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Drought threatens plant growth and related ecosystem services. The emergence of plant drought stress under edaphic drought is well studied, whilst the importance of atmospheric drought only recently gained momentum. Yet, little is known about the interaction and relative contribution of edaphic and atmospheric drought on the emergence of plant drought stress. We conducted a gradient experiment, fully crossing gravimetric water content (GWC: maximum water holding capacity—permanent wilting point) and vapour pressure deficit (VPD: 1−2.25 kPa) using five wheat varieties from three species (Triticum monococcum, T. durum & T. aestivum). We quantified the occurrence of plant drought stress on molecular (abscisic acid), cellular (stomatal conductance), organ (leaf water potential) and stand level (evapotranspiration). Plant drought stress increased with decreasing GWC across all organizational levels. This effect was magnified nonlinearly by VPD after passing a critical threshold of soil water availability. At around 20%GWC (soil matric potential 0.012 MPa), plants lost their ability to regulate leaf water potential via stomata regulation, followed by the emergence of hydraulic dysfunction. The emergence of plant drought stress is characterized by changing relative contributions of soil versus atmosphere and their non‐linear interaction. This highly non‐linear response is likely to abruptly alter plant‐related ecosystem services in a drying world. Summary statement: Plant drought stress emerges from a nonlinear interaction of soil water availability (here estimated based on gravimetric water content, GWC) and atmospheric water demand (vapour pressure deficit, VPD) with the relative contribution of VPD accelerating below a critical threshold of GWC. [ABSTRACT FROM AUTHOR]

The response of mesophyll conductance (gm) to CO2 plays a key role in photosynthesis and ecosystem carbon cycles under climate change. Despite numerous studies, there is still debate about how gm responds to short‐term CO2 variations. Here we used multiple methods and looked at the relationship between stomatal conductance to CO2 (gsc) and gm to address this aspect. We measured chlorophyll fluorescence parameters and online carbon isotope discrimination (Δ) at different CO2 mole fractions in sunflower (Helianthus annuus L.), cowpea (Vigna unguiculata L.), and wheat (Triticum aestivum L.) leaves. The variable J and Δ based methods showed that gm decreased with an increase in CO2 mole fraction, and so did stomatal conductance. There were linear relationships between gm and gsc across CO2 mole fractions. gm obtained from A‐Ci curve fitting method was higher than that from the variable J method and was not representative of gm under the growth CO2 concentration. gm could be estimated by empirical models analogous to the Ball‐Berry model and the USO model for stomatal conductance. Our results suggest that gm and gsc respond in a coordinated manner to short‐term variations in CO2, providing new insight into the role of gm in photosynthesis modelling. Summary statement: For photosynthesis modelling, the response of gm to short‐term CO2 changes is essential. Using variable J and carbon isotope discrimination methods, we showed that gm decreased with an increase in CO2 mole fraction, which contradicts the assumption of a constant gm in photosynthesis models. [ABSTRACT FROM AUTHOR]

The GSK3/SHAGGY‐like kinase plays critical roles in plant development and response to stress, but its specific function remains largely unknown in wheat (Triticum aestivum L.). In this study, we investigated the function of TaGSK3, a GSK3/SHAGGY‐like kinase, in wheat development and response to stress. Our findings demonstrated that TaGSK3 mutants had significant effects on wheat seedling development and brassinosteroid (BR) signalling. Quadruple and quintuple mutants showed amplified BR signalling, promoting seedling development, while a sextuple mutant displayed severe developmental defects but still responded to exogenous BR signals, indicating redundancy and non‐BR‐related functions of TaGSK3. A gain‐of‐function mutation in TaGSK3‐3D disrupted BR signalling, resulting in compact and dwarf plant architecture. Notably, this mutation conferred significant drought and heat stress resistance of wheat, and enhanced heat tolerance independent of BR signalling, unlike knock‐down mutants. Further research revealed that this mutation maintains a higher relative water content by regulating stomatal‐mediated water loss and maintains a lower ROS level to reduces cell damage, enabling better growth under stress. Our study provides comprehensive insights into the role of TaGSK3 in wheat development, stress response, and BR signal transduction, offering potential for modifying TaGSK3 to improve agronomic traits and enhance stress resistance in wheat. Summary statement: Our findings elucidated the redundant role of TaGSK3 in wheat brassinosteroid (BR) signalling and developmental phenotypes, as well as its unique ability to enhance heat resistance independently of the BR signal. [ABSTRACT FROM AUTHOR]

Bainong sterility (BNS) is a thermo‐sensitive genic male sterile wheat line, characterised by anther fertility transformation in response to low temperature (LT) stress during meiosis, the failure of vacuole decomposition and the absence of starch accumulation in sterile bicellular pollen. Our study demonstrates that the late microspore (LM) stage marks the transition from the anther growth to anther maturation phase, characterised by the changes in anther structure, carbohydrate metabolism and the main transport pathway of sucrose (Suc). Fructan is a main storage polysaccharide in wheat anther, and its synthesis and remobilisation are crucial for anther development. Moreover, the process of pollen amylogenesis and the fate of the large vacuole in pollen are closely intertwined with fructan synthesis and remobilisation. LT disrupts the normal physiological metabolism of BNS anthers during meiosis, particularly affecting carbohydrate metabolism, thus determining the fate of male gametophytes and pollen abortion. Disruption of fructan synthesis and remobilisation regulation serves as a decisive event that results in anther abortion. Sterile pollen exhibits common traits of pollen starvation and impaired starch accumulation due to the inhibition of apoplastic transport starting from the LM stage, which is regulated by cell wall invertase TaIVR1 and Suc transporter TaSUT1. Summary statement: The manuscript provides new insight into the role of carbohydrate metabolism in regulating anther development and the molecular mechanisms underlying pollen abortion in a thermo‐sensitive genic male sterile winter wheat line under low temperature during meiosis. [ABSTRACT FROM AUTHOR]

Grain protein content (GPC) is a crucial quality trait in bread wheat, which is influenced by the key transcription factor TaNAM. However, the regulatory mechanisms of TaNAM have remained largely elusive. In this study, a new role of TaNAM was unveiled in regulating nitrogen remobilisation which impacts GPC. The TaNAM knockout mutants generated by clustered regularly interspaced short palindromic repeats/Cas9 exhibited significantly delayed senescence and lower GPC, while overexpression of TaNAM‐6A resulted in premature senility and much higher GPC. Further analysis revealed that TaNAM directly activates the genes TaNRT1.1 and TaNPF5.5s, which are involved in nitrogen remobilisation. This activity aids in the transfer of nitrogen from leaves to grains for protein synthesis. In addition, an elite allele of TaNAM‐6A, associated with high GPC, was identified as a candidate gene for breeding high‐quality wheat. Overall, our work not only elucidates the potential mechanism of TaNAM‐6A affecting bread wheat GPC, but also highlights the significance of nitrogen remobilisation from senescent leaves to grains for protein accumulation. Moreover, our research provides a new target and approach for improving the quality traits of wheat, particularly the GPC. Summary statement: Grain protein content (GPC), a trait that affects both food processing quality and nutritional value, is a decisive factor for measuring the commercial value of new wheat varieties. Here, new results were revealed including: (1) We identified new targets of TaNAM‐6A, TaNRT1.1, and TaNPF5.5s, which are indispensable for nitrogen remobilisation from leaves to grains, especially during grain filling; (2) We identified an elite allele in natural populations, TaNAM‐6A‐Hap1, for wheat GPC that could be used in the genetic improvement of wheat quality. [ABSTRACT FROM AUTHOR]

The spike growth phase is critical for the establishment of fertile floret (grain) numbers in wheat (Triticum aestivum L.). Then, how to shorten the spike growth phase and increase grain number synergistically? Here, we showed high‐resolution analyses of floret primordia (FP) number, morphology and spike transcriptomes during the spike growth phase under three light regimens. The development of all FP in a spike could be divided into four distinct stages: differentiation (Stage I), differentiation and morphology development concurrently (Stage II), morphology development (Stage III), and polarization (Stage IV). Compared to the short photoperiod, the long photoperiod shortened spike growth and stimulated early flowering by shortening Stage III; however, this reduced assimilate accumulation, resulting in fertile floret loss. Interestingly, long photoperiod supplemented with red light shortened the time required to complete Stages I–II, then raised assimilates supply in the spike and promoted anther development before polarization initiation, thereby increasing fertile FP number during Stage III, and finally maintained fertile FP development during Stage IV until they became fertile florets via a predicted dynamic gene network. Our findings proposed a light regimen, critical stages and candidate regulators that achieved a shorter spike growth phase and a higher fertile floret number in wheat. Summary statement: A light regimen could achieve a 'shorter spike growth phase' and 'higher fertile floret number' in wheat by regulating gene expression, assimilate accumulation and morphology development in the critical stages of floret development. [ABSTRACT FROM AUTHOR]

