Wheat Accessions Research Articles

Favorable Loci Identified for Stripe Rust Resistance in Chinese Winter Wheat Accessions via Genome-Wide Association Study.

Stripe rust (or yellow rust), caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most devastating diseases of wheat worldwide. Currently, the utilization of resistant cultivars is the most viable way to reduce yield losses. In this study, a panel of 188 wheat accessions from China was evaluated for stripe rust resistance, and genome-wide association studies were performed using high-quality Diversity Arrays Technology markers. According to the phenotype and genotype data, a total of 26 significant marker-trait associations were identified, representing 18 quantitative trait loci (QTLs) on chromosomes 1B, 2A, 2B, 3A, 3B, 5A, 5B, 6B, 7B, and 7D. Of the 18 QTLs, almost all were associated with adult plant resistance (APR) except QYr.nwsuaf-6B.2, which was associated with all-stage resistance (also known as seedling resistance). Three of the 18 QTLs were mapped far from previously identified Pst resistance genes and QTLs and were considered potentially new loci. The other 15 QTLs were mapped close to known resistance genes and QTLs. Subsequent haplotype analysis for QYr.nwsuaf-2A and QYr.nwsuaf-7B.3 revealed the degrees of resistance of the panel in the APR stage. In summary, the favorable alleles identified in this study may be useful in breeding for disease resistance to stripe rust.

Resistance of old winter bread wheat landraces to tan spot

Background. The most effective and environmentally safe way to combat wheat diseases is to produce cultivars resistant to their pathogens. For this purpose, old landraces are often used as genetically diverse sources of traits important for breeding. In the process of wheat breeding for resistance to tan spot caused by the fungus Pyrenophora tritici-repentis (Died.) Drechs. (abbr. Ptr), selection is carried out against the dominant allele of Tsn1, the gene of sensitivity to the toxin Ptr ToxA, which induces necrosis and represents the main pathogenicity factor of Ptr controlled by the ToxA gene. The aim of the study was to characterize a set of bread wheat (Triticum aestivum L.) accessions from the VIR collection for resistance to various Ptr populations, genotype these accessions using Xfcp623 – a DNA marker of the Tsn1 gene, and identify sources of tan spot resistance.Materials and methods. Sixty-seven accessions of winter bread wheat landraces were studied. Seedling resistance to two Ptr populations was assessed using a 5-point scale adopted at VIZR. The allelic state of Tsn1 was identified by PCR.Results. Dominant alleles of Tsn1 were found for 55% of the studied accessions. Seventeen accessions were resistant or moderately resistant to two Ptr populations and an isolate from Krasnodar Territory previously used for their characterization. Nine of them had the tsn1tsn1 genotype, and 8 had Tsn1Tsn1. The accessions mainly belonged to three agroecological groups proposed by N. I. Vavilov: “steppe winter bread wheat (Banatka wheats)”, “North European forest awnless bread wheats (Sandomirka wheats)”, and “Caucasian mountain winter bread wheat”.Conclusion. The identified 17 accessions resistant to Ptr are potential breeding sources of resistance. In the studied set of accessions, no significant relationship was found between the allelic state of the Tsn1 gene in the accession and its response to the infection with pathogen populations, including isolates with the ToxA gene.

