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    Wheat growth, photosynthesis and physiological characteristics under different soil Zn levels
    LI Si-ping, ZENG Lu-sheng, SU Zhong-liang
    2022, 21 (7): 1927-1940.   DOI: 10.1016/S2095-3119(21)63643-2
    Abstract174)      PDF in ScienceDirect      
    In recent years, heavy metal hazards in the soil have seriously affected agricultural production.  This study aims to examine the effects of different levels of heavy metal Zn on the growth, photosynthesis and physiological characteristics of wheat, and provide a theoretical basis for the diagnosis and control of heavy metal pollution in agricultural production.  The field test method was used to explore the changes of wheat agronomic traits, photosynthetic capacity, chlorophyll fluorescence parameters, spectral characteristic curve, active oxygen metabolism system, cell ultrastructure, and yield, under different Zn levels (0, 250, 500, 750, and 1 000 mg kg–1).  The results show that, low-level Zn treatments can effectively promote the synthesis of wheat chlorophyll, improve photosynthetic capacity, and increase yield.  The yield of ZnL1 (250 mg kg–1) was the highest in the two-year test, which increased by 20.4% in 2018 and 13.9% in 2019 compared with CK (0 mg kg–1).  However, a high Zn level had a significant stress effect on the photosystem of wheat.  PIabs (reaction center performance index) and Fv/Fm (maximum photochemical efficiency) were significantly reduced, the active oxygen metabolism system was damaged, and the photosynthetic capacity was reduced, which in turn led to reduced yield.  Among them, the yield of ZnL4 (1 000 mg kg–1) was the lowest in the two-year test, which was 28.1 and 16.4% lower than CK in 2018 and 2019, respectively.  The green peak position of ZnL3 and ZnL4 had “red shift” to the long wave direction, while the red valley position of ZnL4 had “blue shift” to the short wave direction.  Under ZnL4, some wheat leaf organelles began to decompose, vacuoles increased, cytoplasm decreased, cell walls thickened, chloroplast basal lamellae were disordered, and mitochondrial membranes disintegrated.  Stepwise regression and Path analysis showed that Pn (net photosynthetic rate) played a leading role in the formation of yield.  Redundancy (RDA) analysis showed that the optimal Zn level for wheat growth was about 250 mg kg–1, and wheat would be stressed when the soil Zn level exceeded 500 mg kg–1 in the test condition of this study.  Findings of this study provide a theoretical basis for the diagnosis and prevention of heavy metal (Zn) pollution in the soil.
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    Source–sink relations and responses to sink–source manipulations during grain filling in wheat
    WU Xiao-li, LIU Miao, LI Chao-su, Allen David (Jack) MCHUGH, LI Ming, XIONG Tao, LIU Yu-bin, TANG Yong-lu
    2022, 21 (6): 1593-1605.   DOI: 10.1016/S2095-3119(21)63640-7
    Abstract131)      PDF in ScienceDirect      
    The source–sink ratio during grain filling is a critical factor that affects crop yield in wheat, and the main objective of this study was to determine the source–sink relations at both the canopy scale and the individual culm level under two nitrogen (N) levels at the post-jointing stage.  Nine widely-used cultivars were chosen for analyzing source–sink relations in southwestern China; and three typical cultivars of different plant types were subjected to artificial manipulation of the grain-filling source–sink ratio to supplement crop growth measurements.  A field experiment was conducted over two consecutive seasons under two N rates (N+, 150 kg ha–1; N–, 60 kg ha–1), and three manipulations were imposed after anthesis: control (Ct), removal of flag and penultimate leaves (Lr) and removal of spikelets on one side of each spike (Sr).  The results showed that the single grain weights in the three cultivars were significantly decreased by Lr and increased by Sr, which demonstrated that wheat grain yield potential seems more source-limited than sink-limited during grain filling, but the source–sink balance was obviously changed by climatic variations and N deficient environments.  Grain yield was highly associated with sink capacity (SICA), grain number, biomass, SPAD values, and leaf area index during grain filling, indicating a higher degree of source limitation with an increase in sink capacity.  Therefore, source limitation should be taken into account by breeders when SICA is increased, especially under non-limiting conditions.  Chuanmai 104, a half-compact type with a mid-sized spike and a long narrow upper leaf, showed relatively better performance in source–sink relations.  Since this cultivar showed the characteristics of a lower reduction in grain weight after Lr, a larger increase after Sr, and a lower reduction in post-anthesis dry matter accumulation, then the greater current photosynthesis during grain filling contributed to the grain after source and sink manipulation. 
