Grain-filling Rate Research Articles

Identification of genetic loci for grain yield-related traits in the wheat population Zhongmai 578/Jimai 22

The identification of stable quantitative trait locus (QTL) for yield-related traits and tightly linked molecular markers is important for improving wheat grain yield. In the present study, six yield-related traits in a recombinant inbred line (RIL) population derived from the Zhongmai 578/Jimai 22 cross were phenotyped in five environments. The parents and 262 RILs were genotyped using the wheat 50K single nucleotide polymorphism (SNP) array. A high-density genetic map was constructed with 1 501 non-redundant bin markers, spanning 2 384.95 cM. Fifty-three QTLs for six yield-related traits were mapped on chromosomes 1D (2), 2A (9), 2B (6), 2D, 3A (2), 3B (2), 4A (5), 4D, 5B (8), 5D (2), 7A (7), 7B (3) and 7D (5), which explained 2.7–25.5% of the phenotypic variances. Among the 53 QTLs, 23 were detected in at least three environments, including seven for thousand-kernel weight (TKW), four for kernel length (KL), four for kernel width (KW), three for average grain filling rate (GFR), one for kernel number per spike (KNS) and four for plant height (PH). The stable QTLs QKl.caas-2A.1, QKl.caas-7D, QKw.caas-7D, QGfr.caas-2B.1, QGfr.caas-4A, QGfr.caas-7A and QPh.caas-2A.1 are likely to be new loci. Six QTL-rich regions on 2A, 2B, 4A, 5B, 7A and 7D, showed pleiotropic effects on various yield traits. TaSus2-2B and WAPO-A1 are potential candidate genes for the pleiotropic regions on 2B and 7A, respectively. The pleiotropic QTL on 7D for TKW, KL, KW and PH was verified in a natural population. The results of this study enrich our knowledge of the genetic basis underlying yield-related traits and provide molecular markers for high-yield wheat breeding.

Effects of High Temperature and Drought Stresses on Growth and Yield of Summer Maize during Grain Filling in North China

High sensitivity to climate change has been demonstrated in global maize production, especially the extreme high temperature and drought events. At present, the interactive effects of those extreme event stresses on maize growth at the grain filling stage are less well studied. In this study, a two-year field experiment was conducted to evaluate the compound effects of three stressors (high temperature, drought, and stress duration) at the filling phase on phenological period, grain filling rate, yield component, and yield of summer maize. The precipitation and temperature were controlled by using a rain-shelter systems and a warming system with infrared radiation lamps in field plots. The results indicated the significant influences of high temperature, drought stress, and the interaction on the growth and yield of summer maize. Under the individual factor of drought, compared to normal irrigation (NI), the significant decrease in grain-filling rate for mild drought (LD) and severe drought (SD) were 70.7% and 60.6%, respectively, while the decrease in grain yield for LD and SD were 80.1% and 93.6%, respectively. Under the individual factor of temperature, the consequences on grain-filling rate and grain yield were more severe at high temperature (temperature increase by 4.5 °C) than low temperature (temperature increase by 2.3 °C). The compound of high temperature and drought indicated that the grain yield increase by the compound effects of 3 °C for 5 days under normal irrigation (NIT3D5) and the compound effects of 3 °C for 7 days under mild drought (LDT3D7) were 3.5% and 10.9%, respectively, compared to without temperature stress. The grain yields were reduced by the other compound effects. The preferential temperature (temperature increase by 2.3 °C) promoted maize growth under normal irrigation and mild drought, while high temperature (temperature increase by 4.5 °C) significantly inhibited maize growth under normal irrigation and heavy drought. The warming climate is favorable to maize production within certain limits, and will provide a scientific basis for agricultural disaster prevention and mitigation.

