Grain Weight In Wheat Research Articles

Overexpression of TaSTT3b-2B improves resistance to sharp eyespot and increases grain weight in wheat.

SummarySTAUROSPORINE 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.

Source‐sink limitations for grain weight in wheat and barley under waterlogging conditions during pre‐anthesis

AbstractIn wheat and barley, grain yield is strongly affected by waterlogging, especially during the period immediately previous to anthesis. Although waterlogging reduces grain yield mainly by reductions in grain number, mean grain weight (MGW) is also frequently reduced. The aim of this work was to determine whether increases in the source‐sink ratio produces smaller reductions in MGW due to waterlogging in wheat and barley. Two experiments were carried out combining a waterlogging condition 20 days pre‐anthesis, two soil N conditions at sowing and source‐sink manipulations during grain‐filling (untrimmed or 50% trimmed spikes). Waterlogging reduced MGW in both species up to 35% in wheat and 44% in barley. The negative effect of waterlogging on MGW was intensified with warmer temperatures and higher atmospheric demand. Increases in the source‐sink ratio during the grain‐filling period (by trimming treatments) showed a positive impact on MGW in wheat (up to 40%) and barley (up to 20%) under waterlogging conditions. For both species, grain weight response to increases in source‐sink ratio was higher at lower grain weight and/or spike hierarchies (i.e. spikes from tillers). Our results showed that waterlogging during pre‐anthesis affected grain weight through a reduction in the source during grain‐filling and a possible impact on potential grain weight, depending on the intensity of the stress.

Fine mapping and validation of a major QTL for grain weight on chromosome 5B in bread wheat.

A major QTL QTgw.caas-5B for thousand grain weight in wheat was fine mapped on chromosome 5B, and TraesCS5B02G044800 was predicted to be the candidate gene. Thousand grain weight (TGW), determined by grain length and width, and is an important yield component in wheat; understanding of the underlying genes and molecular mechanisms remains limited. A stable QTL QTgw.caas-5B for TGW was identified previously in a RIL population developed from a cross between Zhongmai 871 (ZM871) and a sister line Zhongmai 895 (ZM895), and the aim of this study was to perform fine mapping and validate the genetic effect of the QTL. It was delimited to an interval of approximately 2.0Mb flanked by markers Kasp_5B29 and Kasp_5B31 (49.6-51.6Mb) using 12 heterozygous recombinant plants obtained by selfing a residual BC1F6 line selected from the ZM871/ZM895//ZM871 population. A candidate gene was predicted following sequencing and differential expression analyses. Marker Kasp_5B_Tgw based on a SNP in TraesCS5B02G044800, the QTgw.caas-5B candidate, was developed and validated in a diversity panel of 166 cultivars. The precise mapping of QTgw.caas-5B laid a foundation for cloning of a predicted causal gene and provides a molecular marker for improving grain yield in wheat.

Identification of Single Nucleotide Polymorphism in TaSBEIII and Development of KASP Marker Associated With Grain Weight in Wheat

Manipulation of genes involved in starch synthesis could significantly affect wheat grain weight and yield. The starch-branching enzyme (SBE) catalyzes the formation of branch points by cleaving the α-1,4 linkage in polyglucans and reattaching the chain via an α-1,6 linkage. Three types of SBE isoforms (SBEI, SBEII, and SBEIII) exist in higher plants, with the number of SBE isoforms being species-specific. In this study, the coding sequence of the wheat TaSBEIII gene was amplified. After the multiple sequence alignment of TaSBEIII genome from 20 accessions in a wheat diversity panel, one SNP was observed in TaSBEIII-A, which formed the allelic marker allele-T. Based on this SNP at 294 bp (C/T), a KASP molecular marker was developed to distinguish allelic variation among the wheat genotypes for thousand grain weight (TGW). The results were validated using 262 accessions of mini core collection (MCC) from China, 153 from Pakistan, 53 from CIMMYT, and 17 diploid and 18 tetraploid genotypes. Association analysis between TaSBEIII-A allelic variation and agronomic traits found that TaSBEIII-A was associated with TGW in mini core collection of China (MCC). The accessions possessing Allele-T had higher TGW than those possessing Allele-C; thus, Allele-T was a favorable allelic variation. By analyzing the frequency of the favorable allelic variation Allele-T in MCC, it increased from pre-1950 (25%) to the 1960s (45%) and increased continuously from 1960 to 1990 (80%). The results suggested that the KASP markers can be utilized in grain weight improvement, which ultimately improves wheat yield by marker-assisted selection in wheat breeding. The favorable allelic variation allele-T should be valuable in enhancing grain yield by improving the source and sink simultaneously. Furthermore, the newly developed KASP marker validated in different genetic backgrounds could be integrated into a breeding kit for screening high TGW wheat.