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    Genotype×tillage interaction and the performance of winter bread wheat genotypes in temperate and cold dryland conditions
    Ebrahim ROOHI, Reza MOHAMMADI, Abdoul Aziz NIANE, Javad VAFABAKHSH, Mozaffar ROUSTAEE, Mohammad Reza JALAL KAMALI, Shahriar SOHRABI, Shahriar FATEHI, Hossain TARIMORADI
    2022, 21 (11): 3199-3215.   DOI: 10.1016/j.jia.2022.08.096
    Abstract129)      PDF in ScienceDirect      

    Growing concerns for food security and the alleviation of hunger necessitate knowledge-based crop management technologies for sustainable crop production.  In this study, 13 winter bread wheat genotypes (old, relatively old, modern, and breeding lines) were evaluated under three different tillage systems, i.e., conventional tillage (CT, full tillage with residue removed), reduced tillage (RT, chisel tillage with residue retained) and no-tillage (NT, no-tillage with residue retained on the soil surface) in farmer’s fields under rainfed conditions using strip-plot arrangements in a randomized complete block design with three replications in the west of Iran (Kamyaran and Hosseinabad locations) over two cropping seasons (2018–2019 and 2019–2020).  The main objectives were to investigate the effects of tillage systems and growing conditions on the agronomic characteristics, grain yield and stability performance of rainfed winter bread wheat genotypes.  Significant (P<0.01) genotype×tillage system interaction effects on grain yield and agronomic traits suggested that the genotypes responded differently to the different tillage systems.  The number of grains per spike and plant height were positively (P<0.0) associated with grain yield under the NT system, so they may be considered as targeted traits for future wheat breeding.  Using statistical models, the modern cultivars (“Sadra” and “Baran”) were identified as high yielding and showed yield stability across the different tillage systems.  As per each tillage system, genotype “Sadra” followed by “Zargana-6//Dari 1-7 Sabalan” exhibited higher adaption to CT; while cultivars “Jam” and “Azar2” showed better performance under the RT system; and cultivars “Varan” and “Baran” tended to have better performance expression in the NT condition.  The increased grain yields achieved in combination with lower costs and greater profits from conservation agriculture suggest that adapted cultivar and NT systems should be evaluated and promoted more widely to farmers in the west of Iran as an attractive package of crop management technologies.  In conclusion, variations in the performance of genotypes and the significant genotype×tillage system interaction effects on grain yield and some agronomic traits assessed in this study suggest that the development and selection of cultivars adapted to the NT system should be considered and included in the strategies and objectives of winter wheat breeding programs for the temperate and cold dryland conditions of Iran.

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    Analysis of combining ability for stem-related traits and its correlations with lodging resistance heterosis in hybrid wheat
    YANG Wei-bing, QIN Zhi-lie, SUN Hui, HOU Qi-ling, GAO Jian-gang, CHEN Xian-chao, ZHANG Li-ping, WANG Yong-bo, ZHAO Chang-ping, ZHANG Feng-ting
    2022, 21 (1): 26-35.   DOI: 10.1016/S2095-3119(20)63408-6
    Abstract154)      PDF in ScienceDirect      
    With the application of hybrid wheat, lodging is becoming one of the major factors limiting high yield in its production.  However, few studies have focused on combining ability and heterosis analysis of stem-related traits.  In this study, 24 crosses were made according to NCII genetic design, using the three (photo-sensitive male sterile lines)×eight (restorer lines) incomplete diallel crosses.  The length of basal second internode (LBSI) and breaking strength of basal second internode (BSBSI) as well as other stem-related traits were used to perform the principal component analysis (PCA), combining ability and heterosis analysis.  The PCA results showed that the variables could be classified into two main factors, which were named as the positive factor (factor 1) and the negative factor (factor 2), and accounted for 52.3 and 33.2%, respectively, of the total variance in different variables, combined with the analysis for index weight indicated that the factor 1-related traits play positive roles in lodging resistance formation of hybrids.  Combining ability variance analysis indicated that its genetic performance was mainly dominated by additive gene effects, and the hybrid combinations with higher lodging resistance can be selected by using of 14GF6085 (R1), 14GF6343-2 (R4), 14GF6937 (R6), 14GF7433-1 (R7), and BS1086 (M3), which are with the features with lower general combining ability (GCA) effects of factor 2-related traits whereas higher GCA effects of factor 1-related traits.  The heterosis analysis showed that the wide range of heterosis varied with the traits and combinations, and GCA or specific combining ability (SCA) effects of factor 1-related traits except wall thickness of basal second internode (WTBSI) were positively and closely related to the heterosis of lodging resistance.  Generally, the correlation coefficients of heterosis to GCA effects of sterile lines (GCAm) of factor 1-related traits are significantly higher than that to GCA of restorer lines (GCAr) and SCA, combined with the higher GCAm variance values of factor 1-related traits compared to GCAr, the GCAm of factor 1-related traits should be particularly considered when breeding hybrid combinations.  The heritability analysis showed that the narrow-sense heritability of the diameter of basal second internode (DBSI) and the center of gravity height (TCGH) were obviously lower (<60%) than other traits, suggesting that these two traits were suitable for selection in higher generation for parental breeding.  These could provide a theoretical basis for parental breeding and heterosis utilization of lodging resistance. 