Puccinia striiformis f. sp. tritici (Pst) secretes effector proteins that enter plant cells and manipulate host processes. In a previous study, we identified a glycine‐serine‐rich effector PstGSRE4, which was proven to regulate the reactive oxygen species (ROS) pathway by interacting with TaCZSOD2. In this study, we further demonstrated that PstGSRE4 interacts with wheat glyceraldehyde‐3‐phosphate dehydrogenase TaGAPDH2, which is related to ROS signalling. In wheat, silencing of TaGAPDH2 by virus‐induced gene silencing increased the accumulation of ROS induced by the Pst virulent race CYR31. Overexpression of TaGAPDH2 decreased the accumulation of ROS induced by the avirulent Pst race CYR23. In addition, TaGAPDH2 suppressed Pst candidate elicitor Pst322‐triggered cell death by decreasing ROS accumulation in Nicotiana benthamiana. Knocking down TaGAPDH2 expression attenuated Pst infection, whereas overexpression of TaGAPDH2 promoted Pst infection, indicating that TaGAPDH2 is a negative regulator of plant defence. In N. benthamiana, PstGSRE4 stabilized TaGAPDH2 through inhibition of the 26S proteasome‐mediated destabilization. Overall, these results suggest that TaGAPDH2 is hijacked by the Pst effector as a negative regulator of plant immunity to promote Pst infection in wheat. Summary statement: TaGAPDH2 is hijacked by the Pst effector PstGSRE4 as a negative regulator of plant immunity to promote Pst infection in wheat. [ABSTRACT FROM AUTHOR]

Soil salinity can adversely affect crop growth and yield, and an improved understanding of the genetic factors that confer salt tolerance could inform breeding strategies to engineer salt‐tolerant crops and improve productivity. Here, a group of K+‐preferring HKT transporters, TaHKT8, TaHKT9 and TaHKT10, were identified and negatively regulate the wheat shoot K+ accumulation and salt tolerance. A genome‐wide association study (GWAS) and candidate gene association analysis further revealed that TaHKT9‐B substantially underlies the natural variation of wheat shoot K+ accumulation under saline soil conditions. Specifically, an auxin responsive element (ARE) within an 8‐bp insertion in the promoter of TaHKT9‐B is strongly associated with shoot K+ content among wheat accessions. This ARE can be directly bound by TaARF4 for transcriptional activation of TaHKT9‐B, which subsequently attenuates shoot K+ accumulation and salt tolerance. Moreover, the tae‐miR390/TaTAS3/TaARF4 pathway was identified to regulate the salt‐induced root development and salt tolerance in wheat. Taken together, our study describes the genetic basis and accompanying mechanism driving phenotypic variation in wheat shoot K+ accumulation and salt tolerance. The identified tae‐miR390/TaTAS3/TaARF4/TaHKT9‐B module is an important regulator in wheat subjected to salt stress, which provides the potentially important genetic resources for breeders to improve wheat salt tolerance. Summary statement: Here, a genome‐wide association study and candidate gene association analysis revealed that TaHKT9‐B substantially underlies the natural variation of wheat shoot K+ accumulation under saline soil conditions. In addition, this study provides the first evidence of which we are aware showing that the tae‐miR390/TaTAS3/TaARF4/TaHKT9‐B module is a key regulator of root growth in salt‐stressed wheat, providing a genetic basis for enhancing salt tolerance in wheat and other crops. [ABSTRACT FROM AUTHOR]

Wheat (Triticum aestivum L.) is an important food crop mainly grown in arid and semiarid regions worldwide, whose productivity is severely limited by drought stress. Although various E3 ubiquitin (Ub) ligases regulate drought stress, only a few SINA‐type E3 Ub ligases are known to participate in such responses. Herein, we identified and cloned 15 TaSINAs from wheat. The transcription level of TaSINA2B was highly induced by drought, osmotic and abscisic acid treatments. Two‐type promoters of TaSINA2B were found in 192 wheat accessions; furthermore wheat accessions with promoter TaSINA2BII showed a considerably higher level of drought tolerance and gene expression levels than those characterizing accessions with promoter TaSINA2BI that was mainly caused by a 64 bp insertion in its promoter. Enhanced drought tolerance of TaSINA2B‐overexpressing (OE) transgenic wheat lines was found to be associated with root growth promotion. Further, an interaction between TaSINA2B and TaSINA1D was detected through yeast two‐hybrid and bimolecular fluorescence complementation assays. And TaSINA1D‐OE transgenic wheat lines showed similar drought tolerance and root growth phenotype to those observed when TaSINA2B was overexpressed. Therefore, the variation of TaSINA2B promoter contributed to the drought stress regulation, while TaSINA2B, interacting with TaSINA1D, positively regulated drought tolerance by promoting root growth. Summary Statement: TaSINA2B is closely associated to drought tolerance, and the 64 bp insertion in promoter drives the enhanced expression of TaSINA2B. TaSINA2B interact with TaSINA1D, both of which positively regulates drought tolerance and root growth in wheat. [ABSTRACT FROM AUTHOR]

Plant evolutionary history has had profound effects on belowground traits, which is likely to have impacted the ability to interact with microorganisms, but consequences on root colonization and gene expression by plant growth‐promoting rhizobacteria (PGPR) remain poorly understood. Here, we tested the hypothesis that wheat genomic content and domestication are key factors determining the capacity for PGPR interaction. Thus, 331 wheat representatives from eight Triticum or Aegilops species were inoculated under standardized conditions with the generalist PGPR Pseudomonas ogarae F113, using an autofluorescent reporter system for monitoring F113 colonization and expression of phl genes coding for the auxinic inducing signal 2,4‐diacetylphloroglucinol. The interaction with P. ogarae F113 was influenced by ploidy level, presence of genomes AA, BB, DD, and domestication. While root colonization was higher for hexaploid and tetraploid species, and phl expression level higher for hexaploid wheat, the diploid Ae. tauschii displayed higher phl induction rate (i.e., expression:colonisation ratio) on roots. However, a better potential of interaction with F113 (i.e., under non‐stress gnotobiotic conditions) did not translate, after seed inoculation, into better performance of wheat landraces in non‐sterile soil under drought. Overall, results showed that domestication and especially plant genomic content modulate the PGPR interaction potential of wheats. Summary statement: Wheat has undergone a particular evolutionary history, with several genomic hybridizations and domestications. Its ability to interact with Pseudomonas plant‐growth promoting rhizobacteria is strongly influenced by plant genomic content, whereas wheat domestication status is of less importance. [ABSTRACT FROM AUTHOR]

The developmental process of spike is critical for spike fertility through affecting floret primordia fate in wheat; however, the genetic regulation of this dynamic and complex developmental process remains unclear. Here, we conducted a high temporal‐resolution analysis of spike transcriptomes and monitored the number and morphology of floret primordia within spike. The development of all floret primordia in a spike was clearly separated into three distinct phases: differentiation, pre‐dimorphism and dimorphism. Notably, we identified that floret primordia with meiosis ability at the pre‐dimorphism phase usually develop into fertile floret primordia in the next dimorphism phase. Compared to control, increasing plant space treatment achieved the maximum increasement range (i.e., 50%) in number of fertile florets by accelerating spike development. The process of spike fertility improvement was directed by a continuous and dynamic regulatory network involved in transcription factor and genes interaction. This was based on the coordination of genes related to heat shock protein and jasmonic acid biosynthesis during differentiation phase, and genes related to lignin, anthocyanin and chlorophyll biosynthesis during dimorphism phase. The multi‐dimensional association with high temporal‐resolution approach reported here allows rapid identification of genetic resource for future breeding studies to realise the maximum spike fertility potential in more cereal crops. Summary statement: Floret primordia fates are determined by meiotic ability at the pre‐dimorphism phase: floret primordia with meiotic ability always develop into fertile florets, whereas meiotically incapable floret primordia usually abort. [ABSTRACT FROM AUTHOR]

The genetic heritage of wheat (Triticum spp.) crops has been shaped by millions of years of predomestication natural selection, often driven by competition among individuals. However, genetic improvements in yield potential are thought to involve selection towards reduced competitiveness, thus enhancing adaptation to the crop environment. We investigated potential trade‐offs between individual plant fitness and community performance using a population of introgression lines carrying chromosome segments of wild emmer (nondomesticated) in the background of an elite durum cultivar. We focused on light as a primary factor affecting plant–plant interactions and assessed morphological and biomass phenotypes of single plants grown in mixtures under sunlight and a simulated canopy shade, and the relevance of these phenotypes for the monoculture community in the field. We found that responses to canopy shade resemble responses to high density and contribute to both the individual and the community. Stepwise regressions suggested that grain number per spike and its persistence under shade are essential attributes of productive communities, advocating their use as a breeding target during early‐generation selection. Overall, multiple phenotypes attained under shade could better explain community performance. Our novel, applicable, high‐throughput set‐up provides new prospects for studying and selecting single‐plant phenotypes in a canopy‐like environment. Summary statement: Individual fitness and the performance of the monoculture community are associated with distinct and conflicting plant behaviours, some related to response to shade. Simulation of canopy shade on single plants can improve our predictions of the genotype performance as a community. [ABSTRACT FROM AUTHOR]

