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Table of Content

    01 November 2020, Volume 53 Issue 21
    CONTENTS
    Scientia Agricultura Sinica. 2020, 53(21):  0. 
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    CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS
    Screening for Resistance to Fusarium Head Blight and Agronomic Traits of Wheat Germplasms from Yangtze River Region
    WenJing HU,ChunMei ZHANG,Di WU,ChengBin LU,YaChao DONG,XiaoMing CHENG,Yong ZHANG,DeRong GAO
    Scientia Agricultura Sinica. 2020, 53(21):  4313-4321.  doi:10.3864/j.issn.0578-1752.2020.21.001
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    【Objective】Fusarium head blight seriously damages the grain yield and quality in China as well as in the world. Breeding and cultivating resistant varieties is the most economical, effective and safe method to combat this disease. A prominent gene Fhb1 conferring stable FHB resistance with the major phenotypic has been the major source of resistance in wheat breeding. The aim of this study was to screen for resistant varieties with excellent agronomic traits and evaluate the effects of Fhb1 on FHB resistance under different genetic backgrounds, so as to provide theoretical basis and material source for wheat FHB resistance breeding. 【Method】75 cultivars and 18 landraces which have been widely planted in Yangtze river region over the years were selected to evaluate their FHB response using point inoculation from 2016 to 2018. The tested varieties were classified into four classes based on the average percentage of scabbed spikelets (PSS) for FHB severity, i.e. resistant (R), moderately resistant (MR), moderately susceptible (MS) and susceptible (S). KASP diagnostic markers for Fhb1 were used to genotype the tested varieties. In 2019 we investigated the agronomical characteristics such as plant height, kernels per spike and spikelet per spike of the varieties with ≤50% of PSS. 【Result】The results showed that there were 2 varieties with PSS of 7.8%-9.7%( R), 65 varieties with PSS of 13.2%-49.5% (MR-MS), and 26 varieties with PSS of 53.6%-78.5% (S). 22 varieties carried Fhb1 resistant allele (Fhb1+), 71 carried the Fhb1 susceptible allele (Fhb1-) and the average PSS of the Fhb1+ was significantly lower than that of the Fhb1-(P<0.05). There were 67 varieties showed an average PSS≤50%, of which Ningmai 19, Yangmai 29, Yangmai 16, Yangmai 23, Yangnuomai 1, Yangmai 20, Ningmai 12 and Yangfumai 4 could be used as FHB resistance donors in breeding, due to the combination of good FHB resistance and agronomic traits.【Conclusion】No variety with R were identified in this study except Sumai 3 and Wangshuibai. Some Yangmai varieties exhibited both good FHB resistance and comprehensive agronomic traits, of which only Yangfumai 4 carried the Fhb1 resistance gene. Utilizing Fhb1 is not the only way to combat FHB, and more FHB-resistant germplasms and new FHB-resistant genes should be studied and applied in breeding programs.