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    Characteristics of lodging resistance of high-yield winter wheat as affected by nitrogen rate and irrigation managements
    LI Wen-qian, HAN Ming-ming, PANG Dang-wei, CHEN Jin, WANG Yuan-yuan, DONG He-he, CHANG Yong-lan, JIN Min, LUO Yong-li, LI Yong, WANG Zhen-lin
    2022, 21 (5): 1290-1309.   DOI: 10.1016/S2095-3119(20)63566-3
    Abstract147)      PDF in ScienceDirect      
    High yields of wheat are mainly obtained through a high level of nitrogen and irrigation supplementation.  However, excessive nitrogen and irrigation supplication increase the risk of lodging.  The main objectives of this work were to clarify the capacity of lodging resistance of wheat in response to nitrogen and irrigation, as well as to explore the effective ways of improving lodging resistance in a high-yield wheat cultivar. In this study, field experiments were conducted in the 2015–2016 and 2016–2017 growing seasons.  A wheat cultivar Jimai 22 (JM22), which is widely planted in the northern of Huang-Huai winter wheat region, was grown at Tai’an, Shandong Province, under three nitrogen rates and four irrigation treatments.  The lodging risk was increased with increased nitrogen rate, as indicated by increasing lodging index (LI) and lodging rate across both growing seasons.  With nitrogen increasing, the plant height, the basal internode length and the center of gravity height, which were positively correlated with LI, increased significantly.  While the density of the basal 2nd internode (for culm and leaf sheath) and cell wall component contents, which were negatively correlated with LI, decreased conspicuous along with nitrogen increased.  Increasing irrigation supplementation increased the 2nd internode culm wall thickness, breaking strength and leaf sheath density within limits which increased stem strength.  Among the treatments, nitrogen application at a rate of 240 kg ha–1 and irrigation application at 600 m3 ha–1 at both the jointing and anthesis stages resulted in the highest yield and strongest stem.  A suitable plant height ensures sufficient biomass for high yield, and higher stem stiffness, which was primarily attributed to thicker culm wall, greater density of the culm and leaf sheaths and higher cell wall component contents are the characteristics that should be taken into account to improving wheat lodging resistance.

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    An economic and viable approach to improve wheat quality in Qinghai–Tibetan Plateau, China
    WANG Yu-jiao, TAO Zhi-qiang, WANG De-mei, WANG Yan-jie, YANG Yu-shuang, ZHAO Guang-cai, SHI Shu-bing, CHANG Xu-hong
    2022, 21 (8): 2227-2240.   DOI: 10.1016/S2095-3119(21)63677-8
    Abstract89)      PDF in ScienceDirect      

    Wheat flour products are the main dietary component of the Qinghai–Tibetan Plateau (QTP) population in China.  However, the high altitude restricts the local wheat quality and quantity, and the applied nitrogen rate is higher than the optimal rate for wheat planting.  In this study, we considered whether reducing the amount of nitrogen fertilizer and introducing the superior varieties from the North China Plain (NCP) are viable ways to increase the wheat quality and quantity in the QTP.  Three and four winter wheat cultivars from QTP and NCP, respectively, were planted in Lhasa at an altitude of 3 647 m with reduced topdressing nitrogen application at the jointing stage.  The wheat from NCP exhibited higher grain hardness index and test weight, and better flour and dough quality.  Reducing the topdressing nitrogen fertilizer from 135 to 75 kg N ha−1 at the jointing stage (with the same basal fertilization of 105 kg N ha−1) did not significantly (P<0.05) affect the grain yield, grain quality, flour quality or dough quality in any of the cultivars.  In summary, introducing high-quality winter wheat varieties from the NCP to the Lhasa plateau is a viable way to enhance the wheat supply and quality in the QTP.  Reducing a certain amount of the nitrogen fertilizer is an economic and feasible approach for the QTP region.

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    Effects of sodium benzoate on growth and physiological characteristics of wheat seedlings under compound heavy metal stress
    LIANG Pan-pan, ZHAO Chen, LIN Yuan, GENG Ji-jia, CHEN Yuan, CHEN De-hua, ZHANG Xiang
    2020, 19 (4): 1010-1018.   DOI: 10.1016/S2095-3119(19)62723-1
    Abstract68)      PDF in ScienceDirect      
    In this study, we investigated the effect of exogenous sodium benzoate on wheat seedlings (Yangmai 16) grown under heavy metal stress.  The results showed that 2.4 mmol kg–1 of heavy metals significantly inhibited growth and delayed emergence of wheat seedlings.  Under compound heavy metal stress, application of 2–4 g L–1 sodium benzoate significantly increased (P<0.01) chlorophyll content and chlorophyll fluorescence parameters Fv/Fm and Fv/Fo of wheat, compared to the control (water treatment).  Further analysis showed that application of 2–4 g L–1 sodium benzoate alleviated osmotic stress by promoting the accumulation of osmolytes such as soluble proteins and free proline, increased the activity of superoxide dismutase (SOD) and reduced malondialdehyde content (MDA).  In contrast, higher concentrations of sodium benzoate solution (>6 g L–1) inhibited the growth of wheat seedlings and even caused damage to seedlings.  Correlation analysis showed that when the sodium benzoate concentration was in the range of 1.97–3.12 g L–1 (2016) and 1.58–3.27 g L–1 (2017), values of chlorophyll and its components, root activity, SOD activity, soluble protein, and free proline content were the highest.  When the sodium benzoate concentration was raised to 2.59 g L–1 (2016) or 3.02 g L–1 (2017), MDA content was the lowest.  Ultimately, exogenous sodium benzoate (2–4 g L–1) facilitates root development and improves the root activity of wheat seedlings grown under compound heavy metals stress, thereby effectively alleviating the damage of compound heavy metal stress in wheat seedlings.