PHOSPHORUS‐STARVATION TOLERANCE 1 (OsPSTOL1) is a variably present gene that benefits crown root growth and phosphorus (P) sufficiency in rice (Oryza sativa). To explore the ecophysiological importance of this gene, we performed a biogeographic survey of landraces and cultivars, confirming that functional OsPSTOL1 alleles prevail in low nutrient and drought‐prone rainfed ecosystems, whereas loss‐of‐function and absence haplotypes predominate in control‐irrigated paddy varieties of east Asia. An evolutionary history analysis of OsPSTOL1 and related genes in cereal, determined it and other genes are kinase‐only domain derivatives of membrane‐associated receptor like kinases. Finally, to evaluate the potential value of this kinase of unknown function in another Gramineae, wheat (Triticum aestivum) lines overexpressing OsPSTOL1 were evaluated under field and controlled low P conditions. OsPSTOL1 enhances growth, crown root number, and overall root plasticity under low P in wheat. Survey of root and shoot crown transcriptomes at two developmental stages identifies transcription factors that are differentially regulated in OsPSTOL1 wheat that are similarly controlled by the gene in rice. In wheat, OsPSTOL1 alters the timing and amplitude of regulators of root development in dry soils and hastens induction of the core P‐starvation response. OsPSTOL1 and related genes may aid more sustainable cultivation of cereal crops. Summary statement: Might a rice gene that controls root plasticity confer a similar benefit in another grain crop? Here, we evaluate the genetic variation and evolutionary history of OsPSTOL1 and demonstrate its impact in wheat. [ABSTRACT FROM AUTHOR]

Wheat (Triticum aestivum L.) is a critical food crop feeding the world, but pathogens threaten its production. Wheat Heat Shock Protein 90.2 (HSP90.2) is a pathogen‐inducible molecular chaperone folding nascent preproteins. Here, we used wheat HSP90.2 to isolate clients regulated at the posttranslational level. Tetraploid wheat hsp90.2 knockout mutant was susceptible to powdery mildew, while the HSP90.2 overexpression line was resistant, suggesting that HSP90.2 was essential for wheat resistance against powdery mildew. We next isolated 1500 clients of HSP90.2, which contained a wide variety of clients with different biological classifications. We utilized 2Q2, a nucleotide‐binding leucine repeat‐rich protein, as a model to investigate the potential of HSP90.2 interactome in fungal resistance. The transgenic line co‐suppressing 2Q2 was more susceptible to powdery mildew, suggesting 2Q2 as a novel Pm‐resistant gene. The 2Q2 protein resided in chloroplasts, and HSP90.2 played a critical role in the accumulation of 2Q2 in thylakoids. Our data provided over 1500 HSP90.2 clients with a potential regulation at the protein folding process and contributed a nontypical approach to isolate pathogenesis‐related proteins. Summary Statement: This work revealed over 1500 clients of wheat Heat Shock Protein 90.2, a highly conserved pathogen molecular chaperone folding a wide range of signal transducers. 2Q2, a chloroplast‐localized nucleotide‐binding leucine repeat‐rich (NB‐LRR) protein, was discovered as a novel powdery mildew‐resistant protein, showing the potential of HSP90.2 chaperome in future plant fungal resistance study. [ABSTRACT FROM AUTHOR]

Low light stress seriously decreased wheat grain number through the formation of aborted spike during the reproductive period and induced new tiller regeneration to offset the loss of grain number. However, the mechanism by which plants coordinate spike aborted growth and the regeneration of new tillers remains unknown. To better understand this coordinated process, morphological, physiological and transcriptomic analyses were performed under low light stress at the young microspore stage. Our findings indicated that leaves exhausted most stored carbohydrates in 1 day of darkness. However, spike and uppermost internode (UI) were converted from sink to source, due to increased abscisic acid (ABA) content and decreased cytokinin content. During this process, genes encoding amylases, Sugars Will Eventually be Exported Transporters (SWEET) and sucrose transporters or sucrose carriers (SUT/SUC) were upregulated in spike and UI, which degraded starch into soluble sugars and loaded them into the phloem. Subsequently, soluble sugars were transported to tiller node (TN) where cytokinin and auxin content increased and ABA content decreased, followed by unloading into TN cells by upregulated cell wall invertase (CWINV) genes and highly expressed H+/hexose symporter genes. Finally, expansin genes integrated the sugar pathway and hormone pathway, and regulate the formation of new tillers directly. Summary Statement: Low light stress changed source–sink relationship by regulating the expression of sugar metabolism genes and sugar transport genes as well as hormone content in spike, uppermost internode and tiller node. Meanwhile, expansin genes integrated the sugar pathway and hormone pathway and regulated the formation of new tillers. [ABSTRACT FROM AUTHOR]

Salt stress reduces plant water flow during day and night. It is not known to which extent root hydraulic properties change in parallel. To test this idea, hydroponically grown wheat plants were grown at four levels of salt stress (50, 100, 150 and 200 mM NaCl) for 5–8d before harvest (d14–18) and subjected to a range of analyses to determine diurnal changes in hydraulic conductivity (Lp) at cell, root and plant level. Cell pressure probe analyses showed that the Lp of cortex cells was differentially affected by salt stress during day and night, and that the response to salt stress differed between the main axis of roots and lateral roots. The Aquaporin (AQP) inhibitor H2O2 reduced Lp to a common, across treatments, level as observed in salt‐stressed plants during the night. Analyses of transpiring plants and exuding root systems provided values of root Lp which were in the same range as values modeled based on cell‐Lp. The results can best be explained through a change in root Lp in response to salt stress and day/night, which results from an altered activity of AQPs. qPCR gene expression analyses point to possible candidate AQP isoforms. Summary statement: We show for wheat that the hydraulic response of root systems and root cells to salt stress differs between day and night and between root regions. Changes in root hydraulics involve changes in aquaporin (AQP) activity, and candidate AQP isoforms are identified through gene expression studies. [ABSTRACT FROM AUTHOR]

Genetic markers can be linked with eco‐physiological crop models to accurately predict genotype performance and individual markers' contributions in target environments, exploring interactions between genotype and environment. Here, wheat (Triticum aestivum L.) yield was dissected into seven traits corresponding to cultivar genetic coefficients in an eco‐physiological model. Loci for these traits were discovered through the genome‐wide association studies (GWAS). The cultivar genetic coefficients were derived from the loci using multiple linear regression or random forest, building a marker‐based eco‐physiological model. It is then applied to simulate wheat yields and design virtual ideotypes. The results indicated that the loci identified through GWAS explained 46%–75% variations in cultivar genetic coefficients. Using the marker‐based model, the normalized root mean square error (nRMSE) between the simulated yield and observed yield was 13.95% by multiple linear regression and 13.62% by random forest. The nRMSE between the simulated and observed maturity dates was 1.24% by multiple linear regression and 1.11% by random forest, respectively. Structural equation modelling indicated that variations in grain yield could be well explained by cultivar genetic coefficients and phenological data. In addition, 24 pleiotropic loci in this study were detected on 15 chromosomes. More significant loci were detected by the model‐based dissection method than considering yield per se. Ideotypes were identified by higher yield and more favourable alleles of cultivar genetic traits. This study proposes a genotype‐to‐phenotype approach and demonstrates novel ideas and tools to support the effective breeding of new cultivars with high yield through pyramiding favourable alleles and designing crop ideotypes. Summary statement: This study developed a novel gene‐based eco‐physiological model by linking genetic markers with cultivar genetic parameters to support effective breeding of new cultivars through pyramiding favourable alleles, designing crop ideotypes and predicting genotype and environment interactions. [ABSTRACT FROM AUTHOR]

Wheat has undergone a complex evolutionary history, which led to allopolyploidization and the hexaploid bread wheat Triticum aestivum. However, the significance of wheat genomic architecture for beneficial plant–microbe interactions is poorly understood, especially from a functional standpoint. In this study, we tested the hypothesis that wheat genomic architecture was an overriding factor determining root recruitment of microorganisms with particular plant‐beneficial traits. We chose five wheat species representing genomic profiles AA (Triticum urartu), BB {SS} (Aegilops speltoides), DD (Aegilops tauschii), AABB (Triticum dicoccon) and AABBDD (Triticum aestivum) and assessed by quantitative polymerase chain reaction their ability to interact with free‐nitrogen fixers, 1‐aminocyclopropane‐1‐carboxylate deaminase producers, 2,4‐diacetylphloroglucinol producers and auxin producers via the phenylpyruvate decarboxylase pathway, in combination with Illumina MiSeq metabarcoding analysis of N fixers (and of the total bacterial community). We found that the abundance of the microbial functional groups could fluctuate according to wheat genomic profile, as did the total bacterial abundance. N fixer diversity and total bacterial diversity were also influenced significantly by wheat genomic profile. Often, rather similar results were obtained for genomes DD (Ae. tauschii) and AABBDD (T. aestivum), pointing for the first time that the D genome could be particularly important for wheat–bacteria interactions. Summary statement: Genome D is important for rhizosphere interactions of wheat with phytobeneficial microbial functional groups. [ABSTRACT FROM AUTHOR]

Wheat plants are ubiquitously simultaneously exposed to salinity and limited iron availability caused by soil saline‐alkalisation. Through this study, we found that both low Fe and NaCl severely inhibited the growth of seminal roots in wheat seedlings; however, sufficient Fe caused greater growth cessation of seminal roots than low Fe under salt stress. Low Fe improved the root meristematic division activity, not altering the mature cell sizes compared with sufficient Fe under salt stress. Foliar Fe spray and split‐root experiments showed that low Fe‐alleviating the salinity‐induced growth cessation of seminal roots was dependent on local low Fe signals in the roots. Ionomics combined with TEM/X‐ray few differences in the root Na+ uptake and vacuolar Na+ sequestration between two Fe levels under salt stress. Phytohormone profiling and metabolomics revealed salinity‐induced overaccumulation of ACC/ethylene and tryptophan/auxin in the roots under sufficient Fe than under low Fe. Differential gene expression, pharmacological inhibitor addition and the root growth performance of transgenic wheat plants revealed that the rootward auxin efflux and was responsible for the low Fe‐mediated amelioration of the salinity‐induced growth cessation of seminal roots. Our findings will provide novel insights into the modulation of crop root growth under salt stress. Summary statement: We found that low Fe ameliorated the salinity‐induced growth cessation of wheat seminal roots, and our findings will provide novel insights into the understanding of Fe involved nutrient interactions and the modulation of crop root growth under salt stress. [ABSTRACT FROM AUTHOR]

