Triticum Aestivum Research Articles

Unlocking the roles of wheat root exudates in regulating laccase-catalyzed estrogen humification

While laccase humification has an efficient capacity to convert estrogenic pollutants, the roles of wheat (Triticum aestivum L.) root exudates (W-REs) in the enzymatic humification remain poorly understood. Herein, we presented the research into the effects of W-REs on 17β-estradiol (E2) and bisphenol A (BPA) conversion in vitro laccase humification. W-REs inhibited E2 removal but promoted BPA conversion in the enzymatic humification, and the first-order kinetic constants for E2 and BPA were 0.27–0.69 and 0.28–0.55 h−1, respectively. Specialized small phenols and amino acids in W-REs were susceptible to laccase humification, resulting in increased copolymerization of estrogen and W-REs. In greenhouse hydroponics, the accumulated amounts of E2 (BPA) in the roots and shoots were estimated to be 0.87 (2.15) and 0.43 (0.51) nmol·plant−1 at day 3, respectively. By forming low- and eventually non-toxic copolymeric precipitates between estrogen and W-REs, laccase humification lowered the phytotoxicity and bioavailability of estrogen in the rhizosphere solution, consequently relieving its uptake, accumulation, and distribution in the wheat cells. This work sheds light on the roles of W-REs in regulating laccase-catalyzed estrogen humification, and gives an insight into the path of addressing organic contamination in the rhizosphere and ensuring food safety.

Genome-wide identification of phytosulfokine (PSK) peptide family reveals TaPSK1 gene involved in grain development of wheat (Triticum aestivum L.)

BackgroundPhytosulfokine (PSK) functions as a plant peptide growth factor that plays important and diverse roles in plant development and stress responses. Nevertheless, PSKs have not been systematically analyzed in wheat.ResultsA genome-wide comparative analysis of PSK genes in wheat was conducted and 15 TaPSKs were identified and divided into four subgroups in the wheat genome based on sequence similarity. The examination of motif compositions of TaPSK genes revealed the presence of the YIYTQ signature motif in the C-terminus of all TaPSK polypeptide precursors, with a highly conserved feature across different species. Exogenous application of TaPSK peptide promoted root growth in wheat. Quantitative RT-PCR analysis revealed that the TaPSKs exhibited preferential or tissue-specific expression patterns in wheat. In particular, three homologs of the TaPSK1 genes were specifically expressed in grains, with the strongest expression observed in the developing grains at 15 days after anthesis. Compared with wild type, transgenic rice lines overexpressing TaPSK1-A exhibited larger grain size and higher thousand-grain weight. The promoter region and genomic sequence of the wheat TaPSK1-A gene were cloned. Sequence polymorphism showed that five single-nucleotide polymorphisms (SNPs) were identified in the promoter region of TaPSK1-A. A Kompetitive Allele-Specific PCR (KASP) marker was developed for TaPSK1-A based on –806 bp SNP (C/T transition), and two haplotypes, TaPSK1-A-HapI and TaPSK1-A-HapII were detected in 260 wheat accessions collected from different regions. The expression of TaPSK1-A, promoter activity, and thousand-grain weight (TGW) in the TaPSK1-A-HapII haplotype were higher than those in the TaPSK1-A-HapI haplotype. Furthermore, yeast one-hybrid assays revealed the binding of TaNF-YB1 and TaERF39 to the promoter regions of the TaPSK1-A gene, and TaMADS29 could bind to the promoters of TaPSK1-B and TaPSK1-D genes.ConclusionsComparative genome-wide analysis of TaPSK peptide family revealed that the TaPSK1 gene is involved in wheat grain development, and the developed TaPSK1-A-KASP marker could be utilized for marker-assisted selection breeding of wheat.Graphical

Translationally controlled tumor protein interacts with TaCIPK23 to positively regulate wheat resistance to Puccinia triticina.

