Spring Wheat Genotypes Research Articles

Polymeric Gluten Proteins as Climate-Resilient Markers of Quality: Can LC-MS/MS Provide Valuable Information about Spring Wheat Grown in Diverse Climates?

In this study, the impact of the varying environments, wet-cool (2017), dry-hot (2018), and fluctuating (2019), on two spring wheat genotypes, Diskett and Bumble, grown in field conditions in southern Sweden was studied. From harvested grains, polymeric gluten proteins were fractionated and collected using SE-HPLC and then analyzed with LC-MS/MS. Proteins and peptides identified through searches against the protein sequences ofTriticum aestivum (taxon 4565) from the UniProtKB database showed 7 high molecular weight glutenin subunits (HMW-GS) and 24 low molecular weight glutenin subunits (LMW-GS) with different enrichment levels for both genotypes. Glu-B1 for HMW-GS and Glu D3 and m- and s-types for LMW-GS were dominated in both genotypes, and a small proportion of α-, γ-, and ω-gliadins were also present. A minor variation in HMW-GS and LMW-GS compositions was observed between the years, while small amounts of heat shock proteins were identified under the "dry-hot" period for Diskett. In conclusion, Diskett showed more stable and climate-resistant protein patterns in the studied varying climate as compared to Bumble. The study highlights the use of proteomics and LC-MS/MS for differentiation of wheat genotypes, although it shows low sensitivity in measuring the diverse environment impact on the polymeric proteins.

Accounting for the impact of genotype and environment on variation in leaf respiration of wheat in Mexico and Australia.

An approach to improving radiation use efficiency (RUE) in wheat is to screen for variability in rates of leaf respiration in darkness (Rdark). We used a high-throughput system to quantify variation in Rdark among a diverse range of spring wheat genotypes (301 lines) grown in two countries (Mexico and Australia) and two seasons (2017 and 2018), and in doing so quantify the relative importance of genotype (G) and environment (E) in influencing variations in leaf Rdark. Through careful design, residual (unexplained) variation represented less than 10% of the total observed. Up to a third of the variation in Rdark (and related traits) was under genetic control. This suggests opportunities for breeders to use Rdark as a novel selection tool. In addition, E accounted for more than half of the total variation in area-based rates of Rdark. Here, the day of measurement was crucial, suggesting that day-to-day variations in the environment influence rates of Rdark measured at a common temperature. Overall, this study provides new insights into the role G and E play in determining variation in rates of leaf Rdark of one of the most important cereal crops, with implications for future improvements in carbon use efficiency and yield.

Drought Stress, Elevated CO2 and Their Combination Differentially Affect Carbon and Nitrogen in Different Organs of Six Spring Wheat Genotypes

This study aimed to analyze the combined impact of CO2 and drought stress at the flowering stage on carbon (C), nitrogen (N), and CN ratios in leaves, stem, and grains of bread wheat. Six diverse bread wheat genotypes, comprised of two commercial checks, two landraces, and two synthetics derivatives, were grown at two levels of CO2, i.e., 400 ppm and 800 ppm, and drought stress was imposed at the flowering stage through progressive soil drying. Stem, leaf, and grain samples were taken at maturity and concentrations of C and N were determined. Our results indicate that the threshold value of fraction of transpirable soil water (CFTSW) at which it diverges towards closure of stomata was different among genotypes and a higher range of values was estimated under elevated CO2. Drought significantly increased C levels in leaves and N levels in grains but decreased N levels in leaves, which increased CN ratios in leaves. In contrast, drought significantly reduced CN ratios in grains. Genotypes differed significantly in N content in grains, where the landrace derivative L2 maintained the highest N content. Moreover, pronounced changes in leaf N and CN ratios were induced by the combination of elevated CO2 and drought stress. Additionally, combined correlation and biplot analyses indicate a strong positive association of grain CN (GCN) with grain number, weight, and grain yield. These effects possibly interact with drought to strongly interfere with the impact of elevated CO2. The differential performance of the tested genotypes shows that selection of appropriate germplasm is essential to maintain agricultural production.

