Identification and characterization of Sr13, a tetraploid wheat gene that confers resistance to the Ug99 stem rust race group
- Proceedings of the National Academy of Sciences of the United States of America
- Published over 2 years ago
The Puccinia graminis f. sp. tritici (Pgt) Ug99 race group is virulent to most stem rust resistance genes currently deployed in wheat and poses a threat to global wheat production. The durum wheat (Triticum turgidum ssp. durum) gene Sr13 confers resistance to Ug99 and other virulent races, and is more effective at high temperatures. Using map-based cloning, we delimited a candidate region including two linked genes encoding coiled-coil nucleotide-binding leucine-rich repeat proteins designated CNL3 and CNL13. Three independent truncation mutations identified in each of these genes demonstrated that only CNL13 was required for Ug99 resistance. Transformation of an 8-kb genomic sequence including CNL13 into the susceptible wheat variety Fielder was sufficient to confer resistance to Ug99, confirming that CNL13 is Sr13CNL13 transcripts were slightly down-regulated 2-6 days after Pgt inoculation and were not affected by temperature. By contrast, six pathogenesis-related (PR) genes were up-regulated at high temperatures only when both Sr13 and Pgt were present, suggesting that they may contribute to the high temperature resistance mechanism. We identified three Sr13-resistant haplotypes, which were present in one-third of cultivated emmer and durum wheats but absent in most tested common wheats (Triticum aestivum). These results suggest that Sr13 can be used to improve Ug99 resistance in a large proportion of modern wheat cultivars. To accelerate its deployment, we developed a diagnostic marker for Sr13 The identification of Sr13 expands the number of Pgt-resistance genes that can be incorporated into multigene transgenic cassettes to control this devastating disease.
The growing human population and a changing environment have raised significant concern for global food security, with the current improvement rate of several important crops inadequate to meet future demand 1 . This slow improvement rate is attributed partly to the long generation times of crop plants. Here, we present a method called ‘speed breeding’, which greatly shortens generation time and accelerates breeding and research programmes. Speed breeding can be used to achieve up to 6 generations per year for spring wheat (Triticum aestivum), durum wheat (T. durum), barley (Hordeum vulgare), chickpea (Cicer arietinum) and pea (Pisum sativum), and 4 generations for canola (Brassica napus), instead of 2-3 under normal glasshouse conditions. We demonstrate that speed breeding in fully enclosed, controlled-environment growth chambers can accelerate plant development for research purposes, including phenotyping of adult plant traits, mutant studies and transformation. The use of supplemental lighting in a glasshouse environment allows rapid generation cycling through single seed descent (SSD) and potential for adaptation to larger-scale crop improvement programs. Cost saving through light-emitting diode (LED) supplemental lighting is also outlined. We envisage great potential for integrating speed breeding with other modern crop breeding technologies, including high-throughput genotyping, genome editing and genomic selection, accelerating the rate of crop improvement.
Foods with elevated levels of resistant starch (RS) may have beneficial effects on human health. Pasta was enriched with commercial resistant starches (RSII, Hi Maize™ 1043; RSIII, Novelose 330™) at 10%, 20% and 50% substitution of semolina for RSII and 10% and 20% for RSIII and compared with pasta made from 100% durum wheat semolina to investigate technological, sensory, in vitro starch digestibility and structural properties. The resultant RS content of pasta increased from 1.9% to ∼21% and was not reduced on cooking. Significantly, the results indicate that 10% and 20% RSII and RSIII substitution of semolina had no significant effects on pasta cooking loss, texture and sensory properties, with only a minimal reduction in pasta yellowness. Both RS types lowered the extent of in vitro starch hydrolysis compared to that of control pasta. X-ray diffraction and small-angle scattering verified the incorporation of RS and, compared to the control sample, identified enhanced crystallinity and a changed molecular arrangement following digestion. These results can be contrasted with the negative impact on pasta resulting from substitution with equivalent amounts of more traditional dietary fibre such as bran. The study suggests that these RS-containing formulations may be ideal sources for the preparation of pasta with reduced starch digestibility.