The stereoselectivity of metconazole on wheat grain filling and harvested seeds germination: Implication for the application of triazole chiral pesticides

Plant growth can be influenced by the application of triazole pesticides as these regulate physiological processes such as plant hormonal levels and enzyme activity. Homology modeling and molecular docking studies suggested that inhibition of ADP-glucose pyrophosphorylase activity in two trans-stereoisomers treatments hinders starch accumulation during the grain filling stage. A field experiment investigated the effects of metconazole racemate, cis-1R,5S-stereostereoisomer, and cis-1S,5R-stereoisomer application at the flowering stage on wheat grain ripening and yield. The concentrations of racemate and both cis-stereoisomers were detected in wheat plant and grain samples. Compared with the racemate, both cis-stereoisomers were more persistent in the matrices. Treatment with cis-1R,5S-stereoisomer decreased grain weight and yield of wheat by delaying chlorophyll degradation, increasing the ethylene content, and decreasing the level of abscisic acid. The germination of harvested seeds was adversely affected by racemate treatment as a result of gibberellin and abscisic acid metabolism regulation and the transcription of signaling-related genes. Therefore, cis-1S,5R-stereoisomer was recommended to be used as metconazole pesticide at the flowering stage.

Carl Ng.

Carl Ng.

Effect of Seed Priming by Salicylic Acid on Emergence Indices and Grain Weight of Wheat (Triticum aestivum Parsi var.) under Water Deficit Stress

Effect of Seed Priming by Salicylic Acid on Emergence Indices and Grain Weight of Wheat (Triticum aestivum Parsi var.) under Water Deficit Stress

Impact of Carbon Coated Urea with Organic Fertilizers on (Soybean -Wheat) Crops Succession

Two field experiments on soybean (Glycine max L.; Variety Giza, 111) wheat (Triticum aestivum L.; Variety Misr 1), were conducted at Agricultural Experimental Research Station of Tag El-ezz, Agricultural Research Centre, El-Dakhalia Governorate, Egypt during two successive summer - winter seasons of (May to November 2019) to (November 2019 to May 2020). The experiment treatments were included eleven (11) treatments (T1- Absolute control, T2- 100% RDUF(recommended dose of urea fertilizer), T3- 100% RDCUF (recommended dose of coated urea fertilizer), T4- 75% RDUF+ 20m3 farm yard manure (FYM), T5- 75% RDUF+10 m3 FYM, T6- 50% RDUF+20m3 FYM, T7- 50% RDUF+10m3 FYM, T8- 75% RDCUF+20m3 FYM, T9- 75% RDCUF +10m3 FYM, T10- 50% RDCUF+20m3 FYM, T11- 50% RDCUF +10m3 FYM).The treatments were layout in complete randomize block plot design with three replicates. The results indicated that the highest mean values of vegetative growth stage (N, P and K % and chlorophyll a, b and Carotene), chemical content of harvest stage(N, P and K % in soybean hay and seeds or wheat grains and straw) and protein%, as well as yield and its components (plant height cm, hay, seeds ton fed-1 and 100 seed weight of soybean or straw, grains yield ton fed-1 and1000 grain weight of wheat) were recorded with integrated application of inorganic and organic fertilizers. T8- 75% RDCUF+ 20m3 FYM, was considered as most suitable treatment for obtaining the highest yield of soybean –wheat under these experimental conditions.