    Breeding and Characteristics of a New Male Sterile Line of Maize, Jinyu1A
    ZHANG HuanHuan,CUI GuiMei,WANG ChangBiao,WANG XiaoQing,HAO YaoShan,DU JianZhong,WANG YiXue,SUN Yi
    Scientia Agricultura Sinica. 2020, 53(21):  4322-4332.  doi:10.3864/j.issn.0578-1752.2020.21.002
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    【Objective】The study was aimed to determine the type of the male sterile line of maize, Jinyu1A, by molecular biology and cytology approaches, identify restoring and maintaining relationships of maize germplasm resources to the sterile line, and to test its general combining ability (GCA) and specific combining ability (SCA).【Method】The stability of sterility of Jinyu1A was investigated at 4 locations (Ledong, Jinzhong, Xinzhou and Yuncheng) for successive 3 years. Tassel, anther and pollen grains of Jinyu1A was observed and compared with Zheng58. F1 pollen grains of Jinyu1A×Chang7-2 were observed by I2-KI staining. The sterility type of Jinyu1A was identified by specific PCR. Jinyu1A was used as the female parent and test-crossed with 158 maize inbred lines. The fertility of F1 plants was investigated to screen for the suitable restorer and maintainer lines. The fertility of F2 and BC1 population plants was investigated. The grain yield general combining ability and specific combining ability of Jinyu1A were estimated by analyzing the data of its F1 hybrids.【Result】The sterility characters of Jinyu1A were stable in the 4 locations for the 3 years. The appearance of tassel of Jinyu1A was similar to that of Zheng58, but its glumes were closed, anthers were withered and could not exert out of the glumes, and I2-KI staining showed that the pollen of Jinyu1A was completely sterile. The microscopical observation on the pollen grains of F1 hybrid plants of Jinyu1A and Chang7-2 showed that 64.4% of the pollen grains could be stained dark by I2-KI and 35.6% pollen grains were aborted, which indicated that the sterile line belonged to S-type cytoplasmic sterile lines. The cytoplasm of Jinyu1A and Chang7-2 were identified as S-type male sterile type by specific PCR. The nuclear genome of Chang7-2 carries restorer genes, which concealed the phenotype of cytoplasmic male sterility. The specific primers suggested by ZHENG et al. were more applicable for categorizing maize cytoplasm sterile types. Among 158 inbred lines test-crossed with Jinyu1A as female parent, 96 maintainers, 47 restorers, and 15 semi-restorers were identified. There were 3.1%-8.7% sterile plants in F2 populations derived from fertile F1 plants of crosses between Jinyu1A and the restorer lines, which indicated that there were minor effect restorer genes in the restorer lines. There was no significant difference in the grain yields of the hybrids between each of Jinyu1A and Zheng58 as females and other 10 inbred lines as males, respectively. However, the F1 combining ability analysis of these hybrids showed that the general combining ability of Jinyu1A was slightly higher than that of Zheng58.【Conclusion】Jinyu1A was a S-type cytoplasmic male sterile line with stable male sterile characters and completely aborted pollen grains. There are a certain amount of restorer and maintainer type breeding stocks for Jinyu1A in the present maize germplasm resources. F1 plants of its hybrid with Chang7-2 could produce normal panicles and disperse fertile pollen. The existence of minor effect restorer gene(s) made the pollen dyeability shift to the direction of fertility, which led to the emergence of a few fertile plants in F2 populations. There was no significant difference in the grain yield between the hybrids with Jinyu1A and Zheng58 each as female parents test-crossed with the same male parents. The general combining ability of Jinyu1A was slightly higher than that of Zheng58, indicating that it could be used in the breeding programs for selecting new maize hybrids and male sterile lines.

    SPECIAL FOCUS: HIGH EFFICIENCY UTILIZATION OF WATER AND FERTILIZER OF WHEAT-MAIZE CROPPING SYSTEM
    Annual High Efficiency Utilization of Water and Fertilizer of a Wheat-Maize Double Cropping System
    LI ZongXin,WANG Liang,LIU ShuTang,ZHAO Bin,QIAN Xin,LI QuanQi,FENG Bo,LI ShengDong,LIU KaiChang
    Scientia Agricultura Sinica. 2020, 53(21):  4333-4341.  doi:10.3864/j.issn.0578-1752.2020.21.003
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    Effects of Base Application Depths of Controlled Release Urea on Yield and Nitrogen Utilization of Summer Maize
    DING XiangPeng,LI GuangHao,ZHANG JiWang,LIU Peng,REN BaiZhao,ZHAO Bin
    Scientia Agricultura Sinica. 2020, 53(21):  4342-4354.  doi:10.3864/j.issn.0578-1752.2020.21.004
