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SUMMARY: Heat stress poses a significant threat to maize, especially when combined with drought. Recent research highlights the potential of water replenishment to ameliorate grain weight loss. However, the mitigating mechanisms of heat in drought stress, especially during the crucial early grain‐filling stage, remain poorly understood. We investigated the mechanism for mitigating heat in drought stress by water replenishment from the 12th to the 32nd days after silking in a controlled greenhouse experiment (Exp. I) and field trial (Exp. II). A significant reduction in grain weight was observed in heat stress compared to normal conditions. When water replenishment was applied to increase soil water content (SWC) under heat stress, the grain yield exhibited a notable increase ranging from 28.4 to 76.9%. XY335 variety was used for transcriptome sequencing to analyze starch biosynthesis and amino acid metabolisms in Exp. I. With water replenishment, the transcripts of genes responsible for trehalose 6‐phosphate phosphates (TPP), alpha‐trehalase (TRE), ADP‐glcpyrophosphorylase, and starch synthase activity were stimulated. Additionally, the expression of genes encoding TPP and TRE contributed to an enhanced conversion of trehalose to glucose. This led to the conversion of sucrose from glucose‐1‐phosphate to ADP‐glucose and ADP‐glucose to amylopectin, ultimately increasing starch production by 45.1%. Water replenishment to boost SWC during heat stress also elevated the levels of essential amino acids in maize, including arginine, serine, tyrosine, leucine, glutamic acid, and methionine, providing valuable support to maize plants in adversity. Field trials further validated the positive impact of water replenishment on SWC, resulting in a notable increase in grain yield ranging from 7.1 to 9.2%. This study highlights the vital importance of adapting to abiotic stress and underscores the necessity of developing strategies to counteract its adverse effects on crop yield. [ABSTRACT FROM AUTHOR]

Grain yield is determined mainly by grain number and grain weight. In this study, we identified and characterized MORE GRAINS1 (MOG1), a gene associated with grain number and grain weight in rice (Oryza sativa L.), through map‐based cloning. Overexpression of MOG1 increased grain yield by 18.6%–22.3% under field conditions. We determined that MOG1, a bHLH transcription factor, interacts with OsbHLH107 and directly activates the expression of LONELY GUY (LOG), which encodes a cytokinin‐activating enzyme and the cell expansion gene EXPANSIN‐LIKE1 (EXPLA1), positively regulating grain number per panicle and grain weight. Natural variations in the promoter and coding regions of MOG1 between Hap‐LNW and Hap‐HNW alleles resulted in changes in MOG1 expression level and transcriptional activation, leading to functional differences. Haplotype analysis revealed that Hap‐HNW, which results in a greater number and heavier grains, has undergone strong selection but has been poorly utilized in modern lowland rice breeding. In summary, the MOG1–OsbHLH107 complex activates LOG and EXPLA1 expression to promote cell expansion and division of young panicles through the cytokinin pathway, thereby increasing grain number and grain weight. These findings suggest that Hap‐HNW could be used in strategies to breed high‐yielding temperate japonica lowland rice. [ABSTRACT FROM AUTHOR]

This article, published in the Plant Biotechnology Journal, discusses the discovery of a gene in wheat called GRAIN WIDTH2 (TaGW2) that has a dual effect on enhancing leaf rust resistance and increasing grain weight. Leaf rust, caused by the fungal pathogen Puccinia triticina Eriksson, is a major threat to global wheat production. The limited number of cloned resistance genes often have undesirable agronomic traits, so finding new resistance genes while balancing yield is important for breeding strategies. The researchers used CRISPR/Cas9 technology to edit TaGW2 and found that knockout plants had increased resistance to leaf rust and increased grain weight, offering a novel approach to enhancing wheat's resistance without sacrificing yield. [Extracted from the article]

Postharvest management is critical to attaining household food, nutrition, and income security. Hermetic grain storage bags offer an effective pesticide‐free way to protect stored grain against fungal and insect infestation. We evaluated articles indexed in the Web of Science that included experiments comparing the storage efficacy of conventional and hermetic storage bags based on grain germination rate, insect infestation, physical damage, mycotoxin contamination, and changes in weight and moisture content. Compared with grain stored in hermetic bags, grain stored in conventional bags lost 3.6‐fold more seed viability, contained 42‐fold more insects, had 11‐fold more physical damage, and lost 23‐fold more grain weight, while grain moisture levels were similar for both hermetic and conventional storage bags. Mycotoxin contamination levels were not as frequently assessed. Levels could be low in grain stored in both types of bags, or levels could be low in hermetic bags and significantly higher in conventional bags. The improved properties of grain stored in hermetic bags can increase food security and household income by providing safe storage options for maintaining seed germinability, and for consumption and/or sale when food supplies are high, or when prices are low. Hermetic bags are economically feasible for use by subsistence farmers in Sub‐Saharan Africa for grain for household consumption and for carrying‐over seed for planting in the next season. Additional studies are needed to verify the mycotoxin contamination results and to determine if there are differences in functional food characteristics, e.g. flavor and cooking properties, that have not been as comprehensively studied. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

SUMMARY: Grain size is a key factor in determining rice (Oryza sativa) yield, and exploring new pathways to regulate grain size has immense potential to improve yield. In this study, we report that OsCBL5 encodes a calcineurin B subunit protein that significantly promotes grain size and weight. oscbl5 plants produced obviously smaller and lighter seeds. We further revealed that OsCBL5 promotes grain size by affecting cell expansion in the spikelet hull. Biochemical analyses demonstrated that CBL5 interacts with CIPK1 and PP23. Furthermore, double and triple mutations were induced using CRISPR/Cas9 (cr) to analyze the genetic relationship. It was found that the cr‐cbl5/cipk1 phenotype was similar to that of cr‐cipk1 and that the cr‐cbl5/pp23, cr‐cipk1/pp23, and cr‐cbl5/cipk1/pp23 phenotype was similar to that of cr‐pp23, indicating that OsCBL5, CIPK1, and PP23 act as a molecular module influencing seed size. In addition, the results show that both CBL5 and CIPK1 are involved in the gibberellic acid (GA) pathway and significantly affect the accumulation of endogenous active GA4. PP23 participates in GA signal transduction. In brief, this study identified a new module that affects rice grain size, OsCBL5–CIPK1–PP23, which could potentially be targeted to improve rice yield. Significance Statement: The discovery of the OsCBL5–CIPK1–PP23 module and its role in rice (Oryza sativa) yield represents a significant breakthrough not only in reproductive biology but also in the agricultural field for rice breeding. [ABSTRACT FROM AUTHOR]