Hypersensitive response-programmed cell death (HR-PCD) regulated by Ca2+ signal is considered the major regulator of resistance against Puccinia triticina (Pt.) infection in wheat. In this study, the bread wheat variety Thatcher and its near-isogenic line with the leaf rust resistance locus Lr26 were infected with the Pt. race 260 to obtain the compatible and incompatible combinations, respectively. The expression of translationally controlled tumor protein (TaTCTP) was upregulated upon infection with Pt., through a Ca2+-dependent mechanism in the incompatible combination. The knockdown of TaTCTP markedly increased the area of dying cell and the number of Pt. haustorial mother cells (HMCs) at the infection sites, whereas plants overexpressing the gene exhibited enhanced resistance. The interaction between TaTCTP and calcineurin B-like protein-interacting protein kinase 23 (TaCIPK23) was also investigated, and the interaction was found occurred in the endoplasmic reticulum. TaCIPK23 phosphorylated TaTCTP in vitro. The expression of a phospho-mimic TaTCTP mutant in Nicotiana benthamiana promoted HR-like cell death. Silencing TaCIPK23 or TaCIPK23/TaTCTP co-silencing resulted in the same results as silencing TaTCTP. This suggested that TaTCTP is a novel phosphorylation target of TaCIPK23, and both participate in the resistance of wheat to Pt. in the same pathway.

Identification and precise mapping of PmHSM, a novel recessive powdery mildew resistance allele from wheat landrace Heshangmai.

Common wheat (Triticum aestivum L.) is the world's primary food crop, and ensuring its safe production is of utmost importance for global peace and human development. However, the continuous threat of fungal diseases, including Fusarium head scab, rusts, sharp eyespot, and powdery mildew (PM), poses a significant challenge to production. PM caused by Blumeria graminis f. sp. tritici (Bgt) causes substantial yield losses. Heshangmai (HSM), a wheat landrace originating from Sichuan Province, possesses high levels of resistance to PM. A comprehensive study using a large segregating population of a cross between HSM and Ningmaizi119 (NMZ119) revealed a single recessive allele conferring resistance. The gene, provisionally designated PmHSM, was located on the long arm of chromosome 4A (4AL). Molecular marker analysis, PM response array, and an allelism test indicated that PmHSM is a novel recessive resistance gene that shares an allelic relationship with PmHHXM. Thirteen simple sequence repeat (SSR) markers were developed using the sequence information of the 4AL region in the Chinese spring reference sequence v2.1 (CS RefSeq v2.1). PmHSM was flanked by markers Xmp1567 and Xmp1444 at genetic distances of 0.11 cM and 0.18 cM, respectively, and co-segregated with markers Xmp1439/Xmp1440/Xmp1442.

Radiation synthesis of sodium alginate/gelatin based ultra-absorbent hydrogel for efficient water and nitrogen management in wheat under drought stress

The main focus of this study was on using radiation to make an ultra-absorbent hydrogel (UAH) from sodium alginate (SA) and gelatin (GL) biopolymers. This UAH can effectively handle water and nitrogen in wheat farming during drought stress. The hydrogel was synthesized by gamma irradiation-induced SA/GL/polyacrylamide crosslinking at 10–40 kGy. Varying SA/GL ratios affected swelling and the gel fraction of SA/GL/PAm hydrogels. The (SA/GL 17/83) hydrogel exhibited a 40.03 g/g swelling degree, while increasing SA content resulted in higher swelling, peaking at 75.5 g/g for (SA/GL 83/17). This indicated a synergistic interaction between SA and GL. The gel fraction also increased from 76.8 to 90.3%, with a higher GL content reflecting increased crosslinking. After multiple hydrolysis cycles, the hydrogel achieved 1293 (g/g) swelling and 36 days of water retention. When applied to wheat (Triticuma estivum) under drought stress, it significantly improved shoot length (18%), root length (43%), shoot fresh weight (49%), and shoot dry weight (51%) under extreme drought. The significant increases in protein and carbohydrate content in both shoots (up to 32% and 19%, respectively) and grains (up to 21% and 24%, respectively), along with the reduction in proline content (up to 38%), demonstrate that ultra-absorbent hydrogel (UAH) effectively enhances nitrogen content, photosynthesis, and overall plant health in wheat under varying drought stress levels. This novel SA/GL-based UAH holds promise for addressing water scarcity and agricultural challenges, offering a sustainable solution for water and nitrogen management under drought stress.

