Middle Grain-filling Stages Research Articles

Night warming increases wheat yield by improving pre-anthesis plant growth and post-anthesis grain starch biosynthesis

Global climate change is characterized by asymmetric warming, i.e., greater temperature increases in winter, spring, and nighttime than in summer, autumn, and daytime. Field experiments were conducted using four wheat cultivars, namely 'Yangmai 18' (YM18), 'Sumai 188' (SM188), 'Yannong 19' (YN19), and 'Annong 0711' (AN0711), in the two growing seasons of 2019–2020 and 2020–2021, with passive night warming during different periods in the early growth stage. The treatments were night warming during the tillering–jointing (NWT–J), jointing–booting (NWJ–B), and booting–anthesis (NWB–A) stages, with ambient temperature (NN) as the control. The effects of night warming during different stages on wheat yield formation were investigated by determining the characteristics of dry matter accumulation and translocation, as well as sucrose and starch accumulation in wheat grains. The wheat yields of all four cultivars were significantly higher in NWT–J than in NN in the 2-year experiment. The yield increases of semi-winter cultivars YN19 and AN0711 were greater than those of spring cultivars YM18 and SM188. Treatment NWT–J increased wheat yield mainly by increasing the 1,000-grain weight and the number of fertile spikelets, and it increased dry matter accumulation in various organs of wheat at the anthesis and maturity stages by increasing the growth rate at the vegetative growth stage. The flag leaf and spike showed the largest increases in dry matter accumulation. NWT–J also increased the grain sucrose and starch contents in the early and middle grain-filling stages, promoting yield formation. Overall, night warming between the tillering and jointing stages increased the pre-anthesis growth rate, and thus, wheat dry matter production, which contributed to an increase in wheat yield.

Effects of semi-deep water irrigation on hybrid indica rice lodging resistance.

Recently, rice-aquatic animal integrated farming (RAAIF) has grown rapidly in China due to its favorable benefits and the lower application of pesticides and fertilizers. However, rice lodging occurs frequently under RAAIF, which restricts rice yield. We assumed that semi-deep water irrigation may cause weaker rice-lodging resistance since it is the most significant environmental factor for RAAIF that distinguishes it from rice monoculture. To investigate the response of rice stem lodging resistance to semi-deep water irrigation and its mechanism, three irrigation management modes, namely the typical high-yield irrigation model that is mainly based on swallow and wetting (CK), semi-deep water irrigation from the late tillering stage to the jointing stage (SDI1), and semi-deep water irrigation from the jointing stage to the middle grain-filling stage (SDI2), were conducted using three hybrid indica rice varieties: Shenliangyou136 (SLY136), Huiliangyousimiao (HLYSM), and Wanxiangyou982 (WXY982). Mechanics analysis indicated that the bending moment by the whole plant (WP) and the breaking strength (M) were both decreased by semi-deep water irrigation when compared with CK, while M presented a larger decreasing amplitude than WP, which induced the increased lodging index (LI) of rice, for all the tested varieties. SLY136 and HLYSM were affected more strongly by SDI1, whereas WXY982 was affected more strongly by SDI2. Significant weaker breaking force under two semi-deep water irrigation modes contributed to the decreased M relative to CK. Morphology results showed that semi-deep water irrigation reduced the thickness of mechanical tissues, sclerenchyma cells, and parenchyma cells; reduced the number of vascular bundles; and caused a looser arrangement, inducing the lower fullness of the rice basal internode. Decreased accumulation of lignin and cellulose was also linked to the weaker breaking force of the basal internode under semi-deep water irrigation, which was verified by correlation analysis. WXY982 had obvious lower structural carbohydrates content under semi-deep water irrigation than the other two varieties and thus showed worse breaking force and LI. In conclusion, the worse mechanical strength of the rice basal internode under semi-deep water irrigation was closely associated with weaker vascular bundle development and suppressed structural carbohydrate accumulation, and the decreasing degree of lodging resistance varied between rice varieties and semi-deep water irrigation periods.