Preharvest sprouting (PHS) is an unfavorable trait in cereal crops and causes serious yield loss. However, the molecular mechanism underlying PHS remains largely elusive. Here, we identified a member of 9‐cis‐epoxycarotenoid dioxygenase family, OsNCED3, which regulates PHS and grain development in rice (Oryza sativa L.). OsNCED3 encodes a chloroplast‐localized abscisic acid (ABA) biosynthetic enzyme highly expressed in the embryo of developing seeds. Disruption of OsNCED3 by CRISPR/Cas9‐mediated mutagenesis led to a lower ABA and higher gibberellic acid (GA) levels (thus a skewed ABA/GA ratio) in the embryo, promoting embryos growth and breaking seed dormancy before seed maturity and harvest, thus decreased seed dormancy and enhanced PHS in rice. However, the overexpression of OsNCED3 enhanced PHS resistance by regulating proper ABA/GA ratio in the embryo. Intriguingly, the overexpression of OsNCED3 resulted in increased grain size and weight, whereas the disruption of OsNCED3 function decreased grain size and weight. Nucleotide diversity analyses suggested that OsNCED3 may be selected during japonica populations adaptation of seed dormancy and germination. Taken together, we have identified a new OsNCED regulator involved rice PHS and grain development, and provide a potential target gene for improving PHS resistance and grain development in rice. Summary statement: Preharvest sprouting (PHS) is an unfavorable trait in cereal crops and causes serious yield loss. However, the molecular mechanism underlying PHS remains largely elusive. Here, we identified that overexpression of OsNCED3 enhanced PHS resistance by regulating proper abscisic acidgibberellic acid ratio in the embryo. In addition, the overexpression of OsNCED3 resulted in increased grain size and weight. This study provides a potential target gene for improving PHS resistance and grain development in rice. [ABSTRACT FROM AUTHOR]

There were significantly fewer longitudinal cells in spikelet hulls from the NIL and I GL12 i SP I w i sp -OE than in 9311; however, the spikelet hull cells of the NIL and I GL12 i SP I w i sp -OE were significantly longer than those of 9311 (Figure 1j1-3). Keywords: wild rice; QTL; GL12; grain length; grain weight EN wild rice QTL GL12 grain length grain weight 1513 1515 3 07/26/23 20230801 NES 230801 Grain size and shape are determinants of grain yield and quality and have been selected during early rice domestication (Li I et al i ., [3]). [Extracted from the article]

Summary: Plant transcription factors (TFs), such as basic helix‐loop‐helix (bHLH) and AT‐rich zinc‐binding proteins (PLATZ), play critical roles in regulating the expression of developmental genes in cereals. We identified the bHLH protein TaPGS1 (T. aestivum Positive Regulator of Grain Size 1) specifically expressed in the seeds at 5–20 days post‐anthesis in wheat. TaPGS1 was ectopically overexpressed (OE) in wheat and rice, leading to increased grain weight (up to 13.81% in wheat and 18.55% in rice lines) and grain size. Carbohydrate and total protein levels also increased. Scanning electron microscopy results indicated that the starch granules in the endosperm of TaPGS1 OE wheat and rice lines were smaller and tightly embedded in a proteinaceous matrix. Furthermore, TaPGS1 was bound directly to the E‐box motif at the promoter of the PLATZ TF genes TaFl3 and OsFl3 and positively regulated their expression in wheat and rice. In rice, the OsFl3 CRISPR/Cas9 knockout lines showed reduced average thousand‐grain weight, grain width, and grain length in rice. Our results reveal that TaPGS1 functions as a valuable trait‐associated gene for improving cereal grain yield. [ABSTRACT FROM AUTHOR]

Summary: STAUROSPORINE AND TEMPERATURE SENSITIVE3 (STT3) is a catalytic subunit of oligosaccharyltransferase, which is important for asparagine‐linked glycosylation. Sharp eyespot, caused by the necrotrophic fungal pathogen Rhizoctonia cerealis, is a devastating disease of bread wheat. However, the molecular mechanisms underlying wheat defense against R. cerealis are still largely unclear. In this study, we identified TaSTT3a and TaSTT3b, two STT3 subunit genes from wheat and reported their functional roles in wheat defense against R. cerealis and increasing grain weight. The transcript abundance of TaSTT3b‐2B was associated with the degree of wheat resistance to R. cerealis and induced by both R. cerealis and exogenous jasmonic acid (JA). Overexpression of TaSTT3b‐2B significantly enhanced resistance to R. cerealis, grain weight, and JA content in transgenic wheat subjected to R. cerealis stress, while silencing of TaSTT3b‐2B compromised resistance of wheat to R. cerealis. Transcriptomic analysis showed that TaSTT3b‐2B affected the expression of a series of defense‐related genes and JA biosynthesis–related genes, as well as genes coding starch synthase and sucrose synthase. Application of exogenous JA elevated expression levels of the abovementioned defense‐ and grain weight–related genes, and rescuing the resistance of TaSTT3b‐2B–silenced wheat to R. cerealis, while pretreatment with sodium diethyldithiocarbamate, an inhibitor of JA synthesis, attenuated the TaSTT3b‐2B–mediated resistance to R. cerealis, suggesting that TaSTT3b‐2B played critical roles in regulating R. cerealis resistance and grain weight via JA biosynthesis. Altogether, this study reveals new functional roles of TaSTT3b‐2B in regulating plant innate immunity and grain weight, and illustrates its potential application value for wheat molecular breeding. [ABSTRACT FROM AUTHOR]