Contribution of green organs to grain weight in dryland wheat from the 1940s to the 2010s in Shaanxi Province, China

Eight dryland winter wheat cultivars (Triticum aestivum L.), which were widely cultivated from the 1940s to the 2010s in Shaanxi Province, China, were selected and grown in plots, and two water treatments (irrigation and drought) were used to identify the contribution of ears, leaves and stems to grain weight and grain number associated with cultivar replacement. The plant height and stem dry weight of the dryland wheat decreased significantly during the cultivar replacement process, but there was a remarkable increase in the dry matter translocation of stems under irrigation. Shaded-ear and defoliation treatment could decrease the grain number and grain weight, and the grain weight was more influenced. Both the leaf and ear are important photosynthetic sources for dryland wheat, and the contribution of ear assimilates showed a significant increase over time; however, the contribution of leaf assimilates showed a negative correlation with cultivation over time. The accumulation of stem assimilates and ear photosynthesis both increased the grain weight potential. In the future breeding process, cultivars with more assimilates stored in the stem and greater assimilative capacity of ears, especially a greater contribution of ear assimilates, are expected to increase the grain yield.

Assimilate limitation compensating factors under environmental stresses in wheat

In recent years, considerable efforts have been made to understand the factors controlling grain weight in wheat. In addition to sink capacity, the supply of assimilates for developing grain determines the weight of the grain. The current photosynthesis of the flag leaf is the most important source of assimilation, and the onset and rate of senescence are important factors for determining grain yield. Hence stress induced leaf senescence can reduce the supply of assimilates for grains. Under such conditions, assimilate contributions of stored non structural carbohydrates in stem and photosynthesis of non foliar parts of the plant such as spike are crucial for grain development. Non structural carbohydrates in wheat stem have been estimated and efforts have been made to reveal the mechanisms of assimilate partitioning. The hormone levels and activities of enzymes involved in assimilate partitioning and carbohydrate metabolism in wheat stem and grains have been significantly correlated with grain filling in wheat. Remobilization efficiency of stem reserves is increased under heat or drought stress along with increase in the proteins associated with senescence and ROS handling in the tolerant cultivars. The heat and drought tolerant wheat cultivars have a higher WSC content in stem, higher mobilization efficiency, longer duration of grain filling and stronger sink activity. However, some of the key issues such as intra-spike assimilation distribution have not been sufficiently addressed. This review has been compiled for information related to assimilate supply to the developing wheat grain under stress conditions and also enlists opportunities to translate this knowledge into traits for improvement of climate resilience in wheat.

Overcoming the trade-off between grain weight and number in wheat by the ectopic expression of expansin in developing seeds leads to increased yield potential.

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.

Exogenous abscisic acid coordinating leaf senescence and transport of assimilates into wheat grains under drought stress by regulating hormones homeostasis

Drought at the grain filling stage of wheat will cause premature leaf senescence, thus leading to considerable loss of wheat yield. Therefore, this paper aims to establish a cultivation technology for strong drought resistance, delayed senescence, and yield improvement based on the analysis of hormones homeostasis obtained by applying chemical control substances. Experiments were conducted with two genotypes of wheat. Four water irrigation treatments were applied to impose the water deficit, including well-watered control treatment (WW), mild water deficit (MiWD), moderate water deficit (MoWD), and severe water deficit (SWD). Exogenous abscisic acid (ABA) was sprayed on the plants at the anthesis stage of the wheat. As a result, exogenous ABA reduced initial senescence rate (r0), total duration of chlorophyll (Chltotal), rapid senescence phase (Chlloss), and the accumulated temperature at an inflection point (M) but improved the persistence phase (Chlper) of flag leaves under all of the four treatments. However, exogenous ABA produced inconsistent effects on photoassimilate relocation and grain weight under different treatments. It produced positive regulatory effects on grain weight under WW, MiWD, and MoWD treatments. On the one hand, spraying ABA during the persistence phase of flag leaves reduced the ratios of zeatin to gibberellin (Z/GA3), spermine to spermidine (Spm/Spd), and salicylic acid to ABA (SA/ABA), which prolonged active photosynthesis by stimulating high level of proline (Pro) and increased the activities of antioxidant enzymes, such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX). Therefore, drought tolerance was enhanced, and more photosynthetic assimilates were accumulated. On the other hand, the rapid senescence phase and the transport rate of assimilates into grains were accelerated, resulting in higher grain weight, yield, and water use efficiency (WUE). However, under SWD treatment, exogenous ABA improved the ratio of SA/ABA, leading to low Pro content and low antioxidant enzyme activity of flag leaves in the rapid loss phase. Meanwhile, drought resistance declined and the transport duration of assimilates into grains was shortened, thus making photosynthetic assimilates redundant. Therefore, exogenous ABA can lead to the reduction in grain weight, yield, and WUE of wheat under SWD treatment.

