Deciphering the enigma of RNA editing in the ATP1_alpha subunit of ATP synthase in Triticum aestivum

There is evidence that RNA editing is related to plant cellular stress as well as electron transport organelles, such as mitochondria. The mitochondrial atp1 gene encodes the alpha-subunit of Atp synthase. Control as well as two periods of drought stress treatments were analyzed in the cDNAs generated from the mitochondrial atp1 gene of two cultivars of Triticum aestivum [Giza 168 (G168) and Gemmiza 10 (GM10)]. Following RNA-seq data assembly, atp1 cDNAs from the control (acc. no. OQ129415), 2-hour (acc. no. OQ129416), and 12-hour (acc. no. OQ129417) time points of the T. aestivum cultivar G168 were obtained. Control (acc. no. OQ129419), 2-hour (acc. no. OQ129420), and 12-hour (acc. no. OQ129421) samples all included reconstructed atp1 transcripts from Gemmiza 10. Atp1 transcripts were assembled using the wheat atp1 gene (acc. no. NC_036024). RNA-seq raw data was utilized to identify 11 RNA editing sites in atp1 in the tolerant cultivar Giza168 and 6 in the sensitive cultivar Gemmiza10. The significant difference in RNA editing observed between control and drought stress conditions in sites led to synonymous amino acids. This led to no change in tertiary structure between tolerant and sensitive cultivars. But the change was focused between produced protein and its correspondence sequence on DNA.

LMA or vivipary? Wheat grain can germinate precociously during grain maturation under the cool conditions used to induce late maturity alpha-amylase (LMA)

Introduction

This study found that wheat (Triticum aestivum) grain can germinate precociously during the maturation phase of grain development, a phenomenon called vivipary that was associated with alpha-amylase induction. Farmers receive severe discounts for grain with low falling number (FN), an indicator that grain contains sufficiently elevated levels of the starch-digesting enzyme alpha-amylase to pose a risk to end-product quality. High grain alpha-amylase can result from: preharvest sprouting (PHS)/germination when mature wheat is rained on before harvest, or from late maturity alpha-amylase (LMA) when grain experiences cool temperatures during the soft dough stage of grain maturation (Zadoks growth stage 85). An initial LMA-induction experiment found that low FN was associated with premature visible germination, suggesting that cool and humid conditions caused vivipary.

Methods

To examine whether LMA and vivipary are related, controlled environment experiments examined the conditions that induce vivipary, whether LMA could be induced without vivipary, and whether the pattern of alpha-amylase expression during vivipary better resembled PHS or LMA.

Results

Vivipary was induced in the soft to hard dough stages of grain development (Zadok's stages 83-87) both on agar and after misting of the mother plant. This premature germination was associated with elevated alpha-amylase activity. Vivipary was more strongly induced under the cooler conditions used for LMA-induction (18°C day/7.5°C night) than warmer conditions (25°C day/18°C night). Cool temperatures could induce LMA with little or no visible germination when low humidity was maintained, and susceptibility to vivipary was not always associated with LMA susceptibility in a panel of 8 varieties. Mature grain preharvest sprouting results in much higher alpha-amylase levels at the embryo-end of the kernel. In contrast, vivipary resulted in a more even distribution of alpha-amylase that was reminiscent of LMA.

Discussion

Vivipary can occur in susceptible varieties under moist, cool conditions, and the resulting alpha-amylase activity may result in low FN problems when a farm experiences cool, rainy conditions before the crop is mature. While there are genotypic differences in LMA and vivipary susceptibility, overlapping mechanisms are likely involved since they are similarly controlled by temperature and growth stage, and result in similar patterns of alpha-amylase expression.

Isolation of Methane Enriched Bacterial Communities and Application as Wheat Biofertilizer under Drought Conditions: An Environmental Contribution

The search for methanotrophs as plant-growth-promoting rhizobacteria (PGPR) presents an important contribution to mitigating the impact of global warming by restoring the natural soil potential for consuming methane while benefiting plants during droughts. Our in silico simulations suggest that water, produced as a byproduct of methane oxidation, can satisfy the cell growth requirement. In addition to water, methanotrophs can produce metabolites that stimulate plant growth. Considering this, we proposed that applying methanotrophs as PGPR can alleviate the effect of droughts on crops, while stimulating atmospheric methane consumption. In this work, we isolated a series of methanotrophic communities from the rhizospheres of different crops, including Italian sweet pepper and zucchini, using an atmosphere enriched with pure methane gas, to determine their potential for alleviating drought stress in wheat plants. Subsequently, 23 strains of nonmethanotrophic bacteria present in the methanotrophic communities were isolated and characterized. We then analyzed the contribution of the methane-consuming consortia to the improvement of plant growth under drought conditions, showing that some communities contributed to increases in the wheat plants' lengths and weights, with statistically significant differences according to ANOVA models. Furthermore, we found that the presence of methane gas can further stimulate the plant-microbe interactions, resulting in larger plants and higher drought tolerance.