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    Improved soil characteristics in the deeper plough layer can increase grain yield of winter wheat
    CHEN Jin, PANG Dang-wei, JIN Min, LUO Yong-li, LI Hao-yu, LI Yong, WANG Zhen-lin
    2020, 19 (5): 1215-1226.   DOI: 10.1016/S2095-3119(19)62679-1
    Abstract81)      PDF in ScienceDirect      
    In the North China Plain (NCP), soil deterioration threatens winter wheat (Triticum aestivum L.) production.  Although rotary tillage or plowing tillage are two methods commonly used in this region, research characterizing the effects of mixed tillage on soil characteristics and wheat yield has been limited.  A fixed-site field trial was carried out during 2011–2016 to examine the impacts of three tillage practices (5-year rotary tillage with maize straw removal (RT); 5-year rotary tillage with maize straw return (RS); and annual RS and with a deep plowing interval of 2 years (RS/DS)) on soil characteristics and root distribution in the plough layer.  Straw return significantly decreased soil bulk density, increased soil organic carbon (SOC) storage and SOC content, macro-aggregate proportion (R0.25) and its stability in the plough layer.  The RS/DS treatment significantly increased the SOC content, total nitrogen (TN), and root length density (RLD) in the 10–40 cm layer, and enhanced the proportion of RLD in the 20–30 and 30–40 cm layers.  In the 20–30 and 30–40 cm layers, an increase in SOC and TN could lead to higher grain production than commensurate increases in the surface layer, resulting in a sustainable increase in grain yield from the RS/DS treatment.  Thus, the RS/DS treatment could lead to high productivity of winter wheat by improving soil characteristics and root distribution at the deeper plough layer in the NCP.
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    The effects of intraspecific competition and light transmission within the canopy on wheat yield in a wide-precision planting pattern
    LIU Xin, WANG Wen-xin, LIN Xiang, GU Shu-bo, WANG Dong
    2020, 19 (6): 1577-1585.   DOI: 10.1016/S2095-3119(19)62724-3
    Abstract65)      PDF in ScienceDirect      
    The wide-precision planting pattern has become widely used in the North China Plain as a practice for increasing wheat yield.  However, the effects of tillering development and light transmission within canopy on wheat yield under different sowing widths have not been clearly described.  Therefore, a two-year experiment was conducted, including four different seeding widths (6 cm, W6; 8 cm, W8; 10 cm, W10; 12 cm, W12) and the traditional planting pattern with seeding width of 4 cm (W4).  The results indicated mainly positive effects by the reduced intraspecific competition, specifically all three yield components of W6 and W8 were higher than those for W4.  The configurations with more than 10-cm seeding width were mainly affected by the negative effect of a relative homogeneous canopy, leading to the weakened light transmission, leaf senescence, and reduced grain number per spike.  Finally, the yields of W6 and W8 were significantly higher than that of W4, whereas the yield in W12 was lower (though not significantly) than W4.  In wheat production, therefore, the appropriate seeding width of 6–8 cm is recommended for farmers, whereas the too wide seeding width, with more than 10 cm, should be avoided.
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    Heat stability of winter wheat depends on cultivars, timing and protective methods
    LI Qiang, CHANG Xu-hong, MENG Xiang-hai, LI Ding, ZHAO Ming-hui, SUN Shu-luan, LI Hui-min, QIAO Wen-chen
    2020, 19 (8): 1984-1997.   DOI: 10.1016/S2095-3119(19)62760-7
    Abstract95)      PDF in ScienceDirect      
    Heat stress negatively affects wheat production in many regions of the world.  At present, sensitivity to heat stress remains one of the least understood aspects of wheat genetics and breeding, and measures for preventing heat stress are understudied. In this study, we used three cultivars of winter wheat (GY2018, SL02-1 and SY20) to evaluate the effect of heat stress at different days after anthesis (DAA) on yield and quality.  Heat stability of the cultivars were analyzed and evaluated for the effects of two kinds of regulators on wheat under heat stress conditions.  Heat treatment at 7 DAA led to the most substantial reduction in yield while GY2018 had the best heat stability with respect to yield, and demonstrated the most positive effects on several quality traits including protein content, sedimentation volume and glutenin and gliadin contents.  Heat treatment at 14 DAA had the least reduction in yield, while SY20 had the best heat stability with respect to yield and heat treatment had minimal effects on quality.  Heat treatment at 21 DAA had only a limited effect on yield, while SL02-1 had the best heat stability with respect to yield, but it showed the most negative effects on quality.  Stable time at 14 DAA and protein content at 21 DAA can be used as indicators for detecting the stability of quality under heat stress.  Among the three studied cultivars, SY20 was the most sensitive to heat stress with the stable time decreasing from 26.4 to 9.1 min, a higher sedimentation volume at 7 DAA, and a lower γ-gliadin content which increased 2.4-fold under high-temperature treatment.  The addition of various regulators had different effects: potassium dihydrogen phosphate (KDP) was more protective of yield with heat stress at 7 DAA, while Duntianbao (DTB) had better effects on quality with heat stress at 21 DAA.