Genome-wide association study identifies QTL for thousand grain weight in winter wheat under normal- and late-sown stressed environments.

GWAS identified stable loci for TGW and stress tolerance in winter wheat based on two sowing conditions, which will provide opportunities for developing new cultivars with high yield and yield stability. Wheat is an important food crop widely cultivated in the world. Breeding new varieties with high yields and superior adaptability is the main goal of modern wheat breeding program. In order to determine the marker-trait associations (MATs), a set of 688 diverse winter wheat accessions were subjected to genome-wide association study (GWAS) using the wheat 90K array. Field trials under normal-sown (NS) and late-sown (LS) conditions were conducted for thousandgrain weight (TGW) and stress susceptibility index (SSI) at three different sites across two consecutive years. A total of 179 (NS) and 158 (LS) MATs corresponded with TGW; of these, 16 and 6 stable MATs for TGWNS and TGWLS were identified on chromosomes 1B, 2B, 3A, 3B, 5A, 5B, 5D, 6B, and 7D across at least three environments. Notably, a QTL hot spot controlling TGW under NS and LS conditions was found on chromosome 5A (140-142cM). Moreover, 8 of 228 stable MATs on chromosomes 4B, 5A, and 5D for SSI were detected. A haplotype block associated with TGW and SSI was located on chromosome 5A at 91cM, nearby the vernalization gene VRN-A1. Additionally, analysis of wheat varieties from the different eras revealed that the grain weight and stress tolerance are not improved concurrently. Overall, our results provide promising alleles controlling grain weight and stress tolerance (particularly for thermotolerance) for wheat breeders, which can be used in marker-assisted selection for improving grain yield and yield stability in wheat.

High nitrogen application rate and planting density reduce wheat grain yield by reducing filling rate of inferior grain in middle spikelets

Excessive use of nitrogen fertilizer and high planting density reduce grain weight in wheat. However, the effects of high nitrogen and planting density on the filling of grain located in different positions of the wheat spikelet are unknown. A two-year field experiment was conducted to investigate this question and the underlying mechanisms with respect to hormone and carbohydrate activity. Both high nitrogen application and planting density significantly increased spike density, while reducing kernel number per spike and 1000-kernel weight. However, the effects of high nitrogen and high plant density on kernel number per spike and 1000-kernel weight were different. The inhibitory effect of high nitrogen application and high planting density on kernel number per spike was achieved mainly by a reduction in kernel number per spikelet in the top and bottom spikelets. However, the decrease in 1000-kernel weight was contributed mainly by the reduced weight of grain in the middle spikelets. The grain-filling rate of inferior grain in the middle spikelets was significantly decreased under high nitrogen input and high planting density conditions, particularly during the early and middle grain-filling periods, leading to the suppression of grain filling and consequent decrease in grain weight. This effect resulted mainly from inhibited sucrose transport to and starch accumulation in inferior grain in the middle spikelets via reduction of the abscisic acid/ethylene ratio. This mechanism may explain how high nitrogen application and high planting density inhibit the grain filling of inferior wheat grain.

Pericarp growth dynamics associate with final grain weight in wheat under contrasting plant densities and increased night temperature.

The pericarp weight comprises <17 % of wheat grain weight at harvest. The pericarp supports the hydration and nutrition of both the embryo and endosperm during early grain filling. However, studies of the pericarp and its association with final grain weight have been scarce. This research studied the growth dynamics of wheat pericarp from anthesis onwards and its relationship to final grain weight under contrasting plant densities and night warming. Two spring wheat cultivars contrasting in kernel weight (Bacanora and Kambara) were sown in field conditions during seasons 2012-13 and 2014-15. Both genotypes were grown under contrasting plant density (control, 370 plants m-2; and low plant density, 44 plants m-2) and night temperatures, i.e. at ambient and increased (>6 °C) temperature for short periods before and after anthesis. From anthesis onward, grains were harvested every 3 or 4 d. Grain samples were measured and the pericarp was removed with a scalpel. Whole grain and pericarp fresh and dry weight were weighed with a precision balance. At harvest, 20 grains from ten spikes were weighed and grain dimensions were measured. Fresh weight, dry matter and water content of pericarp dynamics showed a maximum between 110 and 235 °Cd. Maximum dry matter of the pericarp ranged between 4.3 and 5.7 mg, while water content achieved values of up to 12.5 mg. Maximum values and their timings were affected by the genotype, environmental condition and grain position. Final grain weight was closely associated with maximum dry matter and water content of the pericarp. Maximum pericarp weight is a determinant of grain weight and size in wheat, which is earlier than other traits considered as key determinants of grain weight during grain filling. Better growing conditions increased maximum pericarp weight, while higher temperature negatively affected this trait.