Powdery mildew (Pm), caused by Blumeria graminis f.sp. tritici (Bgt), is one of the most important wheat diseases. Heavy‐metal‐associated isoprenylated plant protein (HIPP1) has been proved playing important roles in response to biotic and a biotic stress. In present study, we proved HIPP1‐V from Haynalidia villosa is a positive regulator in Pm resistance. HIPP1‐V was rapidly induced by Bgt. Transiently or stably heterologous overexpressing HIPP1‐V in wheat suppressed the haustorium formation and enhanced Pm resistance. HIPP1‐V isoprenylation was critical for plasma membrane (PM) localization, interaction with E3‐ligase CMPG1‐V and function in Pm resistance. Bgt infection recruited the isoprenylated HIPP1‐V and CMPG1s on PM; blocking the HIPP1 isoprenylation reduced such recruitment and compromised the resistance of OE‐CMPG1‐V and OE‐HIPP1‐V. Overexpressing HIPP1‐VC148G could not enhance Pm resistance. These indicated the Pm resistance was dependent on HIPP1‐V's isoprenylation. DGEs related to the ROS and SA pathways were remarkably enriched in OE‐HIPP1‐V, revealing their involvement in Pm resistance. Our results provide evidence on the important role of protein isoprenylation in plant defense. Summary Statement: Heterologous expression of Haynaldia villosa HIPP1‐V in common wheat enhanced powdery mildew (Pm) resistance. HIPP's isoprenylation modification is critical for its plasma membrane localization and function in regulating Pm resistance. [ABSTRACT FROM AUTHOR]

The spectral‐based photochemical reflectance index (PRI) and leaf surface temperature (Tleaf) derived from thermal imaging are two indicative metrics of plant functioning. The relationship of PRI with radiation‐use efficiency (RUE) and Tleaf with leaf transpiration could be leveraged to monitor crop photosynthesis and water use from space. Yet, it is unclear how such relationships will change under future high carbon dioxide concentrations ([CO2]) and drought. Here we established an [CO2] enrichment experiment in which three wheat genotypes were grown at ambient (400 ppm) and elevated (550 ppm) [CO2] and exposed to well‐watered and drought conditions in two glasshouse rooms in two replicates. Leaf transpiration (Tr) and latent heat flux (LE) were derived to assess evaporative cooling, and RUE was calculated from assimilation and radiation measurements on several dates along the season. Simultaneous hyperspectral and thermal images were taken at ~ $\unicode{x0007E}$1.5 m from the plants to derive PRI and the temperature difference between the leaf and its surrounding air (∆ $\unicode{x02206}$Tleaf−air). We found significant PRI and RUE and ∆ $\unicode{x02206}$Tleaf−air and Tr correlations, with no significant differences among the genotypes. A PRI–RUE decoupling was observed under drought at ambient [CO2] but not at elevated [CO2], likely due to changes in photorespiration. For a LE range of 350 W m–2, the ΔTleaf−air range was ~ $\unicode{x0007E}$10°C at ambient [CO2] and only ~ $\unicode{x0007E}$4°C at elevated [CO2]. Thicker leaves in plants grown at elevated [CO2] suggest higher leaf water content and consequently more efficient thermoregulation at high [CO2] conditions. In general, Tleaf was maintained closer to the ambient temperature at elevated [CO2], even under drought. PRI, RUE, ΔTleaf−air, and Tr decreased linearly with canopy depth, displaying a single PRI‐RUE and ΔTleaf−air Tr model through the canopy layers. Our study shows the utility of these sensing metrics in detecting wheat responses to future environmental changes. Highlights: We found significant PRI‐RUE and ∆Tleaf‐air‐Tr correlations in wheat grown under eCO2 (550 ppm) while observing PRI‐RUE decoupling under drought and aCO2 (400 ppm). Leaf thermoregulation was more efficient under eCO2, suggesting potential future global energy balance changes in a world with a higher [CO2]. [ABSTRACT FROM AUTHOR]

Wheat is an essential energy and protein source for humans. Climate change brings daunting challenges to wheat yield through environmental stresses, in which phytohormones play critical roles. Nevertheless, the comprehensive understanding of wheat phytohormone responses remains elusive. Here, we investigated the transcriptome response of wheat seedlings to five phytohormones, cytokinin (6‐BA), abscisic acid (ABA), gibberellic acid (GA), jasmonate (JA) and salicylic acid (SA). We further selected two JA marker genes and cloned their promoters to drive the expression of 3XEGFP (tandem trimeric enhanced green fluorescent protein) in transgenic lines. The JA fluorescent reporter displayed a fast and stable response to JA treatment as an ideal tool to follow JA dynamics during fungal and cold stresses at a cellular resolution. Overall, this study provided a transcriptional landscape and facilitated generating fluorescent reporters to monitor the dynamics of phytohormones in food crops. Summary statement: This work described the transcriptome response of wheat seedlings to five phytohormones, 6‐BA, ABA, GA, JA, and SA. Originated from the above data, a JA fluorescent reporter actualized a fast and stable strategy tracking the cellular JA dynamics in environmental stresses, e.g., fungal pathogens or cold stress. [ABSTRACT FROM AUTHOR]

The combination of a future rise in atmospheric carbon dioxide concentration ([CO2]) and drought will significantly impact wheat production and quality. Genotype phenology is likely to play an essential role in such an effect. Yet, its response to elevated [CO2] and drought has not been studied before. Here we conducted a temperature‐controlled glasshouse [CO2] enrichment experiment in which two wheat cultivars with differing maturity timings and life cycle lengths were grown under ambient (aCO2 approximately 400 μmol mol–1) and elevated (eCO2 approximately 550 μmol mol–1) [CO2]. The two cultivars, bred under dry and warm Mediterranean conditions, were well‐watered or exposed to drought at 40% pot holding capacity. We aimed to explore water × [CO2] × genotype interaction in terms of phenology, physiology, and agronomic trait response. Our results show that eCO2 had a significant effect on plants grown under drought. eCO2 boosted the booting stage of the late‐maturing genotype (cv. Ruta), thereby prolonging its booting‐to‐anthesis period by approximately 3 days (p < 0.05) while unaffecting the phenological timing of the early‐maturing genotype (cv. Zahir). The prolonged period resulted in a much higher carbon assimilation rate, particularly during pre‐anthesis (+87% for Ruta vs. +22% for Zahir under eCO2). Surprisingly, there was no eCO2 effect on transpiration rate and grain protein content in both cultivars and under both water conditions. The higher photosynthesis (and transpiration efficiency) of Ruta was not translated into higher aboveground biomass or grain yield, whereas both cultivars showed a similar increase of approximately 20% in these two traits at eCO2 under drought. Overall, Zahir, the cultivar that responded the least to eCO2, had a more efficient source‐to‐sink balance with a lower sink limitation than Ruta. The complex water × [CO2] × genotype interaction found in this study implies that future projections should account for multifactor interactive effects in modeling wheat response to future climate. Summary statement: Our glasshouse [CO2] enrichment experiment showed late‐maturing wheat genotype phenological and photosynthesis advantages over early‐maturing genotype, which were not translated into higher yields. The complex water × [CO2] × genotype interactions imply that multifactor interactive effects should be considered when modeling future wheat responses to drought and elevated [CO2]. [ABSTRACT FROM AUTHOR]

Sensing of neighbours via the Red to Far‐Red light ratio (R:FR) may exert a cap to yield potential in wheat. The effects of an increased R:FR inside the canopy were studied in dense wheat mini canopies grown in controlled environments by lowering FR. To distinguish between effects exerted by light sensing and assimilate supply, the treatments were complemented with elevated CO2, applied between different developmental timepoints to specifically impact tillering, spike growth, floret fertility and grain filling, in different combinations. The yield response to high R:FR was strongly dependent on the developmental stage in all three cultivars and pivoted between positive if applied after the start of stem elongation, and negative or null if applied before. Yield gains of up to 70% and 120% were observed, respectively, in two cultivars, associated with a higher number of tiller spikes and grains per spike in the main shoot. The response to the combination of high R:FR and elevated CO2 or CO2 alone were cultivar dependent. Taken together, our results suggest that R:FR exerts a significant control on yield potential in wheat and achieving a high R:FR from stem elongation to maturity is a promising lever towards a significant increase in grain yield. "We demonstrate light quality is crucially important for wheat yield potential. Our study, using dense mini‐canopies under controlled conditions, shows a High Red:Far Red ratio (due to lower Far Red) during spike growth and grain filling almost doubles grain yield, probably by disrupting the perception of neighbours." [ABSTRACT FROM AUTHOR]