Effect of N and CO2 supply on source size per grain at anthesis and its relationship with grain growth in wheat

AbstractRising atmospheric CO2 concentration ([eCO2]) increases the yield of wheat mainly by increasing grain number, but effects on single grain weight are variable. It is discussed whether single grain growth is limited by the sink or the source size under a non‐stress environment. This study explores the effect of e[CO2] combined with varying N supply on the source and sink size during grain filling. Source size was defined as the amount of stem reserves per grain (SRG) and the proportion of incident radiation intercepted by the green canopy per grain (fIRG) at anthesis. Data from a 2‐year free‐air CO2 enrichment experiment with wheat with three N levels (on average 38 [Nd], 190 [Nad] and 320 kg N ha−1 [Nex]) and two CO2 levels (393 and 600 ppm) on SRG, fIRG and grain filling rate (GFR) and duration (GFD) were evaluated. SRG ranged from 2.5 to 12.9 mg and fIRG from 4.0 × 0.001% to 6.8 x 0.001%. Rising N supply or e[CO2] decreased SRG and fIRG via their increases in grain number. Accordingly, there was a negative linear relationship between grain number and SRG (r2 ≥ 0.84) or fIRG (r2 ≥ 0.97). Increasing N supply decreased GFR, but increased GFD, and GFR was increased by e[CO2] under Nad and Nex. For GFR and final grain weight, there was a strong positive (r2 ≥ 0.85), and for GFD, a strong negative linear relationship (r2 ≥ 0.76) with fIRG under Nad and Nex. Under these N levels, fIRG supplied the largest share (>86%) for grain growth and thus single grain growth was possibly source limited under Nad and Nex. Under high grain number such as under Nex and e[CO2], there might be a risk for low final grain weight due to the low SRG that is insufficient for buffering assimilate shortage under unfavourable environmental conditions in early grain filling.

Response of Rice with Overlapping Growth Stages to Water Stress by Assimilates Accumulation and Transport and Starch Synthesis of Superior and Inferior Grains.

Drought stress at jointing–booting directly affects plant growth and productivity in rice. Limited by natural factors, the jointing and booting stages of short-growth-period rice varieties are highly overlapped in high-latitude areas, which are more sensitive to water deficit. However, little is known about the dry matter translocation in rice and the strategies of starch synthesis and filling of superior and inferior grains under different drought stress was unclear. In this study, the rice plants were subjected to three degrees of drought stress (−10 kPa, −25 kPa, −40 kPa) for 15 days during the jointing–booting stage; we investigated dry matter accumulation and translocation, grain filling and enzyme activities to starch synthesis of superior and inferior grains in rice with overlapping growth stages from 2016 to 2017. The results showed that drought stress significantly reduced dry matter accumulation in the stems and leaves. Mild and moderate drought increased dry matter translocation efficiency. However, severe drought stress largely limited the dry matter accumulation and translocation. A large amount of dry matter remains in vegetative organs under severe drought stress. The high content in NSC in stem and sheath plays a key role in resisting drought stress. The drought stress at jointing–booting directly caused a change in the grain filling strategy. Under moderate and severe drought, the grain-filling active period of the superior grains was shortened to complete the necessary reproductive growth. The grain-filling active period of the inferior grains was significantly prolonged to avoid a decrease in grain yield. The significant decrease in the grain-filling rate of the superior and inferior grains caused a reduction in the thousand-grain weight. In particular, the influence of the grain-filling rate of inferior grains on the thousand-grain weight was more significant. Drought stress changed the starch synthesis strategies of the superior and inferior grains. Soluble starch synthase and starch branching enzyme activities of inferior grains increased significantly under drought stress. GBSS activity was not sensitive to drought stress. Therefore, amylose content was decreased and amylopectin synthesis was enhanced under drought stress, especially in inferior grains.

Wheat yield and nitrogen use efficiency enhancement through poly(aspartic acid)-coated urea in clay loam soil based on a 5-year field trial.

The innovation of N fertilizer and N management practices is essential to maximize crop yield with fewer N inputs. A long-term field fertilization experiment was established in 2015 on the North China Plain (NCP) to determine the effects of a control treatment (CN) and the eco-friendly material poly(aspartic acid)-coated urea (PN), applied as a one-time basal application method, on winter wheat yield and N use efficiency at four N application rates: 0 (N0), 63 (N63), 125 (N125), and 188 (N188) kg N ha–1. The results indicated that compared to CN, PN resulted in a significant increase in wheat yield by 9.6% and 9.2% at N63 and N125, respectively, across the three experimental years, whereas no significant (p < 0.05) difference was detected at N188. Leaf area duration (LAD), crop growth rate (CGR), and dry matter accumulation (DMA) increased with increasing N rates, while PN significantly increased LAD and CGR by 5.1%–16.4% and 5.4%–64.3%, respectively, during the anthesis-ripening growth stage and DMA by 13.7% and 10.1% at N63 and N125, respectively, after the anthesis stage compared to CN. During the grain-filling stage, PN significantly increased the kernel maximum grain-filling rate (Gmax) by 21.7% and the kernel weight at the maximum grain-filling rate (Wmax) by 6.7% at N125 compared to CN. Additionally, compared to CN, PN significantly improved the stover and grain N content at harvest and increased NUT, NPFP, and NAE by 5.7%–40.1%, 2.5%–23.3%, and 3.9%–42.8%, respectively, at N63–N125. Therefore, PN applied using a single basal nitrogen fertilizer application method showed promising potential in maintaining a stable wheat yield and increasing N use efficiency with a 33% urea cut (approximately 63 kg N ha–1) compared to CN at the current wheat yield level on the NCP.