Dissection and validation of a QTL cluster linked to Rht-B1 locus controlling grain weight in common wheat (Triticum aestivum L.) using near-isogenic lines.

This study dissected and validated a QTL cluster associated with thousand grain weight on chromosome 4B using multiple near-isogenic lines in common wheat. Grain size and weight are crucial components of wheat yield. Previously, we identified a QTL cluster for thousand grain weight (TGW) on chromosome 4B using the Nongda3338 (ND3338)/Jingdong6 (JD6) doubled haploid population. Here, near-isogenic lines (NILs) in the ND3338 background were developed to dissect and validate the QTL cluster. Based on six independent BC3F3:4 heterogeneous inbred families, the 4B QTL cluster was divided into two linked QTL intervals (designated 4B.1 and 4B.2 QTL). For the 4B.1 QTL, the Rht-B1 gene, of which Rht-B1b allele reduces plant height (PH) by 21.18-29.34cm (34.34-53.71%), was demonstrated to be the most likely candidate gene with pleiotropic effects on grain size and TGW. For the 4B.2 QTL, the NILJD6 consistently showed an increase in TGW of 3.51-7.68g (8.84-22.77%) compared with NILND3338 across different field trials, along with a significant increase in PH of 2.26-6.71cm (3.92-12.01%). Moreover, both QTL intervals had a larger effect on grain width than on grain length. Additionally, the first significant difference in 100-grain fresh weight and 100-grain dry weight between the NIL pairs of the 4B.1 QTL interval (Rht-B1) was observed at 6days after pollination (DAP), while the differences were first visible at 30 DAP for the 4B.2 QTL interval. Collectively, our work provides a new example of QTL dissection for grain weight in wheat and lays a foundation for further map-based cloning of the major QTL that have potential applications in wheat molecular breeding for high yield.

Performance Evaluation and Response of Yield Components and Yield of Bread Wheat to NPK Fertilizers at Hidebu Abote District of North Shewa Zone, Oromia

A field experiment was carried out on nitisols of Hidebu Abote district, North Shewa Zone, Oromia where wheat production is severely constrained by lack of an appropriate rate and types of fertilizer recommendation to evaluate wheat crop response to NPK fertilizer application. Fifteen NPK nutrients levels were considered and applied as treatments along with control (no fertilizer) at yaya Deka Bora peasant association were arranged in randomized complete block design (RCBD) with three replications at two farmers field. The ANOVA result indicated that plant height (PH), above ground biomass yield (AGBMY), straw yield (SY), Thousand grain weight (TGW), grain yield (GY) and harvest index (HI) of bread wheat showed significant (P ≤ 0.05) response to the NPK fertilizer application at both sites. The highest AGBMY (13.61 and 12.46 tons ha-1), SY (8.13 and 7.33 tons ha-1) and GY (5475.00 and 5414.33 kg ha-1) were recorded with the application of 69:30:20 NPK fertilizer combination at (site 1 and site 2) respectively and the lowest were recorded on control treatments. However the highest PH (103.8 and 97.27 cm) at site 1 and site 2 was recorded respectively with the application of 92:10:20 NPK nutrients combinations. Both the statically and economical analysis showed that 69:30:20 NPK kg ha-1 of fertilizer application results in higher yield and economically profitable for bread wheat production in the study area. However further research experiment with multi locations, cropping seasons and different bread wheat cultivar have to be required in order to give best conclusive recommendation for the farmers.