Stomata are important channels for the control of gas exchange between plants and the atmosphere. To examine the genetic architecture of wheat stomatal index, we performed a genome‐wide association study (GWAS) using a panel of 539 wheat accessions and 450 678 polymorphic single nucleotide polymorphisms (SNPs) that were detected using wheat‐specific 660K SNP array. A total of 130 SNPs were detected to be significantly associated with stomatal index in both leaf surfaces of wheat seedlings. These significant SNPs were distributed across 16 chromosomes and involved 2625 candidate genes which participate in stress response, metabolism and cell/organ development. Subsequent bulk segregant analysis (BSA), combined with GWAS identified one major haplotype on chromosome 2A, that is responsible for stomatal index on the abaxial leaf surface. Candidate gene association analysis revealed that genetic variation in the promoter region of the hexokinase gene TaHXK3‐2A was significantly associated with the stomatal index. Moreover, transgenic analysis confirmed that TaHXK3‐2A overexpression in wheat decreased the size of leaf pavement cells but increased stomatal density through the glucose metabolic pathway, resulting in drought sensitivity among TaHXK3‐2A transgenic lines due to an increased transpiration rate. Taken together, these results provide valuable insights into the genetic control of the stomatal index in wheat seedlings. Summary Statement: Here, we performed a genome‐wide association study to screen for genetic variation in the stomatal index using 539 wheat accessions which revealed a candidate Hexokinase gene, TaHXK3‐2A, that contributes to the stomatal index via regulation of glucose metabolism, consequently affecting drought tolerance. [ABSTRACT FROM AUTHOR]

The natural 13C abundance (δ13C) in plant leaves has been used for decades with great success in agronomy to monitor water‐use efficiency and select modern cultivars adapted to dry conditions. However, in wheat, it is also important to find genotypes with high carbon allocation to spikes and grains, and thus with a high harvest index (HI) and/or low carbon losses via respiration. Finding isotope‐based markers of carbon partitioning to grains would be extremely useful since isotope analyses are inexpensive and can be performed routinely at high throughput. Here, we took the advantage of a set of field trials made of more than 600 plots with several wheat cultivars and measured agronomic parameters as well as δ13C values in leaves and grains. We find a linear relationship between the apparent isotope discrimination between leaves and grain (denoted as Δδcorr), and the respiration use efficiency‐to‐HI ratio. It means that overall, efficient carbon allocation to grains is associated with a small isotopic difference between leaves and grains. This effect is explained by postphotosynthetic isotope fractionations, and we show that this can be modelled by equations describing the carbon isotope composition in grains along the wheat growth cycle. Our results show that 13C natural abundance in grains could be useful to find genotypes with better carbon allocation properties and assist current wheat breeding technologies. Summary Statement: Finding isotope‐based markers of optimal carbon partitioning to grains would be extremely useful since isotope analyses are inexpensive and can be performed routinely at high throughput. Here, we show there is a linear relationship between the apparent isotope discrimination between leaves and grain (denoted as Δδcorr), and the respiration use efficiency‐to‐harvest index ratio. 13C natural abundance in grains has thus some potential to help finding genotypes with better carbon allocation properties and assisting current wheat breeding technologies. [ABSTRACT FROM AUTHOR]

We assessed how the temperature response of leaf day respiration (Rd) in wheat responded to contrasting water regimes and growth temperatures. In Experiment 1, well‐watered and drought‐stressed conditions were imposed on two genotypes; in Experiment 2, the two water regimes combined with high (HT), medium (MT) and low (LT) growth temperatures were imposed on one of the genotypes. Rd was estimated from simultaneous gas exchange and chlorophyll fluorescence measurements at six leaf temperatures (Tleaf) for each treatment, using the Yin method for nonphotorespiratory conditions and the nonrectangular hyperbolic fitting method for photorespiratory conditions. The two genotypes responded similarly to growth and measurement conditions. Estimates of Rd for nonphotorespiratory conditions were generally higher than those for photorespiratory conditions, but their responses to Tleaf were similar. Under well‐watered conditions, Rd and its sensitivity to Tleaf slightly acclimated to LT, but did not acclimate to HT. Temperature sensitivities of Rd were considerably suppressed by drought, and the suppression varied among growth temperatures. Thus, it is necessary to quantify interactions between drought and growth temperature for reliably modelling Rd under climate change. Our study also demonstrated that the Kok method, one of the currently popular methods for estimating Rd, underestimated Rd significantly. Summary Statement: Leaf day respiration (Rd) plays an essential role in maintaining the primary metabolic and physiological functions of plants. Here, we estimated Rd under various water and growth temperature regimes to explore how Rd acclimates to environmental variables and evaluated if a simple method can estimate Rd for photorespiratory conditions by using gas exchange and chlorophyll fluorescence data. [ABSTRACT FROM AUTHOR]

Plants require zinc (Zn) as an essential cofactor for diverse molecular, cellular and physiological functions. Zn is crucial for crop yield, but is one of the most limiting micronutrients in soils. Grasses like rice, wheat, maize and barley are crucial sources of food and nutrients for humans. Zn deficiency in these species therefore not only reduces annual yield but also directly results in Zn malnutrition of more than two billion people in the world. There has been good progress in understanding Zn homeostasis and Zn deficiency mechanisms in plants. However, our current knowledge of monocots, including grasses, remains insufficient. In this review, we provide a summary of our knowledge of molecular Zn homeostasis mechanisms in monocots, with a focus on important cereal crops. We additionally highlight divergences in Zn homeostasis of monocots and the dicot model Arabidopsis thaliana, as well as important gaps in our knowledge that need to be addressed in future research on Zn homeostasis in cereal monocots. Summary statement: Zinc is an essential nutrient, determining yield and grain quality in monocotyledonous crops. The manuscript reviews our current understanding of the molecular network underlying zinc homeostasis in monocots, highlighting gaps in knowledge and the specificities of monocots compared to Arabidopsis. [ABSTRACT FROM AUTHOR]

Plant–soil feedbacks refer to effects on plants that are mediated by soil modifications caused by the previous plant generation. Maize conditions the surrounding soil by secretion of root exudates including benzoxazinoids (BXs), a class of bioactive secondary metabolites. Previous work found that a BX‐conditioned soil microbiota enhances insect resistance while reducing biomass in the next generation of maize plants. Whether these BX‐mediated and microbially driven feedbacks are conserved across different soils and response species is unknown. We found the BX‐feedbacks on maize growth and insect resistance conserved between two arable soils, but absent in a more fertile grassland soil, suggesting a soil‐type dependence of BX feedbacks. We demonstrated that wheat also responded to BX‐feedbacks. While the negative growth response to BX‐conditioning was conserved in both cereals, insect resistance showed opposite patterns, with an increase in maize and a decrease in wheat. Wheat pathogen resistance was not affected. Finally and consistent with maize, we found the BX‐feedbacks to be cultivar‐specific. Taken together, BX‐feedbacks affected cereal growth and resistance in a soil and genotype‐dependent manner. Cultivar‐specificity of BX‐feedbacks is a key finding, as it hides the potential to optimize crops that avoid negative plant–soil feedbacks in rotations. We had discovered earlier that chemical compounds exuded from roots of maize, impacted the growth and insect defence of the following maize generation. In this study, we investigated whether these feedbacks could be relevant in agriculture. We demonstrated that such feedbacks also occur in other soils and that they also impact wheat. Finally, these feedbacks are wheat cultivar specific, offering the opportunity to optimize crop cultivars to avoid negative plant–soil feedbacks in rotations. [ABSTRACT FROM AUTHOR]

Aegilops tauschii, the progenitor of the wheat D genome, contains extensive diversity for biotic and abiotic resistance. Lr21 is a leaf rust resistance gene, which did not enter the initial gene flow from Ae. tauschii into hexaploid wheat due to restrictive hybridization events. Here, we used population genetics and high‐resolution comparative genomics to study evolutionary and functional divergence of Lr21 in diploid and hexaploid wheats. Population genetics identified the original Lr21, lr21‐1 and lr21‐2 alleles and their evolutionary history among Ae. tauschii accessions. Comparative genetics of Lr21 variants between Ae. tauschii and cultivated genotypes suggested at least two independent polyploidization events in bread wheat evolution. Further, a recent re‐birth of a unique Lr21‐tbk allele and its neofunctionalization was discovered in the hexaploid wheat cv. Tobak. Altogether, four independent alleles were investigated and validated for leaf rust resistance in diploid, synthetic hexaploid and cultivated wheat backgrounds. Besides seedling resistance, we uncover a new role of the Lr21 gene in conferring an adult plant field resistance. Seedling and adult plant resistance turned out to be correlated with developmentally dependent variation in Lr21 expression. Our results contribute to understand Lr21 evolution and its role in establishing a broad‐spectrum leaf rust resistance in wheat. The present study uncovers evolutionary divergence of Lr21 in Aegilops tauschii accessions and its transfer to hexaploid wheat as well as its new role in conferring broad‐spectrum resistance against leaf rust in bread wheat. [ABSTRACT FROM AUTHOR]

Recently, heat stress-induced reactive oxygen species signalling was shown to propagate through tissues such as mesophyll cells, and not only through vascular bundles in plants (Zandalinas & Mittler, 2021). Single cell gene regulatory networks in plants: Opportunities for enhancing climate change stress resilience. CARBON DYNAMICS AS A KEY REGULATOR OF PLANT HEAT STRESS RESPONSES The dynamics of carbon regulation under warmer conditions are key to ensuring plant productivity. [Extracted from the article]