The role of salicylic acid in modulating phenotyping in spring wheat varieties for mitigating drought stress

Climate change-related droughts that recur frequently are one of the biggest obstacles to wheat (Triticum aestivum L.) productivity. Worldwide, attempts are being done to establish drought-resistant cultivars. However, progress is slow since drought tolerance is a complex trait controlled by numerous genes, and its expression is influenced by the environment. Phenotypic, biochemical physiological, and genotyping approaches are highlighted as critical research components for leveraging genetic variation in eight wheat genotypes. Treatments included eight spring wheat genotypes (IPK_040, IPK_046, IPK_050, IPK_071, IPK_105, WAS_007, WAS_024 and WAS_031), normal irrigation (NI), drought stress (D) (30% field capacity (FC)), normal irrigation with 0.5 mM SA (NSA), and drought treated with SA (DSA). The results revealed that there was a reduction in relative water content, an increase membrane leakage, and leaf chlorophyll content under drought stress. SA induced the defense responses against drought by increasing the osmolytes and the antioxidative enzymes activities. Compared to the NI group, the DSA treatment improved the water regulation, antioxidant capacity, and drought stress resistance. SA significantly reduced the deleterious effects of water stress on phenotyping more in WAS_ 024 and IPK_ 105 genotypes. The most responsive genotypes to salicylic acid were IPK_ 046 among the IPK genotypes, whereas WAS_031 genotype was amongst WAS genotypes based on the morpho-physiological traits. The findings of this study give a solid foundation for assessing drought resistance in T. aestivum and developing cultivation-specific water management methods.Graphical

Leaf gas exchange responses to combined heat and drought stress in wheat genotypes with varied stomatal density

Stomata regulate the plant’s gas exchange and water balance, and their density may be a crucial factor in the response to abiotic stresses. The aim of this study was to investigate the response of leaf gas exchange of three spring wheat genotypes with different stomatal density to progressive drought and combined heat and drought stress. The stomatal conductance (gs) was the most sensitive parameter that declined with increasing drought stress. This negatively affected transpiration and leaf cooling, and limited photosynthesis (A) when gs decreased to < 550 mmol m−2 s−1. The treatments affected all three genotypes similarly over time irrespective of stomatal density. However, when related to the fraction of transpirable soil water (FTSW) in the pot, gs and A of the low and high stomatal density cultivars responded differently when heat was added to the drought stress. The high stomatal density cultivar showed no difference in maximum gs at FTSW > 0.3, and a similar decline of gs and A at FTSW < 0.3 in drought alone and combined drought and heat. The low stomatal density cultivar showed a higher maximum gs and the most severe decline of gs under combined heat and drought stress and a significantly slower decline of gs under drought alone, which was also reflected in a significantly slower reduction in A under drought compared to the combined stress. Overall, the drought response of stomatal closure dominated the physiological response under simultaneous heat and drought irrespective of stomatal density, and it was only in the combined stress that the maximum photochemical efficiency Fv/Fm was negatively affected. In conclusion, to elucidate the effect of drought and combined drought and heat on the leaf gas exchange in wheat cultivars with varied stomatal density, it is crucial to relate the parameters to the available soil water, not the duration of the drought.

Phenotypic diversity of key adaptive traits in advanced Nordic and Baltic spring wheat (Triticum aestivum L.) breeding material

Wheat (Triticum aestivum L.) has become the most widely grown cereal crop in the Nordic-Baltic region, but due to climate change, its yields are under increasing risk. Here we present results of an international effort to use available wheat germplasm from the region to identify tools and genotypes for breeding wheat varieties with improved stability. We formed a panel of 300 spring wheat genotypes from the Nordic-Baltic region and studied their phenotypic diversity across environments to identify genotypes with high potential for adaptation to a changing climate. Field experiments were carried out in 2021 and 2022 in Estonia, Latvia, Lithuania and Norway. The performance and stability of yield (GY), protein content (PC), thousand kernel weight (TKW), test weight (TW), length of growing period (GP), and nine other traits were studied. Drought and excessive rainfall occurred in the Baltic countries in 2021–2022, whereas the weather in Norway was more stable. High variability for most traits, and significant GxE effects for all studied traits, were identified. We identified stable genotypes combining yield and quality using the AMMI model-based Weighted Average of Absolute Scores index (WAASB). Finally, we selected nineteen superior genotypes that combined high yield with high values of important quality traits. Thus, combining broad Nordic-Baltic wheat germplasm with extensive field phenotyping, we identified promising breeding material to develop climate-ready spring wheat varieties for the region.