Virulence diversity of the yellow rust pathogen population in Dagestan

Background. Yellow rust incidence on Triticum L. has been observed to surge up in Dagestan in recent years, facilitating selection of highly resistant genotypes. Information on the effectiveness of Yr genes and the pathogen’s virulence and racial composition is needed to interpret field assessment data correctly. The objective of this study was to describe the virulence of the Dagestan population of Puccinia striiformis West. at the seedling stage, evaluate the resistance of differentiators to yellow rust in the field, and identify invasive PstS1 and PstS2 races.Materials and methods. Leaves with urediniopustules were collected from bread wheat accessions at Dagestan Experiment Station of VIR (DЕS VIR) in 2020–2022. Virulence was analyzed in the laboratory using 14 AvYr lines (Avocet NIL) and 15 differential wheat cultivars. Age-specific resistance of virulence testers under high natural infection pressure was studied in the field of DES VIR. A set of SCAR markers (SCP19M24a1, SCP19M24a2, SCP19M26a1, and SCP19M26a2) were used to identify invasive races.Results and discussion. Avocet lines with Yr5, Yr10, Yr15, Yr24, and Yr26, and cv. ‘Moro’ (Yr10, YrMor) manifested resistance to all isolates. Virulence to Yr17 was detected only in the isolates from cvs. ‘Graf’ and ‘Svarog’ carrying this gene, and ‘Siete Ceros’. The Dagestan collection demonstrated high genetic diversity. Common phenotypes were identified on cv. ‘Graf’ in 2021 and 2020. There was no temporal differentiation between pathogen collections in the years of testing. High field resistance to yellow rust was recorded in lines with Yr5, Yr8, Yr10, Yr15 and Yr24, and in cvs. ‘Moro’, ‘Compair’, ‘Carstens’ and ‘Spaldings Prolific’. Cvs. ‘Reichersberg 42’ and ‘Heines Peko Vilmorin 23’ were resistant in 2020 and 2022, and moderately affected (up to 10%) in 2021. Molecular analysis identified all three isolates belonging to the invasive PstS2 group on cv. ‘Siete Cerros’ and L 650 in 2021, and cv. ‘Vassa’ in 2022.

Diversification of quantitative morphological traits in wheat.

The development and morphology of crop plants have been profoundly altered by evolution under cultivation, initially through unconscious selection, without deliberate foresight, and later by directed breeding. Wild wheats remain an important potential source of variation for modern breeders; however, the sequence and timing of morphological changes during domestication are not fully resolved. We grew and measured 142 wheat accessions representing different stages in wheat evolution, including three independent domestication events, and compared their morphological traits to define the morphospace of each group. The results show that wild and domesticated wheats have overlapping morphospaces, but each also occupies a distinct area of morphospace from one another. Polyploid formation in wheat increased leaf biomass and seed weight but had its largest effects on tiller loss. Domestication continued to increase the sizes of wheat leaves and seeds and made wheat grow taller, with more erect architecture. Associated changes to the biomass of domesticated wheats generated more grains and achieved higher yields. Landrace improvement subsequently decreased the numbers of tillers and spikes, to focus resource allocation to the main stem, accompanied by a thicker main stem and larger flag leaves. During the Green Revolution, wheat height was reduced to increase the harvest index and therefore yield. Modern wheats also have more erect leaves and larger flower biomass proportions than landraces. Quantitative trait history in wheat differs by trait. Some trait values show progressive changes in the same direction (e.g. leaf size, grain weight), whereas others change in a punctuated way at particular stages (e.g. canopy architecture), and other trait values switch directions during wheat evolution (e.g. plant height, flower biomass proportion). Agronomically valued domestication traits arose during different stages of wheat history, such that modern wheats are the product of >10 000 years of morphological evolution.

Genetic variation, genetic advance, heritability and correlation analysis of phenotypic traits in tetraploid wheat (Triticum turgidum spp.) landraces and some improved cultivars of Ethiopia

AbstractTetraploid wheat species from Ethiopia hold ample genetic variation, which could provide a source for improvement of wheat. A total of 196 Ethiopian tetraploid wheat (Triticum turgidum spp.) accessions, including 174 landraces and 22 improved cultivars, were evaluated at Sinana and Debrezeit to assess morphological variation, genetic advance, heritability and correlation based on 11 phenotypic traits. Except for spike length, highly significant variation (P < 0.001) among genotypes for all traits was observed. The observed mean and range values of the phenotypic traits revealed high variability in the accessions. Phenotypic coefficient of variation (PCV) and genotypic coefficient of variation (GCV) values were high for grain yield, biomass yield and harvest index. Seed yield showed highly significant (P < 0.001) negative correlation with days to booting and days to maturity and positive correlation with all traits. The estimates of heritability (H2) for grain yield and the number of spikelets per spike respectively ranged from 41.78 to 84.62%. The genetic advance as a percentage of mean was low for the number of seeds per spikelet, days to booting and days to maturity; intermediate for plant height, thousand kernel weight and spike length and high for the number of spikelets per spike, the number of effective tillers per plant, grain yield, biomass yield and harvest index, respectively. The number of spikelets per spike gave a high value of genetic advance and heritability implying high genetic gain from its selection.