Understanding physiological mechanisms of variation in grain filling of maize under high planting density and varying nitrogen applicate rate.

Grain filling is a critical process for achieving a high grain yield in maize (Zea mays L.), which can be improved by optimal combination with genotype and nitrogen (N) fertilization. However, the physiological processes of variation in grain filling in hybrids and the underlying mechanisms of carbon (C) and N translocation, particularly under various N fertilizations, remain poorly understood. The field experiment was conducted at Gongzhuling Farm in Jilin, China. In this study, two maize hybrids, i.e., Xianyu 335 (XY335) and Zhengdan958 (ZD958) were grown with N inputs of 0, 150, and 300 kg N ha–1 (N0, N150, and N300) in 2015 and 2016. Results showed that the N application significantly optimized grain-filling parameters for both maize hybrids. In particular, there was an increase in the maximum filling rate (Gmax) and the mean grain-filling rate (Gmean) in XY335 by 8.1 and 7.1% compared to ZD958 under the N300 kg ha–1 (N300) condition, respectively. Simultaneously, N300 increased the small and big vascular bundles area of phloem, and the number of small vascular bundles in peduncle and cob at the milking stage for XY335. XY335 had higher root bleeding sap (10.4%) and matter transport efficiency (8.4%) of maize under N300 conditions, which greatly enhanced the 13C assimilates and higher C and N in grains to facilitate grain filling compared to ZD958. As a result, the grain yield and the sink capacity for XY335 significantly increased by 6.9 and 6.4% compared to ZD958 under N300 conditions. These findings might provide physiological information on appropriate agronomy practices in enhancing the grain-filling rate and grain yield for maize under different N applications, namely the optimization variety and N condition noticeably increased grain filling rate after silking by improving ear vascular structure, matter transport efficiency, and enhancing C and N assimilation translocation to grain, eventually a distinct improvement in the grain sink and the grain yield.

Can rainwater harvesting replace conventional irrigation for winter wheat production in dry semi-humid areas in China?

The plastic-mulched ridge and furrow rainwater harvesting (PRFRH) planting practice is widely used in rain-fed arid and semi-arid areas. However, it remains unknown whether PRFRH can replace or reduce irrigation to achieve a high and stable wheat yield in dry semi-humid areas. In this study, two cultivation practices (PRFRH and conventional flat planting [CK]) were used in combination with three irrigation regimes (0, 75, and 150 mm) to evaluate the efficacy of PRFRH in different precipitation year types (dry, normal, and wet years). Results showed that PRFRH increased soil temperature and pre-jointing soil water storage at 0–80 cm depth, whereas irrigation increased post-anthesis soil water storage at 0–80 cm depth. Furthermore, PRFRH prolonged the duration of the jointing–anthesis stages and thereby increasing the kernel number. Both PRFRH and irrigation increased dry matter accumulation and the leaf area index. PRFRH accelerated the grain-filling rate but shortened the effective grain-filling duration, while irrigation extended the effective grain-filling duration. PRFRH did not significantly influence kernel weight, whereas irrigation increased kernel weight. Overall, PRFRH reduced the effective wheat planted area and thereby reducing spike number, although it increased the kernel number, resulting in yields that were 13.7% lower than those under CK. The yield under PRFRH was significantly higher than that under CK only in the dry year but lower in the normal and wet years. Irrigation increased the yield; however, the yield did not significantly differ between the 75 and 150 mm irrigation regimes. The water productivity and net profit under 75 mm irrigation were relatively high. In conclusion, in dry semi-humid areas, PRFRH combined with a 75 mm irrigation volume could mitigate drought stress to improve yield, water productivity, and net profit in dry years only.

Quantitative Relationship Between Solar Radiation and Grain Filling Parameters of Maize.