Genetic Diversity of Promising Spring Wheat Accessions from Russia and Kazakhstan for Rust Resistance.

Spring bread wheat (Triticum aestivum) is a major crop in Russia and in Kazakhstan. The rust pathogens, leaf rust caused by the fungus Puccinia triticina, stem rust incited by P. graminis and yellow rust caused by P. striiformis, are the significant biotic factors affecting wheat production. In this study, 40 new promising spring wheat genotypes from the Kazakhstan-Siberia Network for Spring Wheat Improvement (KASIB) were tested for resistance to leaf, stem and yellow rust at the seedling stage, and for identification of rust resistance genes using molecular markers. In addition, the collection was tested for leaf rust resistance and grain yields in the South Urals agroclimatic zone of Russia in 2023. As a result, 16 accessions with seedling resistance to leaf rust, 21 to stem rust and 4 to yellow rust were identified. Three breeding accessions were resistant to all rust species, and nine to P. triticina and P. graminis. Wheat accessions resistant to leaf rust at the seedling stage were also resistant in the field. Molecular analysis showed the presence of cataloged resistance genes, Lr1, Lr3a, Lr9, Lr10, Lr19, Lr20, Lr24, Lr26, Sr15, Sr24, Sr25, Sr31, Sr38, Yr9 and Yr18; uncatalogued genes Lr6Agi1 and Lr6Agi2 from Thinopyrum intermedium and LrAsp from Aegilops speltoides; and 1AL.1RS translocation. The current analysis showed an increase in leaf and stem rust resistance of new KASIB genotypes and their genetic diversity due to the inclusion of alien genetic material in breeding.

Genome-wide association study of lignin trait in elite spring wheat against spot blotch disease

Spot blotch disease in wheat is one of major yield-limiting factor in warm humid conditions of South Asia. Developing the disease-resistant variety through molecular methods is an economically and environmentally eco-friendly approach. Diseased wheat leaves associated with lignin content increased by two or three times at 72 h compared with control. The genomic region associated with lignin content was investigated in a set of 289 diverse spring wheat genotypes. The genome - wide association studies panel employed a 90K Illumina SNP array and phenotyped in four environments. The GWAS analysis showed a total of 86 marker-trait associations on 1A, 1B, 2A, 2B, 2D, 3A, 3D, 4A, 5A, 5B, 6A, 6D, 7A, 7B, 7D were linked lignin trait. Insilco analysis revealed that significant SNPs were located on import putative candidate genes thirteen in the Transmembrane domain of the protein-kinase family and were involved in the host-pathogen interaction. The identified significant MTAs for further validation and useful for the wheat breeding programs to develop the spot blotch disease resistance.

Performance of Biofortified Spring Wheat Genotypes for Grain Zinc and Iron Concentrations, Grain Yield and Associated Traits in Terai/plains of Nepal