Preferentially expressed endosperm genes reveal unique activities in wheat endosperm during grain filling

BackgroundBread wheat (Triticum aestivum L.) endosperm contains starch and proteins, which determine the final yield, quality, and nutritional value of wheat grain. The preferentially expressed endosperm genes can precisely provide targets in the endosperm for improving wheat grain quality and nutrition using modern bioengineering technologies. However, the genes specifically expressed in developing endosperms remain largely unknown.ResultsIn this study, 315 preferentially expressed endosperm genes (PEEGs) in the spring wheat landrace, Chinese Spring, were screened using data obtained from an open bioinformatics database, which reveals a unique grain reserve deposition process and special signal transduction in a developing wheat endosperm. Furthermore, transcription and accumulation of storage proteins in the wheat cultivar, XC26 were evaluated. The results revealed that 315 PEEG plays a critical role in storage protein fragment deposition and is a potential candidate for modifying grain quality and nutrition.ConclusionThese results provide new insights into endosperm development and candidate genes and promoters for improving wheat grain quality through genetic engineering and plant breeding techniques.

Natural variation in photosynthetic electron transport of wheat flag leaves in response to dark-induced senescence

Early leaf senescence affects photosynthetic efficiency and limits growth during the late production stage of winter wheat (Triticum aestivum). Natural variation in photosystem response to senescence represents a valuable resource for improving the aging traits of flag leaves. To explore the natural variation of different phases of photosynthetic electron transport in modern wheat cultivars during senescence, we exposed the flag leaves of 32 wheat cultivars to dark conditions to induce senescence process, and simultaneously measured prompt fluorescence and modulated 820 nm reflection. The results showed that the chlorophyll content, activity of PSII donor side, PSI and electron transfer between PSII and PSI were all decreased during dark-induced senescence, but they showed different sensitivity to dark-induced senescence. Furthermore, natural variation in photosynthetic parameters among the 32 wheat cultivars were also observed and showed by variation coefficient of the different parameters. We observed that PSII and PSI activity showed less sensitivity to dark-induced senescence than electron transfer between them, while PSII and PSI activity exhibit greater natural variation than electron transport between PSII and PSI. It suggests that Cytb6f might degrade faster and have less variation than PSII and PSI during dark-induced senescence.

Assessment of Plant Growth Promoters on Growth Characteristics, Yield Attributes and Yield of Wheat (Triticum aestivum L.) Varieties in Central Plain Zone of Uttar Pradesh, India

Assessment of Plant Growth Promoters on Growth Characteristics, Yield Attributes and Yield of Wheat (Triticum aestivum L.) Varieties in Central Plain Zone of Uttar Pradesh, India

Impact of Farm Management Practices on Tick Infestation in Punjab's Livestock: A Comprehensive Epidemiological Study.

Tick infestation poses an important challenge to livestock in Pakistan. Farm management practices and environmental variables can influence tick infestation prevalence in animals. To this end, a cross-sectional survey of 96 farms in four different geographical districts (24 farms from each district) was conducted in Punjab, Pakistan, between October 2021 and January 2022. An epidemiological questionnaire was designed focusing on farm management practices and their impact on tick infestations at these farms. Data were collected via in-person interviews. Regional and farm-specific variables' associations were evaluated using Pearson's chi-square test and Fischer's exact test, respectively. A multivariable logistic regression model was used to identify significant risk factors. This study identified that using soft bedding materials, e.g., wheat straw, leaf litter or plain soil posed a significant risk of tick infestation. Additionally, the absence of quarantine measures, open sheds and inadequate drainage were found as contributing factors in univariable analysis. Higher tick prevalence in the hotter seasons highlighted the influence of Punjab's extreme weather on tick infestation. Despite regular veterinary visits and the use of acaricidal drugs, the prevalence of tick infestation at these farms suggested potential drug resistance in the ticks. The study recommended establishing quarantine practices, improving farms' drainage systems and bedding and using a combination of chemical and traditional remedies to tackle drug resistance in ticks. Education and awareness programs on tick-borne diseases and control measures are advocated to reduce the tick infestation burden on animals. Further research on longitudinal studies to better understand tick population dynamics and develop effective acaricides is encouraged. This called for collaborative control efforts among farmers, veterinarians and research institutions.

MnasNet-SimAM: An Improved Deep Learning Model for the Identification of Common Wheat Diseases in Complex Real-Field Environments.