Unraveling the diversity and functions of sugar transporters for sustainable management of wheat rust

Plant diseases threaten global food security by reducing the production and quality of produce. Identification of disease resistance sources and their utilization in crop improvement is of paramount significance. However, constant evolution and occurrence of new, more aggressive and highly virulent pathotypes disintegrates the resistance of cultivars and hence demanding the steady stream of disease resistance cultivars as the most sustainable way of disease management. In this context, molecular tools and technologies facilitate an efficient and rational engineering of crops to develop cultivars having resistance to multiple pathogens and pathotypes. Puccinia spp. is biotrophic fungi that interrupt crucial junctions for causing infection, thus risking nutrient access of wheat plants and their subsequent growth. Sugar is a major carbon source taken from host cells by pathogens. Sugar transporters (STPs) are key players during wheat-rust interactions that regulate the transport, exchange, and allocation of sugar at plant-pathogen interfaces. Intense competition for accessing sugars decides fate of incompatibility or compatibility between host and the pathogen. The mechanism of transport, allocation, and signaling of sugar molecules and role of STPs and their regulatory switches in determining resistance/susceptibility to rusts in wheat is poorly understood. This review discusses the molecular mechanisms involving STPs in distribution of sugar molecules for determination of rust resistance/susceptibility in wheat. We also present perspective on how detailed insights on the STP's role in wheat-rust interaction will be helpful in devising efficient strategies for wheat rust management.

Transient drought during flowering modifies the grain proteome of bread winter wheat

Drought is among the most limiting factors for sustainable agricultural production. Water shortage at the onset of flowering severely affects the quality and quantity of grain yield of bread wheat (Triticum aestivum). Herein, we measured oxidative stress and photosynthesis-related parameters upon applying transient drought on contrasting wheat cultivars at the flowering stage of ontogenesis. The sensitive cultivar (Darunok Podillia) showed ineffective water management and a more severe decline in photosynthesis. Apparently, the tolerant genotype (Odeska 267) used photorespiration to dissipate excessive light energy. The tolerant cultivar sooner induced superoxide dismutase and showed less inhibited photosynthesis. Such a protective effect resulted in less affected yield and spectrum of seed proteome. The tolerant cultivar had a more stable gluten profile, which defines bread-making quality, upon drought. Water deficit caused the accumulation of medically relevant proteins: (i) components of gluten in the sensitive cultivar and (ii) metabolic proteins in the tolerant cultivar. We propose specific proteins for further exploration as potential markers of drought tolerance for guiding efficient breeding: thaumatin-like protein, 14-3-3 protein, peroxiredoxins, peroxidase, FBD domain protein, and Ap2/ERF plus B3 domain protein.

Effects of leaf age during drought and recovery on photosynthesis, mesophyll conductance and leaf anatomy in wheat leaves

statement: Mesophyll conductance (g _m) was negatively correlated with wheat leaf age but was positively correlated with the surface area of chloroplasts exposed to intercellular airspaces (S _c). The rate of decline in photosynthetic rate and g _m as leaves aged was slower for water-stressed than well-watered plants. Upon rewatering, the degree of recovery from water-stress depended on the age of the leaves, with the strongest recovery for mature leaves, rather than young or old leaves. Diffusion of CO₂ from the intercellular airspaces to the site of Rubisco within C₃ plant chloroplasts (g_m) governs photosynthetic CO₂ assimilation (A). However, variation in g _m in response to environmental stress during leaf development remains poorly understood. Age-dependent changes in leaf ultrastructure and potential impacts on g _m, A, and stomatal conductance to CO₂ (g _sc) were investigated for wheat (Triticum aestivum L.) in well-watered and water-stressed plants, and after recovery by re-watering of droughted plants. Significant reductions in A and g _m were found as leaves aged. The oldest plants (15 days and 22 days) in water-stressed conditions showed higher A and gm compared to irrigated plants. The rate of decline in A and g _m as leaves aged was slower for water-stressed compared to well-watered plants. When droughted plants were rewatered, the degree of recovery depended on the age of the leaves, but only for g _m. The surface area of chloroplasts exposed to intercellular airspaces (S _c) and the size of individual chloroplasts declined as leaves aged, resulting in a positive correlation between g _m and S _c. Leaf age significantly affected cell wall thickness (t _cw), which was higher in old leaves compared to mature/young leaves. Greater knowledge of leaf anatomical traits associated with g _m partially explained changes in physiology with leaf age and plant water status, which in turn should create more possibilities for improving photosynthesis using breeding/biotechnological strategies.

Optimizing genomic selection of agricultural traits using K-wheat core collection