Genome-wide association study of agronomic traits related to nitrogen use efficiency in Henan wheat

BackgroundNitrogen use efficiency (NUE) is closely related to crop yield and nitrogen fertilizer application rate. Although NUE is susceptible to environments, quantitative trait nucleotides (QTNs) for NUE in wheat germplasm populations have been rarely reported in genome-wide associated study.ResultsIn this study, 244 wheat accessions were phenotyped by three NUE-related traits in three environments and genotyped by 203,224 SNPs. All the phenotypes for each trait were used to associate with all the genotypes of these SNP markers for identifying QTNs and QTN-by-environment interactions via 3VmrMLM. Among 279 QTNs and one QTN-by-environment interaction for low nitrogen tolerance, 33 were stably identified, especially, one large QTN (r2 > 10%), qPHR3A.2, was newly identified for plant height ratio in one environment and multi-environment joint analysis. Among 52 genes around qPHR3A.2, four genes (TraesCS3A01G101900, TraesCS3A01G102200, TraesCS3A01G104100, and TraesCS3A01G105400) were found to be differentially expressed in low-nitrogen-tolerant wheat genotypes, while TaCLH2 (TraesCS3A01G101900) was putatively involved in porphyrin metabolism in KEGG enrichment analyses.ConclusionsThis study identified valuable candidate gene for low-N-tolerant wheat breeding and provides new insights into the genetic basis of low N tolerance in wheat.

Evaluation of salt stress resistance in diploid wheat species

The National Gene Bank of the Genetic Resources Institute of Azerbaijan houses over 2,000 wheat accessions, vital for breeding plants resilient to environmental stresses. This study focuses on comparing the salinity stress resistance of three diploid wheat species: Triticum monococcum L., Triticum boeoticum (L.) Boiss, and Triticum urartu Thum. ex Gandil., comprising 170 accessions from the ICARDA gene bank. Salinity stress resistance was assessed according to the capacity of the genotypes to exclude Na+ ions from leaves. A wide variation was observed among accessions for stress response, allowing for classification them into resistant, moderately resistant, and susceptible groups within each species. Analysis revealed differing resistance percentages among species. T. boeoticum had 61% resistant, 20.8% moderately resistant, and 18.2% susceptible accessions. T. monococcum showed 40%, 33.3%, 26.7%, and T. urartu had 23%, 50.6%, 26.4% respectively. Notably, T. boeoticum exhibited greater resistance than T. monococcum and T. urartu, attributed to its wild-growing nature and distinct biomorphological, biochemical, and molecular features. Salt-tolerant accessions are recommended for breeding programs and stored in both the National Gene Bank of Azerbaijan and the ICARDA Gene Bank. These findings highlight the potential of utilizing salt-tolerant accessions, particularly Triticum boeoticum genotypes, in targeted breeding programs to enhance wheat's resilience to salinity stress.

Identification of Sr67, a new gene for stem rust resistance in KU168-2 located close to the Sr13 locus in wheat

Key messageSr67 is a new stem rust resistance gene that represents a new resource for breeding stem rust resistant wheat cultivarsRe-appearance of stem rust disease, caused by the fungal pathogen Puccinia graminis f. sp. tritici (Pgt), in different parts of Europe emphasized the need to develop wheat varieties with effective resistance to local Pgt populations and exotic threats. A Kyoto University wheat (Triticum aestivum L.) accession KU168-2 was reported to carry good resistance to leaf and stem rust. To identify the genomic region associated with the KU168-2 stem rust resistance, a genetic study was conducted using a doubled haploid (DH) population from the cross RL6071 × KU168-2. The DH population was phenotyped with three Pgt races (TTKSK, TPMKC, and QTHSF) and genotyped using the Illumina 90 K wheat SNP array. Linkage mapping showed the resistance to all three Pgt races was conferred by a single stem rust resistance (Sr) gene on chromosome arm 6AL, associated with Sr13. Presently, four Sr13 resistance alleles have been reported. Sr13 allele-specific KASP and STARP markers, and sequencing markers all showed null alleles in KU168-2. KU168-2 showed a unique combination of seedling infection types for five Pgt races (TTKSK, QTHSF, RCRSF, TMRTF, and TPMKC) compared to Sr13 alleles. The phenotypic uniqueness of the stem rust resistance gene in KU168-2 and null alleles for Sr13 allele-specific markers showed the resistance was conferred by a new gene, designated Sr67. Since Sr13 is less effective in hexaploid background, Sr67 will be a good source of stem rust resistance in bread wheat breeding programs.