Deep learning approaches have been widely applied for agricultural disease detection. However, considerable challenges still exist, such as low recognition accuracy in complex backgrounds and high misjudgment rates for similar diseases. This study aimed to address these challenges through the detection of six prevalent wheat diseases and healthy wheat in images captured in a complex natural context, evaluating the recognition performance of five lightweight convolutional networks. A novel model, named MnasNet-SimAM, was developed by combining transfer learning and an attention mechanism. The results reveal that the five lightweight convolutional neural networks can recognize the six different wheat diseases with an accuracy of more than 90%. The MnasNet-SimAM model attained an accuracy of 95.14%, which is 1.7% better than that of the original model, while only increasing the model's parameter size by 0.01 MB. Additionally, the MnasNet-SimAM model reached an accuracy of 91.20% on the public Wheat Fungi Diseases data set, proving its excellent generalization capacity. These findings reveal that the proposed model can satisfy the requirements for rapid and accurate wheat disease detection.

Characterization of New Wheat-Thinopyrum intermedium Derivative Lines with Superior Genes for Stripe Rust and Powdery Mildew Resistance.

The wild species Thinopyrum intermedium (genome JJJSJSStSt) serves as a valuable germplasm resource providing novel diseases resistance and agronomically important genes for wheat improvement. Two wheat-Th. intermedium partial amphiploids, TAI7045 (2n = 56) and 78784 (2n = 56), exhibit high resistance to stripe rust and powdery mildew, and their chromosome constitutions have been characterized. With the aim to transfer novel resistance genes from Th. intermedium, the crosses of common wheat line MY11 with TAI7045 and 78784 were produced, and their individual F2-F5 progenies were characterized using sequential non-denaturing fluorescence in situ hybridization (ND-FISH) and molecular markers. We identified a set of wheat-Th. intermedium addition lines, involving the chromosomes 1St-JS, 2St, 2St-JS, 3St, 4J, 4St, 5St, 5J.St, 6JS.J, and 7JS. Above all, the stable wheat-Th. intermedium small segmental translocation lines with chromosomes 4DS.4DL-4StL-4DL-4JL and 4DS.4DL-4StL-4DL were selected. Combining data from specific marker amplification and resistance evaluation, we mapped the gene(s) for resistance to powdery mildew and stripe rust in the 233.56-329.88 Mb region of the long arm of the 4St chromosome from the reference Th. intermedium genome. The new wheat-Th. intermedium introgressions will be used as novel germplasm for breeding purposes.

Assessing the Influence of Integrated Nutrient Management on Yield and Economics of Wheat (Triticum aestivum L.) in North Indian Plains

A field experiment was conducted during rabi season of 2022-2023 to study the effect of integrated nutrient management on yield and economic sustainability of wheat (Triticum aestivum L.) in Uttarakhand at the Agriculture Research Farm, Graphic Era Hill University, Dehradun, Uttarakhand. The experiment was conducted in randomized block design and consisted of eight treatments viz., T1 – Control, T2 – 100% RDF, T3- 100% RDF + FYM @ 5t ha-1, T4- 100 % RDF + VC @ 5t ha-1, T5- 75% RDF + FYM @ 5t ha-1, T6- 75% RDF + VC @ 5t ha-1, T7- 75% RDF + FYM @ 5t ha-1 + Azotobacter, T8- 75% RDF + VC @ 5t ha-1 + Azotobacter with three replications. The wheat variety used for the field experiment was HD-2967 with a seed rate of 100 kg ha-1. Row-row spacing of 20 cm and plant -plant spacing of 10 cm was maintained. Different nutrient sources used were urea, DAP, MOP, FYM, VC and Azotobacter. Seed were primed with Azotobacter @ 20g kg-1 seed as per the treatment. The investigation revealed that, application of 75% RDF + VC @ 5t ha-1 + Azotobacter (T8) resulted in significantly higher yield attributes no. of spikes/m2, spike length (cm), grain/spike, 1000 grain weight (g) over control. The maximum grain yield (50.2 q ha-1) of wheat were obtained with application of 75% RDF + VC @ 5t ha-1 + Azotobacter (T8) closely followed by 75% RDF + FYM @ 5t ha-1 + Azotobacter (T7). Moreover, straw yield was 85.92% higher over the control. The maximum gross return (₹ 141646.0), and net return (₹ 100045.0) of wheat was obtained with application of 75% RDF + VC @ 5t ha-1 + Azotobacter (T8) followed by the 75% RDF + FYM @ 5t ha-1 + Azotobacter (T7). The maximum benefit-cost ratio (2.79) was obtained with the application of 75% RDF + FYM @ 5t ha-1 + Azotobacter (T7). From the above investigation it can be concluded that 75% RDF + VC @ 5t ha-1 + Azotobacter is superior to other treatment in improving the productivity and economic returns of wheat.

