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    Characteristics of the root system in the diploid genome donors of hexaploid wheat (Triticum aestivum L.)
    (GENETIC RESOURCES AND CROP EVOLUTION, 2017) BEKTAS, HARUN; HOHN, CHRISTOPHER E.; WAINES, J. GILES
    Wild crop relatives are of considerable interest in plant breeding and significant efforts have been made to transfer their genetic variation into modern crops. Of the three diploid progenitors of bread wheat (Triticum aestivum L.), only Aegilops tauschii Coss. has been explored and exploited and only for some above ground characteristics. The three wild progenitors (Aegilops speltoides Tausch., Triticum urartu Tumanian ex Gandilyan, and Aegilops tauschii) have never been assayed for root traits. Here we report such a root study, and include Triticum monococcum L. subsp. boeoticum (Boiss.) Hayek and T. turgidum L. subsp. dicoccoides (Koern. ex Asch. et Graebn.) Thell. Fifteen accessions were selected from the above wild species and tested in the presence of one bread wheat cultivar Pavon F76. Significant variation was observed between and within the taxa. Of all accessions tested, cv. Pavon F76 had the smallest root system at maturity while A. speltoides had the largest root system. Moreover, Aegilops spp. had larger mean values for root biomass when compared with Triticum spp. These results suggest there is significant unexplored potential for the use of wheat wild relatives in wheat breeding to improve the root system, or to develop synthetic mapping populations to study root traits.
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    Erratum to: QTLs for root traits at mid-tillering and for root and shoot traits at maturity in a RIL population of spring bread wheat grown under well-watered conditions
    (Euphytica, 2016) EHDAIE, BAHMAN; MOHAMMADI, SEYED ABOLGHASEM; NOURAEİN, M.; BEKTAS, HARUN; WAINES, J. GILES
    Root system traits have positive effects on wheat grain yield, particularly in drought environments. Root traits are difficult to manipulate using conventional selection procedures. Marker-assistedselection (MAS) could be helpful for the improvement of root morphological traits. A recombinant inbred line (RIL) population of 168 lines derived from the cross Iran #49 9 Yecora Rojo was used to map quantitative trait loci (QTLs) for root traits at midtillering stage for one season and for root and shoot traits at plant maturity for two seasons using two different subsets. The RILs were grown in sand-tube experiments in a glasshouse under well-watered conditions. Longest root (LR), total root length longer 30 cm (TRL30), shallow root weight (roots between 0 and 30 cm, SRW), deep root weight (roots bellow 30 cm, DRW), total root biomass (RBio), ratio of root to shoot (RTS) and to plant (RTP) biomass were measured at mid-tillering. At maturity, number of days to booting (DTB), to heading (DTH), to anthesis (DTA), and to maturity (DTM), plant height (PH), flag leaf area (FLA), number of tillers (NTP) and spikes (NSP) per plant, number of grains (NGP), grain weight (GW), grain yield (GY) per plant, LR, SRW, DRW, RBio, PBio, and RTP were measured. At mid-tillering, a total of 18 putative QTLs were detected with individual QTL accounted for between 6.5 and 26.5 % of the variation in the traits. The QTLs were distributed on chromosomes 1B, 2A, 2D, 4B, 6B, 7A, and 7D. A major and two minor QTLs were identified for LR, with the major QTL (qLR-2D) explaining 26.5 % of variation. Two QTLs were detected for DRW on chromosome 4B between markers Gwm6 and Sukkula.1220 that together explained 23.1 % of variation. One region between marker Wmc198 and Cfa2263 on chromosome 2A contained four QTLs affecting PH, SRW, RTS, and RTP. At maturity, 70 putative QTLs were detected across the two seasons with a single QTL accounted for between 7.7 and 40.6 % of variation in the traits. Three major colocalized QTLs for SRW, DRW, and RBio were identified on chromosome 2D between markers Wms515 andWms102 that accounted for 19.8, 20.5, and 22.4 %0f variation, respectively. Two major colocalized QTLs for SRW and RBio were detected on chromosome 3A that explained 17.8 and 13.4 % of variation, respectively. One major QTL for DRW was identified on chromosome 1B that accounted for 20.3 % of variation. Chromosome 2B harbored major QTLs for GY, NGS, and NGP. A major QTL cluster was detected on chromosome 2D and on chromosome 4A relating 11 and eight QTLs for phenological periods, root traits, RTS, and RTP, indicating pleiotropic effects on these traits. Of the four common root traits studied at mid-tillering and at maturity, only SRW had linked QTLs on chromosome 2A at both stages of plant growth, indicating selection for root traits at seedling stage alone may not be effective in changing root morphological characteristics at later stages of plant growth. It appeared that chromosome 2A, 2D, and 4B harbored genes regulating growth of root traits at early and later stages of plant growth. The molecular markers closely linked to QTLs for root and shoot traits may be used in wheat breeding program using MAS procedures.