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    Detection and enumeration of wheat grains based on a deep learning method under various scenarios and scales
    WU Wei, YANG Tian-le, LI Rui, CHEN Chen, LIU Tao, ZHOU Kai, SUN Cheng-ming, LI Chun-yan, ZHU Xin-kai, GUO Wen-shan
    2020, 19 (8): 1998-2008.   DOI: 10.1016/S2095-3119(19)62803-0
    Abstract91)      PDF in ScienceDirect      
    Grain number is crucial for analysis of yield components and assessment of effects of cultivation measures.  The grain number per spike and thousand-grain weight can be measured by counting grains manually, but it is time-consuming, tedious and error-prone.  Previous image processing algorithms cannot work well with different backgrounds and different sizes.  This study used deep learning methods to resolve the limitations of traditional image processing algorithms.  Wheat grain image datasets were collected in the scenarios of three varieties, six background and two image acquisition devices with different heights, angles and grain numbers, 1 748 images in total.  All images were processed through color space conversion, image flipping and rotation.  The grain was manually annotated, and the datasets were divided into training set, validation set and test set.  We used the TensorFlow framework to construct the Faster Region-based Convolutional Neural Network Model.  Using the transfer learning method, we optimized the wheat grain detection and enumeration model.  The total loss of the model was less than 0.5 and the mean average precision was 0.91.  Compared with previous grain counting algorithms, the grain counting error rate of this model was less than 3% and the running time was less than 2 s.  The model can be effectively applied under a variety of backgrounds, image sizes, grain sizes, shooting angles, and shooting heights, as well as different levels of grain crowding.  It constitutes an effective detection and enumeration tool for wheat grain.  This study provides a reference for further grain testing and enumeration applications.
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    The influence of drought stress on malt quality traits of the wild and cultivated barleys
    HONG Ye, ZHANG Guo-ping
    2020, 19 (8): 2009-2015.   DOI: 10.1016/S2095-3119(19)62794-2
    Abstract77)      PDF in ScienceDirect      
    As a major abiotic stress, drought causes instability and deterioration of malt barley quality.  There is distinct difference among barley cultivars in the responses of the main malt quality traits to drought stress.  In the previous study, we identified some Tibetan wild barley accessions with relatively less change of malt quality traits under drought.  In this study, we examined the impact of drought stress during grain filling stage on grain weight and several important malt quality traits, including total protein content, β-glucan content, limit dextrinase activity, β-amylase activity, and protein fractions in four barley genotypes (two Tibetan wild accessions and two cultivars).  Drought treatment reduced grain weight, β-glucan content, and increased total protein content, β-amylase activity.  These changes differed among barley genotypes and treatments, and are closely associated with grain filling process and kernel weight.  All the results indicated Tibetan wild barley had great potential for developing drought tolerant barley cultivars.  Relatively stable kernel weight or filling process under water stress should be highlighted in malt barley breeding in order to reduce the effect of water stress on malt barley quality.
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    Calibration and validation of SiBcrop Model for simulating LAI and surface heat fluxes of winter wheat in the North China Plain
    CHEN Ying, LIU Feng-shan, TAO Fu-lu, GE Quan-sheng, JIANG Min, WANG Meng, ZHAO Feng-hua
    2020, 19 (9): 2206-2215.   DOI: 10.1016/S2095-3119(20)63178-1
    Abstract79)      PDF in ScienceDirect      
    The accurate representation of surface characteristic is an important process to simulate surface energy and water flux in land-atmosphere boundary layer.  Coupling crop growth model in land surface model is an important method to accurately express the surface characteristics and biophysical processes in farmland.  However, the previous work mainly focused on crops in single cropping system, less work was done in multiple cropping systems.  This article described how to modify the sub-model in the SiBcrop to realize the accuracy simulation of leaf area index (LAI), latent heat flux (LHF) and sensible heat flux (SHF) of winter wheat growing in double cropping system in the North China Plain (NCP).  The seeding date of winter wheat was firstly reset according to the actual growing environment in the NCP.  The phenophases, LAI and heat fluxes in 2004–2006 at Yucheng Station, Shandong Province, China were used to calibrate the model.  The validations of LHF and SHF were based on the measurements at Yucheng Station in 2007–2010 and at Guantao Station, Hebei Province, China in 2009–2010.  The results showed the significant accuracy of the calibrated model in simulating these variables, with which the R2, root mean square error (RMSE) and index of agreement (IOA) between simulated and observed variables were obviously improved than the original code.  The sensitivities of the above variables to seeding date were also displayed to further explain the simulation error of the SiBcrop Model.  Overall, the research results indicated the modified SiBcrop Model can be applied to simulate the growth and flux process of winter wheat growing in double cropping system in the NCP. 