Climate change and future warming will significantly affect crop yield. The capacity of crops to dynamically adjust physiological processes (i.e., acclimate) to warming might improve overall performance. Understanding and quantifying the degree of acclimation in field crops could ensure better parameterization of crop and Earth System models and predictions of crop performance. We hypothesized that for field‐grown wheat, when measured at a common temperature (25°C), crops grown under warmer conditions would exhibit acclimation, leading to enhanced crop performance and yield. Acclimation was defined as (a) decreased rates of net photosynthesis at 25°C (A25) coupled with lower maximum carboxylation capacity (Vcmax25), (b) reduced leaf dark respiration at 25°C (both in terms of O2 consumption Rdark_O225 and CO2 efflux Rdark_CO225) and (c) lower Rdark_CO225 to Vcmax25 ratio. Field experiments were conducted over two seasons with 20 wheat genotypes, sown at three different planting dates, to test these hypotheses. Leaf‐level CO2‐based traits (A25, Rdark_CO225 and Vcmax25) did not show the classic acclimation responses that we hypothesized; by contrast, the hypothesized changes in Rdark_O2 were observed. These findings have implications for predictive crop models that assume similar temperature response among these physiological processes and for predictions of crop performance in a future warmer world. In field‐grown wheat, leaf‐level CO2‐based traits (photosynthesis, carboxylation capacity and respiration measured at 25°C) did not exhibit classic acclimation responses to warming generated by varying time of sowing; by contrast, O2‐based respiration did. [ABSTRACT FROM AUTHOR]

Through a combination of physiological, pharmacological, molecular and targeted metabolomics approaches, we showed that retention of wheat (Triticum aestivum L.) seed dormancy levels induced by low and high seed development temperatures during post‐desiccation phases is associated with modulation of gibberellin (GA) level and seed responsiveness to abscisic acid (ABA) and GA via expression of TaABI5 and TaGAMYB, respectively. Dormancy retention during imbibition, however, is associated with modulations of both ABA level and responsiveness via expression of specific ABA metabolism (TaNCED2 and TaCYP707A1) and signalling (TaPYL2, TaSnRK2, TaABI3, TaABI4 and TaABI5) genes, and alterations of GA levels and responsiveness through expression of specific GA biosynthesis (TaGA20ox1, TaGA20ox2 and TaGA3ox2) and signalling (TaGID1 and TaGID2) genes, respectively. Expression patterns of GA signalling genes, TaRHT1 and TaGAMYB, lacked positive correlation with that of GA regulated genes and dormancy level observed in seeds developed at the two temperatures, implying their regulation at post‐transcriptional level. Our results overall implicate that a shift in ABA/GA balance underlies retention of dormancy levels induced by seed development temperature during post‐desiccation and imbibition phases. Consistently, genes regulated by ABA and GA during imbibition overlapped with those differentially expressed between imbibed seeds developed at the two temperatures and mediate different biological functions. Seed development temperature influences the level of dormancy manifested in mature seeds of wheat (Triticum aestivum L.). A shift in abscisic acid/gibberellin balance underlies the retention of dormancy level induced by seed development temperatures during post‐desiccation and imbibition phases. [ABSTRACT FROM AUTHOR]

Understanding the interactive effects of different warming levels and tillage managements on crop morphological and physiological traits and radiation use efficiency (RUE) is essential for breeding climate‐resilient cultivars. Here, we conducted temperature free‐air controlled enhancement (T‐FACE) experiments on winter wheat during two growth seasons in the North China Plain. The experiments consisted of three warming treatments and two tillage treatments (CT: conventional tillage and NT: no‐tillage). In the normal season, warming had significant positive effects on major morphological and physiological traits and increased significantly RUE of yield (RUEY) and biomass (RUEDM) by 13.3 and 11.3%, 19.3 and 12.4%, 42.3 and 43.7%, respectively, under the treatments of CTT1, CTT2 and NTT1 relative to the control (CTN, NTN). By contrast, in the warmer season, warming had negative effects on leaf width, light extinction coefficient, light‐saturated net photosynthetic rate, aboveground, stems and spike biomass and RUE from anthesis to maturity, and consequently grain yield under conventional tillage, but positive effects under no‐tillage. Our findings bring new insights into the mechanisms on the interactive effects of warming and tillage treatments on wheat growth and productivity; provide valuable information on crop ideotypic traits for breeding climate‐resilient crop cultivars. Understanding the interactive effects of different warming levels and tillage managements on crop morphological and physiological traits and radiation use efficiency (RUE) is essential for breeding climate‐resilient cultivars, which, however, have rarely been investigated. Here, we conducted temperature free‐air controlled enhancement (T‐FACE) experiments on winter wheat during two growth seasons (2018/19, 2019/20) in the North China Plain. The experiments consisted of three warming treatments (CK: no warming, T1: warming 1.3°C and T2: warming 2.3°C above ambient temperature) and two tillage treatments (CT: conventional tillage and NT: no‐tillage). We investigated the interactive effects of different warming levels and tillage managements on winter wheat morphological and physiological traits and radiation use efficiency. The results showed that the interactive effects of warming and tillage treatments had major impacts on wheat morphological and physiological traits, and subsequently on canopy light interception, photosynthesis, biomass and RUE. In the normal season (2018/19), warming had significant positive effects on major morphological and physiological traits and increased significantly RUE of yield (RUEY) and biomass (RUEDM) by 13.3 and 11.3%, 19.3 and 12.4%, 42.3 and 43.7%, respectively, under the treatments of CTT1, CTT2 and NTT1 relative to the control (CTN, NTN). By contrast, in the warmer season (2019/20), warming had negative effects on leaf width, light extinction coefficient, light‐saturated net photosynthetic rate, aboveground, stems and spike biomass, and RUE from anthesis to maturity and consequently grain yield under conventional tillage, but positive effects under no‐tillage. Our findings bring new insights into the mechanisms on the interactive effects of warming and tillage treatments on wheat growth and productivity; provide valuable information on crop ideotypic traits for breeding climate‐resilient crop cultivars. [ABSTRACT FROM AUTHOR]

Plants rely on their microbiota for improving the nutritional status and environmental stress tolerance. Previous studies mainly focused on bipartite interactions (a plant challenged by a single microbe), while plant responses to multiple microbes have received limited attention. Here, we investigated local and systemic changes induced in wheat by two plant growth‐promoting bacteria (PGPB), Azospirillum brasilense and Paraburkholderia graminis, either alone or together with an arbuscular mycorrhizal fungus (AMF). We conducted phenotypic, proteomic, and biochemical analyses to investigate bipartite (wheat–PGPB) and tripartite (wheat–PGPB–AMF) interactions, also upon a leaf pathogen infection. Results revealed that only AMF and A. brasilense promoted plant growth by activating photosynthesis and N assimilation which led to increased glucose and amino acid content. The bioprotective effect of the PGPB–AMF interactions on infected wheat plants depended on the PGPB‐AMF combinations, which caused specific phenotypic and proteomic responses (elicitation of defense related proteins, immune response and jasmonic acid biosynthesis). In the whole, wheat responses strongly depended on the inoculum composition (single vs. multiple microbes) and the investigated organs (roots vs. leaf). Our findings showed that AMF is the best‐performing microbe, suggesting its presence as the crucial one for synthetic microbial community development. We investigate local and systemic effects on wheat caused by two plant growth promoting bacteria alone and upon co‐inoculation with an arbuscular mycorrhizal fungus. Overall, our results indicate that while AMF promotes both plant growth and immunity, the PGPB differentially modulates the effect of AMF on these plant processes. [ABSTRACT FROM AUTHOR]

Root axial conductance, which describes the ability of water to move through the xylem, contributes to the rate of water uptake from the soil throughout the whole plant lifecycle. Under the rainfed wheat agro‐system, grain‐filling is typically occurring during declining water availability (i.e., terminal drought). Therefore, preserving soil water moisture during grain filling could serve as a key adaptive trait. We hypothesized that lower wheat root axial conductance can promote higher yields under terminal drought. A segregating population derived from a cross between durum wheat and its direct progenitor wild emmer wheat was used to underpin the genetic basis of seminal root architectural and functional traits. We detected 75 QTL associated with seminal roots morphological, anatomical and physiological traits, with several hotspots harbouring co‐localized QTL. We further validated the axial conductance and central metaxylem QTL using wild introgression lines. Field‐based characterization of genotypes with contrasting axial conductance suggested the contribution of low axial conductance as a mechanism for water conservation during grain filling and consequent increase in grain size and yield. Our findings underscore the potential of harnessing wild alleles to reshape the wheat root system architecture and associated hydraulic properties for greater adaptability under changing climate. We harnessed the wide diversity of wild emmer wheat to uncover, for the first time, the genetic basis of seminal roots architectural and functional traits. Field validation suggests that reduce axial conductance could promote higher yield stability under terminal drought. [ABSTRACT FROM AUTHOR]