Using UAV-Based Temporal Spectral Indices to Dissect Changes in the Stay-Green Trait in Wheat.

Stay-green (SG) in wheat is a beneficial trait that increases yield and stress tolerance. However, conventional phenotyping techniques limited the understanding of its genetic basis. Spectral indices (SIs) as non-destructive tools to evaluate crop temporal senescence provide an alternative strategy. Here, we applied SIs to monitor the senescence dynamics of 565 diverse wheat accessions from anthesis to maturation stages over 2 field seasons. Four SIs (normalized difference vegetation index, green normalized difference vegetation index, normalized difference red edge index, and optimized soil-adjusted vegetation index) were normalized to develop relative stay-green scores (RSGS) as the SG indicators. An RSGS-based genome-wide association study identified 47 high-confidence quantitative trait loci (QTL) harboring 3,079 single-nucleotide polymorphisms associated with SG and 1,085 corresponding candidate genes. Among them, 15 QTL overlapped or were adjacent to known SG-related QTL/genes, while the remaining QTL were novel. Notably, a set of favorable haplotypes of SG-related candidate genes such as TraesCS2A03G1081100, TracesCS6B03G0356400, and TracesCS2B03G1299500 are increasing following the Green Revolution, further validating the feasibility of the pipeline. This study provided a valuable reference for further quantitative SG and genetic research in diverse wheat panels.

Molecular Description for Some Promising Wheat Accessions Tolerated to water Stress

Molecular Description for Some Promising Wheat Accessions Tolerated to water Stress

Breeding value and homeostaticity of the spike performance and its constituents in medium tall winter bread wheat (Triticum aestivum L.) accessions in relation to resistance to the pathogens of powdery mildew (Blumeria graminis (DC.)...

Identification of sources of group resistance in winter bread to the pathogens B. graminis (DC.) E.O. Speer f. sp. tritici Em. Marchal and S. tritici Rob. et Desm. and of high performance of the spike and its constituents is a necessary and relevant step towards the creation of comprehensively valuable and adaptable genotypes. The paper presents the results of evaluation of the breeding value and homeostaticity of the spike performance and its constituents in medium tall winter bread wheat in relation to resistance to powdery mildew and Septoria leaf blotch. New sources of consistently high group resistance to the powdery mildew and Septoria leaf blotch pathogens have been identified: Kyivska 17, Zorianka, Sicheslava, and Svitiaz (UKR). We have selected accessions with high performance of the spike and its constituents in combination with high breeding value and homeostaticity of these characteristics: the kernel weight per spike (Kyivska 17 (Sc = 1.8; Hom = 21.9) (UKR)); the kernel number per spike (Svitohliad (Sc = 37.8; Hom = 554.1), Stritenska (Sc = 36.4; Hom = 452.5), Svitiaz (Sc = 35.8; Hom = 451.8), MIP Lada (Sc = 33.6; Hom = 572.7) (UKR), and Manella (Sc = 33.1; Hom = 460.8) (NLD)); and the thousand kernel weight (Kyivska 17 (Sc = 42.9; Hom = 1053.7), Sicheslava (Sc = 42.6; Hom = 873.2) (UKR), and Turanus (Sc = 41.3; Hom = 707.5) (AUT)). It was found that the percentage of accessions with high homeostaticity of the thousand kernel weight, the kernel number per spike and the kernel weight per spike was 63.6%, 31.8%, and 22.7%, respectively. In the medium tall winter bread wheat accessions, there were strong positive correlations between the breeding value of the kernel weight per spike and resistance to Septoria leaf blotch (r = 0.77, P < 0.01) and between the kernel number per spike and resistance to powdery mildew (r = 0.71, P < 0.01). Significant positive correlations were observed between the breeding value of the thousand kernel weight and resistance to Septoria leaf blotch (r = 0.61, P < 0.01), between the homeostaticity of the thousand kernel weight and resistance to Septoria leaf blotch (r = 0.51, P < 0.01) and between the breeding value of the kernel number per spike and resistance to Septoria leaf blotch (r = 0.56, P < 0.01). The selected sources of high group resistance to powdery mildew and Septoria leaf blotch, high performance of the spike and its constituents in combination with the breeding value and homeostaticity of these traits are valuable starting materials to create highly promising winter bread wheat cultivars, which would be adaptable to limiting biotic factors.