Exploring the effects of spontaneous and solid-state fermentation on the physicochemical, functional and structural properties of whole wheat flour (Triticum aestivum L.)

The effects of fermentation on various physicochemical and functional properties of whole wheat flour (Triticum aestivum L.) were investigated in this study. Firstly, changes in pH and total titratable acidity (TTA) were observed during spontaneous and solid-state fermentation. Spontaneous and solid-state fermentation led to a decrease in pH and a rapid increase in TTA, indicating effective acidification due to organic acid production. Both fermentation approaches significantly influenced the total starch and amylose content of wheat. The total starch content was decreased accompanied by a significant increase in apparent amylose content. This phenomenon was attributed to starch hydrolysis facilitated by microbial enzymes and organic acids, resulting in a higher amylose/amylopectin ratio. Chemical composition and mineral content of whole wheat flour were also affected. Fermentation led to reductions in moisture, crude fat, and crude protein content, while ash content increased. Furthermore, fermentation significantly impacted the soluble and total dietary fiber content of whole wheat flour, with an increase in soluble dietary fiber and a decrease in total dietary fiber. These changes were attributed to increased synthesis of non-cellulosic polysaccharides and β-glucans during fermentation. Moreover, fermentation resulted in reductions in gluten content, alterations in functional properties such as water and oil absorption capacity, changes in protein solubility, and modifications in gel texture properties. Finally, X-ray diffraction (XRD) and scanning electron microscopy (SEM) revealed minimal changes in the crystalline structure and morphology of starch granules during fermentation, with some signs of surface erosion and degradation, particularly in solid-state fermented samples. The results highlight the potential benefits of fermentation for improving the properties of whole wheat flour. This study contributes to a better understanding of the effects of fermentation on whole wheat flour, offering insights for the development of novel and improved whole wheat flour-based food products.

Genetic dissection of value-added quality traits and agronomic parameters through genome-wide association mapping in bread wheat (T. aestivum L.).

Bread wheat (T. aestivum) is one of the world's most widely consumed cereals. Since micronutrient deficiencies are becoming more common among people who primarily depend upon cereal-based diets, a need for better-quality wheat varieties has been felt. An association panel of 154 T. aestivum lines was evaluated for the following quality traits: grain appearance (GA) score, grain hardness (GH), phenol reaction (PR) score, protein percent, sodium dodecyl sulfate (SDS) sedimentation value, and test weight (TWt). In addition, the panel was also phenotyped for grain yield and related traits such as days to heading, days to maturity, plant height, and thousand kernel weight for the year 2017-18 at the Borlaug Institute for South Asia (BISA) Ludhiana and Jabalpur sites. We performed a genome-wide association analysis on this panel using 18,351 genotyping-by-sequencing (GBS) markers to find marker-trait associations for quality and grain yield-related traits. We detected 55 single nucleotide polymorphism (SNP) marker trait associations (MTAs) for quality-related traits on chromosomes 7B (10), 1A (9), 2A (8), 3B (6), 2B (5), 7A (4), and 1B (3), with 3A, 4A, and 6D, having two and the rest, 4B, 5A, 5B, and 1D, having one each. Additionally, 20 SNP MTAs were detected for yield-related traits based on a field experiment conducted in Ludhiana on 7D (4) and 4D (3) chromosomes, while 44 SNP MTAs were reported for Jabalpur on chromosomes 2D (6), 7A (5), 2A (4), and 4A (4). Utilizing these loci in marker-assisted selection will benefit from further validation studies for these loci to improve hexaploid wheat for better yield and grain quality.

Genome-Wide Characterization of Glyceraldehyde-3-Phosphate Dehydrogenase Genes and Their Expression Profile under Drought Stress in Quercus rubra.