The agricultural traits that constitute basic plant breeding information are usually quantitative or complex in nature. This quantitative and complex combination of traits complicates the process of selection in breeding. This study examined the potential of genome-wide association studies (GWAS) and genomewide selection (GS) for breeding ten agricultural traits by using genome-wide SNPs. As a first step, a trait-associated candidate marker was identified by GWAS using a genetically diverse 567 Korean (K)-wheat core collection. The accessions were genotyped using an Axiom^® 35K wheat DNA chip, and ten agricultural traits were determined (awn color, awn length, culm color, culm length, ear color, ear length, days to heading, days to maturity, leaf length, and leaf width). It is essential to sustain global wheat production by utilizing accessions in wheat breeding. Among the traits associated with awn color and ear color that showed a high positive correlation, a SNP located on chr1B was significantly associated with both traits. Next, GS evaluated the prediction accuracy using six predictive models (G-BLUP, LASSO, BayseA, reproducing kernel Hilbert space, support vector machine (SVM), and random forest) and various training populations (TPs). With the exception of the SVM, all statistical models demonstrated a prediction accuracy of 0.4 or better. For the optimization of the TP, the number of TPs was randomly selected (10%, 30%, 50% and 70%) or divided into three subgroups (CC-sub 1, CC-sub 2 and CC-sub 3) based on the subpopulation structure. Based on subgroup-based TPs, better prediction accuracy was found for awn color, culm color, culm length, ear color, ear length, and leaf width. A variety of Korean wheat cultivars were used for validation to evaluate the prediction ability of populations. Seven out of ten cultivars showed phenotype-consistent results based on genomics-evaluated breeding values (GEBVs) calculated by the reproducing kernel Hilbert space (RKHS) predictive model. Our research provides a basis for improving complex traits in wheat breeding programs through genomics assisted breeding. The results of our research can be used as a basis for improving wheat breeding programs by using genomics-assisted breeding.

Identification of Novel QTLs/Defense Genes in Spring Wheat Germplasm Panel for Seedling and Adult Plant Resistance to Stem Rust and Their Validation Through KASP Marker Assays

Stem rust is one of the major diseases threatening wheat production globally. To identify novel resistance quantitative trait loci (QTLs), we performed 35K Axiom Array SNP genotyping assays on an association mapping panel of 400 germplasm accessions, including Indian landraces, in conjunction with phenotyping for stem rust at seedling and adult plant stages. Association analyses using three genome wide association study (GWAS) models (CMLM, MLMM, and FarmCPU) revealed 20 reliable QTLs for seedling and adult plant resistance. Among these 20 QTLs, five QTLs were found consistent with three models, i.e., four QTLs on chromosome 2AL, 2BL, 2DL, and 3BL for seedling resistance and one QTL on chromosome 7DS for adult plant resistance. Further, we identified a total of 21 potential candidate genes underlying QTLs using gene ontology analysis, including a leucine rich repeat receptor (LRR) and P-loop nucleoside triphosphate hydrolase, which have a role in pathogen recognition and disease resistance. Furthermore, four QTLs (Qsr.nbpgr-3B_11, QSr.nbpgr-6AS_11, QSr.nbpgr-2AL_117-6, and QSr.nbpgr-7BS_APR) were validated through KASP located on chromosomes 3B, 6A, 2A, and 7B. Out of these QTLs, QSr.nbpgr-7BS_APR was identified as a novel QTL for stem rust resistance which has been found effective in both seedling as well as the adult plant stages. Identified novel genomic regions and validated QTLs have the potential to be deployed in wheat improvement programs to develop disease resistant varieties for stem rust and can diversify the genetic basis of resistance.

A split GAL4 RUBY assay for visual in planta detection of protein-protein interactions

Protein-protein interactions (PPIs) are a fundamental process in cellular biogenesis. Here we have developed a split GAL4 RUBY assay that enables macroscopically visual PPI detection in plant leaves in real time. Candidate interacting protein partners are fused to specific domains of the yeast GAL4 and herpes simplex virus VP16 transcription factors and transiently expressed in Nicotiana benthamina leaves by Agrobacterium infiltration. PPI, that may be either direct or indirect, results in transcriptional activation of a RUBY reporter gene leading to the production of the highly visual metabolite, betalain, in leaf tissue of living plants. Samples require no processing for in planta visual qualitative assessment, but with very simple processing steps the assay is quantitative. Its accuracy is demonstrated using a series of known interacting protein partners and mutant derivatives including transcription factors, signalling molecules and plant resistance proteins with cognate pathogen effectors. Using this assay, association between the wheat Sr27 stem rust disease resistance protein and corresponding AvrSr27 avirulence effector family produced by the rust pathogen is detected. Interaction is also observed between this resistance protein and the effector encoded by the corresponding avrSr27-3 virulence allele. However, this association appears weaker in the split GAL4 RUBY assay, which coupled with lower avrSr27-3 expression during stem rust infection, likely enables virulent races of the rust pathogen to avoid Sr27-mediated detection.

Economic versus technical efficiency in using ASM combined with fungicides to elicit wheat varieties with different disease susceptibilities

Despite the positive results of using elicitors to induce resistance against plant diseases, some factors have inhibited the popularization of their use in agriculture. There is an energetic cost related to the elicitors' induced response which can cause undesired effects on growth under low-pressure disease conditions. Elicitors can create phytotoxicity and show high variation in their efficiency between different genotypes within the same crop; in addition, the positive results related to the induced resistance may not repeat in field treatments, adding to the possibility that they are not economically viable. Thus, we carried out two experiments to investigate the technical and economic efficiency of acibenzolar-S-methyl (ASM) and its association with fungicides in the control of leaf diseases of susceptible and resistant wheat varieties, and as how it reflects on the photosynthetic and production performance of wheat. This study showed the limitations of incorporating ASM into foliar fungal disease control in economic terms. However, it was evident that ASM effectively induced plant resistance against Leaf Rust and Powdery Mildew in the field and can be considered a sustainable option for wheat cultivation. Even though its association with chemical control was not the best economic strategy the use of ASM is a tool that can be incorporated into wheat cultivation to minimize the emergence of fungicide-resistant pathogens due to the diversification of modes of action employed and reduce the toxic residue deposition to the environment and human health.