This paper presents a study on the effect of carob flour addition from 1% to 5% (w/w) on phenolics content, antioxidant activity, nutritional quality, and sensory attributes of wheat pasta. An increase of about 2-folds, 18-folds and 3-folds in phenolics content, antiradical activity and reducing power for pasta fortified with 5% of carob flour was observed, respectively, compared to the control. Expected glycemic index (eGI) was increased proportionally to the substitution level and ranged between 72.2 and 83.9 for 1-5% of supplement, respectively. Furthermore, pasta fortification affected the in vitro bioaccessibility of nutrients. In case of 5% supplemented pasta, the digestibility of starch and protein decreased by about 9% compared to the control. The replacement of semolina with carob flour from 1% to 5% had no significant effect on pasta sensory attributes. In conclusion, carob flour seems to be a promising functional ingredient for pasta fortification.
Fine-tuning production inputs such as seeding rate, nitrogen (N), and genotypes may improve end-use quality of hard red winter wheat (Triticum aestivium L.) when growing conditions are unpredictable. Studies were conducted at the Agronomy Research Farm (ARF; Lincoln) and the High Plains Agricultural Laboratory (HPAL; Sidney) in 2014 and 2015 in Nebraska, USA to determine the effects of genotype (6), environment (4), seeding rate (3), and flag leaf top-dressed N (0 and 34 kg N ha(-1) ) on the end-use quality of winter wheat.
Domestication and breeding have influenced the genetic structure of plant populations due to selection for adaptation from natural habitats to agro-ecosystems. Here, we investigate the effects of selection on the contents of 51 primary kernel metabolites and their relationships in three Triticum turgidum L. subspecies (i.e., wild emmer, emmer, durum wheat) that represent the major steps of tetraploid wheat domestication. We present a methodological pipeline to identify the signature of selection for molecular phenotypic traits (e.g., metabolites and transcripts). Following the approach, we show that a reduction in unsaturated fatty acids was associated with selection during domestication of emmer (primary domestication). We also show that changes in the amino acid content due to selection mark the domestication of durum wheat (secondary domestication). These effects were found to be partially independent of the associations that unsaturated fatty acids and amino acids have with other domestication-related kernel traits. Changes in contents of metabolites were also highlighted by alterations in the metabolic correlation networks, indicating wide metabolic restructuring due to domestication. Finally, evidence is provided that wild and exotic germplasm can have a relevant role for improvement of wheat quality and nutritional traits.
Durum wheat (Triticum turgidum subsp. durum) is a key crop worldwide, and yet, its improvement and adaptation to emerging environmental threats is made difficult by the limited amount of allelic variation included in its elite pool. New allelic diversity may provide novel loci to international crop breeding through quantitative trait loci (QTL) mapping in unexplored material. Here, we report the extensive molecular and phenotypic characterization of hundreds of Ethiopian durum wheat landraces and several Ethiopian improved lines. We test 81 587 markers scoring 30 155 single nucleotide polymorphisms and use them to survey the diversity, structure, and genome-specific variation in the panel. We show the uniqueness of Ethiopian germplasm using a siding collection of Mediterranean durum wheat accessions. We phenotype the Ethiopian panel for ten agronomic traits in two highly diversified Ethiopian environments for two consecutive years and use this information to conduct a genome-wide association study. We identify several loci underpinning agronomic traits of interest, both confirming loci already reported and describing new promising genomic regions. These loci may be efficiently targeted with molecular markers already available to conduct marker-assisted selection in Ethiopian and international wheat. We show that Ethiopian durum wheat represents an important and mostly unexplored source of durum wheat diversity. The panel analysed in this study allows the accumulation of QTL mapping experiments, providing the initial step for a quantitative, methodical exploitation of untapped diversity in producing a better wheat.