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is crucial in plant metabolism and responses to various abiotic stresses. In the glycolysis pathway, glyceraldehyde-3-phosphate (G3P) is oxidized to 1,3-bisphosphate glycerate (1,3-BPG) through the catalytic action of GAPDH. However, the GAPDH gene family in Quercus rubra has been minimally researched. In this study, we identified 13 GAPDH-encoding genes in Q. rubra through a bioinformatics analysis of genomic data. Evolutionary studies suggest that these QrGAPDH genes are closely related to those in Glycine max and Triticum aestivum. We conducted a comprehensive whole-genome study, which included predictions of subcellular localization, gene structure analysis, protein motif identification, chromosomal placement, and analysis of cis-acting regions. We also examined the expression of GAPDH proteins and genes in various tissues of Q. rubra and under drought stress. The results indicated diverse expression patterns across different tissues and differential expression under drought conditions. Notably, the expression of Qurub.02G290300.1, Qurub.10G209800.1, and Qrub.M241600.1 significantly increased in the leaf, stem, and root tissues under drought stress. This study provides a systematic analysis of QrGAPDH genes, suggesting their pivotal roles in the drought stress response of trees.

Zinc supply effects on wheat production in a low precipitation zone

AbstractZinc (Zn) fertilization of hard red and soft white winter wheat (Triticum aestivum L.) is uncommon in the low precipitation zone of the inland Pacific Northwest. It is uncommon because there have been no indications of deficiency. Soil test data, however, show Zn levels have been declining over time. We conducted a four‐site‐year experiment to evaluate effects of fertilization on early‐season tissue Zn concentration (TZC), dry matter accumulation (DMA), Zn uptake (ZNU), the grain test weight (TWT), protein content (PRO), and yield (YLD) of two regionally adapted cultivars. Planting occurred late in September or early in October. Zinc fertilizer, placed with the seed while planting, was applied at rates of 0 and 5 kg Zn ha−1. Application of 5 kg Zn ha−1 increased TZC and ZNU at one of two sites. There were corresponding trends of increased DMA and improved YLD. Response to fertilization occurred on a relatively shallow soil that had a diethylenetriamine‐pentaacidic acid–extractable Zn test level of 0.3 mg kg−1.

A genotype–phenotype approach to discriminate Central European spelt landraces from modern wheat-spelt intercrosses in the Swiss context

Marketed as a healthier alternative to bread wheat, spelt (Triticum aestivum ssp. spelta) is in increasing demand from consumers and bakers in Switzerland. The Swiss spelt landscape is currently dominated by two varieties—Ostro and Oberkulmer Rotkorn—considered as references for Swiss “typical” spelt. However, these two varieties are rather old and deliver low yields; the market therefore needs improved spelt varieties with higher agronomic potential while keeping the essential attributes of typical spelt. As spelt and winter wheat can be interbred, modern spelt varieties often result from crosses between the two. It has therefore become increasingly difficult to distinguish between typical spelt and modern wheat-spelt intercrosses. This project aims to clarify the phenotypic distinction between typical spelt and modern wheat-spelt intercrosses in the Swiss context. To do this, we performed field trials with 50 spelt varieties, including typical and modern cultivars from Switzerland and Central Europe. We measured agronomic, rheological and nutritional parameters of each variety. In addition, these cultivars were genotyped using a 25 K Illumina Wheat SNP array. This allowed us to identify which phenotypic parameters were associated with genetic proximity to typical spelt. Swiss typical spelt varieties were characterized by highly extensible doughs, later phenology, low harvest index, high thousand kernel weights, and lower Zeleny/protein ratio. By linking phenotypic characteristics, easily measurable in fields, to the underlying genetic information of each variety, these results will help to better classify spelt varieties in Switzerland and pave the way for more clarity and transparency on the Swiss spelt market.

Chromosome-specific painting reveals the Y genome origin and chromosome rearrangements of the St genome in Triticeae.

Karyotypes provide key cytogenetic information on phylogenetic relationships and evolutionary origins in related plant species. The St genome of Pseudoroegneria contributes to eight alloploid genera, representing over half of the species that are highly valuable for wheat (Triticum aestivum) breeding and for understanding Triticeae species evolution. However, St chromosome characterization is challenging due to limited cytogenetic markers and DNA information. We developed a complete set of St genome-specific chromosome painting probes for identification of the individual chromosomes 1St to 7St based on the genome sequences of Pse. libanotica and wheat. We revealed the conservation of St chromosomes in St-containing species by chromosome painting, including Pseudoroegneria, Roegneria, Elymus, and Campeiostachys. Notably, the Y genome showed hybridization signals, albeit weaker than those of the St genome. The awnless species harboring the Y genome exhibited more intense hybridization signals compare to the awned species in Roegneria and Campeiostachys, yet weaker than the hybridization signals of the St genome in autotetraploid Pse. strigosa. Although awnless species were morphologically more similar to each other, phenotypic divergence progressively increased from awnless to awned species. Our results indicate that the Y genome originated from the St genome and shed light on the possible origin of the Roegneria and Campeiostachys species, enhancing our understanding of St-genome-containing species evolution.