Barley yellow dwarf Virus-GAV movement protein activating wheat TaATG6-Mediated antiviral autophagy pathway

Barley yellow dwarf virus-GAV (BYDV-GAV) is a highly destructive virus that is transmitted by aphids and can cause substantial yield losses in crops such as wheat (Triticum aestivum), barley (Hordeum vulgare) and oat (Avena sativa). Autophagy is an evolutionarily conserved degradation process that eliminates damaged or harmful intracellular substances during stress conditions or specific developmental processes. However, the mechanism of autophagy involved in disease resistance in wheat remains unknown. In this study, we demonstrate that BYDV-GAV infection could induces the upregulation of genes related to the autophagy pathway in wheat, accompanied by the production of autophagosomes. Furthermore, we confirmed the direct interaction between the viral movement protein (MP) and wheat autophagy-related gene 6 (TaATG6) both in vivo and in vitro. Through yeast function complementation experiments, we determined that TaATG6 can restore the autophagy function in a yeast mutant, atg6. Additionally, we identified the interaction between TaATG6 and TaATG8, core factors of the autophagic pathway, using the yeast two-hybrid system. TaATG6 and TaATG8-silenced wheat plants exhibited a high viral content. Overall, our findings suggest that wheat can recognize BYDV-GAV infection and activate the MP-TaATG6-TaATG8 regulatory network of defense responses through the induction of the autophagy pathway.

Seed dressing with M451 promotes seedling growth in wheat and reduces root phytopathogenic fungi without affecting endophytes

Fungal plant infections result in substantial losses to the agricultural sector. A range of fungicide seed dressings are available to control seed-borne fungal diseases; however, they lack sufficient efficacy because of intrinsic tolerance and acquired resistance. Moreover, many fungicide seed dressings can also penetrate plants, negatively affecting plant growth owing to their toxic effects on endophytes, as well as contributing to the spread of antibiotic resistance. Here, we evaluated the efficacy of M451, a member of a new class of antimicrobial agents that are not relevant to human healthcare. As a seed dressing for wheat seeds, M451 exhibited significant antifungal activity against one of the most devastating plant fungal pathogens, Fusarium spp. Furthermore, M451 was more active than the commercially used fungicide Maxim XL against both seed-borne and soil-borne F. oxysporum infection. Importantly, and unlike other antifungals, M451 seed dressing did not inhibit any of the major characteristics of wheat grains and seedlings, such as germination percentage, germination time, grain vigor, shoot- and root weight and length, but rather improved some of these parameters. The results also demonstrated that M451 had no negative impacts on endophytes and did not accumulate in grains. Thus, M451 may have potential applications as an antifungal agent in wheat cultivation.

Characterization and Differentiation of Grain Proteomes from Wild-Type Puroindoline and Variants in Wheat

Premium wheat with a high end-use quality is generally lacking in China, especially high-quality hard and soft wheat. Pina-D1 and Pinb-D1 (puroindoline genes) influence wheat grain hardness (i.e., important wheat quality-related parameter) and are among the main targets in wheat breeding programs. However, the mechanism by which puroindoline genes control grain hardness remains unclear. In this study, three hard wheat puroindoline variants (MY26, GX3, and ZM1) were compared with a soft wheat variety (CM605) containing the wild-type puroindoline genotype. Specifically, proteomic methods were used to screen for differentially abundant proteins (DAPs). In total, 6253 proteins were identified and quantified via a high-throughput tandem mass tag quantitative proteomic analysis. Of the 208 DAPs, 115, 116, and 99 proteins were differentially expressed between MY26, GX3, and ZM1 (hard wheat varieties) and CM605, respectively. The cluster analysis of protein relative abundances divided the proteins into six clusters. Of these proteins, 67 and 41 proteins were, respectively, more and less abundant in CM605 than in MY26, GX3, and ZM1. Enrichment analyses detected six GO terms, five KEGG pathways, and five IPR terms that were shared by all three comparisons. Furthermore, 12 proteins associated with these terms or pathways were found to be differentially expressed in each comparison. These proteins, which included cysteine proteinase inhibitors, invertases, low-molecular-weight glutenin subunits, and alpha amylase inhibitors, may be involved in the regulation of grain hardness. The candidate genes identified in this study may be relevant for future analyses of the regulatory mechanism underlying grain hardness.