Screening of Grain Development Heterosis Candidate Genes by Integrating QTL Mapping and RNA-Seq in Super Hybrid Rice WFYT025

The application of heterosis during plant breeding increases rice grain yield. However, there have been limited studies on heterosis during rice grain development during the grain-filling stage; therefore, the genetic basis of heterosis for grain development during the grain-filling stage should be highly valued. In this study, a hybrid combination with the super hybrid rice WFYT025 was used to perform a transcriptomic dynamic analysis in grains at the beginning and middle grain-filling stages. A total of 1556 and 1507 transcripts that were differentially expressed between WFYT025 and its parents (DGHP) were identified at 1-day post-anthesis (DPA) and at 10 DPA, respectively. The analysis of the genetic effects of heterosis showed that the over-dominant effect (66.90% and 55.87%) was the main mode of action during grain development. The KEGG pathway and GO analysis of the DGHP indicated that the gibberellin biosynthetic, starch metabolic, and diterpenoid biosynthetic signaling pathways may be associated with heterosis during grain development. To further explore the candidate genes for grain development heterosis, a recombinant inbred line (RILs) population with a high-density genetic map of 2578 bin markers was constructed by crossing the parents of WFYT025, and nine stable QTLs for grain weight-related traits were identified. By comparing the DGHP with 20 QTLs, LOC_Os02g28820, LOC_Os02g32580, LOC_Os04g25440, and LOC_Os12g04980 were identified as grain development heterosis-related candidate genes. These findings provide resources for the study of heterosis during the grain development of super hybrid rice and provide valuable theoretical references for the cloning and functional analysis of heterosis-related genes.

Strip rotary tillage with subsoiling increases winter wheat yield by alleviating leaf senescence and increasing grain filling

Sustainable agriculture in the Huang–Huai–Hai Plain of China is threatened by subsoil compaction and the decline of winter wheat productivity induced by inappropriate tillage regimes. We investigated the effects of optimizing the tillage regime on grain filling and its relationship with flag leaf senescence post-anthesis in winter wheat. Four treatments were compared: rotary tillage, strip rotary tillage, strip rotary tillage with a 2-year subsoiling interval (STS), and conventional plowing tillage. STS produced higher chlorophyll content and leaf area indexes than other treatments, resulting in a greater photosynthetically active radiation capture ratio. The net photosynthesis rate of flag leaves from 14 to 28 days after anthesis and dry matter accumulation at maturity were higher in STS than in other treatments. Sucrose content and sucrose phosphate synthase activity of flag leaves first increased and then decreased during grain filling and were highest in STS. STS increased superoxide dismutase activity, increased soluble protein content, and reduced malondialdehyde concentrations in flag leaves after the middle grain-filling stages, resulting in reduced premature senescence. This consequence extended the active grain filling period and increased grain weight. The highest yields were observed in STS, reaching 10,451 kg ha−1 in 2014–2015 and 10,074 kg ha−1 in 2015–2016, owing to increased spike numbers and 1000-kernel weight. Overall, our study suggested that STS could substantially increase photosynthetic capacity and delay leaf senescence, thus promoting grain filling rate and increasing winter wheat yields.

Increasing the abscisic acid level in maize grains induces precocious maturation by accelerating grain filling and dehydration

Elevated levels of abscisic acid (ABA) are closely associated with cereal grain filling under water deficit. However, grain dehydration during grain filling has received little attention. In this paper, three experiments with drought stress and exogenous ABA treatments were conducted to investigate the relationship between ABA and grain dehydration in maize (Zea mays L.) during the grain-filling period. The results indicated that exogenous ABA application and drought stress led to the same tendency of the grain ABA concentration, carbohydrate concentration and dehydration rate to increase but the moisture content to decrease. Moreover, the time to reach the maximum grain-filling rate was advanced, and the grain-filling period was shortened. In in vitro culture experiments, the sucrose-to-starch conversion was promoted, mainly influenced by sucrose synthase, ADP-glucose pyrophosphorylase (AGPase), and soluble starch synthase during the middle grain-filling stage, and the improvement in starch synthesis was possibly induced by AGPase. Correlation analysis showed that the ABA level was significantly negatively correlated with the moisture content and positively correlated with the starch level. A close and notably negative correlation was observed between the grain moisture content and starch level. In summary, adequate grain ABA promoted sucrose-to-starch conversion, shortened the duration of grain filling and accelerated grain dehydration, resulting in precocious grain maturation.