Bread wheat cultivar Popo harbors QTLs for seedling and adult plant resistance to leaf rust in South African and Argentine environments

Leaf rust, caused by the fungus Puccinia triticina Eriks (Pt), is a destructive disease affecting wheat (Triticum aestivum L.) production in many countries, and a serious threat to food security. As a result, several breeding programs have included leaf rust resistance as an important trait. The discovery and identification of new resistance genes that could aid in incorporating durable or long-lasting leaf rust resistance into wheat is fundamental in these breeding programs. The present study aimed to identify quantitative trait loci (QTLs) for leaf rust resistance in 127 recombinant inbred lines (RIL) developed from the cross between the resistant wheat cultivar Popo and the susceptible cultivar Kariega. The RIL population and parental lines were phenotyped for leaf rust infection type and severity at seedling and adult plant stage, respectively. The former in the greenhouse (in Argentina) and the latter in multiple field test environments comprising 3 locations in South Africa (in Tygerhoek in the Western Cape Province during the 2014, 2015, 2017 and 2018 cropping seasons; Clarens during 2014, 2016 and 2017 cropping seasons and in Bethlehem in the Free State Province during 2017 cropping season) and in 1 location in Argentina (during the 2017 and 2018 cropping seasons in Marcos Juárez, Córdoba Province). The population was genotyped using genotyping-by-sequencing. A total of 12,080 silicoDArT and 2,669 SNP markers were used for QTL analysis. In total, 25 putative QTLs for resistance to leaf rust at seedling and adult plant stages were identified, including 5 QTLs for seedling and 20 QTLs for adult plant resistance (APR). Interestingly, both Popo and Kariega contributed with alleles for resistance. Significant loci for reducing leaf rust infection at seedling stage were designated QLr.arc-1A, QLr.arc-2B, QLr.arc-5B, QLr.arc-6A and QLr.arc-6D. Three minor QTLs derived from Popo designated as QLr.arc-1B1, QLr.arc-2D and QLr.arc-3D were also detected from the field tests, explaining 5–10%, 10–16% and 5–7% of the phenotypic variance, respectively. The identified QTLs and their closely linked silicoDArT and SNP-based markers can be used for fine mapping and candidate gene discovery in wheat breeding programs targeting durable leaf rust resistance.

Fine mapping of stem rust resistance derived from soft red winter wheat cultivar AGS2000 to an NLR gene cluster on chromosome 6D

The Puccinia graminis f. sp. tritici (Pgt) Ug99-emerging virulent races present a major challenge to global wheat production. To meet present and future needs, new sources of resistance must be found. Identification of markers that allow tracking of resistance genes is needed for deployment strategies to combat highly virulent pathogen races. Field evaluation of a DH population located a QTL for stem rust (Sr) resistance, QSr.nc-6D from the breeding line MD01W28-08-11 to the distal region of chromosome arm 6DS where Sr resistance genes Sr42, SrCad, and SrTmp have been identified. A locus for seedling resistance to Pgt race TTKSK was identified in a DH population and an RIL population derived from the cross AGS2000 × LA95135. The resistant cultivar AGS2000 is in the pedigree of MD01W28-08-11 and our results suggest that it is the source of Sr resistance in this breeding line. We exploited published markers and exome capture data to enrich marker density in a 10 Mb region flanking QSr.nc-6D. Our fine mapping in heterozygous inbred families identified three markers co-segregating with resistance and delimited QSr.nc-6D to a 1.3 Mb region. We further exploited information from other genome assemblies and identified collinear regions of 6DS harboring clusters of NLR genes. Evaluation of KASP assays corresponding to our co-segregating SNP suggests that they can be used to track this Sr resistance in breeding programs. However, our results also underscore the challenges posed in identifying genes underlying resistance in such complex regions in the absence of genome sequence from the resistant genotypes.