Characterization of the starch molecular structure of wheat varying in the content of resistant starch

Resistant starch (RS) is the total amount of starch that is incompletely or not digested and absorbed in the small intestine. It plays a role similar to dietary fibre with beneficial effects for human health. In this study, the RS content of 129 wheat accessions was determined, and the relationship between the several starch physical properties and resistant starch content were analyzed. By comparing the total starch content, amylose starch content, starch chain length distribution, starch crystallization type, starch branching degree, and starch granule morphology between the high RS and low RS content wheat accessions, it was found that the amylose content and RS content were significantly positively correlated. However, in the range of chain length fb 3 (DP ≥ 37), there was a significant negative correlation between amylopectin content and RS content. The surface of starch granules became increasingly smooth as the content of RS increased.

CHARACTERIZATION OF CIMMYT BREAD WHEAT GERMPLASM FOR RESISTANCE TO YELLOW RUST AND ENVIRONMENTAL FACTORS

One of the major tasks faced by wheat breeders in Uzbekistan is to enhance wheat genotypes’ adaptability to soil and other environmental conditions and improve the grain quality, making the country self-sufficient in wheat grains and later becoming an exporter. Better results are achievable using the world wheat collection, including the CIMMYT germplasm. Determination of the positive correlation of physiological traits of new wheat cultivars, the importance of physiological indicators of water balance with productivity, and the vital role of these indicators in productivity level were the chief concerns. The timely study evaluated heat resilience, rust resistance, and grain yield in bread wheat genotypes. Bread wheat germplasm obtained from CIMMYT with a background of artificial infection of yellow rust incurred scrutiny for their rust resistance. A 15% incidence was detectable in seven genotypes; however, necrosis quickly formed around the symptoms of the disease in plant leaves, preventing its further development. Resistant wheat accessions, i.e., 1088, 1164 (R), 1006, and 1251 (MR), occurred as moderately resistant, showing high leaf area and grain yield. The average value of the genotypes was low, mainly due to the two rust-resistant samples, and the 1000-grain weight was 34.8 g and 34.6 g, respectively, and the grains per spike and grain yield were lower than the average. The chlorophyll a and b, total chlorophyll, carotenoid content, relative water content, flag leaf area, and production traits of the genotypes К-1088 and К-1164 gained assessment, revealed to be physiologically effective under the field conditions of Tashkent, Uzbekistan. Quantitative indicators of the productivity of these wheat genotypes indicated positive differentiation. Selection ensued for promising accessions to develop initial sources for producing the wheat genotypes with rust resistance and high grain yield under the environmental conditions of Uzbekistan.

Nanopore Amplicon Sequencing Allows Rapid Identification of Glutenin Allelic Variants in a Wheat Collection

Genetic variation in high molecular weight glutenin (HMW-GS) genes is tightly linked with the breadmaking quality of wheat. Hundreds of different alleles have been identified in HMW-GS genes worldwide. Such huge variability makes it difficult to distinguish them using conventional genotyping methods (for example, SDS-PAGE, SNP detection, etc.). Here, we exploited the nanopore amplicon sequencing technique (Amplicon-Seq) to uncover genetic variants distributed along the full-length sequence of six HMW-GSs, including the promoter and protein-coding regions. We analyzed 23 wheat accessions for allelic variants of HMW-GSs using the Amplicon-Seq and SDS-PAGE methods. We obtained sufficient (>50×) target gene coverage by ONT reads in just one hour. Using the obtained data, we identified numerous single nucleotide polymorphisms and InDels in the protein coding and promoter regions. Moreover, Amplicon-Seq allowed for the identification of new alleles (Glu-A1x1-T) of the Glu-1Ax gene that could not be recognized by SDS-PAGE. Collectively, our results showed that Amplicon-Seq is a rapid, multiplexed, and efficient method for high-throughput genotyping of full-length genes in large and complex genomes. This opens new avenues for the assessment of target gene variation to select novel alleles and create unique combinations of desirable traits in plant breeding programs.