Summary: Increasing grain yield has always been the primary goal of crop breeding. KLUH/CYP78A5 has been shown to affect seed size in several plant species, but the relevant molecular mechanism is still unclear and there are no reports of this gene contributing to yield. Here, we demonstrate that modified expression of TaCYP78A5 can enhance wheat grain weight and grain yield per plant by accumulating auxin. TaCYP78A5 is highly expressed in maternal tissues, including ovary and seed coat during wheat development. The constitutive overexpression of TaCYP78A5 leads to significantly increased seed size and weight but not grain yield per plant due to the strengthening of apical dominance. However, localized overexpression of TaCYP78A5 in maternal integument enhances grain weight and grain yield per plant by 4.3%–18.8% and 9.6%–14.7%, respectively, in field trials. Transcriptome and hormone metabolome analyses reveal that TaCYP78A5 participates in auxin synthesis pathway and promotes auxin accumulation and cell wall remodelling in ovary. Phenotype investigation and cytological observation show that localized overexpression of TaCYP78A5 in ovary results in delayed flowering and prolonged proliferation of maternal integument cells, which promote grain enlargement. Moreover, naturally occurring variations in the promoter of TaCYP78A5‐2A contribute to thousand‐grain weight (TGW) and grain yield per plant of wheat;TaCYP78A5‐2A haplotype Ap‐HapII with higher activity is favourable for improving grain weight and grain yield per plant and has been positively selected in wheat breeding. Then, a functional marker of TaCYP78A5 haplotype Ap‐HapII is developed for marker‐assisted selection in wheat grain and yield improvement. [ABSTRACT FROM AUTHOR]

Summary: Auxin signaling is essential for the development of grain size and grain weight, two important components for crop yield. However, no auxin/indole acetic acid repressor (Aux/IAA) has been functionally characterized to be involved in the development of wheat (Triticum aestivum L.) grains to date. Here, we identified a wheat Aux/IAA gene, TaIAA21, and studied its regulatory pathway. We found that TaIAA21 mutation significantly increased grain length, grain width, and grain weight. Cross‐sections of mutant grains revealed elongated outer pericarp cells compared to those of the wild type, where the expression of TaIAA21 was detected by in situ hybridization. Screening of auxin response factor (ARF) genes highly expressed in early developing grains revealed that TaARF25 interacts with TaIAA21. In contrast, mutation of the tetraploid wheat (Triticum turgidum) ARF25 gene significantly reduced grain size and weight. RNA sequencing analysis revealed upregulation of several ethylene response factor genes (ERFs) in taiaa21 mutants which carried auxin response cis‐elements in their promoter. One of them, ERF3, was upregulated in the taiaa21 mutant and downregulated in the ttarf25 mutant. Transactivation assays showed that ARF25 promotes ERF3 transcription, while mutation of TtERF3 resulted in reduced grain size and weight. Analysis of natural variations identified three TaIAA21‐A haplotypes with increased allele frequencies in cultivars relative to landraces, a signature of breeding selection. Our work demonstrates that TaIAA21 works as a negative regulator of grain size and weight development via the ARF25–ERFs module and is useful for yield improvement in wheat. [ABSTRACT FROM AUTHOR]

Summary: Wheat is the most widely grown crop globally, providing 20% of all human calories and protein. Achieving step changes in genetic yield potential is crucial to ensure food security, but efforts are thwarted by an apparent trade‐off between grain size and number. Expansins are proteins that play important roles in plant growth by enhancing stress relaxation in the cell wall, which constrains cell expansion.Here, we describe how targeted overexpression of an α‐expansin in early developing wheat seeds leads to a significant increase in grain size without a negative effect on grain number, resulting in a yield boost under field conditions.The best‐performing transgenic line yielded 12.3% higher average grain weight than the control, and this translated to an increase in grain yield of 11.3% in field experiments using an agronomically appropriate plant density.This targeted transgenic approach provides an opportunity to overcome a common bottleneck to yield improvement across many crops. See also the Commentary on this article by Cosgrove, 230: 403‐405. [ABSTRACT FROM AUTHOR]

Background and objectives: There are no published data on the effect of sowing rate on rice grain quality traits of medium‐ and short‐grain cultivars within the Australian environment. Studies that have reported on the impact of sowing rate on grain quality in other rice growing regions have assessed differences between densities below 100 plants/m2, which is the minimum target for Australian grown rice. Furthermore, the cultivars evaluated were long‐grain cultivars only. The effect of sowing rate (25–150 kg/ha) on the quality traits of a short (YRK5)‐ and medium (Viand)‐grain rice cultivar was investigated over two seasons. Nitrogen (N) application was included in the study as the appropriate combination of sowing and N rate for maximum yield for both cultivars was unknown. Findings: Sowing and N rate affected the number of grains per panicle and plants established per m2 of both cultivars; however, changes in these parameters did not affect crop yield. The number of grains per panicle affected thousand‐grain weight (TGW) and head rice yield (HRY; the percentage of grain that remains whole or at least 75% of the original length after milling), and the response differed between cultivars. Decreasing sowing rate increased the number of grains per panicle, reduced grain length and TGW, and slightly increased HRY in Viand. In YRK5, decreased sowing rate increased TGW and in season two reduced HRY. Protein content was negatively correlated with TGW and positively correlated with HRY. There were no consistent differences in the physicochemical and cooking parameters between densities over both seasons in both cultivars. Conclusion: These results indicate that plant density has an indirect effect on milling quality by influencing TGW, which affected total protein content, and thus, HRY and the response differ between cultivars. Furthermore, this study demonstrated that within a population of 18 to 231 plants/m2 at establishment, the physicochemical and cooking parameters are not affected by sowing rate. Significance and novelty: This study is the first to analyze the grain physicochemical and cooking quality parameters at densities above 100 plants/m2 and evaluate the effect of sowing rate on the grain quality of differing grain types within Australia. Comparisons between the low (50–70 kg/ha) and standard sowing rate (130–150 kg/ha) revealed no difference in HRY, and these results are important to farmers and demonstrate a reduction in plant density due to poor establishment, environmental or bird damage does not affect crop yield or grain quality and thus their economic return. [ABSTRACT FROM AUTHOR]

To examine the extent to which heat stress during grain filling impacts on the development and yield of winter wheat (Triticum aestivum L.), a 3‐year field experiment was conducted on a loess soil with high water holding capacity in the North German Plain. Thirty‐two mostly European winter wheat cultivars were exposed to heat stress in a mobile foil tunnel with maximum air temperatures of 45.7, 45.4, and 47.2°C in 2015, 2016, and 2017, respectively. The 14‐day post‐anthesis heat stress treatment caused an average 57.3% grain yield reduction compared to a close‐by non‐stressed control. The proportion of green crop area after the heat stress phase varied from 7% to 98% in 2016 and from 37% to 94% in 2017. The green crop area percentage did not significantly correlate with grain yield, indicating that the delayed senescence of stay‐green phenotypes offers no yield advantage under terminal heat stress. The water soluble carbohydrate (WSC) concentration of the stems at crop maturity varied between 6 and 92 g/kg dry matter, showing that the genotypes differed in their efficiency at using the stem carbohydrate reserves for grain filling under heat stress. The stem WSC concentration correlated positively with the beginning of anthesis (r = 0.704; p <.001) but negatively with the grain yield (r = −0.431; p <.05). For heat tolerance breeding, the stem reserve strategy, i. e. the rapid and full exhaustion of the temporary carbohydrate storage therefore seems more promising than the stay‐green strategy. [ABSTRACT FROM AUTHOR]