Breeding for nutrient-rich high yielding wheat varieties is one of the most economical and feasible ways to improve micronutrient deficiency ad hoc building better consumer health among the rural people of South Asia. To identify the Zinc (Zn) and Iron (Fe) enriched high yielding wheat genotypes, 7th Harvest Plus Yield Trial (7th HPYT) and 8th Harvest Plus Yield Trial (8th HPYT) both composed of 50 genotypes (including two CIMMYT checks " Kachu#1" and "Baj#1" and one Local Check "Gautam") were evaluated in alpha lattice design with 2 replications under timely sown irrigated condition at NWRP, Bhairahawa during 2016/17 and 2017/18. The grain Zn concentration and Fe concentration varies among genotypes from 23.8 to 42.4 ppm and 20.6 to 60.6 ppm, respectively. The highly significant positive correlation was found between grain zinc and iron concentration (r = 0.74** in 7th HPYT and r=0.67** in 8th HPYT). This highly positive significant relation between grain Zn and grain Fe indicates that it is feasible to simultaneously improve both micronutrients. In addition, this study reveals that thousand grains weight (TGW) has shown highly significant positive correlation (r = 0.3) with grain zinc and (r=0.4) with grain iron in 7th HPYT to non-significant negative correlation (r = -0.1) with grain zinc and (r=-0.1) with grain iron in 8th HPYT. As Nepali farmers major trait of interest second to grain yield is TGW, this showed that Zn and Fe enriched wheat varieties with higher TGW (bold grain) is feasible. The 9 genotypes in 7th HPYT and 48 genotypes in 8th HPYT showed higher grain yield than local check variety "GAUTAM" which indicates that bio-fortified genotypes are capable of producing higher grain yield with added micronutrient supplements in them. This study recommended 17 genotypes from the 7th HPYT and 38 genotypes from the 8thHPYT based on higher grain yield, grain Zn and Fe concentration and these lines were included in national yield trial for further evaluation in different agro-ecological domain of Nepal. The genotypes with higher grain Zn and Fe concentration viz., 7HPYT409, 7HPYT410, 8HPYT417, 8HPYT404 and 7HPYT442 could be used as donor parents in national wheat breeding program and high yielding genotypes 7HPYT448, 7HPYT418, 7HPYT426, 7HPYT413, 8HPYT415, 8HPYT431, 8HPYT429, 8HPYT407 and 8HPYT405 would be further evaluated throughout the Terai region of Nepal, and outstanding genotype could be recommended as variety for Terai/plains of Nepal.

GWAS elucidated grain yield genetics in Indian spring wheat under diverse water conditions.

Underpinned natural variations and key genes associated with yield under different water regimes, and identified genomic signatures of genetic gain in the Indian wheat breeding program. A novel KASP marker for TKW under water stress was developed and validated. A comprehensive genome-wide association study was conducted on 300 spring wheat genotypes to elucidate the natural variations associated with grain yield and its eleven contributing traits under fully irrigated, restricted water, and simulated no water conditions. Utilizing the 35K Wheat Breeders' Array, we identified 1155 quantitative trait nucleotides (QTNs), with 207 QTNs exhibiting stability across diverse conditions. These QTNs were further delimited into 539 genomic regions using a genome-wide LD value of 3.0Mbp, revealing pleiotropic control across traits and conditions. Sub-genome A was significantly associated with traits under irrigated conditions, while sub-genome B showed more QTNs under water stressed conditions. Favourable alleles with significantly associated QTNs were delineated, with a notable pyramiding effect for enhancing trait performance. Additionally, allele of only 921 QTNs significantly affected the population mean. Allele profiling highlighted C-306 as a most potential source of drought tolerance. Moreover, 762 genes overlapping significant QTNs were identified, narrowing down to 27 putative candidate genes overlapping 29 novel and functional SNPs expressing (≥ 0.5tpm) relevance across various growth conditions. A new KASP assay was developed, targeting a gene TraesCS2A03G1123700 regulating thousand kernel weight under severe drought condition. Genomic selection models (GBLUP, BayesB, MxE, and R-Norm) demonstrated an average prediction accuracy of 0.06-0.58 across environments, indicating potential for trait selection. Retrospective analysis of the Indian wheat breeding program supported a genetic gain in GY at the rate of ca. 0.56% per breeding cycle, since 1960, supporting the identification of genomic signatures driving trait selection and genetic gain. These findings offer insight into improving the rate of genetic gain in wheat breeding programs globally.

Yield, Protein Content and Water-Related Physiologies of Spring Wheat Affected by Fertilizer System and Weather Conditions