High-density genetic mapping of Fusarium head blight resistance and agronomic traits in spring wheat

Fusarium head blight (FHB) has rapidly become a major challenge to successful wheat production and competitive end-use quality in western Canada. Continuous effort is required to develop germplasm with improved FHB resistance and understand how to incorporate the material into crossing schemes for marker-assisted selection and genomic selection. The aim of this study was to map quantitative trait loci (QTL) responsible for the expression of FHB resistance in two adapted cultivars and to evaluate their co-localization with plant height, days to maturity, days to heading, and awnedness. A large doubled haploid population of 775 lines developed from cultivars Carberry and AC Cadillac was assessed for FHB incidence and severity in nurseries near Portage la Prairie, Brandon, and Morden in different years, and for plant height, awnedness, days to heading, and days to maturity near Swift Current. An initial linkage map using a subset of 261 lines was constructed using 634 polymorphic DArT and SSR markers. QTL analysis revealed five resistance QTL on chromosomes 2A, 3B (two loci), 4B, and 5A. A second genetic map with increased marker density was constructed using the Infinium iSelect 90k SNP wheat array in addition to the previous DArT and SSR markers, which revealed two additional QTL on 6A and 6D. The complete population was genotyped, and a total of 6,806 Infinium iSelect 90k SNP polymorphic markers were used to identify 17 putative resistance QTL on 14 different chromosomes. As with the smaller population size and fewer markers, large-effect QTL were detected on 3B, 4B, and 5A that were consistently expressed across environments. FHB resistance QTL were co-localized with plant height QTL on chromosomes 4B, 6D, and 7D; days to heading on 2B, 3A, 4A, 4B, and 5A; and maturity on 3A, 4B, and 7D. A major QTL for awnedness was identified as being associated with FHB resistance on chromosome 5A. Nine small-effect QTL were not associated with any of the agronomic traits, whereas 13 QTL that were associated with agronomic traits did not co-localize with any of the FHB traits. There is an opportunity to select for improved FHB resistance within adapted cultivars by using markers associated with complementary QTL.

Halotolerant plant growth-promoting bacteria, Bacillus pumilus, modulates water status, chlorophyll fluorescence kinetics and antioxidant balance in salt and/or arsenic-exposed wheat

Seed priming is an effective and novel technique and the use of eco-friendly biological agents improves the physiological functioning in the vegetative stage of plants. This procedure ensures productivity and acquired stress resilience in plants against adverse conditions without contaminating the environment. Though the mechanisms of bio-priming-triggered alterations have been widely explained under induvial stress conditions, the interaction of combined stress conditions on the defense system and the functionality of photosynthetic apparatus in the vegetative stage after the inoculation to seeds has not been fully elucidated. After Bacillus pumilus inoculation to wheat seeds (Triticum aestivum), three-week-old plants were hydroponically exposed to the alone and combination of salt (100 mM NaCl) and 200 μM sodium arsenate (Na₂HAsO₄·7H₂O, As) for 72 h. Salinity and As pollutant resulted in a decline in growth, water content, gas exchange parameters, fluorescence kinetics and performance of photosystem II (PSII). On the other hand, the seed inoculation against stress provided the alleviation of relative growth rate (RGR), relative water content (RWC) and chlorophyll fluorescence. These negative impacts were reversed by B. pumilus inoculation. Since there was no effective antioxidant capacity, As and/or salinity caused induction of H₂O₂ accumulation and thiobarbituric acid reactive substances content (TBARS) in wheat leaves. The inoculated leaves had high activity of superoxide dismutase (SOD) under stress. B. pumilis decreased the NaCl-induced toxic H₂O₂ levels by increasing peroxidase (POX) and enzymes/non-enzymes related to ascorbate-glutathione (AsA-GSH) cycle. In the presence of As exposure, the inoculated plants exhibited an induction in CAT activity. On the other hand, for H₂O₂ scavenging, the improvement in the AsA-GSH cycle was observed in bacterium priming plants plus the combined stress treatment. Since B. pumilus inoculation reduced H₂O₂ levels against all stress treatments, lipid peroxidation subsequently decreased in wheat leaves. The findings obtained from our study explained that the seed inoculation with B. pumilus provided an activation in the defense system and protection in growth, water status, and gas exchange regulation in wheat leaves against the combination of salt and As.

Nitrogen uptake and remobilization from pre- and post-anthesis stages contribute towards grain yield and grain protein concentration in wheat grown in limited nitrogen conditions

Background

In wheat, nitrogen (N) remobilization from vegetative tissues to developing grains largely depends on genetic and environmental factors. The evaluation of genetic potential of crops under limited resource inputs such as limited N supply would provide an opportunity to identify N-efficient lines with improved N utilisation efficiency and yield potential. We assessed the genetic variation in wheat recombinant inbred lines (RILs) for uptake, partitioning, and remobilization of N towards grain, its association with grain protein concentration (GPC) and grain yield.

Methods

We used the nested association mapping (NAM) population (195 lines) derived by crossing Paragon (P) with CIMMYT core germplasm (P × Cim), Baj (P × Baj), Watkins (P × Wat), and Wyalkatchem (P × Wya). These lines were evaluated in the field for two seasons under limited N supply. The plant sampling was done at anthesis and physiological maturity stages. Various physiological traits were recorded and total N uptake and other N related indices were calculated. The grain protein deviation (GPD) was calculated from the regression of grain yield on GPC. These lines were grouped into different clusters by hierarchical cluster analysis based on grain yield and N-remobilization efficiency (NRE).