Maize grain filling (GF) and grain weight (GW) are closely associated with grain yield. In our study, the ZmARM4 locus affecting GF and GW was identified using a reverse genetics screen of UniformMutator (Mu). First, MutatorDR‐flanking sequence (MuDRFs) was isolated from the mutant by the MuDR‐amplified fragment length polymorphism method, and it was verified by cosegregation (between MuDRFs and phenotype) and linkage analyses. Second, the target gene of the MuDRFs was found to encode the Armadillo domain of the repeat protein gene families and has high expression in the GF stage. Third, association mapping between SNPs in the ZmARM4 region and the GW of 489 maize lines indicated that ZmARM4 is a functional gene that is closely related to GW. Moreover, bioinformatics analysis suggested that ZmARM4 may be relevant for the activity of sucrose transport or the number of cell divisions in endosperm cells. Therefore, ZmARM4 may be used as an important locus for maize GW in molecular breeding. [ABSTRACT FROM AUTHOR]

Summary: Argonaute (AGO) proteins and small RNAs (sRNAs) are core components of the RNA‐induced silencing complex (RISC). It has been reported that miRNAs regulate plant height and grain size in rice, but which AGO is involved in grain size regulation remains unclear. Here, we report that enhanced expression of OsAGO17, a putative AGO protein, could improve grain size and weight and promote stem development in rice. Cytological evidence showed that these effects are mainly caused by alteration of cell elongation. Expression analyses showed that OsAGO17 was highly expressed in young panicles and nodes, which was consistent with the expression pattern of OsmiR397b. SRNA sequencing, stem‐loop RT‐PCR and sRNA blotting showed that the expression of OsmiR397b was reduced in ago17 and enhanced in the OsAGO17 OE lines. Four OsmiR397b target laccase (LAC) genes showed complementary expression patterns with OsAGO17 and OsmiR397b. Combined with the results of immunoprecipitation (IP) analysis, we suggested that OsAGO17 formed an RISC with OsmiR397b and affected rice development by suppression of LAC expression. In conclusion, OsAGO17 might be a critical protein in the sRNA pathway and positively regulates grain size and weight in rice. [ABSTRACT FROM AUTHOR]

Flowering time is the most critical developmental stage in wheat, as it determines environmental conditions during grain filling. Thirty‐five spring durum genotypes carrying all known allele variants at Ppd‐1 loci were evaluated in fully irrigated field experiments for three years at latitudes of 41°N (Spain), 27°N (northern Mexico) and 19°N (southern Mexico). Relationships between weight of central grains of main spikes (W) and thermal time from flowering to maturity were described by a logistic equation. Differences in flowering time between the allele combination causing the earliest (GS100/Ppd‐B1a) and the latest (Ppd‐A1b/Ppd‐B1a) flowering were 7, 20 and 18 days in Spain, northern Mexico and southern Mexico, respectively. Flowering delay drastically reduced the mean grain filling rate (R) and W at all sites. At autumn‐sowing sites, an increase of 1°C in mean temperature during the first half of the grain filling period decreased W by 5.2 mg per grain. At these sites, W was strongly dependent on R. At the spring‐sowing site (southern Mexico), W depended on both R and grain filling duration. Our results suggest that incorporating the allele combinations GS100/Ppd‐B1a and GS105/Ppd‐B1a (alleles conferring photoperiod insensitivity) in newly released varieties can reduce the negative effects of climate change on grain filling at the studied latitudes. [ABSTRACT FROM AUTHOR]

Summary: Starch is the most important form of energy storage in cereal crops. Many key enzymes involved in starch biosynthesis have been identified. However, the molecular mechanisms underlying the regulation of starch biosynthesis are largely unknown. In this study, we isolated a novel floury endosperm rice (Oryza sativa) mutant flo16 with defective starch grain (SG) formation. The amylose content and amylopectin structure were both altered in the flo16 mutant. Map‐based cloning and complementation tests demonstrated that FLO16 encodes a NAD‐dependent cytosolic malate dehydrogenase (CMDH). The ATP contents were decreased in the mutant, resulting in significant reductions in the activity of starch synthesis‐related enzymes. Our results indicated that FLO16 plays a critical role in redox homeostasis that is important for compound SG formation and subsequent starch biosynthesis in rice endosperm. Overexpression of FLO16 significantly improved grain weight, suggesting a possible application of FLO16 in rice breeding. These findings provide a novel insight into the regulation of starch synthesis and seed development in rice. [ABSTRACT FROM AUTHOR]

This article is a Commentary on Calderini et al. (2021), 230: 629‐640. [ABSTRACT FROM AUTHOR]

Summary: Marker‐based prediction holds great promise for improving current plant and animal breeding efficiencies. However, the predictabilities of complex traits are always severely affected by negative factors, including distant relatedness, environmental discrepancies, unknown population structures, and indeterminate numbers of predictive variables. In this study, we utilised two independent F1 hybrid populations in the years 2012 and 2015 to predict rice thousand grain weight (TGW) using parental untargeted metabolite profiles with a partial least squares regression method. A stable predictive model for TGW was built based on hybrids from the population in 2012 (r = 0.75) but failed to properly predict TGW for hybrids from the population in 2015 (r = 0.27). After integrating hybrids from both populations into the training set, the TGW of hybrids could be predicted but was largely dependent on population structures. Then, core hybrids from each population were determined by principal component analysis and the TGW of hybrids in both environments were successfully predicted (r > 0.60). Moreover, adjusting the population structures and numbers of predictive analytes increased TGW predictability for hybrids in 2015 (r = 0.72). Our study demonstrates that the TGW of F1 hybrids across environments can be accurately predicted based on parental untargeted metabolite profiles with a core hybridisation strategy in rice. Metabolic biomarkers identified from early developmental stage tissues, which are grown under experimental conditions, may represent a workable approach towards the robust prediction of major agronomic traits for climate‐adaptive varieties. [ABSTRACT FROM AUTHOR]