The aim of the present study was to examine the effect of a replacement diet with organic, semi-whole-grain products derived from Triticum turgidum subsp. turanicum (ancient) wheat on irritable bowel syndrome (IBS) symptoms and inflammatory/biochemical parameters. A double-blinded randomised cross-over trial was performed using twenty participants (thirteen females and seven males, aged 18-59 years) classified as having moderate IBS. Participants received products (bread, pasta, biscuits and crackers) made either from ancient or modern wheat for 6 weeks in a random order. Symptoms due to IBS were evaluated using two questionnaires, which were compiled both at baseline and on a weekly basis during the intervention period. Blood analyses were carried out at the beginning and end of each respective intervention period. During the intervention period with ancient wheat products, patients experienced a significant decrease in the severity of IBS symptoms, such as abdominal pain (P< 0·0001), bloating (P= 0·004), satisfaction with stool consistency (P< 0·001) and tiredness (P< 0·0001). No significant difference was observed after the intervention period with modern wheat products. Similarly, patients reported significant amelioration in the severity of gastrointestinal symptoms only after the ancient wheat intervention period, as measured by the intensity of pain (P= 0·001), the frequency of pain (P< 0·0001), bloating (P< 0·0001), abdominal distension (P< 0·001) and the quality of life (P< 0·0001). Interestingly, the inflammatory profile showed a significant reduction in the circulating levels of pro-inflammatory cytokines, including IL-6, IL-17, interferon-γ, monocyte chemotactic protein-1 and vascular endothelial growth factor after the intervention period with ancient wheat products, but not after the control period. In conclusion, significant improvements in both IBS symptoms and the inflammatory profile were reported after the ingestion of ancient wheat products.
Increasing wheat yield is a key global challenge to producing sufficient food for a growing human population. Wheat grain yield can be boosted by exploiting heterosis, the superior performance of hybrids compared with midparents. Here we present a tailored quantitative genetic framework to study the genetic basis of midparent heterosis in hybrid populations derived from crosses among diverse parents. We applied this framework to an extensive data set assembled for winter wheat. Grain yield was assessed for 1,604 hybrids and their 135 parental elite breeding lines in 11 environments. The hybrids outperformed the midparents by 10% on average, representing approximately 15 years of breeding progress in wheat, thus further substantiating the remarkable potential of hybrid-wheat breeding. Genome-wide prediction and association mapping implemented through the developed quantitative genetic framework showed that dominance effects played a less prominent role than epistatic effects in grain-yield heterosis in wheat.
Durum wheat semolina was fermented with sourdough lactic acid bacteria and fungal proteases aiming at a complete gluten hydrolysis. The gluten-free (GF) semolina, added with naturally GF ingredients and structuring agents, was used to produce bread (rendered GF bread; rGFB) at industrial level. An integrated approach including the characterization of the main chemical, nutritional, structural, and sensory features was used to compare rGFB to a gluten-containing bread and to 5 commercial naturally GF breads. High-performance liquid chromatography was used for free amino acids (FAAs), organic acids, and ethanol analysis. A methanolic extract was used for determining total phenols and antioxidant activity. The bread characterization also included the analysis of dietary fibers, mycotoxins, vitamins, and heavy metals. Beyond chemical analysis, nutritional profile was evaluated considering the in vitro protein digestibility and the predicted glycemic index, while the instrumental texture profile analysis was performed to investigate the structure and the physical/mechanical properties of the baked goods. Beyond the huge potential of market expansion, the main advantages of durum wheat semolina rendered GF can be resumed in the high availability of FAAs, the high protein digestibility, the low starch hydrolysis index, and the better technological properties of bread compared to the commercial GF products currently present on the market. Vitamins, minerals, and dietary fiber profiles are comparable to those of gluten-containing wheat bread. Also the sensory profile, determined by a panel test, can be considered the most similar to those of conventional baked goods, showing all the sourdough bread classic attributes.