Technological and climatic factors significantly influence the expression of quality and quantity properties of spring wheat. This study aims to quantify the effects of weather conditions and fertilizer systems on spring wheat yield, quality (protein content), and physiological indicators (leaf vapor pressure deficit, evapotranspiration, surface temperature of the flag leaf) and to identify a suitable spring wheat genotype for the Transylvanian Plain. The experimental factors were: Y represents the year (Y1, 2019; Y2, 2020); F represents the fertilizer variant (F1, a single rate of fertilization: 36 kg ha−1 of nitrogen; F2, two rates of fertilization: 36 kg ha−1 of nitrogen + 72 kg ha−1 of nitrogen; F3, two rates of fertilization: 36 kg ha−1 of nitrogen + 105 kg ha−1 of nitrogen); and S represents the genotype (S1, Pădureni; S2, Granny; S3, Triso; S4, Taisa; S5, Ciprian; and S6, Lennox). This multifactorial experiment with three factors was conducted on Phaeozem soil. Regardless of weather conditions, fertilization with N100–110 at the head swollen sheath (stage 10, Feeks Growth Scale for Wheat) is deemed the most suitable variant because it yields an average grain yield of 5000 kg ha−1 of good quality (13.84% protein) with a considerable flag leaf area (29 cm2) where physiological processes can optimally support the well-being of the spring wheat plants. Beyond this level of fertilization, the average grain yield tends to plateau, but the protein content considerably increases by 13–23%, depending on the genotype. High yields were achieved in the Lennox and Triso genotypes.

Identification of Wheat Septoria tritici Resistance Genes in Wheat Germplasm Using Molecular Markers.

Zymoseptoria tritici (Z. tritici) is the main threat to global food security; it is a fungal disease that presents one of the most serious threats to wheat crops, causing severe yield losses worldwide, including in Kazakhstan. The pathogen leads to crop losses reaching from 15 to 50%. The objectives of this study were to (1) evaluate a wheat collection for Z. tritici resistance during the adult plant and seedling growth stages, (2) identify the sources of resistance genes that provide resistance to Z. tritici using molecular markers linked to Stb genes, and (3) identify potentially useful resistant wheat genotypes among cultivars and advanced breeding lines. This study evaluated 60 winter and spring wheat genotypes for Z. tritici resistance. According to the field reactions, 22 entries (35.7%) showed ≤10% disease severity in both years. The resistant reaction to a mix of Z. tritici isolates in the seedling stage was associated with adult plant resistance to disease in four wheat entries. The resistance of Rosinka 3 was due to the presence of Stb8; Omskaya 18 showed an immune reaction in the field and a moderately susceptible reaction in the seedling stage, possibly provided by a combination of the Stb7 and Stb2 genes. The high resistance in both the adult and seedling stages of Omskaya 29 and KR11-03 was due to the Stb4 and Stb2 genes and, possibly, due to the presence of unknown genes. A linked marker analysis revealed the presence of several Stb genes. The proportion of wheat entries with Stb genes was quite high at twenty-seven of the genotypes tested (45.0%), including four from Kazakhstan, nine from Russia, nine from the CIMMYT-ICARDA-IWWIP program, and five from the CIMMYT-SEPTMON nursery. Among the sixty entries, ten (16.7%) carried the resistance genes Stb2 and Stb8, and the gene Stb4 was found in seven cultivars (11.6%). Marker-assisted selection can be efficiently applied to develop wheat cultivars with effective Stb gene combinations that would directly assist in developing durable resistance in Kazakhstan. Resistant genotypes could also be used as improved parents in crossing programs to develop new wheat cultivars.

Evaluation of elite spring wheat genotypes for grain yield and other agronomic attributes in hills of Sudurpaschim Province, Nepal