Some Agronomic Properties of Winter Wheat Genotypes Grown at Different Locations in Croatia

A collection of fourteen winter wheat accessions was evaluated to describe agro-morphological traits over a two-year study at four locations. Changes in grain yield, test weight, and plant height were related to differences in growing seasons, locations, genotypes, and their interactions. Thus, some genotypes are suitable for one location but not for another. However, a PCA showed that genotypes 2, 26, 28, 32, and 31 were the most stable across environments. In the 2022/2023 season, a negative relationship was observed between septoria leaf blotch, septoria nodorum blotch, yellow rust, fusarium head blight, and grain yield. Grain yield decreased by 84.8, 72.3, 37.4, and 4.3% in Kutjevo, Osijek, Tovarnik, and Zagreb, respectively, compared to the 2021/2022 season. Additionally, in the 2022/2023 season, barley yellow dwarf virus weakened wheat plants, especially at the locations Kutjevo, Tovarnik, and Osijek, where a relationship was observed with septoria leaf blotch and powdery mildew. At the Zagreb location, wheat genotypes were planted at the latest sowing date, probably escaping the virus pressure after plants easily tolerated diseases, resulting in a significantly higher mean grain yield.

The wheat sucrose synthase gene TaSus1 is a determinant of grain number per spike

Some haplotypes of the sucrose synthase gene TaSus1 are associated with thousand-grain weight (TGW) in wheat (Triticum aestivum L.). However, no mutations have been identified within the gene to test this association. The effects of TaSus1 on grain number per spike (GNS) also are largely unknown. Our previous genome-wide association study identified TaSus-A1 as a candidate gene controlling fertile spikelet number per spike (FSN). In the present study, we generated two independent mutants for the three TaSus1 homoeologs by CRISPR/Cas9-mediated genome editing. The triple mutants displayed lower FSN, GNS, grain number per spikelet (GNST), and TGW than wild-type plants. In 306 hexaploid wheat accessions, two single-nucleotide polymorphisms in TaSus-A1 contributed differently to GNS. Introgression of the two alleles into a wheat genetic background confirmed their effects. The alleles differed in geographical distribution among the accessions.

Phytosanitary management of ICARDA’s germplasm seed collections for safe movement and better future use

Abstract Germplasm exchange from international genebanks and breeding programs is vital for successful crop improvement programs. More than 10,000 different accessions of wheat, barley, lentil, faba bean, chickpea, grasspea, and pasture and forage crops are distributed by the International Center for Agricultural Research in the Dry Areas (ICARDA) every year to around 70 countries. New accessions are added to the germplasm collections in the Center's genebank and utilized in the breeding programs. Recent years have witnessed an increasing global concern about the loss of plant genetic resources because of conflicts, human pandemic diseases, extreme weather events, pest and disease outbreaks, and natural calamities such as earthquakes, floods, etc., which led to disrupting access to germplasm and undermining social protection systems. Safety duplication of germplasm collections held in genebanks in other institutions, including international, regional, and national genebanks, as well as the Svalbard Global Seed Vault (SGSV), is one of the essential measures to safeguard germplasm and also to replenish any lost accessions and resume use and distribution of seeds to users internationally. Germplasm distribution procedures are conducted per International Plant Protection Convention phytosanitary regulations to avoid the transboundary spread of seed-borne pests and pathogens. The ICARDA’s Seed Health Laboratory exercises maximum efforts to maintain the “phytosanitary clean” health status of germplasm during regeneration, conservation, distribution and ensure compliance with phytosanitary regulations in international germplasm distributions to guarantee minimum loss of genetic resources. These efforts include the development of new methods to detect and manage seed-borne pathogens. An increase in global awareness to preserve germplasm for current and future use is crucial to combat climate challenge, malnutrition, and food insecurity.