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    Yield-related agronomic traits evaluation for hybrid wheat and relations of ethylene and polyamines biosynthesis to filling at the mid-grain filling stage
    YANG Wei-bing, QIN Zhi-lie, SUN Hui, LIAO Xiang-zheng, GAO Jian-gang, WANG Yong-bo, HOU Qi-ling, CHEN Xian-chao, TIAN Li-ping, ZHANG li-ping, MA Jin-xiu, CHEN Zhao-bo, ZHANG Feng-ting, ZHAO Chang-ping
    2020, 19 (10): 2407-2418.   DOI: 10.1016/S2095-3119(19)62873-X
    Abstract61)      PDF in ScienceDirect      
    Because of the yield increase of 3.5–15% compared to conventional wheat, hybrid wheat is considered to be one of the main ways to greatly improve the wheat yield in the future.  In this study, we performed a principal component analysis (PCA) on two-line hybrids wheat and their parents using the grain weight (GW), the length of spike (LS), the kernel number of spike (KSN), and spike number (SPN) as variables.  The results showed that the variables could be classified into three main factors, the weight factor (factor 1), the quantity factor 1 (factor 2) and the quantity factor 2 (factor 3), which accounted for 37.1, 22.6 and 18.5%, respectively of the total variance in different agronomic variables, suggesting that the GW is an important indicator for evaluating hybrid combinations, and the grain weight of restorer line (RGW) could be used as a reference for parents selection.  The hybrid combination with a higher score in factor 1 direction and larger mid-parent heterosis (MPH) of the GW and its parents were used to carry out the analysis of grain filling, 1-aminocylopropane-1-carboxylicacid (ACC) and polyamine synthesis related genes.  The results suggested that the GW of superior grain was significantly higher than that of inferior grains in BS1453×JS1 (H) and its parents.  Both grain types showed a weight of H between BS1453 (M) and JS1(R), and a larger MPH, which may be caused by their differences in the active filling stage and the grain filling rate.  The ADP-glucose pyrophosphorylase (AGPase), granule bound starch synthase I (GBSSI), starch synthase III (SSS), and starch branching enzyme-I (SBE-I) expression levels of H were intermediated between M and R, which might be closely related to MPH formation of the GW.  Compared with R and H, the GW of M at maturity was the lowest.  The expression levels of spermidine synthase 2 (Spd2), ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (SAMDC) had significantly positive correlations with the grain filling rate (r=0.77*, 0.51*, 0.59*), suggesting their major roles in the grain filling and heterosis formation.  These provide a theoretical basis for improving the GW of photo-thermo-sensitive male sterile lines (PTSMSL) by changing the endogenous polyamine synthesis in commercial applications.
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    Effects of post-heading high temperature on some quality traits of malt barley
    NI sheng-jing, ZHAO Hui-fang, ZHANG Guo-ping
    2020, 19 (11): 2674-2679.   DOI: 10.1016/S2095-3119(19)62878-9
    Abstract60)      PDF in ScienceDirect      
    Global change is bringing barley with more frequency of suffering from high temperature.  However, little has been known about the influence of high temperature on malt quality traits.  In this study, we investigated the impact of 1-wk heat stress (32°C/26°C, day/night, 12 h/12 h) initiating from the 7th (HT7) and 14th (HT14) days after heading on some grain and malt quality traits of two barley cultivars.  In comparison with normal temperature (24°C/18°C, day/night, 12 h/12 h), heat stress significantly reduced kernel weight, seed setting rate and grains per spike: HT7 having a larger effect than HT14.  Meanwhile, total protein and β-glucan contents, and β-amylase and limit dextrinase activities were significantly increased under high temperature, with HT7-treated plants showing larger changes.  Moreover, the different changes of four protein fractions under heat stress were found in the two barley cultivars, indicating the possibility of breaking positive association between protein content and enzyme activity.