Effects of different water regimes and nitrogen application strategies on grain filling characteristics and grain yield in hybrid rice

ABSTRACTIn order to optimize N application and understand how the different combinations of water and N management affect grain filling characteristics and yield, we designed three irrigation regimes (W1 submerged irrigation, W2 alternate irrigation, W3 dry cultivation), and different N application strategies at 180 kg ha−1 in 2010 and 2011. The relationship between grain filling characteristics and grain yield formation were respectively investigated. The results revealed that there were obvious interacting effects of irrigation regime and N application strategies on grain yield and grain-filling characteristics as well. Compared with W1 and W3 treatments, under W2, the N-fertilizer should account for 30% base, 30% tillering, and 40% panicle fertilizer with the last being applied equally at 4th and 2nd leaves emerged from the top. Correlation analysis revealed that grain filling rate during middle grain-filling stage was the largest and contribute more than 50% to grain-filling. Grain yield was significantly related to grain filling rate (Gmax or Gmean), final weight of a kernel (A), and mean grain filling rate (MGR) of the early, mid and late stages during grain filling in inferior spikelets, which is the important reason for water and N coupling effect further to increase yield and fertilizer use efficiency.

Characterization and expression patterns of key C4 photosynthetic pathway genes in bread wheat (Triticum aestivum L.) under field conditions

Wheat is a C3 plant with relatively low photosynthetic efficiency and is a potential target for C4 photosynthetic pathway engineering. Here we reported the characterization of four key C4 pathway genes and assessed their expression patterns and enzymatic activities at three growth stages in flag leaves of 59 bread wheat genotypes. The C4-like genes homologous to PEPC, NADP-ME, MDH, and PPDK in maize were identified in the A, B, and D sub-genomes of bread wheat, located on the long arms of chromosomes 3 and 5 (TaPEPC), short arms of chromosomes 1 and 3 (TaNADP-ME), long arms of chromosomes 1 and 7 (TaMDH), and long arms of chromosome 1 (TaPPDK), respectively. All the four C4-like genes were expressed in the flag leaves at the three growth stages with considerable variations among the 59 bread wheat genotypes. Significant differences were observed between the photosynthesis rates (A) of wheat genotypes with higher expressions of TaPEPC_5, TaNADP-ME_1, and TaMDH_7 at heading and middle grain-filling stages and those with intermediate and low expressions. Our results also indicated that the four C4 enzymes showed activity in the flag leaves and were obviously different among the 59 wheat genotypes. The activities of PEPcase and PPDK decreased at anthesis and slightly increased at grain-filling stage, while NADP-ME and MDH exhibited a decreasing trend at the three stages. The results of the current study could be very valuable and useful for wheat researchers in improving photosynthetic capacity of wheat.

Effect of field border width for irrigation on dry matter accumulation and distribution, yield, and water use efficiency of wheat

A field experiment was conducted using high-yielding winter wheat cultivar Jimai22 as a test material to examine the effects of different border widths for irrigation on dry matter accumulation and distribution, yield, and water use efficiency of wheat during the wheat growing seasons in 2010 to 2013. Four treatments were installed, i.e., field border widths at 1.0 (W10), 1.5 (W15), 2.0 (W20), and 2.5m (W25), respectively. In early and middle grain-filling stages, the net photosynthetic rate of W20 was remarkably higher than that of W10 and W15; however, no difference was observed between W20 and W25 at 0m to 20m, 20m to 40m, and 40m to 60m. The net photosynthetic rate of W20 was remarkably higher than that of other treatments. In the late grain-filling stage, the net photosynthetic rate of W20 was remarkably higher than that of other treatments at 0m to 20m, 20m to 40m, and 40m to 60m. In middle and late grain-filling stages, W20 showed the highest transpiration rate and leaf water use efficiency among the treatments, which greatly increased grain filling. Dry matter accumulation in the maturity stage of W20 was considerably higher than that of other treatments. The dry matter distribution to grain and contribution proportion to grain after anthesis, grain filling rate, and 1000-kernel weight of W20 were markedly higher than those of other treatments. The W20 treatment exhibited the highest average grain yield; no difference in grain yield was found in the three regions of the same treatment regardless of the initial border width. Moreover, W20 yielded the highest water use efficiency and irrigation water use efficiency; thus, W20 exhibited the most efficient field border width for irrigation in our study.