A quantitative understanding of the factors driving changes in grain filling is essential for effective prioritization of increasing maize yield. Grain filling is a significant stage in maize yield formation. Solar radiation is the energy source for grain filling, which is the ultimate driving factor for final grain weight and grain filling capacity that determine maize yield. Here, we first confirmed the quantitative relationships between grain filling parameters and photosynthetically active radiation (PAR) by conducting field experiments using different shading and plant density conditions and cultivars in 2019 and 2020 in Xinjiang, China. The results showed that with every 100 MJ m−2 increase in PAR, the average grain filling rate (Gave), maximum grain-filling rate (Gmax), and the kernel weight at the time of maximum grain-filling rate (Wmax) increased by 0.073 mg kernel−1 day−1, 0.23 mg kernel−1 day−1, and 0.24 mg kernel−1, and the time of maximum grain-filling rate (Tmax) delayed by 0.91 day. Relative changes in PAR were significantly and positively correlated with relative changes in yield and Gave. With every 1% change in PAR, yield and Gave changed by 1.16 and 0.17%, respectively. From the perspective of grain filling capacity, DH618 was a more shade-resistant cultivar than XY335 and ZD958. It is urgent to breed maize cultivars with low light tolerance and high grain yield in the face of climate change, particularly the decrease in solar radiation.

Effects of Rice Straw Combined with Inorganic Fertilizer on Grain Filling and Yield of Common Buckwheat

This study aims to clarify the effect of rice straw combined with inorganic fertilizer on the grain-filling characteristics and yield formation of common buckwheat (Fagopyrum esculentum Moench) and provide a scientific basis for straw fertilizer utilization and the scientific fertilization of common buckwheat in Guizhou Province.Common buckwheat ‘Fengtian1’ was field-grown and treated with no straw and no fertilization (CK), no straw with normal fertilizer (SF), full straw with 20% reduction in conventional fertilization (SH), full straw with 40% reduction in conventional fertilization (SM), full straw with 80% reduction inconventional fertilization (SL), and full straw with no fertilization (HT). The results showed that the initial growth power (R0), maximum and average grain-filling rate, and starch synthase activity of the superior grains were higher than those of the inferior grains. Compared with CK, the treatments with straw and inorganic fertilizers remarkably increased the contents of available nitrogen, available potassium, available phosphorus, and organic matter in the rhizosphere of common buckwheat. SH and SF treatments remarkablyimproved the fertilizer contribution rate and fertilizer agronomic utilization rate, promoted root growth, and enhanced the starch branching enzyme and soluble starch synthase activities of superior and inferior grains. Compared with CK, SH treatment considerably increased the number of grains per plant, grain weight per plant, 100-grain weight, and final yield. Thus, straw combined with inorganic fertilizers, particularlythe SH treatment, should be recommended as an agronomic method for promoting grain filling and increasing the yield of common buckwheat.

Grain-Filling Rate Improves Physical Grain Quality in Barley Under Heat Stress Conditions During the Grain-Filling Period.

Heat stress is a primary constraint to Australia's barley production. In addition to impacting grain yield, it adversely affects physical grain quality (weight and plumpness) and market value. The incidence of heat stress during grain filling is rising with global warming. However, breeding for new superior heat-tolerant genotypes has been challenging due to the narrow window of sensitivity, the unpredictable nature of heat stress, and its frequent co-occurrence with drought stress. Greater scientific knowledge regarding traits and mechanisms associated with heat tolerance would help develop more efficient selection methods. Our objective was to assess 157 barley varieties of contrasting genetic backgrounds for various developmental, agro-morphological, and physiological traits to examine the effects of heat stress on physical grain quality. Delayed sowing (i.e., July and August) increased the likelihood of daytime temperatures above 30°C during grain-filling. Supplementary irrigation of field trials ensured a reduced impact of drought stress. Heat tolerance appeared to be the primary factor determining grain plumpness. A wide variation was observed for heat tolerance, particularly among the Australian varieties. Genotypic variation was also observed for grain weight, plumpness, grain growth components, stay-green and stem water-soluble carbohydrates (WSC) content, and mobilisation under normal and delayed sown conditions. Compared to normal sowing, delayed sowing reduced duration of developmental phases, plant height, leaf size, head length, head weight, grain number, plumpness, grain width and thickness, stem WSC content, green leaf area retention, and harvest index (HI), and increased screenings, grain length, grain-filling rate (GFR), WSC mobilisation efficiency (WSCME), and grain protein content. Overall, genotypes with heavier and plumper grains under high temperatures had higher GFR, longer grain-filling duration, longer green leaf area retention, higher WSCME, taller stature, smaller leaf size, greater HI, higher grain weight/plumpness potentials, and earlier flowering. GFR played a significant role in determining barley grain weight and plumpness under heat-stress conditions. Enhancing GFR may provide a new avenue for improving heat tolerance in barley.