Carbon loss under high night‐time temperature (HNT) leads to significant reduction in wheat yield. Growth chamber studies were carried out using six winter wheat genotypes, to unravel postheading HNT (23°C)–induced alterations in carbon balance, source‐sink metabolic changes, yield, and yield‐related traits compared with control (15°C) conditions. Four of the six tested genotypes recorded a significant increase in night respiration after 4 days of HNT exposure, with all the cultivars regulating carbon loss and demonstrating different degree of acclimation to extended HNT exposure. Metabolite profiling indicated carbohydrate metabolism in spikes and activation of the TriCarboxylic Acid (TCA) cycle in leaves as important pathways operating under HNT exposure. A significant increase in sugars, sugar‐alcohols, and phosphate in spikes of the tolerant genotype (Tascosa) indicated osmolytes and membrane protective mechanisms acting against HNT damage. Enhanced night respiration under HNT resulted in higher accumulation of TCA cycle intermediates like isocitrate and fumarate in leaves of the susceptible genotype (TX86A5606). Lower grain number due to lesser productive spikes and reduced grain weight due to shorter grain‐filling duration determined HNT‐induced yield loss in winter wheat. Traits and mechanisms identified will help catalyze the development of physiological and metabolic markers for breeding HNT‐tolerant wheat. Carbon loss under high night‐time temperature (HNT) leads to significant yield decline in wheat. Winter wheat genotypes exhibited considerable variation for HNT‐induced enhanced night respiration in flag leaves and acclimation upon extended HNT exposure. Alterations in carbohydrate metabolism in spikes with increased sugars acting as osmoprotectants and activation of TCA cycle in leaves due to enhanced night respiration, provides novel insights into metabolites involved in HNT response in wheat. [ABSTRACT FROM AUTHOR]

Summary: GW2 is emerging as a key genetic determinant of grain weight in cereal crops; it has three homoeologs (TaGW2‐A1, ‐B1 and ‐D1) in hexaploid common wheat (Triticum aestivum L.). Here, by analyzing the gene editing mutants that lack one (B1 or D1), two (B1 and D1) or all three (A1, B1 and D1) homoeologs of TaGW2, several insights are gained into the functions of TaGW2‐B1 and ‐D1 in common wheat grain traits. First, both TaGW2‐B1 and ‐D1 affect thousand‐grain weight (TGW) by influencing grain width and length, but the effect conferred by TaGW2‐B1 is stronger than that of TaGW2‐D1. Second, there exists functional interaction between TaGW2 homoeologs because the TGW increase shown by a double mutant (lacking B1 and D1) was substantially larger than that of their single mutants. Third, both TaGW2‐B1 and ‐D1 modulate cell number and length in the outer pericarp of developing grains, with TaGW2‐B1 being more potent. Finally, TaGW2 homoeologs also affect grain protein content as this parameter was generally increased in the mutants, especially in the lines lacking two or three homoeologs. Consistent with this finding, two wheat end‐use quality‐related parameters, flour protein content and gluten strength, were considerably elevated in the mutants. Collectively, our data shed light on functional difference between and additive interaction of TaGW2 homoeologs in the genetic control of grain weight and protein content traits in common wheat, which may accelerate further research on this important gene and its application in wheat improvement. [ABSTRACT FROM AUTHOR]

Grain yield is the most important and complicated trait in maize. In this study, a total of 498 recombinant inbred lines ( RIL) derived from a biparental cross of two elite inbred lines, 178 and P53, were grown in six different environments. Quantitative trait locus ( QTL) mapping was conducted for three grain yield component traits (100 grain weight, ear weight and kernel weight per plant). Subsequently, meta-analysis was performed after a comprehensive review of the research on QTL mapping for grain weight (100, 300 and 1000) using BioMercator V4.2. In total, 62 QTLs were identified for 100 grain weight, ear weight and kernel weight per plant in six environments. Forty-three meta- QTLs ( MQTLs) were detected by meta-analysis. A total of 13 candidate genes homologous to eight functionally characterized rice genes were found, and four candidate genes were located in the two hot spot regions of MQTL1.5 and MQTL2.3. Our results suggest that the combination of literature collection, meta-analysis and homologous blast searches can offer abundant information for further fine mapping, marker-assisted selection ( MAS) breeding and map-based cloning for maize. [ABSTRACT FROM AUTHOR]

Drought and heat are among the main abiotic stresses causing severe damage to the cereal productivity when occur at reproductive stages. In this study, ten wheat cultivars were screened for combined heat and drought tolerance imposed at booting, heading, anthesis and post-anthesis stages, and role of the foliage applied plant extracts was evaluated in improving the performance of differentially responding wheat cultivars under terminal heat and drought stresses. During both years, wheat crop was raised under ambient temperature and 70% water holding capacity ( WHC) till leaf boot stage. The plant extracts (3% each) of sorghum, brassica, sunflower and moringa were foliage applied at booting, anthesis and post-anthesis stage; and after one week of application of these plant extracts, combined heat and drought was imposed at each respective stage. Heat and drought stresses were imposed at each respective stage by placing pots in glass canopies with temperature of 4 ± 2°C above than the ambient temperature in combination with drought stress (35% WHC) until maturity. Combination of drought and heat stresses significantly reduced the performance of tested wheat cultivars; however, stress at the booting and heading stages was more damaging than the anthesis and post-anthesis stages. Cultivars Mairaj-2008 and Chakwal-50 remained green with extended duration for grain filling, resulting in the maintenance of number of grains per spike and 100-grain weight under stress conditions and thus had better grain yield and water-use efficiency. However, in cultivars Fsd-2008, and Shafaq-2006, the combined imposition of drought and heat accelerated the grain filling rate with decrease in grain filling duration, grain weight and grain yield. Foliar application of all the plant extracts improved the wheat performance under terminal heat and drought stress; however, brassica extract was the most effective. This improvement in grain yield, water-use efficiency and transpiration efficiency due to foliage applied plant extracts, under terminal heat and drought stress, was owing to better stay-green character and accumulation of more soluble phenolics, which imparted stress tolerance as indicated by relatively stable grain weight and grain number. In crux, growing of stay-green wheat cultivars with better grain filling and foliage application of plant extracts may help improving the performance of bread wheat under combined heat and drought stresses. [ABSTRACT FROM AUTHOR]