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    【Objective】 The effects of different fertilization depths of controlled-release urea on nitrogen absorption and utilization were investigated, and then the suitable fertilization depth for achieving high, efficient and stable yield of controlled- release urea in the Huang-Huai-Hai summer maize area was determined.【Method】 Zhengdan958 was selected as the test variety under field conditions, and seven treatments were set, including no nitrogen fertilizer (CK), surface application (DP0), furrow dressing depth of 5 cm (DP5), 10 cm (DP10), 15 cm (DP15), 20 cm (DP20) and 25 cm (DP25). The effects of urea application depth on growth, yield and nitrogen utilization of summer maize were studied systematically.【Result】Under the same amount of controlled-release urea application, the yield of summer maize was significantly affected by fertilization depth. The yield of summer maize increased at first and then decreased with the increase of basal fertilization depth. Moreover, the relationship between maize yield and fertilization depth in the summer of 2013 and 2014 conformed to the quadratic curve and the correlation between them reached a significant level as well. The theoretical fertilization depth that obtained the highest yield was 12.5 cm and 12.2 cm in 2013 and 2014, respectively. While in actual production, the DP15 treatment produced the highest yield with no significant difference between DP15 and DP10 treatment, with a significant increase of 16.72% and 16.50%, separately, compared with CK (P<0.05). Compared with DP0, nitrogen harvest index, partial nitrogen productivity, nitrogen agronomic efficiency and nitrogen utilization rate of summer maize all showed a trend of first increasing and then decreasing with the increase of basal fertilization depth. The agricultural efficiency of nitrogen fertilizer and the utilization rate of nitrogen fertilizer fit the quadratic curve. The nitrogen harvest index and nitrogen fertilizer agronomic efficiency were the largest under DP10 treatment in two years, achieving to 61.91% and 6.68 kg·kg-1, respectively, however, the highest nitrogen fertilizer efficiency was 47.27 kg·kg-1 and 46.97% under DP15 treatment, respectively. Compared with DP0, fertilization depth of 10 cm and 15 cm could increase soil nitrate and ammonium nitrogen content and reduce nitrogen loss. The mean value of nitrogen accumulation after flowering was 38.93% and 41.88% in 2013 and 2014, respectively, which promoted the post-flowering nitrogen accumulation and significantly increased the total nitrogen uptake above-ground by 20.45% and 22.36%, respectively. Correlation analysis showed that summer maize yield was significantly positively correlated with dry matter accumulation, total nitrogen accumulation, partial nitrogen productivity, nitrogen agronomic efficiency and nitrogen use efficiency, and significantly negatively correlated with nitrogen grain production efficiency.【Conclusion】 In nitrogen application rate of 225 kg N·hm-2, controlled release urea one-time basal application depth in 10 to 15 cm could significantly improve nitrogen absorption accumulation of summer maize, increase nitrogen use efficiency, reduce nitrogen loss, improve the dry matter accumulation, eventually obtain higher grain yield. Furthermore, it also realized higher production and efficiency, and could be used as controlled release urea suitable fertilization depth for summer maize sowing and manuring simultaneously.

    Organic-Inorganic Coordinated Regulation to Wheat-Maize Double Crop Yield and Soil Fertility
    ZHENG FuLi,LIU Ping,LI GuoSheng,ZHANG BoSong,LI Yan,WEI JianLin,TAN DeShui
    Scientia Agricultura Sinica. 2020, 53(21):  4355-4364.  doi:10.3864/j.issn.0578-1752.2020.21.005
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    【Objective】The objectives of this study were to discuss the effects of different organic-inorganic operation modes on crop yield, nitrogen efficiency and soil nutrients characteristics under the condition that wheat-maize straw returning to the field completely in two seasons, so as to provide a theoretical support for rational utilization of organic nutrient resources and scientific soil fertility culture in a wheat-maize cropping system.【Method】The experiment studied effects of different organic-inorganic operation modes on yield composition, nitrogen nutrient absorption, soil organic matter and stable aggregate, through designing the combination of chemical fertilizer with different amounts of organic fertilizer and straw-decomposing inoculant. Six experiment treatments were designed: F treatment was only chemical fertilizer, FA treatment was chemical fertilizer and straw-decomposing inoculants, FM1 treatment was chemical fertilizer and 1 500 kg·hm-2 organic fertilizer, FM2 treatment was chemical fertilizer and 3 000 kg·hm-2 organic fertilizer, FM3 treatment was chemical fertilizer and 4 500 kg·hm-2 organic fertilizer, FAM2 treatment was chemical fertilizer and 3 000 kg·hm-2 organic fertilizer and straw-decomposing inoculants.