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    Phenotyping and Genetic Analysis of Root and Shoot Traits of Recombinant Inbred Lines of Bread Wheat Under Well- Watered Conditions
    (Journal of Crop Improvement, 2014) EHDAIE, BAHMAN; MAHEEPALA, DINUSHA C.; BEKTAS, HARUN; WAINES, J. GILES
    Phenotyping root traits and understanding their inheritance are critical for crop improvement, as the root system plays an important role in crop performance under well-watered and drought conditions. A set of 118 F8 recombinant inbred lines (RILs) of bread wheat (Triticum aestivum L.) derived from the cross Iran #49 (a landrace) × Yecora Rojo (a standard variety) plus the two parents was used to phenotype root traits at mid-tillering stage and at physiological maturity in sand-tube experiments under well-watered conditions. Iran #49 and Yecora Rojo were different for grain yield per plant (20.4 vs.13.8), shallow-root weight per plant (5.3 vs. 1.3 g, roots developed between 0 and 30 cm), deep-root weight per plant (4.5 vs. 0.5 g, roots developed below 30 cm), and root biomass per plant (9.8 vs. 1.8 g). Although there were significant differences among the RILs for number of roots longer than 30 cm, total length of roots longer than 30 cm, longest root, shallow-root weight, deep-root weight, and root biomass, the estimate of narrow-sense heritability was relatively low for shallow-root weight (26%), deep- -root weight (14%), and root biomass (22%) at mid-tillering stage. At maturity, the estimate of heritability for these root traits was 81%, 79%, and 83%, respectively. Additive × additive epistasis was detected for deep-root weight at maturity. Genotypic differences in root traits among the RILs were highest at maturity. The root traits measured at mid-tillering and at maturity showed significant, but weak correlation coefficients ranging from 0.20 to 0.40. Grain yield per plant showed significant genotypic correlation with root traits at maturity. Harvest index showed strong negative correlation with root traits ranging from -0.69 to -0.78. Our studies indicated that the appropriate time for phenotyping root traits in wheat is at maturity.
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    Root and shoot traits in parental, early and late generation Green Revolution wheats (Triticum spp.) under glasshouse conditions
    (GENETIC RESOURCES AND CROP EVOLUTION, 2017) BEKTAS, HARUN; WAINES, J. GILES
    Introduction of stem-dwarfing genes had a major impact on wheat breeding and production. It is estimated that 70–90% of modern wheats carry one or more such genes. These genes were the cornerstone of the Green Revolution. They solved the lodging problem by reducing stem height, thus allowing a marked increase in mineral fertilizer use. These genes also changed biomass allocation and allowed more carbon assimilates to be stored as grain. With heavy fertilization and irrigation, plants had little use for an extensive and expensive root system for uptake of water and nutrients. However, with climate change and limited water and nutrient sources, there is a need to remodel crops with novel genetic variation available in landraces and old varieties. In this study, we evaluated nine accessions of wheat representing gene pools of parental, early-tall and late-semi-dwarf Green Revolution wheats for root and shoot biomass and grain yield under well-watered conditions in a glasshouse. Significant genotypic variation was found for total root biomass and root distribution in the soil profile as well as for plant height and days to anthesis. Modern wheats have reduced root-system size relative to their predecessors. This may be the effect of the dwarfing genes or an indirect effect of negative selection pressure, but the wheat
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    Root and shoot traits of bread wheat (Triticum aestivum L.) landraces and cultivars
    (EUPHYTICA, 2016) BEKTAS, HARUN; HOHN, CHRISTOPHER E.; WAINES, J. GILES
    In order to break the current grain yield barriers, breeders require genetic variation. Breeding for resistance to abiotic stresses may lead to better plant survival and improved grain yield. Exploring landraces may expand the genetic diversity of modern wheats. Five Turkish bread wheat landraces and 14 modern durum and bread wheat cultivars were evaluated for root and shoot biomass as well as grain yield for 2 years in three experiments. Root and shoot traits were measured in plants grown in 1 and 1.5 m PVC tubes in a glasshouse. Significant genotypic differences were found within and between landraces and modern wheats. Shoot biomass, total root biomass, shallow root weight, deep root weight, number of tillers per plant, and plant height were significantly greater in landraces compared to modern wheats. Correlation coefficients were positive between root biomass and shoot biomass (0.78), and number of fertile tillers (0.76). Plant height, shallow and deep root weights, as well as the total root biomass were positively correlated. Semi-dwarf and mid-height cultivars had greater grain yield than tall lines: winter wheats had greater harvest index, whereas intermediate (facultative) wheats had greater shallow root weights and total root biomass. Results highlight the mode of adaptation in landraces to water stress and suggest that landraces may be a valuable resource in breeding for altered root architecture.