Plants must carefully coordinate their growth and development with respect to prevailing environmental conditions. To do this, plants can use a range of nutritional and non‐nutritional information that allows them to proactively modulate their growth to avoid resource limitations. As is well‐known to gardeners and horticulturists alike, substrate volume strongly influences plant growth, and maybe a key source of non‐nutritional information for plants. However, the mechanisms by which these substrate volume effects occur remain unclear. Here, we show that wheat plants proactively modulate their shoot growth with respect to substrate volume, independent of nutrient availability. We show that these effects occur in two phases; in the first phase, the dilution of a mobile 'substrate volume‐sensing signal' (SVS) allows plants to match their shoot (but not root) growth to the total size of the substrate, irrespective of how much of this they can occupy with their roots. In the second phase, the dilution of a less mobile 'root density‐sensing signal' (RDS) allows plants to match root growth to actual rooting volume, with corresponding effects on shoot growth. We show that the effects of soil volume and plant density are largely interchangeable and that plants may use both SVS and RDS to detect their neighbours and to integrate growth responses to both volume and the presence of neighbours. Our work demonstrates the remarkable ability of plants to make proactive decisions about their growth, and has implications for mitigating the effects of dense sowing of crops in agricultural practice. Plants can measure both substrate volume and root density using mobile signals, which allows them to modify their shoot growth to match the size of their soil volume and neighbour density, and thereby avoid resource limitations later in life. [ABSTRACT FROM AUTHOR]

Rising tropospheric ozone affects the performance of important cereal crops thus threatening global food security. In this study, genetic variation of wheat regarding its physiological and yield responses to ozone was explored by exposing a diversity panel of 150 wheat genotypes to elevated ozone and control conditions throughout the growing season. Differential responses to ozone were observed for foliar symptom formation quantified as leaf bronzing score (LBS), vegetation indices and yield components. Vegetation indices representing the carotenoid to chlorophyll pigment ratio (such as Lic2) were particularly ozone‐responsive and were thus considered suitable for the non‐invasive diagnosing of ozone stress. Genetic variation in ozone‐responsive traits was dissected by a genome‐wide association study (GWAS). Significant marker‐trait associations were identified for LBS on chromosome 5A and for vegetation indices (NDVI and Lic2) on chromosomes 6B and 6D. Analysis of linkage disequilibrium (LD) in these chromosomal regions revealed distinct LD blocks containing genes with a putative function in plant redox biology such as cytochrome P450 proteins and peroxidases. This study gives novel insight into the natural genetic variation in wheat ozone response, and lays the foundation for the molecular breeding of tolerant wheat varieties. Bread wheat (Triticum aestivum L.) shows substantial variation in response to elevated ozone in yield, symptom formation and vegetation indices. This phenotypic variation was genetically dissected by genome‐wide association study. [ABSTRACT FROM AUTHOR]

Malate exudation through wheat (Triticum aestivum L) aluminium‐activated malate transporter 1 (TaALMT1) confers Al3+ tolerance at low pH, but is also activated by alkaline pH, and is regulated by and facilitates significant transport of gamma‐aminobutyric acid (GABA, a zwitterionic buffer). Therefore, TaALMT1 may facilitate acidification of an alkaline rhizosphere by promoting exudation of both malate and GABA. Here, the performance of wheat near isogenic lines ET8 (Al+3‐tolerant, high TaALMT1 expression) and ES8 (Al+3‐sensitive, low TaALMT1 expression) are compared. Root growth (at 5 weeks) was higher for ET8 than ES8 at pH 9. ET8 roots exuded more malate and GABA at high pH and acidified the rhizosphere more rapidly. GABA and malate exudation was enhanced at high pH by the addition of aluminate in both ET8 and transgenic barley expressing TaALMT1. Xenopus laevis oocytes expressing TaALMT1 acidified an alkaline media more rapidly than controls corresponding to higher GABA efflux. TaALMT1 expression did not change under alkaline conditions but key genes involved in GABA turnover changed in accordance with a high rate of GABA synthesis. We propose that TaALMT1 plays a role in alkaline tolerance by exuding malate and GABA, possibly coupled to proton efflux. Aluminium‐activated malate transporter 1 in wheat roots is activated by high pH and enhanced by aluminate to release gamma‐aminobutyric acid and malate, which facilitates rhizosphere acidification and tolerance to high pH. [ABSTRACT FROM AUTHOR]

In dry conditions, tall and fast‐growing wheat plants with good tolerance to drought may offer higher grain yields than 'Green revolution' wheat. [ABSTRACT FROM AUTHOR]

Improving salinity tolerance in the most widely cultivated cereal, bread wheat (Triticum aestivum L.), is essential to increase grain yields on saline agricultural lands. A Portuguese landrace, Mocho de Espiga Branca accumulates up to sixfold greater leaf and sheath sodium (Na+) than two Australian cultivars, Gladius and Scout, under salt stress in hydroponics. Despite high leaf and sheath Na+ concentrations, Mocho de Espiga Branca maintained similar salinity tolerance compared to Gladius and Scout. A naturally occurring single nucleotide substitution was identified in the gene encoding a major Na+ transporter TaHKT1;5-D in Mocho de Espiga Branca, which resulted in a L190P amino acid residue variation. This variant prevents Mocho de Espiga Branca from retrieving Na+ from the root xylem leading to a high shoot Na+ concentration. The identification of the tissue-tolerant Mocho de Espiga Branca will accelerate the development of more elite salt-tolerant bread wheat cultivars. [ABSTRACT FROM AUTHOR]

Drought is a major cause of losses in crop yield. Under field conditions, plants exposed to drought are usually also experiencing rapid changes in light intensity. Accordingly, plants need to acclimate to both, drought and light stress. Two crucial mechanisms in plant acclimation to changes in light conditions comprise thylakoid protein phosphorylation and dissipation of light energy as heat by non‐photochemical quenching (NPQ). Here, we analyzed the acclimation efficacy of two different wheat varieties, by applying fluctuating light for analysis of plants, which had been subjected to a slowly developing drought stress as it usually occurs in the field. This novel approach allowed us to distinguish four drought phases, which are critical for grain yield, and to discover acclimatory responses which are independent of photodamage. In short‐term, under fluctuating light, the slowdown of NPQ relaxation adjusts the photosynthetic activity to the reduced metabolic capacity. In long‐term, the photosynthetic machinery acquires a drought‐specific configuration by changing the PSII‐LHCII phosphorylation pattern together with protein stoichiometry. Therefore, the fine‐tuning of NPQ relaxation and PSII‐LHCII phosphorylation pattern represent promising traits for future crop breeding strategies. Elucidating the regulation of photosynthesis under the combination of abiotic stress and fluctuating light is crucial for understanding the plant physiology in realistic conditions and for crop improvement. Wheat copes with drought by reconfiguring the photosynthetic machinery and by slowing down the NPQ relaxation in fluctuating light before photodamage becomes detectable. [ABSTRACT FROM AUTHOR]

Studies on the temperature (T) responses of photosynthesis and leaf hydraulic conductance (Kleaf) are important to plant gas exchange. In this study, the temperature responses of photosynthesis and Kleaf were studied in Shanyou 63 (Oryza sativa) and Yannong 19 (Triticum aestivum). Leaf water potential (Ψleaf) was insensitive to T in Shanyou 63, while it significantly decreased with T in Yannong 19. The differential Ψleaf − T relationship partially accounted for the differing gm–T relationships, where gm was less sensitive to T in Yannong 19 than in Shanyou 63. With different gm–T and Ψleaf–T relationships, the temperature responses of photosynthetic limitations were surprisingly similar between the two lines, and the photosynthetic rate was highly correlated with gm. With the increasing T, Kleaf increased in Shanyou 63 while it decreased in Yannong 19. The different Kleaf–T relationships were related to different Ψleaf–T relationships. When excluding the effects of water viscosity and Ψleaf, Kleaf was insensitive to T in both lines. gm and Kleaf were generally not coordinated across different temperatures. This study highlights the importance of Ψleaf on leaf carbon and water exchanges, and the mechanisms for the gm–T and Kleaf–T relationships were discussed. Studies on the temperature (T) responses of photosynthesis and leaf hydraulic conductance (Kleaf) are important to plant carbon gain and water loss. Our data showed that the temperature response of leaf water potential (Ψleaf) was different between Shanyou 63 (Oryza sativa) and Yannong 19 (Triticum aestivum), which, at least partially, accounted for different temperature responses of Kleaf and mesophyll conductance (gm) between the tested lines. The mechanisms underlying the temperature responses of Kleaf and gm were discussed. [ABSTRACT FROM AUTHOR]

The species Deschampsia antarctica (DA) is one of the only two native vascular species that live in Antarctica. We performed ecophysiological, biochemical, and metabolomic studies to investigate the responses of DA to low temperature. In parallel, we assessed the responses in a non‐Antarctic reference species (Triticum aestivum [TA]) from the same family (Poaceae). At low temperature (4°C), both species showed lower photosynthetic rates (reductions were 70% and 80% for DA and TA, respectively) and symptoms of oxidative stress but opposite responses of antioxidant enzymes (peroxidases and catalase). We employed fused least absolute shrinkage and selection operator statistical modelling to associate the species‐dependent physiological and antioxidant responses to primary metabolism. Model results for DA indicated associations with osmoprotection, cell wall remodelling, membrane stabilization, and antioxidant secondary metabolism (synthesis of flavonols and phenylpropanoids), coordinated with nutrient mobilization from source to sink tissues (confirmed by elemental analysis), which were not observed in TA. The metabolic behaviour of DA, with significant changes in particular metabolites, was compared with a newly compiled multispecies dataset showing a general accumulation of metabolites in response to low temperatures. Altogether, the responses displayed by DA suggest a compromise between catabolism and maintenance of leaf functionality. Deschampsia antarctica is one of the only two native vascular species in Antarctica. Its response to low temperature suggests a compromise between catabolism and leaf function maintenance in a highly orchestrated manner: osmoprotection, membrane stabilization, and antioxidant secondary metabolism. [ABSTRACT FROM AUTHOR]