Grain size and shape are two crucial traits that influence grain yield and grain appearance in rice. Although several factors that affect grain size have been described in rice, the molecular mechanisms underlying the determination of grain size and shape are still elusive. In this study we report that WIDE AND THICK GRAIN 1 ( WTG1) functions as an important factor determining grain size and shape in rice. The wtg1-1 mutant exhibits wide, thick, short and heavy grains and also shows an increased number of grains per panicle. WTG1 determines grain size and shape mainly by influencing cell expansion. WTG1 encodes an otubain-like protease, which shares similarity with human OTUB1. Biochemical analyses indicate that WTG1 is a functional deubiquitinating enzyme, and the mutant protein (wtg1-1) loses this deubiquitinating activity. WTG1 is expressed in developing grains and panicles, and the GFP- WTG1 fusion protein is present in the nucleus and cytoplasm. Overexpression of WTG1 results in narrow, thin, long grains due to narrow and long cells, further supporting the role of WTG1 in determining grain size and shape. Thus, our findings identify the otubain-like protease WTG1 to be an important factor that determines grain size and shape, suggesting that WTG1 has the potential to improve grain size and shape in rice. [ABSTRACT FROM AUTHOR]

Increasing grain yield and improving grain quality are two important goals for rice breeding. A better understanding of the factors that contribute to the overall grain quantity and nutritional quality of rice will lay the foundation for developing new breeding strategies. RAG2 is a member of 14-to-16- kDa α-amylase/trypsin inhibitors in rice, which belong to the albumin of seed storage proteins. We found that RAG2 was specifically expressed in ripening seed and its transcription peak was between 14 and 21 days after flowering. Grain size and 1000-grain weight were obviously increased in RAG2-overexpressed lines compared with wild type, and grain size was reduced in RAG2-suppressed lines. In addition, the major storage substances of the seeds differed significantly in RAG2-overexpressed and RAG2-suppressed lines compared to wild type. The protein content and amount of total lipids were increased and decreased, respectively, in the seeds of RAG2-overexpressed and RAG2-suppressed lines. Overexpression of RAG2 significantly increased grain size and improved grain quality and yield simultaneously. These results imply that RAG2 might play an important role in regulating grain weight and seed quality of rice. The functional characterization of rice RAG2 facilitates a further understanding of the mechanisms involved in grain size and seed quality and may be helpful in improving grain yield and quantity in cereal crops. [ABSTRACT FROM AUTHOR]

Waterlogging, if occurring within the stem elongation period ( SE), is particularly critical for yield determination. We quantified for the first time the effect of waterlogging duration during SE on yield and studied whether the effects were only direct on resource capture or whether there were feed-forward effects as well. We grew wheat (cv. Soissons) outdoors in long tubes (1.25 m deep) forming a normal canopy and imposed different treatments in SE to finish simultaneously around anthesis (0, 4, 8, 12, 16, 20 and 24 days) plus two complementary treatments (8 and 16 days) starting 10 days after the onset of SE. Yield was reduced linearly with the duration of waterlogging c. 2 % dwaterlogging−1. Treatments mainly affected pre-anthesis spike growth reducing the number of fertile florets and grains, not affecting fruiting efficiency. The magnitude of grain number loss was inversely proportional to the hierarchy of the spikes and spikelets. Grain weight was more marginally reduced, likely through the effects on the size of the ovaries of the developing florets. This reveals a direct effect of waterlogging on the capture of resources with no major feed-forward effects. Losses were in agreement with those from other studies for particular durations of waterlogging. [ABSTRACT FROM AUTHOR]

Water scarcity is threatening the sustainability of global food grain production systems. Devising management strategies and identification of crop species and genotypes are direly required to meet the global food demands with limited supply. This study, consisted of two independent experiments, was conducted to compare faba bean ( Vicia faba L.) genotypes Giza Blanka, Goff-1, Hassawi-1, Hassawi-2 and Gazira-2 in terms of physiological attributes and yield under water-limited environments. In first experiment, conducted in a growth chamber, osmotic stress of −0.78, −0.96, −1.19 and −1.65 MPa was induced using polyethylene glycol for 4 weeks. In second experiment, conducted in open field for two consecutive growing seasons, water deficit treatments were applied 3 weeks after sowing. In this experiment, irrigation was applied when an amount of evaporated water from the 'class A pan' evaporation reached 50 mm (well watered), 100 mm (moderate drought) and 150 mm (severe drought). Water deficit, applied in terms of osmotic stress or drought, reduced the root and shoot length, related leaf water contents, total chlorophyll contents and efficiency of photosystem-II, plant height, grain yield and related attributes in faba bean; increased the leaf free proline, leaf soluble proteins and malondialdehyde contents, and triggered the maturity in tested faba bean genotypes. However, substantial genetic variation was observed in the tested genotypes in this regard. For instance, root length of genotypes Giza Blanka and Hassawi-2 decreased gradually, whereas it was increased in genotypes Goff-1, Hassawi-1 and Gazira-2 with increase in the level of osmotic stress. Genotypes Gazira-2 and Hassawi-2 had better relative leaf water contents, leaf free proline and soluble proteins under water deficit conditions; however, these were minimum in genotype Giza Blanka. Better accumulation of leaf free proline, soluble proteins, and maintenance of chlorophyll contents, tissue water, efficiency of photosystem-II and grain weight in water-limited conditions helped some genotypes like Hassawi-2 to yield better. Future breeding programs for developing new faba bean genotypes for water-limited environments may consider these traits. [ABSTRACT FROM AUTHOR]

The cytokinin oxidase/dehydrogenase ( CKX) gene plays a principal role in controlling cytokinin levels and has been shown to be a major quantitative trait locus (QTL) affecting grain number in rice. However, the function and evaluation of the haplotypes of the wheat CKX gene have yet to be illustrated., In this study, TaCKX6-D1, a wheat ortholog of rice OsCKX2, was cloned and its haplotype variants were determined to be significantly associated with the 1000-grain weight on the basis of linkage mapping, association analysis and gene expression analysis., Five TaCKX6-D1 haplotypes, designated a-e, were identified. An indel marker was developed to identify haplotype a, which was associated with higher grain weight. Haplotype a showed decreased expression relative to haplotype b in seeds at 8 d after pollination. Sequence variations among modern cultivars, landraces and wild species suggest a significant domestication signature at the TaCKX6-D1 locus in Chinese wheat germplasm., TaCKX6-D1 may serve as a useful gene for the breeding of high-yielding wheat. A strategy for allele mining and utilization of TaCKX6-D1 was proposed. Our study also sheds light on the mechanisms of grain development and domestication of wheat, as well as the functional divergence of orthologs in comparative genomics. [ABSTRACT FROM AUTHOR]