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    Changes of oxidative metabolism in the roots of wheat (Triticum aestivum L.) seedlings in response to elevated ammonium concentrations
    LIU Yang, LI Yu-xiang, LI Yi-xiang, TIAN Zhong-wei, HU Jin-ling, Steve ADKINS, DAI Ting-bo
    2021, 20 (5): 1216-1228.   DOI: 10.1016/S2095-3119(20)63216-6
    Abstract84)      PDF in ScienceDirect      
    To elucidate the response of oxidative metabolism, triggered by elevated ammonium (NH4+) concentrations, on root growth of wheat seedlings, Yumai 49 (NH4+-tolerant) and Lumai 15 (NH4+-sensitive) cultivars were supplied with either 5.0 mmol L–1 NH4+-N (EAC) or 5.0 mmol L–1 NO3-N (CON) under hydroponic conditions.  Root growth in both cultivars was significantly reduced under EAC, and the negative effect was greater in Lumai 15.  EAC enhanced the activities of monodehydroascorbate reductase and dehydroascorbate reductase in the roots of both cultivars, while it decreased ascorbic acid (ASA) content and GDP-mannose pyrophosphorylase (GMPase) activity at the 12th day after treatment in Lumai 15 by 62.0 and 71.4%; and in Yumai 49 by 38.8 and 62.2%, respectively, indicating that the regeneration of ASA was increased, but the biosynthesis of ASA was reduced under EAC treatment.  Moreover, EAC increased DHA/ASA, reactive oxygen species (ROS), and malondialdehyde contents, as well as antioxidant enzyme activities in the roots of both cultivars.  Relatively greater increases in ROS and soluble sugar, and lower antioxidant enzyme activities in Lumai 15 indicate severe disruption of oxidative metabolism when compared to Yumai 49.  Results reveal that the reduction of ASA biosynthesis via decreased GMPase activity under the EAC condition probably acts as a trigger for accumulated ROS and imbalanced redox status, resulting in root growth inhibition during wheat seedling growth stage.  Yumai 49, being an NH4+-tolerant cultivar, had the stronger capacity to protect itself from oxidative stress, which allowed it to retain a lower DHA to ASA ratio by maintaining a better redox homeostasis than could be maintained in the NH4+-sensitive cultivar Lumai 15.
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    Physiological response of flag leaf and yield formation of winter wheat under different spring restrictive irrigation regimes in the Haihe Plain, China
    LIU Xue-jing, YIN Bao-zhong, HU Zhao-hui, BAO Xiao-yuan, WANG Yan-dong, ZHEN Wen-chao
    2021, 20 (9): 2343-2359.   DOI: 10.1016/S2095-3119(20)63352-4
    Abstract75)      PDF in ScienceDirect      
    In order to identify the optimum period of spring water-restrictive irrigation for winter wheat (Triticum aestivum L.) in the Haihe Plain, China and elucidate its effects on flag leaf senescence and yield formation, field experiments were conducted at the Xinji Experimental Station of Hebei Agricultural University from 2016 to 2019 by using different irrigation regimes in spring, including the conventional regime involving two irrigation periods (control (CK), the 3-leaf unfolding stage and the anthesis stage) and a series of single, restrictive irrigation regimes (SRI) comprising irrigation at the 3-leaf unfolding stage (3LI), 4LI, 5LI, and 6LI.  There are five major findings: (1) The senescence (determined by the green leaf area, GLA) in the 4LI treatment occurred moderately earlier than that in CK, showed no significant difference with that in 5LI and 6LI, and occurred significantly later than that in 3LI.  (2) Compared with other SRI treatments, the GLA value and photosynthetic rate in 4LI were 14.82 and 20.1% higher, respectively.  Microstructural analysis of flag leaf also revealed that the mesophyll cells and chloroplasts were irregularly arranged under drought stress in 3LI and 6LI; however, drought stress had minimal negative effects on the microstructure in 4LI and 5LI.  (3) Postponed irrigation in spring could significantly increase superoxide dismutase (SOD) and catalase (CAT) activities in the early stage of grain filling; however, these activities would subsequently decrease.  Among the four SRI treatments, the overall enzyme activities were the highest in 4LI, and the combined malondialdehyde (MDA) content in flag leaves in 4LI and 5LI was 14.5% lower on average than that in 3LI and 6LI.  (4) The soluble sugar (SS) and proline (Pro) contents in 4LI were the highest among the four SRI treatments; however, they were lower than those in CK.  The abscisic acid (ABA) hormone content in 4LI and 5LI was lower than that in 3LI and 6LI, respectively, suggesting a smaller drought stress effect in 4LI and 5LI.  (5) In two growing seasons, there was a larger number of spikes per unit area in 4LI (i.e., 13.4% higher than that in 5LI and 6LI) and the 1 000-grain weight in 4LI was the highest among the four SRI treatments (i.e., 6.0% higher than that in the other three SRI treatments).  Therefore, a single restrictive irrigation regime at the 4-leaf unfolding stage is recommended to be effective in slowing down the senescence process of flag leaves and achieving high yield.