Selection and release of high yielding and disease resistant varieties is the cost effective and ecologically sound approach for increasing the production and productivity of agricultural crop in Nepal. Twenty-two advanced bread wheat (Triticum aestivum L.) genotypes including commercial check variety "Sorgadwari", newly released check variety "Khumal Shakti" and Local Check variety " Jhadde" were evaluated under irrigated conditions at Gokuleshwor Agriculture and Animal Science College (GAASC), Baitadi, Nepal during 2022/2023. This study was carried out for the identification of high yielding genotypes under irrigated condition in western hills. The experiment was conducted in Alpha lattice design with two replications. The highly significant difference (p&lt;0.01) among the genotypes was found for most of the traits viz., days to heading, days to anthesis, days to maturity, plant height, spikes per square meter, number of grains per spike, grain weight per spike, flag leaf area, thousand kernel weight, biomass yield and grain yield and non-significant difference for spike length. The mean grain yield ranged from 1908 to 4146 kg/ha with grand mean of 2766 kg/ha. The highest grain yield was produced by genotype NL 1474 (4146 kg/ha) which was followed by NL 1475 (3994 kg/ha), NL1597 (3536 kg/ha) and NL 1590 (3070 kg/ha). The check variety Sorgadwari and Khumal Shakti produced 3480 and 3070 kg/ha respectively while the local check variety Jhadde produced 2655 kg/ha. Similarly, highest TKW was produced by NL 1487 (68.5 g) followed by BL 5148 (67.2 g) and WK 3730 (66.3 g). The correlation analysis revealed that grain yield showed highly significant positive correlation with biomass yield (0.90**) and number of grains per spike (0.6**), spikes per square meter (0.7**), plant height (0.5**) and non-significant positive correlation with spike length (0.21) and grain weight per spike (0.1) and non-significant negative correlation with days to heading (-0.2) and days to maturity (-0.2). Cluster analysis revealed that Cluster III consists of 4 genotypes namely NL 1474, NL 1475, NL 1597 and Sorgadwari. This cluster represent with highest grain yield, number of spikes per meter square, number of grains per spike and grain weight per spike. Among the tested genotypes, NL 1474, NL 1475, NL 1597 and NL 1590 were found superior for grain yield and yield-related traits in comparison to three checks and could be recommended for hills of Sudurpaschim province after further testing in multi-environment and in farmer's field.

Evaluation of speed breeding conditions for accelerating Fusarium head blight and deoxynivalenol screening in wheat

AbstractFeeding the world's ever‐increasing population requires continuous development of high‐yielding and disease‐resistant cultivars of food crops such as wheat (Triticum aestivum L.). Speed breeding, which utilizes longer photoperiod times and higher temperatures, is a technique that accelerates plant development and is rapidly being adopted by wheat breeders across the globe to fast‐track cultivar development. Plant diseases are a major threat to crop production, and breeding for disease resistance is a major goal of crop breeders. Fusarium head blight (FHB), caused by Fusarium graminearum, is a major disease of small grain cereals, affecting their yield and quality. The aim of present work was to assess if speed breeding conditions can be used to accelerate reliable assessment of FHB severity and mycotoxin deoxynivalenol (DON) accumulation in wheat varieties. We screened a set of six spring wheat genotypes with different levels of genetic resistance (two moderately susceptible, two highly susceptible, one moderately resistant, and one resistant) for their response to FHB at 14 days after inoculation (dai) and 21 dai and DON accumulation under normal versus speed breeding conditions. FHB severity and DON accumulation were found to be highly correlated at all time points under normal and speed breeding conditions. Robust differentiation between resistant and susceptible genotypes could be achieved at 14 dai rather than the normal period of 21 dai, saving at least a week in phenotyping. Combined with the accelerated growth, flowering, and maturity under these conditions, efficient FHB screening and DON evaluation under speed breeding conditions will fast‐track development of resistant wheat varieties.

Genome-wide scanning to identify and validate single nucleotide polymorphism markers associated with drought tolerance in spring wheat seedlings.

Unlike other growth stages of wheat, very few studies on drought tolerance have been done at the seedling stage, and this is due to the complexity and sensitivity of this stage to drought stress resulting from climate change. As a result, the drought tolerance of wheat seedlings is poorly understood and very few genes associated with drought tolerance at this stage were identified. To address this challenge, a set of 172 spring wheat genotypes representing 20 different countries was evaluated under drought stress at the seedling stage. Drought stress was applied on all tested genotypes by water withholding for 13 days. Two types of traits, namely morphological and physiological traits were scored on the leaves of all tested genotypes. Genome-wide association study (GWAS) is one of the effective genetic analysis methods that was used to identify target single nucleotide polymorphism (SNP) markers and candidate genes for later use in marker-assisted selection. The tested plant materials were genotyped using 25k Infinium iSelect array (25K) (herein after it will be identified as 25K) (for 172 genotypes) and genotyping-by-sequencing (GBS) (for 103 genotypes), respectively. The results of genotyping revealed 21,093 25K and 11,362 GBS-SNPs, which were used to perform GWAS analysis for all scored traits. The results of GWAS revealed that 131 and 55 significant SNPs were controlling morphological and physiological traits, respectively. Moreover, a total of eight and seven SNP markers were found to be associated with more than one morphological and physiological trait under drought stress, respectively. Remarkably, 10 significant SNPs found in this study were previously reported for their association with drought tolerance in wheat. Out of the 10 validated SNP markers, four SNPs were associated with drought at the seedling stage, while the remaining six SNPs were associated with drought stress at the reproductive stage. Moreover, the results of gene enrichment revealed 18 and six pathways as highly significant biological and molecular pathways, respectively. The selection based on drought-tolerant alleles revealed 15 genotypes with the highest number of different drought-tolerant alleles. These genotypes can be used as candidate parents in future breeding programs to produce highly drought-tolerant genotypes with high genetic diversity. Our findings in this study provide novel markers and useful information on the genetic basis of drought tolerance at early growth stages.