高温、干旱及其互作对两个筋力小麦品种淀粉糊化特性的影响

以强筋和弱筋的两个代表性小麦品种为材料，采用盆栽与人工气候箱模拟的方法，研究了花后不同时期高温、干旱及其互作对籽粒淀粉糊化特性的影响。结果表明，高温和干旱均显著影响淀粉糊化特性，但两品种表现有所不同：高温胁迫使强筋小麦品种豫麦34的峰值黏度、最终黏度（除花后5 d外）、稀懈值（除花后15 d外）和反弹值显著增大；而弱筋小麦品种豫麦50低谷黏度和最终黏度显著下降，其峰值黏度、反弹值变化不明显，从不同时期看，花后15 d影响较大。干旱胁迫使豫麦34多数黏度参数增大；而使豫麦50峰值黏度、反弹值和稀懈值下降，其低谷黏度和最终黏度在灌浆前期和中期干旱胁迫下增大，后期干旱胁迫则明显下降。研究结果还表明，花后高温与干旱胁迫对小麦黏度参数的影响存在显著的互作效应。从<em>F</em> 值大小看，互作对弱筋小麦品种豫麦50多数黏度参数影响较大，而对强筋小麦品种豫麦34淀粉黏度参数影响较小，反映了高温、干旱及其互作对小麦淀粉特性的影响存在着显著的基因型差异。;To evaluate the effects of post-anthesis high-temperature (HT) and drought stress (DS) and their interactions on starch pasting properties in wheat grains, two winter wheat cultivars differing in gluten strength, Yumai 34 (a strong-gluten cultivar) and Yumai 50 (a weak-gluten cultivar) were investigated in pot experiments at the experimental farm of Henan Agricultural University (E113°35', N34°51'). The experiment used a split-plot design of two factors, with three temperature regimes and two soil water treatments. HT treatments were performed in a climate-controlled greenhouse at 38℃ for 2 days (treatment 2, T₂) or 4 days (treatment 3, T₃) at 5 days after anthesis (5 DAA), 15 DAA or 25 DAA, while the control was treated at 28℃ (treatment 1, T₁). For the two soil water treatments, the soil relative water content was maintained at (55±5)% (W₂) for DS treatment and at (75±5)% for the control. The results indicated that both HT and DS and their interactions significantly influenced starch pasting properties in the grains of the two wheat cultivars. However, the responses of pasting parameters to HT and DS were very different between the two wheat cultivars. In the strong-gluten wheat cultivar Yumai 34, DS applied at any grain-filling stage increased most parameters such as peak viscosity, final viscosity and hold-through, among which the final viscosity was significantly improved at the early (5 DAA) and late grain-filling stages (25 DAA), and the peak viscosity was significantly increased at the late grain-filling stage. In Yumai 50, DS applied at any grain-filling stage (early, middle or late) decreased peak viscosity, setback and breakdown. Drought stress applied at the early and middle grain-filling stages (15 DAA) clearly improved hold-through and final viscosity, but significantly decreased both parameters when applied at the late grain-filling stage. Heat stress significantly increased peak viscosity, final viscosity (except when applied at 5 DAA), set-back and breakdown (except when applied at 15 DAA) in grains of the strong-gluten wheat cultivar Yumai 34, while the parameter of hold-through in grains of Yumai 34 had much different responses to HT applied at various stages: it was significantly decreased in both HT treatments (both T₁ and T₂) at 5 DAA, and was decreased in T₂ (2 days HT) but significantly enhanced in T₃ (4 days HT) at 15 DAA. In the weak-gluten wheat cultivar Yumai 50, HT significantly decreased hold-through and final viscosity in the grains, but had little influence on peak viscosity and setback. From the treatment stage results, we concluded that HT applied at the middle grain-filling stage (15 DAA) had the greatest impact on pasting properties in both wheat cultivars. The analysis also indicated that interaction between HT and DS had a significant effect on viscosity parameters in both cultivars, which was much greater in Yumai 50 than in Yumai 34. The effect of HT and DS interaction on pasting properties in Yumai 50 was greater when they were applied at the early grain-filling stage compared with the middle or late grain-filling stages. From our results, we conclude that different wheat genotypes show different responses in grain pasting properties to various environmental stresses, implying that such stresses have a complex effect on starch quality in the grains of winter wheat.