Results

The genetic variation in accumulation of biomass at both pre- and post-anthesis stages were correlated with grain-yield. The NRE significantly correlated with aboveground N uptake at anthesis (AGNa) and grain yield but negatively associated with AGN at post-anthesis (AGNpa) suggesting higher N uptake till anthesis favours high N remobilization during grain filling. Hierarchical cluster analysis of these RILs based on NRE and yield resulted in four clusters, efficient (31), moderately efficient (59), moderately inefficient (58), and inefficient (47). In the N-efficient lines, AGNa contributed to 77% of total N accumulated in grains, while it was 63% in N-inefficient lines. Several N-efficient lines also exhibited positive grain protein deviation (GPD), combining high grain yield and GPC. Among crosses, the P × Cim were superior and N-efficient, while P × Wya responded poorly to low N input.

Conclusions

We propose that traits favouring pre- or post-anthesis biomass accumulation and pre-anthesis N uptake may be targeted for breeding to improve grain-yield under limited N. The lines with positive GPD, a first report of genotype-dependent GPD associated with both AGNpa and AGNa in wheat, may be used as varieties or genetic resources to improve grain yield with high GPC for sustainable development under limited N conditions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s43170-023-00153-7.

Wheat ABA Receptor TaPYL5 Constitutes a Signaling Module with Its Downstream Partners TaPP2C53/TaSnRK2.1/TaABI1 to Modulate Plant Drought Response

Abscisic acid receptors (ABR) play crucial roles in transducing the ABA signaling initiated by osmotic stresses, which has a significant impact on plant acclimation to drought by modulating stress-related defensive physiological processes. We characterized TaPYL5, a member of the ABR family in wheat (Triticum aestivum), as a mediator of drought stress adaptation in plants. The signals derived from the fusion of TaPYL5-GFP suggest that the TaPYL5 protein was directed to various subcellular locations, namely stomata, plasma membrane, and nucleus. Drought stress significantly upregulated the TaPYL5 transcripts in roots and leaves. The biological roles of ABA and drought responsive cis-elements, specifically ABRE and recognition sites MYB, in mediating gene transcription under drought conditions were confirmed by histochemical GUS staining analysis for plants harbouring a truncated TaPYL5 promoter. Yeast two-hybrid and BiFC assays indicated that TaPYL5 interacted with TaPP2C53, a clade A member of phosphatase (PP2C), and the latter with TaSnRK2.1, a kinase member of the SnRK2 family, implying the formation of an ABA core signaling module TaPYL5/TaPP2C53/TaSnRK2.1. TaABI1, an ABA responsive transcription factor, proved to be a component of the ABA signaling pathway, as evidenced by its interaction with TaSnRK2.1. Transgene analysis of TaPYL5 and its module partners, as well as TaABI1, revealed that they have an effect on plant drought responses. TaPYL5 and TaSnRK2.1 positively regulated plant drought acclimation, whereas TaPP2C53 and TaABI1 negatively regulated it. This coincided with the osmotic stress-related physiology shown in their transgenic lines, such as stomata movement, osmolytes biosynthesis, and antioxidant enzyme function. TaPYL5 significantly altered the transcription of numerous genes involved in biological processes related to drought defense. Our findings suggest that TaPYL5 is one of the most important regulators in plant drought tolerance and a valuable target for engineering drought-tolerant cultivars in wheat.

Exogenous Calcium Reinforces Photosynthetic Pigment Content and Osmolyte, Enzymatic, and Non-Enzymatic Antioxidants Abundance and Alleviates Salt Stress in Bread Wheat

One of the main environmental stresses that hinder crop development as well as yield is salt stress, while the use of signal molecules such as calcium (Ca) has a substantial impact on reducing the detrimental effects of salt on different crop types. Therefore, a factorial pot experiment in a completely randomized design was conducted to examine the beneficial role of Ca (0, 2.5, and 5 mM) in promoting the physiological, biochemical, and growth traits of the wheat plant under three salt conditions viz. 0, 30, and 60 mM NaCl. Foliar application of Ca increased the growth of salt-stressed wheat plants through increasing photosynthetic pigments, IAA, proline, and total soluble sugars contents and improving antioxidant enzymes in addition to non-enzymatic antioxidants glutathione, phenol and flavonoids, β-carotene, and lycopene contents, thus causing decreases in the over-accumulation of free radicals (ROS). The application of Ca increased the activity of antioxidant enzymes in wheat plants such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), which scavenge reactive oxygen species (ROS) and relieved salt stress. An additional salt tolerance mechanism by Ca increases the non-antioxidant activity of plants by accumulating osmolytes such as free amino acids, proline, and total soluble sugar, which maintain the osmotic adjustment of plants under salinity stress. Exogenous Ca application is a successful method for increasing wheat plants' ability to withstand salt stress, and it has a considerable impact on the growth of wheat under salt stress.