Narrow lpa1 Metaxylems Enhance Drought Tolerance and Optimize Water Use for Grain Filling in Dwarf Rice.

Rice cultivation needs extensive amounts of water. Moreover, increased frequency of droughts and water scarcity has become a global concern for rice cultivation. Hence, optimization of water use is crucial for sustainable agriculture. Here, we characterized Loose Plant Architecture 1 (LPA1) in vasculature development, water transport, drought resistance, and grain yield. We performed genetic combination of lpa1 with semi-dwarf mutant to offer the optimum rice architecture for more efficient water use. LPA1 expressed in pre-vascular cells of leaf primordia regulates genes associated with carbohydrate metabolism and cell enlargement. Thus, it plays a role in metaxylem enlargement of the aerial organs. Narrow metaxylem of lpa1 exhibit leaves curling on sunny day and convey drought tolerance but reduce grain yield in mature plants. However, the genetic combination of lpa1 with semi-dwarf mutant (dep1-ko or d2) offer optimal water supply and drought resistance without impacting grain-filling rates. Our results show that water use, and transports can be genetically controlled by optimizing metaxylem vessel size and plant height, which may be utilized for enhancing drought tolerance and offers the potential solution to face the more frequent harsh climate condition in the future.

The exogenous GA3 greatly affected the grain-filling process of semi-dwarf gene Rht4 in bread wheat.

Rht4 is characterized as a GA-responsive dwarf gene in bread wheat (Triticum aestivum L.). The responsiveness of Rht4 to exogenous GA3 was characterized in seedlings, but the effects of exogenous GA3 on the important morphological and agronomic traits such as plant height, grain-filling rate, and yield components are unclear. In this study, the Rht4 responsiveness of exogenous GA3 on these traits was evaluated using the homozygous F4:5 and F5:6 lines derived from a cross between Jinmai47 and Burt ert937 (Rht4 donor). After exogenous GA3 application, the plant height of the dwarf lines was, on average, increased by 17.54%, about 7.92% more than that of the tall lines. Compared with the tall lines, application of exogenous GA3 significantly increased the kernel weight, maximum grain-filling rate (Gmax), average grain-filling rate (Gave) and kernel weight increment achieving Gmax (Wmax) in both superior and inferior grains, while the day on which the maximum grain-filling rate was reached (Tmax) in Rht4 dwarf lines was significantly earlier in the two generations. What is more, the grain number spike-1 , grain yield plant-1 , and 1000-kernel weight (TKW) of the dwarf lines notably increased after exogenous GA3 -treatment, while there was no significant change in the tall lines except for TKW. The quality traits of the dwarf lines with GA3 -treatment were greatly improved. Taken together, these results suggested that the application of GA3 could improve the grain-filling process of Rht4 and compensate for some negative influences, which may provide a reference for its application in wheat breeding and promote the characterization of its regulatory mechanisms.

INVESTIGATING THE RESPONSE MECHANISMS OF JAPONICA RICE (𝘖𝘳𝘺𝘻𝘢 𝘴𝘢𝘵𝘪𝘷𝘢 L.) UNDER DIFFERENT MID-HIGH-LATITUDES OF NORTHEAST CHINA FOR BETTER FUTURE ADAPTATION