【Result】(1)Compared with single chemical fertilizer, application organic fertilizer and straw-decomposing inoculant could significantly increase grain yield of wheat-maize. The yield of chemical fertilizer combined with 4 500 kg·hm-2 organic fertilizer was the highest, wheat increased by 20.6%, maize by 10.6%. Combined chemical fertilizer with 3 000 kg·hm-2 organic fertilizer and straw-decomposing inoculant, the yield of wheat and maize increased by 19.5% and 8.2%, respectively. The increase of yield was due to the synergistic improvement of various components. The number of ears and grains per ear of wheat increased significantly and the number of grains per row increased most significantly in maize. (2) The increasing of organic fertilizer and straw-decomposing inoculant could promote the migration of nitrogen to the grain, improve the nitrogen harvest index, and increase the nitrogen accumulation in wheat and maize. The nitrogen accumulation and harvest index for both of FM3 treatment (application with 4 500 kg·hm-2 organic fertilizer) and FAM2 treatment (application with 3 000 kg·hm-2 organic fertilizer and straw-decomposing inoculant) were significantly higher than F treatment with single application of chemical fertilizer. Compared the treatment with non-bacterial, the NPFP of FA and FAM2 treatments that combined with straw-decomposing inoculant increased by 1.3-1.6 kg·kg-1. (3) The content of total nitrogen, alkali-hydrolyzed nitrogen and organic matter in the soil were significantly increased by increasing the organic fertilizer and straw-decomposing inoculant. The content of total nitrogen and organic matter in soil of FM3 treatment was the highest, and the annual total nitrogen increased by 0.17 g·kg-1 and the organic matter increased by 1.97 g·kg-1 compared with F treatment after two years. Different organic and inorganic application modes significantly reduced soil bulk density and increased soil porosity and water-stable aggregates. 【Conclusion】By two years field experiments, the application of organic fertilizer and straw-decomposing inoculant could increase the yield of wheat and maize, promote nitrogen absorption and transport, and improve soil structure and soil fertility. Under the conditions of this experiment, FAM2 treatment was recommended as an effective fertilization technology model for wheat-maize rotation in this region.

    Effects of Nitrogen Application Rate on Assimilate Accumulation, Transportation and Grain Yield in Wheat Under High Temperature Stress After Anthesis
    GAO ChunHua,FENG Bo,CAO Fang,LI ShengDong,WANG ZongShuai,ZHANG Bin,WANG Zheng,KONG LingAn,WANG FaHong
    Scientia Agricultura Sinica. 2020, 53(21):  4365-4375.  doi:10.3864/j.issn.0578-1752.2020.21.006
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    【Objective】This study was aimed to identify the effects of nitrogen application rates on grain yield, assimilate accumulation and translocation, physiological basis of winter wheat under the condition of high temperature stress, so as to provide technical and theoretical support for stress-resistance and stable yield cultivation.【Method】 Field experiments were conducted at Ji’nan experiment station and Jiyang experiment station of Crop Research Institute, Shandong Academy of Agricultural Sciences in 2018 and 2019, designed with two temperature treatments (CK: Control, H: High temperature stress) and three nitrogen levels (N1:Low nitrogen with 180 kg·hm-2, N2: Regular nitrogen with 240 kg·hm-2, and N3: High nitrogen with 300 kg·hm-2) . By analyzing assimilate accumulation, allocation, sucrose synthetase activity in leaf and grain, and grain yield with winter wheat cultivar JM44, the regulation of nitrogen application rates on grain yield of wheat under high temperature stress circumstances was studied. 【Result】 The results showed that grain yield decreased significantly under high temperature stress conditions, and grain yield reduction at N1, N2, and N3 were 54.78%, 24.05%, 54.49% and 50.19%, 25.29%, 44.13% in Ji’nan and Jiyang, respectively. Significant increases were noticed in assimilate accumulation amount, pre-anthesis assimilate translocation amount and rate to grain yield, post-anthesis assimilate accumulation amount and rate, ratio of grain to other organs udner N2 treatment, compared with N1 and N3 treatment, same as in SPAD value, sucrose synthetase-I activity (direction of synthetic) in flag leaf, and sucrose synthetase-Ⅱ activity (direction of decomposition) in grain. 【Conclusion】Higher grain yield could be achieved after high temperature stress during grain-filling stages with nitrogen application rate of 240 kg·hm-2, which could postpone flag leaf senescence, maintain high sucrose synthetase-I activity in flag leaf and sucrose synthetase-Ⅱ activity in grain, and keep high ability cof assimilate accumulate and transport to grain.

