunity for pyramiding QTL to provide more durable resistance to crown rot. [source]

Genomic dissection of drought resistance in durum wheat × wild emmer wheat recombinant inbreed line population

PLANT CELL & ENVIRONMENT, Issue 7 2009
ZVI PELEG
ABSTRACT Drought is the major factor limiting wheat productivity worldwide. The gene pool of wild emmer wheat, Triticum turgidum ssp. dicoccoides, harbours a rich allelic repertoire for morpho-physiological traits conferring drought resistance. The genetic and physiological bases of drought responses were studied here in a tetraploid wheat population of 152 recombinant inbreed lines (RILs), derived from a cross between durum wheat (cv. Langdon) and wild emmer (acc# G18-16), under contrasting water availabilities. Wide genetic variation was found among RILs for all studied traits. A total of 110 quantitative trait loci (QTLs) were mapped for 11 traits, with LOD score range of 3.0,35.4. Several QTLs showed environmental specificity, accounting for productivity and related traits under water-limited (20 QTLs) or well-watered conditions (15 QTLs), and in terms of drought susceptibility index (22 QTLs). Major genomic regions controlling productivity and related traits were identified on chromosomes 2B, 4A, 5A and 7B. QTLs for productivity were associated with QTLs for drought-adaptive traits, suggesting the involvement of several strategies in wheat adaptation to drought stress. Fifteen pairs of QTLs for the same trait were mapped to seemingly homoeologous positions, reflecting synteny between the A and B genomes. The identified QTLs may facilitate the use of wild alleles for improvement of drought resistance in elite wheat cultivars. [source]

Adapting to winter in wheat: a long-term study follows parallel phenotypic and genetic changes in three experimental wheat populations

MOLECULAR ECOLOGY, Issue 3 2008
JARED L. STRASBURG
Abstract Drawing a direct connection between adaptive evolution at the phenotypic level and underlying genetic factors has long been a major goal of evolutionary biologists, but the genetic characterization of adaptive traits in natural populations is notoriously difficult. The study of evolution in experimental populations offers some help , initial conditions are known and changes can be tracked for extended periods under conditions more controlled than wild populations and more realistic than laboratory or greenhouse experiments. In this issue of Molecular Ecology, researchers studying experimental wheat populations over a 12-year period have demonstrated evolution in a major adaptive trait, flowering time, and parallel changes in underlying genetic variation (Rhonéet al. 2008). Their work suggests that cis -regulatory mutations at a single gene may explain most of the flowering time variation in these populations. [source]

Effect of the Rht-D1 dwarfing locus on Fusarium head blight rating in three segregating populations of winter wheat

PLANT BREEDING, Issue 4 2008
H.-H. Voss
Abstract Fusarium head blight (FHB) is one of the major fungal diseases in wheat throughout the world. To control FHB severity, breeding genetically resistant varieties is thought to be the most promising strategy. In wheat breeding programmes, short cultivars predominantly carrying the Norin 10 derived semi-dwarfing allele Rht-D1b (Rht2) are preferred worldwide because of higher achievable grain yields and lower risk of lodging. This study was conducted to determine the influence of different alleles at the Rht-D1 locus on FHB reaction. Three winter wheat populations were produced by crossing rather susceptible varieties ,Biscay', ,Pirat' and ,Rubens' carrying mutant-type allele Rht-D1b with the more resistant varieties ,Apache', ,Romanus' and ,History' containing the Rht-D1a wild-type allele (rht2). The 190, 216 and 103 progeny of the F4 -derived populations were assayed for the presence of Rht-D1a or Rht-D1b, plant height, and mean FHB rating after spray inoculation at flowering time with a highly aggressive isolate of Fusarium culmorum. Comparably, high mean FHB severities ranging from 28% to 49% for all population × environment combinations were achieved, with significant genotypic variation for FHB rating and plant height within all populations. Both traits were negatively correlated with r ranging from ,0.48 to ,0.61 in the complete populations. However, within the subpopulations homozygous for one or other height allele these correlations decreased considerably. The Rht-D1b semi-dwarfing allele resulted in 7,18% shorter plants, depending on the population, but a considerably increased FHB reaction of 22,53%. Nevertheless, significant genotypic variance for FHB resistance remained in all tested Rht-D1b subpopulations indicating that selection for moderately FHB resistant genotypes within agronomically beneficial Rht-D1b genotypes is still feasible. [source]

Identification of novel QTL for resistance to crown rot in the doubled haploid wheat population ,W21MMT70' × ,Mendos'

Allelic diversity associated with aridity gradient in wild emmer wheat populations

PLANT CELL & ENVIRONMENT, Issue 1 2008
ZVI PELEG
ABSTRACT The association between allelic diversity and ecogeographical variables was studied in natural populations of wild emmer wheat [Triticum turgidum ssp. dicoccoides (Körn.) Thell.], the tetraploid progenitor of cultivated wheat. Patterns of allelic diversity in 54 microsatellite loci were analyzed in a collection of 145 wild emmer wheat accessions representing 25 populations that were sampled across naturally occurring aridity gradient in Israel and surrounding regions. The obtained results revealed that 56% of the genetic variation resided among accessions within populations, while only 44% of the variation resided between populations. An unweighted pair-group method analysis (UPGMA) tree constructed based on the microsatellite allelic diversity divided the 25 populations into six major groups. Several groups were comprised of populations that were collected in ecologically similar but geographically remote habitats. Furthermore, genetic differentiation between populations was independent of the geographical distances. An interesting evolutionary phenomenon is highlighted by the unimodal relationship between allelic diversity and annual rainfall (r = 0.74, P < 0.0002), indicating higher allelic diversity in populations originated from habitats with intermediate environmental stress (i.e. rainfall 350,550 mm year,1). These results show for the first time that the ,intermediate-disturbance hypothesis', explaining biological diversity at the ecosystem level, also dominates the genetic diversity within a single species, the lowest hierarchical element of the biological diversity. [source]