This study showed the response characteristics of rice under different climatic conditions which has an important practical and theoretical significance. The objectives of this study were to establish reasonable production measures and theoretical foundation for adjusting the Japanese rice system through investigation of response mechanisms at mid-high latitudes. Replacing time with space, 4 cultivars (late maturing; Longdao-18, Longdao-21, early maturing; Longjing-21, Suijing-18) were selected, the experiment was conducted at Heilongjiang province during 2017 and 2018. The time difference for superior and inferior grains reaching the peak point of the grain-filling curve showed obvious difference, indicating the difference of climatic conditions had different degrees of influence on each cultivar. A great influence on the dry weights of the grain-filling of the Suijing-18 and Longjing-21 was noticed, whereas the dry weights and grain-filling rates were found less affected for Longdao-21 and Longdao-18. Most of the grain filling was seen during the middle period at Harbin as the filling period was divided into three phases ie, early, middle and late, which observed almost 60% of the whole grain filling process. Furthermore, non-adaptability of cultivars to a specific environment or combination of prevailing conditions could cause yield variation. Values for yield components were high at Qiqihar; therefore, there was more potential to get higher yield. The protein and amylose contents, and fine rice rate were higher at Harbin whereas brown rice and chalkiness percentages were higher at Qiqihar. min and earlier transplantation will produce taller plants. It has been indicated that higher temperature on earlier anthesis at the start of the day thereby increased the probability of escape from higher temperatures stresses later during the day. Earlier anthesis under humid conditions will provide potential escape from rising ambient temperatures during the day.

Are the agronomic performance and grain quality characteristics of bread wheat Mediterranean landraces related to the climate prevalent in their area of origin?

This study analyses the relationship between the climate of the countries where wheat landraces are specifically adapted, and their agronomic and grain quality characteristics. Regions with similar climate within the Mediterranean Basin were identified based on long-term climatic data of the 23 countries origin of a collection of 153 bread wheat landraces. The panel was genotyped with 13177 SNP markers and was grown on field experiments for two years under rainfed conditions in north-east Spain and 14 agronomic and 11 grain-quality traits were assessed. Great phenotypic variability was found in the collection. The agronomic performance of the landraces varied according to the climate of the four climatic regions identified within the Mediterranean Basin (south-east, south-west, north coast and north-Balkan), which gradually varies from warm and dry to wet and cold. Cycle length, grain-filling rate and yield increased, but grain-filling duration decreased from south-eastern landraces to north Balkan ones. Grain weight accounted for 25% of yield variations and was lowest in landraces from the south-eastern region. Grain quality showed no geographical pattern related to the climatic region. Landraces from Bosnia-Herzegovina, Bulgaria and Romania differed from the rest in their high gluten strength (W), loaf volume (LV), mixing time (MT) and grain hardness, while opposite attributes were found in accessions from Jordan, Lebanon and Cyprus. Landraces from south-western Mediterranean countries had low MT, alveograph-peak, W and LV. Genotypes suitable for use in breeding programmes may be identified. Molecular analyses revealed that genetic structure was mostly influenced by high temperatures before anthesis and rainfall, solar radiation and sunshine after anthesis.

Nitrogen Supply Affects Yield and Grain Filling of Maize by Regulating Starch Metabolizing Enzyme Activities and Endogenous Hormone Contents.

This study aimed to examine the effect of nitrogen (N) application rate and time on yield, grain filling, starch metabolizing enzymes, and hormones of maize based on a long-term field experiment initiated in 2012. The total N fertilizer dose [(0 (N0), 100 (N1), 200 (N2), and 300 (N3) kg N ha–1] was split into two (T1, one-third at sowing and two-thirds at the six-leaf stage) or three (T2, one-third each at sowing, six-leaf, and eleven-leaf stage) times application. The results showed that the highest yield was obtained under N3T2, N2T1, and N3T2 in 2018, 2019, and 2020, which was 222.49, 185.31, and 194.00% than that of N0 in each year, respectively. N2 and N3 significantly increased the yield through enhancing ears ha–1, grains per plant, and 100-grain weight; however, N2 and N3 did not show a significant difference in yield and above-yield components. In addition, N application time did not significantly change yield under the same N rate. N0 limited the activities of starch metabolizing enzymes, resulting in insufficient accumulation of sucrose and starch. The contents of indole-3-acetic acid, cytokinin, abscisic acid, and gibberellin were decreased under N0 during grain filling. The average grain-filling rate and maximum grain-filling rate (Gmax) and grain weight increment achieving Gmax increased under N2 and N3, and the grain-filling parameters were positively correlated with 100-grain weight. In conclusion, 200 kg N ha–1 with one-third application at sowing and two-thirds application at the six-leaf stage is a suitable N supply way to improve starch metabolizing enzymes, regulate hormone content, and enhance grain-filling rates, and thus increasing the maize yield in the semiarid Loess Plateau of China.