Effects of drought stress and plant cultivar type on demographic characteristics of the rose-grain aphid, Metopolophium dirhodum (Hemiptera: Aphididae)

Drought is a substantial threat to cereal production under global climatic change scenarios, albeit its aftermath on arthropod pests is yet contentious. To address this issue, demographic characteristics of Metopolophium dirhodum (Walker, 1849) (Hemiptera: Aphididae) were studied on one drought-susceptible wheat cultivar and one drought-tolerant wheat cultivar under different water treatments. Some physiological and biochemical features of wheat cultivars including leaf soluble sugar and proline contents and antioxidant enzymes activities were also investigated. Significant differences occurred in the developmental period, survival, and fecundity of M. dirhodum between wheat cultivars under various water treatments. The impact of intermediate and severe water stress on M. dirhodum was neutral and negative for the tolerant cultivar and negative for the water-susceptible cultivar, respectively. Under severe water stress, on both wheat cultivars, the aphids had low net reproductive rates and finite and intrinsic rates of increase in comparison with those reared on unstressed plants. In total, drought resulted in lower growth of population and reduced survival of aphids. Hence, in the context of projected climatic changes, acute water deficiency could probably result in reducing the abundance and menace of outburst of M. dirhodum. However, it should be noted that the potential likelihood of M. dirhodum eruptions can be drastically affected by the degree of drought intensity and host plant cultivar.

Rapid and highly efficient morphogenic gene-mediated hexaploid wheat transformation

The successful employment of morphogenic regulator genes, Zm-Baby Boom (ZmBbm) and Zm-Wuschel2 (ZmWus2), for Agrobacterium-mediated transformation of maize (Zea mays L.) and sorghum (Sorghum bicolor L.) has been reported to improve transformation by inducing rapid somatic embryo formation. Here, we report two morphogenic gene-mediated wheat transformation methods, either with or without morphogenic and marker gene excision. These methods yield independent-transformation efficiency up to 58% and 75%, respectively. In both cases, the tissue culture duration for generating transgenic plants was significantly reduced from 80 to nearly 50 days. In addition, the transformation process was significantly simplified to make the procedure less labor-intensive, higher-throughput, and more cost-effective by eliminating the requirement for embryonic axis excision, bypassing the necessity for prolonged dual-selection steps for callus formation, and obviating the prerequisite of cytokinin for shoot regeneration. Furthermore, we have demonstrated the flexibility of the methods and generated high-quality transgenic events across multiple genotypes using herbicide (phosphinothricin, ethametsulfuron)- and antibiotic (G418)-based selections.

Genetic mapping of leaf rust (Puccinia triticina Eriks) resistance genes in six Canadian spring wheat cultivars

The Canada Western Red Spring wheat (Triticum aestivum L.) cultivars AAC Concord, AAC Prevail, CDC Hughes, Lillian, Glenlea, and elite line BW961 express a spectrum of resistance to leaf rust caused by Puccinia triticina Eriks. This study aimed to identify and map the leaf rust resistance of the cultivars using three doubled haploid populations, AAC Prevail/BW961 (PB), CDC Hughes/AAC Concord (HC), and Lillian/Glenlea (LG). The populations were evaluated for seedling resistance in the greenhouse and adult plant disease response in the field at Morden, MB for 3 years and genotyped with the 90K wheat Infinium iSelect SNP array. Genetic maps were constructed to perform QTL analysis on the seedling and field leaf rust data. A total of three field leaf rust resistance QTL segregated in the PB population, five in the HC, and six in the LG population. In the PB population, BW961 contributed two QTL on chromosomes 2DS and 7DS, and AAC Prevail contributed a QTL on 4AL consistent across trials. Of the five QTL in HC, AAC Concord contributed two QTL on 4AL and 7AL consistent across trials and a QTL on 3DL.1 that provided seedling resistance only. CDC Hughes contributed two QTL on 1DS and 3DL.2. Lillian contributed four QTL significant in at least two of the three trials on 2BS, 4AL, 5AL, and 7AL, and Glenlea two QTL on 4BL and 7BL. The 1DS QTL from CDC Hughes, the 2DS from BW961, the 4AL from the AAC Prevail, AAC Concord, and Lillian, and the 7AL from AAC Concord and Lillian conferred seedling leaf rust resistance. The QTL on 4AL corresponded with Lr30 and was the same across cultivars AAC Prevail, AAC Concord, and Lillian, whereas the 7AL corresponding with LrCen was coincident between AAC Concord and Lillian. The 7DS and 2DS QTL in BW961 corresponded with Lr34 and Lr2a, respectively, and the 1DS QTL in CDC Hughes with Lr21. The QTL identified on 5AL could represent a novel gene. The results of this study will widen our knowledge of leaf rust resistance genes in Canadian wheat and their utilization in resistance breeding.

Appropriate Application Methods for Salicylic Acid and Plant Nutrients Combinations to Promote Morpho-Physiological Traits, Production, and Water Use Efficiency of Wheat under Normal and Deficit Irrigation in an Arid Climate

Freshwater shortage and inadequate nutrient management are the two major challenges for sustainable wheat production in arid agro-ecosystems. Relatively little is known about the positive roles of the application methods for the combination of salicylic acid (SA) and plant nutrients in sustaining wheat production under arid climatic conditions. A two-year field study was undertaken to assess the impact of seven treatments for the integrated application of SA, macronutrients, and micronutrients on the morpho-physiological traits, yield, and irrigation water use efficiency (IWUE) of wheat subjected to full (FL) and limited (LM) irrigation regimes. The results showed that the LM regime caused a significant reduction in different plant growth traits, relative water content, chlorophyll pigments, yield components, and yield, while a significant increase was observed in IWUE. The sole application of SA or co-application with micronutrients through soil did not significantly affect the studied traits under the FL regime, while they achieved some improvement over untreated plants under the LM regime. Based on the different multivariate analyses, the soil and foliar applications for the combinations of SA and micronutrients, as well as a foliar application for the combinations of SA, macronutrients, and micronutrients were identified as an efficient option for mitigating the negative impacts of water deficit stress and enhancing the growth and production of wheat under normal conditions. In conclusion, the results obtained herein indicated that the co-application of SA and macro- and micronutrients is an effective option to greatly enhance and improve the growth and production of wheat crops in water-scarce countries of arid regions, such as Saudi Arabia, while an appropriate application method for this combination was required for positive effects.