Understanding the Competitive Effects of Blessed Milkthistle Densities on Wheat

ABSTRACT: Weed-induced yield loss in wheat crop is a great threat to food security in Pakistan. A comprehensive understanding of weed-crop competition is very important to develop sustainable and cost-effective weed management. For this purpose, two-year field studies were conducted to determine the effect of different blessed milkthistle densities on the phenology and yield of wheat crop in a rice-wheat cropping scheme in Sargodha, Pakistan during 2013-2014 and 2014-2015. The experiment comprised seven treatments: control (weed free), weedy check (weedy without any control) and blessed milkthistle densities of 5, 10, 15, 20 and 25 plants m-2. In response to increasing weed density, a gradual reduction in yield and yield-related traits of wheat was noted. Compared to the weed-free control, a significant reduction in number of productive tillers m-2 (20% and 18%), plant height (15% and 18%), spike length (19% and 26%), number of grains spike-1 (23% and 26%), 1000 grain weight (28% and 28%), grain (29% and 30%) and biological (20% and 24%) yields of wheat occurred at and beyond blessed milkthistle density of 5 plants m-2 during 2013-2014 and 2014-2015 respectively. It can be concluded that blessed milkthistle weed must be controlled if its population density reaches 5 plants m-2 in order to avoid significant grain yield losses in wheat.

Spermidine Increases the Sucrose Content in Inferior Grain of Wheat and Thereby Promotes Its Grain Filling.

The improvement of grain filling is the key issue for promoting wheat thousand grain weight and grain yield. The levels of polyamines (PAs) significantly affect grain filling in cereals, but the mechanism by which PAs affect grain filling in wheat is unclear. In the present study, six wheat cultivars whose grain filling differed were used, and their grain-filling characteristics and endogenous PA contents were measured. In addition, exogenous PAs were supplied during the wheat grain-filling period. The grain-filling characteristics, hormone levels, starch contents, and gene expression [based on RNA sequencing (RNA-seq)] in the grain were analyzed. The objective of the present study was to investigate the effects of PAs on grain filling in wheat. The results suggested that the direct synthetic pathway from putrescine (Put) to spermidine (Spd) in the grain was a key factor in promoting grain filling and thousand grain weight in wheat. Spd through regulates the grain-filling rate of inferior grain during the early grain-filling period to affecting the grain filling and thousand grain weight of wheat. The promotive effect of Spd on the grain filling of inferior wheat grain was notably related to carbohydrate metabolism in that grain. Spd significantly increased the zeatin (Z) + zeatin riboside (ZR) contents but reduced the ethylene (ETH) evolution rate in the inferior grain. In addition, Spd significantly increased the sucrose synthase (SS) and acid invertase (AI) activities in the inferior grain. These effects of Spd led to increased sucrose content in the inferior grain. These reasons might explain why Spd significantly promoted the filling and weight of inferior wheat grain.

GNI-A1 mediates trade-off between grain number and grain weight in tetraploid wheat.

Wild emmer allele of GNI-A1 ease competition among developing grains through the suppression of floret fertility and increase grain weight in tetraploid wheat. Grain yield is a highly polygenic trait determined by the number of grains per unit area, as well as by grain weight. In wheat, grain number and grain weight are usually negatively correlated. Yet, the genetic basis underlying trade-off between the two is mostly unknown. Here, we fine-mapped a grain weight QTL using wild emmer introgressions in a durum wheat background and showed that grain weight is associated with the GNI-A1 gene, a regulator of floret fertility. In-depth characterization of grain number and grain weight indicated that suppression of distal florets by the wild emmer GNI-A1 allele increases weight of proximal grains in basal and central spikelets due to alteration in assimilate distribution. Re-sequencing of GNI-A1 in tetraploid wheat demonstrated the rich allelic repertoire of the wild emmer gene pool, including a rare allele which was present in two gene copies and contained a nonsynonymous mutation in the C-terminus of the protein. Using an F2 population generated from a cross between wild emmer accessions Zavitan, which carries the rare allele, and TTD140, we demonstrated that this unique polymorphism is associated with grain weight, independent of grain number. Moreover, we showed, for the first time, that GNI-A1 proteins are transcriptional activators and that selection targeted compromised activity of the protein. Our findings expand the knowledge of the genetic basis underlying trade-off between key yield components and may contribute to breeding efforts for enhanced grain yield.