冬小麦-夏玉米轮作&amp;ldquo;双晚&amp;rdquo;种植模式下的品种匹配与资源效率

<p id="C3">It is of great significance that exploring the characteristics of wheat-maize varieties combination suitable for stress resistance, high yield, and stable yield under the “double delay” system and their matching properties with natural resources, for ensuring the high yield and high efficiency production of winter wheat and summer maize in this region. In this study, field experiments were conducted from 2017 to 2019. Eight winter wheat and eight summer maize varieties were the main varieties in the North China Plain under winter wheat-summer maize “double delay” system with different irrigation treatments. Based on the analysis and evaluation of water use efficiency, grain filling characteristics, growth process, annual light, temperature, and water use efficiency, etc., the characteristics of wheat-maize varieties combination and resource use efficiency under the “double delay” system of winter wheat and summer maize were explored. The results suggested that among the tested wheat varieties, the yields of Jimai 325, Shimai 15, Nongda 3486, and Jimai 22 under conventional water-saving irrigation and rain-fed mode were higher than the average yield of the tested varieties druing the two growing seasons. In addition, the drought resistance index of Jimai 325 and Shimai 15 were higher than that of Jimai 22. Meanwhile, the grain-filling rate, grain number per spike, grain weight, and high stability coefficients of Jimai 22, Jimai 325, and Shimai 15 were higher than the mean of the tested varieties under different irrigation modes. Among the tested maize variaties, the yield and high stability coefficients of Denghai 605, Weike 702, MC670, and Nonghua 816 were all higher than the means of the tested varieties. The grain-filling rate of MC670, Denghai 605, and Xianyu 335 were higher than the means of the tested varieties during the two growing seasons. While, Dika 517 and Xianyu 335 had the lowest grain water content at harvest stage but the highest average dehydration rate among the tested varieties. Based on the comprehensive analysis of the yield and yield stability, drought resistance, grain-filling properties, and dehydration characteristics, the variety combination of Jimai 325-MC670 was selected with the highest annual yield and resource use efficiency. Compared with the local control combination of Jimai 22-Zhengdan 958, the annual yield increased by 17.2% and 17.9%, the light, temperature and irrigation water use efficiency increased by 18.6% and 20.0%, 18.1% and 18.9%, 17.4% and 18.1%, and increased economic benefit 8800 Yuan hm ^-2 and 9600 Yuan hm ^-2, respectively; to fit the whole-process mechanized management mode of wheat-maize double cropping system, maize could use varieties with fast dehydration rate and low grain water content when harvest, such as Dika 517 or Xianyu 335. Compared with the current local combination of Jimai 22-Zhengdan 958, this combination could increase the annual yield by 4.7% and 14.4%, and increase the light, temperature, and irrigation water use efficiency by 5.6% and 16.3%, 4.7% and 15.4%, 5.0% and 14.6%, and increased economic benefit by 2080 Yuan hm ^-2 and 7080 Yuan hm ^-2, respectively. In summary, optimizing the wheat-maize variety combination under the “double delay” cropping system can further improve the annual yield and resource use efficiency synergistically compared with the local staple wheat-maize variety combination.

A comprehensive method to increase yield and narrow the yield gap of winter wheat for sustainable intensification.

The agricultural production system is facing increasing demand pressure and environmental pressure. Green and efficient production methods are urgently needed in order to further enhance the yield of winter wheat and reduce the negative impact on the environment. Here, we analyzed the potential yield and yield gap of winter wheat in Shandong Province of China from 1981 to 2009. Meanwhile, we specified the effects of sowing time, irrigation and fertilization scheme, and variety characteristics on winter wheat. In the past 29 years, the yield gap in most areas of Shandong has become smaller, because the actual yield has increased and the potential yield has changed little under the background of climate change. In addition, it is found that delaying sowing date is beneficial to increase yield by helping winter wheat avoid adverse climate conditions. Also, an irrigation amount of 240 mm and nitrogen application amount of 180-210 kg ha-1 are best to maintain high yield, high resource utilization rate and low environmental pollution in this area. These suggested levels are lower than those currently used by many local farmers. Wheat varieties with longer grain-filling period and photoperiod response, higher grain-filling rate and grain weight were more adaptable to climate change. Improving agronomic management measures can significantly increase the yield of winter wheat and narrow the yield gap. This study can provide valuable information for improving the production potential of winter wheat, and for reducing the damage of agricultural activities to the environment. © 2022 Society of Chemical Industry.