Characterization of durum wheat resistance against leaf rust under climate change conditions of increasing temperature and [CO2

Durum wheat cultivation in Mediterranean regions is threatened by abiotic factors, mainly related to the effects of climate change, and biotic factors such as the leaf rust disease. This situation requires an in-depth knowledge of how predicted elevated temperatures and [CO2] will affect durum wheat-leaf rust interactions. Therefore, we have characterised the response of one susceptible and two resistant durum wheat accessions against leaf rust under different environments in greenhouse assays, simulating the predicted conditions of elevated temperature and [CO2] in the far future period of 2070–2099 for the wheat growing region of Cordoba, Spain. Interestingly, high temperature alone or in combination with high [CO2] did not alter the external appearance of the rust lesions. However, through macro and microscopic evaluation, we found some host physiological and molecular responses to infection that would quantitatively reduce not only pustule formation and subsequent infection cycles of this pathogen, but also the host photosynthetic area under these predicted weather conditions, mainly expressed in the susceptible accession. Moreover, our results suggest that durum wheat responses to infection are mainly driven by temperature, being considered the most hampering abiotic stress. In contrast, leaf rust infection was greatly reduced when these weather conditions were also conducted during the inoculation process, resembling the effects of possible heat waves not only in disease development, but also in fungal germination and penetration success. Considering this lack of knowledge in plant-pathogen interactions combined with abiotic stresses, the present study is, to the best of our knowledge, the first to include the effects of the expected diurnal variation of maximum temperature and continuous elevated [CO2] in the durum wheat-leaf rust pathosystem.

Characterization of Triticum turgidum sspp. durum, turanicum, and polonicum grown in Central Italy in relation to technological and nutritional aspects.

Wheat is a staple food, with the two most common species being Triticum aestivum and Triticum turgidum ssp. durum. Moreover, the latter, T.turgidum, includes other tetraploid subspecies, among which the sspp. turanicum (Khorasan wheat) and polonicum (Polish wheat), whose importance has increased in the last decades, representing alternative crops for marginal areas, in addition to being a source of genetic diversity. In this work, different accessions of these three subspecies of T.turgidum have been grown in 2 years in the same environment and have been characterized for technological properties and factors affecting nutritional quality, such as fiber amount and the content of micro- and macro-nutrients in grains, and for root morphological traits. These analyses allowed the identification, in particular, of a Polish wheat accession showing better technological performances, a higher amount of positive micro- and macro-elements, and a lower amount of toxic cadmium. The modern variety Svevo and the Polish Pol2 showed the lowest and the highest shoot:root ratio, respectively. The high shoot:root ratio in Pol2 was mainly attributable to the decrease in root growth. Although Pol2 had a lower root biomass, its particular root morphology made it more efficient for nutrient uptake, as evident from the greater accumulation of micro- and macro-nutrients. These results underline that it is not possible to draw general conclusions about the difference between primitive and modern wheats, but rather a case-by-case approach should be chosen.

Genome-wide association analysis of time to heading and maturity in bread wheat using 55K microarrays.

To investigate the genetic mechanisms underlying the reproductive traits (time to flowering and maturity) in wheat and identify candidate genes associated, a phenotypic analysis was conducted on 239 wheat accessions (lines) from around the world. A genome-wide association study (GWAS) of wheat heading and maturity phases was performed using the MLM (Q+K) model in the TASSLE software, combined with the Wheat 55K SNP array. The results revealed significant phenotypic variation in heading and maturity among the wheat accessions across different years, with coefficients of variation ranging from 0.96% to 1.97%. The phenotypic data from different years exhibited excellent correlation, with a genome-wide linkage disequilibrium (LD) attenuation distance of 3 Mb. Population structure analysis, evolutionary tree analysis, and principal component analysis indicated that the 239 wheat accessions formed a relatively homogeneous natural population, which could be divided into three subgroups. The GWAS results identified a total of 293 SNP marker loci that were significantly associated with wheat heading and maturity stages (P ≤ 0.001) in different environments. Among them, nine stable SNP marker loci were consistently detected in multiple environments. These marker loci were distributed on wheat chromosomes 1A、1B、2D、3A、5B、6D and 7A. Each individual locus explained 4.03%-16.06% of the phenotypic variation. Furthermore, through careful analysis of the associated loci with large phenotypic effect values and stable inheritance, a total of nine candidate genes related to wheat heading and maturity stages were identified. These findings have implications for molecular marker-assisted selection breeding programs targeting specific wheat traits at the heading and maturity stages. In summary, this study conducted a comprehensive GWAS of wheat heading and maturity phases, revealing significant associations between genetic markers and key developmental stages in wheat. The identification of candidate genes and marker loci provides valuable information for further studies on wheat breeding and genetic improvement targeted at enhancing heading and maturity traits.