Genome-wide association mapping for field spot blotch resistance in South Asian spring wheat genotypes.

Spot blotch caused by Bipolaris sorokiniana ((Sacc.) Shoemaker) (teleomorph: Cochliobolus sativus [Ito and Kuribayashi] Drechsler ex Dastur) is an economically important disease of warm and humid regions. The present study focused on identifying resistant genotypes and single-nucleotide polymorphism (SNP) markers associated with spot blotch resistance in a panel of 174 bread spring wheat lines using field screening and genome-wide association mapping strategies. Field experiments were conducted in Agua Fria, Mexico, during the 2019-2020 and 2020-2021 cropping seasons. A wide range of phenotypic variation was observed among genotypes tested during both years. Twenty SNP markers showed significant association with spot blotch resistance on 15 chromosomes, namely, 1A, 1B, 2A, 2B, 2D, 3A, 3B, 4B, 4D, 5A, 5B, 6A, 6B, 7A, and 7B. Of these, two consistently significant SNPs on 5A, TA003225-0566 and TA003225-1427, may represent a new resistance quantitative trait loci. Further, in the proximity of Tsn1 on 5B, AX-94435238 was the most stable and consistent in both years. The identified genomic regions could be deployed to develop spot blotch-resistant genotypes, particularly in the spot blotch-vulnerable wheat growing areas.

Genome-wide association study reveals 18 QTL for major agronomic traits in a Nordic-Baltic spring wheat germplasm.

Spring wheat (Triticum aestivum L.) remains an important alternative to winter wheat cultivation at Northern latitudes due to high risk of overwintering or delayed sowing of winter wheat. We studied nine major agronomic traits in a set of 299 spring wheat genotypes in trials across 12-year-site combinations in Lithuania, Latvia, Estonia, and Norway for three consecutive years. The dataset analyzed here consisted of previously published phenotypic data collected in 2021 and 2022, supplemented with additional phenotypic data from the 2023 field season collected in this study. We combined these phenotypic datasets with previously published genotypic data generated using a 25K single nucleotide polymorphism (SNP) array that yielded 18,467 markers with a minor allele frequency above 0.05. Analysis of these datasets via genome-wide association study revealed 18 consistent quantitative trait loci (QTL) replicated in two or more trials that explained more than 5% of phenotypic variance for plant height, grain protein content, thousand kernel weight, or heading date. The most consistent markers across the tested environments were detected for plant height, thousand kernel weight, and days to heading in eight, five, and six trials, respectively. No beneficial effect of the semi-dwarfing alleles Rht-B1b and Rht-D1b on grain yield performance was observed across the 12 tested trials. Moreover, the cultivars carrying these alleles were low yielding in general. Based on principal component analysis, wheat genotypes developed in the Northern European region clustered separately from those developed at the southern latitudes, and markers associated with the clustering were identified. Important phenotypic traits, such as grain yield, days to heading, grain protein content, and thousand kernel weight were associated with this clustering of the genotype sets. Interestingly, despite being adapted to the Nordic environment, genotypes in the Northern set demonstrated lower grain yield performance across all tested environments. The results indicate that spring wheat germplasm harbors valuable QTL/alleles, and the identified trait-marker associations might be useful in improving Nordic-Baltic spring wheat germplasm under global warming conditions.