The effect of source and sink manipulation on accumulation of micronutrients (Fe, Zn, Mn, Cu) and protein in wheat grains was studied in a field experiment and ear culture. The source and sink manipulation was obtained by reducing assimilate source (through defoliation and spike shading) or sink (through 50% spikelets removal) after anthesis in the field and by changing sucrose or NH4NO3 levels of the culture media in ear culture. In the field experiment, reducing source and sink generally increased Fe, Zn, Mn, Cu, and protein concentrations except defoliation which decreased Mn concentration. Grain yield as well as micronutrient and protein contents in grains were all reduced by reducing source and sink sizes, suggesting that the accumulation of micronutrients and protein in grains was restricted by source supply and sink capacity. In ear culture, the supply of 20 to 80 g L-1 sucrose increased grain weight and yield, but decreased grain Fe, Zn, Mn, Cu, and protein concentrations. The supply of 0.57 to 2.28 g L-1 NH4NO3 increased grain yield and the concentrations and contents of micronutrients and protein. All these results show that micronutrient and protein accumulation in grains can be affected by the source-sink relationship of carbohydrate and nitrogen. Adequate N supply can simultaneously increase grain yield and the accumulation of Fe, Zn, Mn, Cu, and protein. [ABSTRACT FROM AUTHOR]

In grain crops, total sink capacity is usually analysed in terms of two components, seed number and individual seed weight. Seed number and potential individual seed weight are established at a similar timing, around the flowering period, and seed weight at maturity is highly correlated with the potential established earlier. It is known that, within a species, available resources during the seed set period are distributed between both yield components, resulting in a trade-off between seed number and seed weight. Here we tested if this concept could apply for interspecific comparisons, where combinations of numbers and size across species could be related to the total available resources being either allocated to more seed or larger potential individual seed weight during the seed set period. Based on this, species differences in seed weight should be related to resource availability per seed around the period when seed number is determined. Resource availability per seed was estimated as the rate of increase in aboveground biomass per seed around the period of seed set. Data from 15 crop species differing in plant growth, seed number, seed weight and seed composition were analysed from available literature. Because species differed in seed composition, seed weight was analysed following an energy requirement approach. There was an interspecific trade-off relationship between seed number per unit of land area and seed weight ( r = 0.92; F(1, 13) = 32.9; n = 15; P < 0.001). Seed weight of different species was positively correlated ( r = 0.90; F(1, 13) = 52.9; n = 15; P < 0.001) with resource availability per seed around the seed set period. This correlation included contrasting species like quinoa ( Chenopodium quinoa; ∼100000 seeds m−2, ∼4 mg equivalent-glucose seed−1) or peanut ( Arachis hypogaea; ∼800 seeds m−2, ∼1000 mg equivalent-glucose seed−1). Seed number and individual seed weight combinations across species were related and could be explained considering resource availability when plants are adjusting their seed number to the growth environment and seeds are establishing their storage capacity. Available resources around the seed set period are proportionally allocated to produce either many small seeds or few larger seeds depending on the particular species. [ABSTRACT FROM AUTHOR]

Heading date is an important agronomic trait in rice. A rice mutant with a late heading date and no photoperiodic sensitivity in long or short day conditions was obtained from rice T-DNA insertion mutants in Zhonghua11 (ZH11). Through isolation and analysis of the flanking sequence of the T-NDA insertion site, the target sequence of insertion was obtained and found to locate in AP003296, the sequence accession number of rice chromosome 1 of RGP ( ). The putative amino acid sequences of this target gene are homologous to the Arabidopsis protein ELF3 encoded by an early flowering gene. The rice target gene orthologous to Arabidopsis ELF3 is named OsEF3; this encodes a putative nematode responsive protein-like protein. OsEF3 has pleiotropic effects in rice that differ from the effects of Arabidopsis ELF3, which only affects biological rhythms. OsEF3 regulates heading date by influencing the BVG stage and does not affect photoperiodic sensitivity, which suggests that the OsEF3 gene may be involved in an autonomous pathway in rice. OsEF3 may affect root development and kilo-grain weight by delaying cell division or cell elongation. [ABSTRACT FROM AUTHOR]

Bread and durum wheat genotypes were submitted to heat stress during the grain filling period, and relationships between grain weight and accumulated time from anthesis until maturity, using days after anthesis and growing degree days, were described by cubic polynomials. Maximum grain weight and the duration and rate of grain filling were estimated from the fitted curves. It was found that bread and durum wheat exposure to high temperatures significantly decreased grain weight and hastens physiological maturity (shortening the grain filling period). High temperatures significantly affected the rate (on a growing degree day basis) and duration (on Julian day units) of grain filling. The grain filling rate, on a thermal time basis, was positively associated with the final grain weight and the estimated maximum grain weight. The duration of grain filling does not appear to be a limiting factor for genotype grain weight stability, being mainly fixed by temperature. Grain weight of the controlled plants was positively correlated with the final and maximum grain weight of heat stressed plants. It was concluded that a high grain filling rate and a high potential grain weight are major traits that can be useful to improve heat tolerance of Triticum under Mediterranean environments. [ABSTRACT FROM AUTHOR]