Shading after anthesis in wheat influences the amount and relative composition of grain proteins

SUMMARYThe high molecular weight glutenin subunits (HMW-GS) and glutenin macropolymer (GMP) in wheat grain are important characteristics that affect the quality of wheat products. Light intensity, as one of the environmental factors affecting grain yield and quality, has been studied extensively; however, little is known about its impact on HMW-GS and distribution of GMP granules in wheat grain. In the present study, two strong-gluten winter wheat cultivars with different subunit compositions were used to evaluate the effect of shading at different grain-filling stages on changes in HMW-GS and distribution of GMP granules in wheat grains. No effects of shading on initial formation time of each individual subunit were found; they responded similarly to shading with an increase in relative content, though the accumulation amount per grain of each individual subunit was decreased due to a decrease in grain weight induced by shading. Shading at different grain-filling stages, especially at the middle grain-filling stage, led to a significant increase in GMP content during grain filling; however, the proportions (by volume, number and surface area) of the larger GMP granules were increased by shading at middle and late grain-filling stages and decreased by shading at early grain-filling stage. It was also found that the content of total HMW-GS was positively correlated with volume proportions of larger GMP granules and negatively correlated with volume proportions of small GMP granules, which indicated that the pattern of response of distribution of GMP granules to shading was closely related to the regulatory effect of shading on the HMW-GS.

Regulation of expression of starch synthesis genes by ethylene and ABA in relation to the development of rice inferior and superior spikelets.

Later-flowering spikelets in a rice panicle, referred to as the inferior spikelets, are usually poorly filled and often limit the yield potential of some rice cultivars. The physiological and molecular mechanism for such poor grain filling remains unclear. In this study the differentially expressed genes in starch synthesis and hormone signalling between inferior and superior spikelets were comprehensively analysed and their relationships with grain filling was investigated. DNA microarray and real-time PCR analysis revealed that a group of starch metabolism-related genes showed enhanced expression profiles and had higher transcript levels in superior spikelets than in inferior ones at the early and middle grain-filling stages. Expression of the abscisic acid (ABA) synthesis genes, 9-cis-epoxycarotenoid dioxygenase 1 (NCED1) and NCED5, and the ethylene synthesis genes, 1-aminocyclopropane-1-carboxylate oxidase 1 (ACO1) and ACO3, declined with development of the caryopses. Meanwhile, if compared with inferior spikelets, expression of these genes in superior spikelets decreased faster and had lower transcript profiles, especially for ethylene. ABA concentration and ethylene evolution rate showed similar trends to their gene expression. Exogenous supply of ABA reduced the sucrose synthase (SUS) mRNA level and its enzyme activity in detached rice grains, while exogenously supplied ethephon (an ethylene-releasing reagent) suppressed the expression of most starch synthesis genes; that is, SUS, ADP-glucose pyrophosphorylase (AGPase), and soluble starch synthase (SSS), and down-regulated their enzyme activities. In summary, it is concluded that the relatively high concentrations of ethylene and ABA in inferior spikelets suppress the expression of starch synthesis genes and their enzyme activities and consequently lead to a low grain-filling rate.

Relationship of Photosynthetic Carbon Assimilation Related Traits of Flag Leaves with Yield Heterosis in a Wheat Diallel Cross

In spite of commercial use of heterosis in agriculture, the physiological basis of heterosis is poorly understood. Photosynthetic carbon assimilation related traits of flag leaves, including photosynthetic capacity, stomatal conductance, intercellular CO 2 concentration, transpiration rate, water use efficiency, and efficiency of primary conversion of light energy, were measured at early, middle, and post grain-filling stages in a wheat ( Triticum aestivum L.) diallel cross containing 20 hybrids and 9 parents. The purpose of this study was to determine the relationship between yield heterosis and these traits. The magnitude of heterosis varied subject to cross combination, trait, and developmental stage. Further analysis indicated that heterosis of photosynthetic carbon assimilation related traits was not correlated with that of spike length and spike number per plant, but significantly correlated with that of other yield components. At middle grain-filling stage, the heterosis of photosynthetic rate, intercellular CO 2 concentration, water use efficiency, and efficiency of primary conversion of light energy were significantly and positively correlated with those of fertile spikelets per plant, thousand-grain weight, yield per plant, and yield of main stem. These results suggested that higher photosynthetic capacity and water use efficiency could be one of the important physiological bases of wheat hybrid vigor.