Long-Term In Situ Conservation Drove Microevolution of Solina d'Abruzzo Wheat on Adaptive, Agronomic and Qualitative Traits

Solina is an example of a bread wheat landrace that has been conserved in situ for centuries in Central Italy. A core collection of Solina lines sampled in areas at different altitudes and climatic conditions was obtained and genotyped. A clustering analysis based on a wide SNP dataset generated from DArTseq analysis outlined the existence of two main groups, which, after F_st analysis, showed polymorphism in genes associated with vernalization and photoperiod response. Starting from the hypothesis that the different pedoclimatic environments in which Solina lines were conserved may have shaped the population, some phenotypic characteristics were studied in the Solina core collection. Growth habit, low-temperature resistance, allelic variations at major loci involved in vernalization response, and sensitivity to photoperiod were evaluated, together with seed morphologies, grain colour, and hardness. The two Solina groups showed different responses to low temperatures and to photoperiod-specific allelic variations as well as the different morphology and technological characteristics of the grain. In conclusion, the long-term in situ conservation of Solina in environments sited at different altitudes has had an impact on the evolution of this landrace which, despite its high genetic diversity, remains clearly identifiable and distinct so as to be included in conservation varieties.

GWAS scans of cereal cyst nematode (Heterodera avenae) resistance in Indian wheat germplasm

Significant yield losses in major cereal-growing regions around the world have been linked to cereal cyst nematodes (Heterodera spp.). Identifying and deploying natural sources of resistance is of utmost importance due to increasing concerns associated with chemical methods over the years. We screened 141 diverse wheat genotypes collected from pan-Indian wheat cultivation states for nematode resistance over two years, alongside two resistant (Raj MR1, W7984 (M6)) and two susceptible (WH147, Opata M85) checks. We performed genome-wide association analysis using four single-locus models (GLM, MLM, CMLM, and ECMLM) and three multi-locus models (Blink, FarmCPU, and MLMM). Single locus models identified nine significant MTAs (-log10 (P) > 3.0) on chromosomes 2A, 3B, and 4B whereas, multi-locus models identified 11 significant MTAs on chromosomes 1B, 2A, 3B, 3D and 4B. Single and multi-locus models identified nine common significant MTAs. Candidate gene analysis identified 33 genes like F-box-like domain superfamily, Cytochrome P450 superfamily, Leucine-rich repeat, cysteine-containing subtype Zinc finger RING/FYVE/PHD-type, etc., having a putative role in disease resistance. Such genetic resources can help to reduce the impact of this disease on wheat production. Additionally, these results can be used to design new strategies for controlling the spread of H. avenae, such as the development of resistant varieties or the use of resistant cultivars. Finally, the obtained results can also be used to identify new sources of resistance to this pathogen and develop novel control methods.

Ca2+-dependent TaCCD1 cooperates with TaSAUR215 to enhance plasma membrane H+-ATPase activity and alkali stress tolerance by inhibiting PP2C-mediated dephosphorylation of TaHA2 in wheat

Alkali stress is a major constraint for crop production in many regions of saline-alkali land. However, little is known about the mechanisms through which wheat responds to alkali stress. In this study, we identified a calcium ion-binding protein from wheat, TaCCD1, which is critical for regulating the plasma membrane (PM) H⁺-ATPase-mediated alkali stress response. PM H⁺-ATPase activity is closely related to alkali tolerance in the wheat variety Shanrong 4 (SR4). We found that two D-clade type 2C protein phosphatases, TaPP2C.D1 and TaPP2C.D8 (TaPP2C.D1/8), negatively modulate alkali stress tolerance by dephosphorylating the penultimate threonine residue (Thr926) of TaHA2 and thereby inhibiting PM H⁺-ATPase activity. Alkali stress induces the expression of TaCCD1 in SR4, and TaCCD1 interacts with TaSAUR215, an early auxin-responsive protein. These responses are both dependent on calcium signaling triggered by alkali stress. TaCCD1 enhances the inhibitory effect of TaSAUR215 on TaPP2C.D1/8 activity, thereby promoting the activity of the PM H⁺-ATPase TaHA2 and alkali stress tolerance in wheat. Functional and genetic analyses verified the effects of these genes in response to alkali stress, indicating that TaPP2C.D1/8 function downstream of TaSAUR215 and TaCCD1. Collectively, this study uncovers a new signaling pathway that regulates wheat responses to alkali stress, in which Ca²⁺-dependent TaCCD1 cooperates with TaSAUR215 to enhance PM H⁺-ATPase activity and alkali stress tolerance by inhibiting TaPP2C.D1/8-mediated dephosphorylation of PM H⁺-ATPase TaHA2 in wheat.