Genetic dissection of the grain-filling rate and related traits through linkage analysis and genome-wide association study in bread wheat

Wheat grain yield is generally sink-limited during grain filling. The grain-filling rate (GFR) plays a vital role but is poorly studied due to the difficulty of phenotype surveys. This study explored the grain-filling traits in a recombinant inbred population and wheat collection using two highly saturated genetic maps for linkage analysis and genome-wide association study (GWAS). Seventeen stable additive quantitative trait loci (QTLs) were identified on chromosomes 1B, 4B, and 5A. The linkage interval between IWB19555 and IWB56078 showed pleiotropic effects on GFR1, GFRmax, kernel length (KL), kernel width (KW), kernel thickness (KT), and thousand kernel weight (TKW), with the phenotypic variation explained (PVE) ranging from 13.38% (KW) to 33.69% (TKW). 198 significant marker-trait associations (MTAs) were distributed across most chromosomes except for 3D and 4D. The major associated sites for GFR included IWB44469 (11.27%), IWB8156 (12.56%) and IWB24812 (14.46%). Linkage analysis suggested that IWB35850, identified through GWAS, was located in approximately the same region as QGFRmax2B.3-11, where two high-confidence candidate genes were present. Two important grain weight (GW)-related QTLs colocalized with grain-filling QTLs. The findings contribute to understanding the genetic architecture of the GFR and provide a basic approach to predict candidate genes for grain yield trait QTLs.

Growth characteristics and grain yield of machine-transplanted medium indica hybrid rice with high daily yield

High-yield rice varieties with a suitable growth duration are required for mechanical transplanting in multiple cropping systems. Daily yield is an appropriate criterion for the selection of machine-transplanted rice varieties. The aim of this study was to investigate the growth characteristics and grain production in machine-transplanted medium indica hybrid rice with a high daily yield. We conducted a field experiment on 20 medium indica hybrid rice varieties in 2017 and 2018. Grain yield decreased significantly with growth duration between jointing and heading, but it increased with dry matter accumulation, growth rate between jointing and heading, dry matter partitioning to the stem plus sheath at heading, daily yield, and number of spikelets per panicle. Compared with the medium and low daily yield variety types, the high daily yield variety type increased shoot biomass by improving crop growth rate and dry matter accumulation amount between jointing and heading and after heading. The high daily yield variety type decreased the growth duration pre-heading and the proportions of dry matter partitioned to the leaf lamina at heading and maturity, but it also increased the post-heading accumulated dry matter in the grain and the remobilization of dry matter stored in the vegetative organs. Furthermore, the high daily yield variety type significantly increased the occurrence rate of tillers, which is beneficial for the formation of a larger panicle size and an increase in the grain-filling rate. These changes contributed to a 6.51–23.16% relative increase in grain yield of the high daily yield variety type. In conclusion, the selection of high daily yield indica hybrid rice varieties with shorter pre-heading growth duration, greater tiller occurrence rate and spikelet numbers per panicle, higher post-jointing growth rates and stem plus sheath dry matter accumulation at heading is suitable for machine-transplanted rice.

Response of physiological characteristics and grain yield of winter wheat varieties to long-term heat stress at anthesis

Heat stress has become more common in recent years, limiting wheat production in Huang-Huai-Hai plain in China. To identify the effect of long-term heat stress on wheat production, two heat-resistant (JM44, JM23) and two heat-sensitive (XM26, GC8901) wheat varieties were sown in heat tents and normal conditions, and heat stress (9 to 12&#x2103; higher than control) was imposed for seven days at post-anthesis. All varieties under heat stress exhibited early senescence and reduced grain-filling rate, while the grain-filling period of heat-tolerant varieties was longer than that of the heat-sensitive. Furthermore, long-term heat stress significantly reduced kernel mass, grain number, harvest index, chlorophyll content, maximum quantum yield of PS&#x2161; photochemistry, effective quantum yield of PS&#x2161; photochemistry, photosynthetic rate, and transpiration efficiency. In addition, the distribution of dry matter to vegetative organs, catalase activity, and malondialdehyde content increased. These results indicated that the lesser yield reduction of heat-resistant varieties (11-26%) than that of heat-sensitive (16-37%) is due to relatively higher antioxidative and photosynthetic performance and higher assimilation in the grain from vegetative organs.