Phenotypic Variation and Relationships between Grain Yield, Protein Content and Unmanned Aerial Vehicle-Derived Normalized Difference Vegetation Index in Spring Wheat in Nordic–Baltic Environments

Accurate and robust methods are needed to monitor crop growth and predict grain yield and quality in breeding programs, particularly under variable agrometeorological conditions. Field experiments were conducted during two successive cropping seasons (2021, 2022) at four trial locations (Estonia, Latvia, Lithuania, Norway). The focus was on assessment of the grain yield (GY), grain protein content (GPC), and UAV-derived NDVI measured at different plant growth stages. The performance and stability of 16 selected spring wheat genotypes were assessed under two N application rates (75, 150 kg N ha−1) and across different agrometeorological conditions. Quantitative relationships between agronomic traits and UAV-derived variables were determined. None of the traits exhibited a significant (p &lt; 0.05) genotype-by-nitrogen interaction. High-yielding and high-protein genotypes were detected with a high WAASB stability, specifically under high and low N rates. This study highlights the significant effect of an NDVI analysis at GS55 and GS75 as key linear predictors, especially concerning spring wheat GYs. However, the effectiveness of these indices depends on the specific growing conditions in different, geospatially distant locations, limiting their universal utility.

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Drought is a significant abiotic stress that negatively impacts plant growth and can lead to substantial crop yield losses. Our study aimed to establish selection criteria for 200 spring-wheat (Triticum aestivum L.) genotypes exposed to three different field-capacity (FC) levels (100%FC, 50%FC, 25%FC) in a growth chamber (seedling traits) and in the field under withholdirrigation conditions (yield traits). Variance, correlation, and principal component analysis (PCA) was performed to identify genotypes with high tolerance to drought stress. The stress induction significantly affects morphophysiological traits i.e., root length, root weight (fresh, dry), fresh shoot weight, relative water contents and root shoot ratio in spring wheat genotypes at seedling stage. The traits flag leaf area, spike weight, grain weight/spike, biological and grain yield were interlinked and strongly influenced by drought in the field. The mean grain yield performance decreased from 21.85 g to 19.46 g under variable water regimes; however, the differences in harvest index and spikelets/spike were not significant. Among the tested genotypes, 9970 and 36-Eswyt-42 showed better root architecture development, leaf water management system, biological yield (66.07 g, 56.23 g) and grain yield (27.47 g, 28.78 g), respectively. The traits we identified may serve as an indirect selection index to enhance current semi-arid wheat germplasm and develop high-yielding drought-tolerant lines in advanced generations. Keywords: Mini core collection, Seedling and yield traits, Selection criteria, Variability analysis

Associations between endogenous spike cytokinins and grain-number traits in spring wheat genotypes

Genetic variation in grain number has been positively associated with levels of cytokinins in inflorescences in cereals, although studies quantifying endogenous levels in the field are currently lacking. The present study, using a spring wheat association mapping panel (HiBAP II) of 150 lines, quantified associations between spike hormone levels and grain number and associated traits. The HiBAP II panel was grown in the field in NW Mexico under irrigated conditions for one year and a subset of ten genotypes in the glasshouse under well-watered conditions for three years. The spike levels of four cytokinins (trans-zeatin riboside, trans-zeatin, isopentenyladenosine, and isopentenyladenine) were measured by using ultra-high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry. In the glasshouse experiments, spike hormone levels were measured at booting and anthesis, and in the field experiment at anthesis. In the glasshouse experiments, cytokinin levels were also measured in the basal, central, and apical spikelets separately in addition to at the whole spike level. The spike cytokinin levels did not differ significantly between the basal, central and apical sections of the spike. or show a spike position × genotype interaction. In the glasshouse experiments, significant genetic variation was detected for the expression of the four cytokinins in spikes at booting. At booting, spike trans-zeatin concentration ranged amongst genotypes from 4.5 to 16.0 ng g−1 FW and was positively correlated with grain number per main shoot (r = 0.77, P < 0.05). In the field at anthesis, the spike levels of each of trans-zeatin, trans-zeatin riboside and isopentenyl adenosine were positively correlated with grains per m2 (r = 0.17–0.19, P < 0.05). Our results indicated that selection for high spike cytokinin levels in wheat germplasm offers scope to raise grain number and yield potential in wheat.