The effects of panicle type and source-sink relation on the variation in grain weight (GW) and quality within a panicle were investigated using four japonica ( Oryza sativa L.) varieties differing in grain density and two source-sink adjusting treatments. There were significant differences in GW and filling grain percentage (FGP) among superior and inferior grains for compact-panicle varieties (Xiushui 994 and Xiushui 63), while not for loose-panicle ones (Xiushui 11 and Chunjiang 15). The floret-removal treatment significantly improved the development of inferior florets and reduced the differences in FGP and GW between superior and inferior grains for the compact-panicle variety, while leaf-deleting treatment reduced FGP and GW of both superior and inferior grains. For the loose-panicle varieties, the two treatments had little effect. The difference in chalky grain percentage (CGP) and amylose content (AC) between the two kinds of florets was larger in compact-panicle varieties than in loose-panicle ones. Both floret-removal and leaf-deleting treatments caused the changes in CGP and AC of superior or inferior grains for compact-panicle varieties, but not for loose-panicle ones. The difference in starch content (SC) between superior and inferior grains was much larger for Xiushui 994 than for Xiushui 11, and the two varieties differed in the response of SC to the change of source-sink relation. The differences in AGP-glucose pyrophosphorylase (ADPG-Ppase), starch branching enzyme (SBE) and soluble starch synthase (SSS) activities between the two kinds of grains were basically same for the two varieties, with superior being higher than inferior ones at early filling stage and smaller at later stage. In floret-removal treatment, the activities of ADPG-PPase, SSS, and SBE in superior grains of Xiushui 994 decreased at early filling stage and increased at middle or later stages. Meanwhile, the activities of SSS and SBE in both kinds of grains at early filling stage, and of ADPG-PPase and granule-bound starch synthase (GBSS) in inferior grains over the whole stage were increased. In leaf-deleting treatment, the activities of ADPG-PPase and SBE at early filling stage and GBSS at later filling stage were reduced in superior grains, while SSS activity at middle filling stage and SBE activity at later stage were increased. [ABSTRACT FROM AUTHOR]

Two wheat genotypes differing in water stress sensitivity (C306, relatively tolerant; HD2329, relatively susceptible) were water stressed during early grain filling by withholding water for 7 days at watery-ripe (WR) stage and examined for water status, abscisic acid (ABA) and osmolytes in grains as well as in flag leaf (FL). Both the genotypes differed significantly from each other in endogenous levels of ABA, proline, glycine betaine, total soluble sugars, reducing sugars, sucrose and potassium. The tolerant genotype showed higher content of ABA, proline, glycine betaine, total sugars, reducing sugars and had higher water content in its FL and grains than the susceptible genotype, which contained more of glycine beatine and potassium but had lower ABA and water content in its FL and grains. Although carbohydrates constituted the major amount of all the solutes, proline and glycine betaine increased manifold during stress. Exogenous application of 2 μ m ABA at 5 days after anthesis to FL of stressed plants increased the endogenous content of ABA, accelerated the accumulation of osmolytes, improved the water status of FL and grains that resulted in higher grain weight, especially in the susceptible genotype. Differential response of contrasting wheat genotypes to water stress may be governed by ABA-dependent solute accumulation in grains and FL. [ABSTRACT FROM AUTHOR]

Grain dry weight, water content and changes in wallbound α-galactosidase and β-glucosidase activities were estimated in three grains (differing in their position on the spike and final dry weight) of wheat (Triticum aestivum L.) cultivar Lok-1 during the entire period of grain development. Considerable differences in the grain weight within a wheat spike are reported, but the physiological and biochemical bases of these differences are poorly understood. The experiments described here indicate that the maximum grain weight is dependent upon the rate of grain filling. A highly significant correlation (P < 0.001) between maximum grain weight and maximum water content per grain, and a close correspondence between the rate of grain filling and wall-located α-galactosidase activity, suggests that the process of cell enlargement may be important in determining the rate of grain filling, and thus, for maximum grain weight in wheat. [ABSTRACT FROM AUTHOR]

Experiments were carried out during 1992 and 1993 growing seasons using in the former year 2 (an early and late) sowing dates. Plants of three isogenic lines (standard height, semidwarf and dwarf) of wheat were grown under field conditions with no restrictions on water or nutrient availability with the objective of determining whether differences in rate of grain growth and in final grain weight were related to differences in leaf area duration postanthesis (LAD). A logistic and an optimization model were used to estimate the components of final grain weight and their performances were compared. The optimization model appeared more appropriate than the logistic to estimate final grain weight and their components (i.e, rate of grain growth and duration of grain filling). The dwarf line presented the lowest average grain weight followed by the semidwarf and standard height lines, respectively. However, changes in grain weight due to the action of Rht alleles were independent of the LAD, suggesting that reductions in grain weight due to delayed sowing date could be associated with a direct effect of temperature on grain development. Changes in final grain weight were associated with changes in rate of grain growth, but not with duration of the grain tilling period, demonstrating that rate of grain growth was the main factor responsible for final grain weight. [ABSTRACT FROM AUTHOR]

The influence of a varied sucrose supply on grain size and hormonal contents of detached wheat ears (Triticum aestivum L. cv. Schirokko) was investigated throughout grain development. In ears fed limited amounts, or no sucrose, grain weights in both proximal and distal grain positions of the ear were reduced. Radioimmunoassay for abscisic acid, indoleacetic acid and zeatin/zeatin riboside showed that the changes in the levels of these hormones in grains and bracts were comparable to intact ears when detached ears were well supplied with sucrose. Under conditions of limited sucrose supply, higher abscisic acid levels in the distal and proximal grains of detached ears were found compared to ears supplied with adequate sucrose. Limiting sucrose supply to the ear did not alter the levels of indoleacetic acid or zeatin/zeatin riboside in either the grains or bracts of detached ears. [ABSTRACT FROM AUTHOR]

The objective of this work is to study the association between the genotypic differences in mean grain weight and grain yield, the relationship of yield and grain weight with culm length, and the differences between the effects of the Rht1 and Rht2 dwarfing alleles on these characters. Yields, grain weight, grains m-2 and culm length were evaluated in two random samples of 19 semi-dwarf early lines, selected in F5 and tested in F7, from two different crosses between cultivars difference in the Rht allele controlling their semi-dwarfness. The lines of each cross were tested in 4-replicated field trails at two different sites. Phenotypic, genotypic, partial and multiple correlations as well as heritability estimates were computed. In each cross the lines differed significantly in their mean values of all the characters tested. In both crosses there was no apparent association between grain weight and grain yield. It therefore seems that in wheat of the type investigated in this study, grain yeild and grain weight are independently controlled and that high grain yield is not restricted to any particular range of mean grain weight. A rather high positive correlation between culm length and grain weight was found in one cross but not in the other indicating the dependence of this relationship on the genetic background. In both crosses no significant differences were found between the performance of the lines carrying the Rht1 dwarfing allele and those carrying the Rht2 allele. [ABSTRACT FROM AUTHOR]