Drought is a major threat to wheat growth and crop productivity. However, there has been only limited success in developing drought‐hardy cultivars. This lack of progress is due, at least in part, to a lack of understanding of the molecular mechanisms of drought tolerance in wheat. Here, we evaluated the potential role of three cytosolic glyceraldehyde‐3‐phosphate dehydrogenases (TaGAPC2/5/6) under drought stress in wheat and Arabidopsis. We found that TaGAPC2/5/6 all positively responded to drought stress via reactive oxygen species (ROS) scavenging and stomatal movement. The results of yeast co‐transformation and electrophoretic mobility shift assay showed that TaWRKY33 acted as a direct regulator of TaGAPC2/5/6 genes. The dual luciferase reporter assay indicated that TaWRKY33 positively activated the expression of TaGAPC2/5/6. The results of bimolecular fluorescence complementation and yeast two‐hybrid system demonstrated that TaGAPC2/5/6 interacted with phospholipase Dδ (PLDδ). We then demonstrated that TaGAPC2/5/6 positively promoted the activity of TaPLDδ in vitro and in vivo. Furthermore, lower PLDδ activity in RNAi wheat could lead to less PA accumulation, causing higher stomatal aperture sizes under drought stress. In summary, our results establish a new positive regulatory mechanism of TaGAPCs which helps wheat fine‐tune their drought responses. Under drought stress, induced TaWRKY33 binds to the W‐box of TaGAPC2/5/6 promoters to improve the transcription. TaGAPC2/5/6 interact directly with TaPLDδ to mediate stomatal movement. In addition, TaGAPC2/5/6 could positively regulate the activity of enzymes involved in ROS scavenging to enhance resistance to drought stress. [ABSTRACT FROM AUTHOR]

Unlike sporadic daytime heat spikes, a consistent increase in night‐time temperatures can potentially derail the genetic gains being achieved. Ten winter wheat genotypes were exposed to six different night‐time temperatures (15–27°C) during flowering and grain‐filling stages in controlled environment chambers. We identified the night‐time temperature of 23oC as the critical threshold beyond which a consistent decline in yields and quality was observed. Confocal laser scanning micrographs of central endosperm, bran, and germ tissue displayed differential accumulation of protein, lipid, and starch with increasing night‐time temperatures. KS07077M‐1 recorded a decrease in starch and an increase in protein and lipid in central endosperm with increasing night‐time temperatures, whereas the same was significantly lower in the tolerant SY Monument. Expression analysis of genes encoding 21 enzymes (including isoforms) involved in grain–starch metabolism in developing grains revealed a high night‐time temperature (HNT)‐induced reduction in transcript levels of adenosine diphosphate glucose pyrophosphorylase small subunit involved in starch synthesis and a ≥2‐fold increase in starch degrading enzymes isoamylase III, alpha‐, and beta‐amylase. The identified critical threshold, grain compositional changes, and the key enzymes in grain starch metabolism that lead to poor starch accumulation in grains establish the foundational knowledge for enhancing HNT tolerance in wheat. High night temperature‐induced reduction in winter wheat grain‐yields and starch accumulation is attributed to decreased transcript levels of AGPase and increased transcript levels of isoamylase III, alpha‐, and beta‐amylases [ABSTRACT FROM AUTHOR]

Deep rooting is critical for access to water and nutrients found in subsoil. However, damage to soil structure and the natural increase in soil strength with depth, often impedes root penetration. Evidence suggests that roots use macropores (soil cavities greater than 75 μm) to bypass strong soil layers. If roots have to exploit structures, a key trait conferring deep rooting will be the ability to locate existing pore networks; a trait called trematotropism. In this study, artificial macropores were created in repacked soil columns at bulk densities of 1.6 g cm−3 and 1.2 g cm−3, representing compact and loose soil. Near isogenic lines of wheat, Rht‐B1a and Rht‐B1c, were planted and root–macropore interactions were visualized and quantified using X‐ray computed tomography. In compact soil, 68.8% of root–macropore interactions resulted in pore colonization, compared with 12.5% in loose soil. Changes in root growth trajectory following pore interaction were also quantified, with 21.0% of roots changing direction (±3°) in loose soil compared with 76.0% in compact soil. These results indicate that colonization of macropores is an important strategy of wheat roots in compacted subsoil. Management practices to reduce subsoil compaction and encourage macropore formation could offer significant advantage in helping wheat roots penetrate deeper into subsoil. Root–macropore interactions were visualized and quantified using X‐ray CT. In compacted soil, 68.8% interactions resulted in pore colonization compared with 12.5% in loose soil. Results indicate that the colonization of macropores is an important strategy of roots to go through compacted subsoil in wheat. [ABSTRACT FROM AUTHOR]

Plant interactions with plant growth‐promoting rhizobacteria (PGPR) are highly dependent on plant genotype. Modern plant breeding has largely sought to improve crop performance but with little focus on the optimization of plant × PGPR interactions. The interactions of the model PGPR strain Pseudomonas kilonensis F113 were therefore compared in 199 ancient and modern wheat genotypes. A reporter system, in which F113 colonization and expression of 2,4‐diacetylphloroglucinol biosynthetic genes (phl) were measured on roots was used to quantify F113 × wheat interactions under gnotobiotic conditions. Thereafter, eight wheat accessions that differed in their ability to interact with F113 were inoculated with F113 and grown in greenhouse in the absence or presence of stress. F113 colonization was linked to improved stress tolerance. Moreover, F113 colonization and phl expression were higher overall on ancient genotypes than modern genotypes. F113 colonization improved wheat performance in the four genotypes that showed the highest level of phl expression compared with the four genotypes in which phl expression was lowest. Taken together, these data suggest that recent wheat breeding strategies have had a negative impact on the ability of the plants to interact with PGPR. [ABSTRACT FROM AUTHOR]

To protect above‐ground plant organs from excessive water loss, their surfaces are coated by waxes. The genes involved in wax formation have been investigated in detail in Arabidopsis but scarcely in crop species. Here, we aimed to isolate and characterize a CER1 enzyme responsible for formation of the very long‐chain alkanes present in high concentrations especially during late stages of wheat development. On the basis of comparative wax and transcriptome analyses of various wheat organs, we selected TaCER1‐1A as a primary candidate and demonstrated that it was located to the endoplasmic reticulum, the subcellular compartment for wax biosynthesis. A wheat nullisomic‐tetrasomic substitution line lacking TaCER1‐1A had significantly reduced amounts of C33 alkane, whereas rice plants overexpressing TaCER1‐1A showed substantial increases of C25–C33 alkanes relative to wild type control. Similarly, heterologous expression of TaCER1‐1A in Arabidopsis wild type and the cer1 mutant resulted in increased levels of unbranched alkanes, iso‐branched alkanes and alkenes. Finally, the expression of TaCER1‐1A was found activated by abiotic stresses and abscisic acid treatment, resulting in increased production of alkanes in wheat. Taken together, our results demonstrate that TaCER1‐1A plays an important role in wheat wax alkane biosynthesis and involved in responding to drought and other environmental stresses. In this paper, the function of TaCER1‐1A involved in wheat alkane biosynthesis was tested using gain‐of‐function (transgenic plants) and loss‐of‐function plants (gene deletion wheat line), and the role of alkanes in drought resistance was assessed. [ABSTRACT FROM AUTHOR]

High yield and wide adaptation are principal targets of wheat breeding but are hindered by limited knowledge on genetic basis of agronomic traits and abiotic stress tolerances. In this study, 277 wheat accessions were phenotyped across 30 environments with non‐stress, drought‐stressed, heat‐stressed, and drought‐heat‐stressed treatments and were subjected to genome‐wide association study using 395 681 single nucleotide polymorphisms. We detected 295 associated loci including consistent loci for agronomic traits across different treatments and eurytopic loci for multiple abiotic stress tolerances. A total of 22 loci overlapped with quantitative trait loci identified by biparental quantitative trait loci mapping. Six loci were simultaneously associated with agronomic traits and abiotic stress tolerance, four of which fell within selective sweep regions. Selection in Chinese wheat has increased the frequency of superior marker alleles controlling yield‐related traits in the four loci during past decades, which conversely diminished favourable genetic variation controlling abiotic stress tolerance in the same loci; two promising candidate paralogous genes colocalized with such loci, thereby providing potential targets for studying the molecular mechanism of stress tolerance–productivity trade‐off. These results uncovering promising alleles controlling agronomic traits and/or multiple abiotic stress tolerances, providing insights into heritable covariation between yield and abiotic stress tolerance, will accelerate future efforts for wheat improvement. We uncovered consistent marker alleles for agronomic traits across different environments and eurytopic marker alleles controlling multiple abiotic stress tolerances in wheat. Selective sweep analysis showed that the gradual loss of advantageous variation for abiotic stress tolerances due to preferential selection for yield potential may be a common phenomenon in current wheat breeding. Two promising candidate genes identified in the present study provide potential targets for studying the molecular mechanism of stress tolerance‐productivity trade‐off. These results are timely in terms of developing efficient molecular markers and dissection of the functions of relevant genes for wheat improvement in times of unexpected climatic fluctuations. [ABSTRACT FROM AUTHOR]