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    Impacts of climate change on drought risk of winter wheat in the North China Plain
    ZHANG Li, CHU Qing-quan, JIANG Yu-lin, CHEN Fu, LEI Yong-deng
    2021, 20 (10): 2601-2612.   DOI: 10.1016/S2095-3119(20)63273-7
    Abstract104)      PDF in ScienceDirect      
    Drought is a major natural disaster causing crop yield losses, while its occurrence mechanism and spatiotemporal variations in a changing climate are still not clear. Based on a long-term climatic dataset (during 1958–2015) from weather stations in the North China Plain (NCP), the influencing mechanism of various climatic factors on drought risk of winter wheat was quantified by using sensitivity analysis, Mann-Kendall trend test and slope estimation. The results indicated that climatic factors have changed considerably over the past six decades in the growth season of winter wheat. As a result, winter wheat suffered from severe droughts (with 350 mm of water deficit during its growth season), particularly at the jointing–heading and heading–mature stages, which were critical to crop yield formation. There were large spatial and temporal variations in drought risk and climatic change factors at different growth stages of winter wheat. Despite precipitation playing a vital role in determining the spatiotemporal patterns of drought risk, high temperature and low humidity along with other climatic factors at key growth stages of winter wheat aggravated drought risk. Particularly, temperature at nearly 90% weather stations showed a notablely upward trend, which exacerbated water deficit and drought risk of winter wheat. Given the complexity and high uncertainty of climate change, these findings provide important information for adapting crop production to future climate change and accompanied droughts while ensuring food security and agricultural sustainability.
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    Rapid determination of leaf water content for monitoring waterlogging in winter wheat based on hyperspectral parameters
    YANG Fei-fei, LIU Tao, WANG Qi-yuan, DU Ming-zhu, YANG Tian-le, LIU Da-zhong, LI Shi-juan, LIU Sheng-ping
    2021, 20 (10): 2613-2626.   DOI: 10.1016/S2095-3119(20)63306-8
    Abstract116)      PDF in ScienceDirect      
    Waterlogging is becoming an obvious constraint on food production due to the frequent occurrence of extremely high-level rainfall events.  Leaf water content (LWC) is an important waterlogging indicator, and hyperspectral remote sensing provides a non-destructive, real-time and reliable method to determine LWC.  Thus, based on a pot experiment, winter wheat was subjected to different gradients of waterlogging stress at the jointing stage.  Leaf hyperspectral data and LWC were collected every 7 days after waterlogging treatment until the winter wheat was mature.  Combined with methods such as vegetation index construction, correlation analysis, regression analysis, BP neural network (BPNN), etc., we found that the effect of waterlogging stress on LWC had the characteristics of hysteresis and all waterlogging stress led to the decrease of LWC.  LWC decreased faster under severe stress than under slight stress, but the effect of long-term slight stress was greater than that of short-term severe stress.  The sensitive spectral bands of LWC were located in the visible (VIS, 400–780 nm) and short-wave infrared (SWIR, 1 400–2 500 nm) regions.  The BPNN Model with the original spectrum at 648 nm, the first derivative spectrum at 500 nm, the red edge position (λr), the new vegetation index RVI (437, 466), NDVI (437, 466) and NDVI´ (747, 1 956) as independent variables was the best model for inverting the LWC of waterlogging in winter wheat (modeling set: R2=0.889, RMSE=0.138; validation set: R2=0.891, RMSE=0.518).  These results have important theoretical significance and practical application value for the precise control of waterlogging stress. 
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    Estimating wheat fractional vegetation cover using a density peak k-means algorithm based on hyperspectral image data
    LIU Da-zhong, YANG Fei-fei, LIU Sheng-ping
    2021, 20 (11): 2880-2891.   DOI: 10.1016/S2095-3119(20)63556-0
    Abstract94)      PDF in ScienceDirect      
    Fractional vegetation cover (FVC) is an important parameter to measure crop growth.  In studies of crop growth monitoring, it is very important to extract FVC quickly and accurately.  As the most widely used FVC extraction method, the photographic method has the advantages of simple operation and high extraction accuracy.  However, when soil moisture and acquisition times vary, the extraction results are less accurate.  To accommodate various conditions of FVC extraction, this study proposes a new FVC extraction method that extracts FVC from a normalized difference vegetation index (NDVI) greyscale image of wheat by using a density peak k-means (DPK-means) algorithm.  In this study, Yangfumai 4 (YF4) planted in pots and Yangmai 16 (Y16) planted in the field were used as the research materials.  With a hyperspectral imaging camera mounted on a tripod, ground hyperspectral images of winter wheat under different soil conditions (dry and wet) were collected at 1 m above the potted wheat canopy.  Unmanned aerial vehicle (UAV) hyperspectral images of winter wheat at various stages were collected at 50 m above the field wheat canopy by a UAV equipped with a hyperspectral camera.  The pixel dichotomy method and DPK-means algorithm were used to classify vegetation pixels and non-vegetation pixels in NDVI greyscale images of wheat, and the extraction effects of the two methods were compared and analysed.  The results showed that extraction by pixel dichotomy was influenced by the acquisition conditions and its error distribution was relatively scattered, while the extraction effect of the DPK-means algorithm was less affected by the acquisition conditions and its error distribution was concentrated.  The absolute values of error were 0.042 and 0.044, the root mean square errors (RMSE) were 0.028 and 0.030, and the fitting accuracy R2 of the FVC was 0.87 and 0.93, under dry and wet soil conditions and under various time conditions, respectively.  This study found that the DPK-means algorithm was capable of achieving more accurate results than the pixel dichotomy method in various soil and time conditions and was an accurate and robust method for FVC extraction. 
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