    The Thresholds of Soil Drought and Its Impacts on Summer Maize in Shandong Province
    DONG ZhiQiang,LI ManHua,LI Nan,XUE XiaoPing,CHEN Chen,ZHANG JiBo,ZHAO Hong,HOU YingYu,PAN ZhiHua
    Scientia Agricultura Sinica. 2020, 53(21):  4376-4387.  doi:10.3864/j.issn.0578-1752.2020.21.007
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    【Objective】This study was aimed to determine the suitable range and the drought stress thresholds of soil water on summer maize in Shandong Province, and to evaluate the effects of different drought degrees on growth and development and yield formation of summer maize quantitatively. So as to provide a basis for improving the utilization efficiency of agricultural water resources and alleviating the adverse impacts of drought stress. 【Method】Based on the data from field experiments, the suitable and unsuitable ranges of soil moisture were determined for the seedling stage, ear stage and grain stage of summer maize. By the model of WOFOST, the drought stress thresholds were analyzed with the relative water content as the driving factor. And the drought effects were assessed quantitatively through different drought degrees and their duration days. 【Result】(1) The suitable ranges of soil water during seedling stage, ear stage and grain stage of summer maize were 62%-91%, 66%-92% and 68%-94%, respectively. And the unsuitable ranges were less than 62%, 66% and 68%, respectively. (2) The thresholds of no drought, light drought, medium drought and severe drought during seedling stage were 53%, 50%, 45% and 40%, respectively. The thresholds of different drought degrees during ear stage were 58%, 48%, 43% and 37%, respectively. The thresholds of different drought degrees during grain stage were 57%, 52%, 49% and 45%, respectively. (3) The drought happened during seedling stage had the greatest effects on the total leaf weight, total stem weight and maximum leaf area index. The drought happened during ear stage and grain stage had the greatest effects on the total ear weight. And the severe drought during ear stage would result in the failure of final yield formation. 【Conclusion】The suitable ranges of soil water and the drought thresholds of summer maize were brought to light in Shandong. The drought happened during ear stage and grain stage of summer maize had more significant impacts on yield formation.

    The Coordination of Nitrogen Optimization with Matched Variety Could Enhance Maize Grain Yield and Nitrogen Use Efficiency of Summer Maize in Saline Land
    GAO YingBo,ZHANG Hui,LIU KaiChang,ZHANG HuaBin,LI YuanFang,FU XiQiang,XUE YanFang,QIAN Xin,DAI HongCui,LI ZongXin
    Scientia Agricultura Sinica. 2020, 53(21):  4388-4398.  doi:10.3864/j.issn.0578-1752.2020.21.008
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    【Objective】In order to achieve synergistic promotion of both maize grain yield and nitrogen use efficiency (NUE) under salt stress, it is essential to explore the performance difference of different salt-tolerant maize varieties on yield formation, nitrogen uptake, transport and utilization, to excavate biological potential of maize varieties using nitrogen, so as to provide matched maize variety for the optimized nitrogen application regime.【Method】In this study, salt-tolerance maize varieties Denghai605, Ludan818 and salt-sensitive maize varieties Ludan981 and Liansheng188 were separately used to systematically study the effects on accumulation and distribution of dry matter and nitrogen, nitrogen utilization efficiency and yield formation under different nitrogen application rates of 0, 180 and 360 kg·hm-2, denoted by N0, N1 and N2 treatments in turn, as well as the interaction of nitrogen levels and maize varieties and inter-annual were analyzed.【Result】Suitable nitrogen application rate could significantly increase grain yield. Compared with N1 treatment, there were no difference in grain yield for salt-tolerance varieties but significant increase for Ludan981 (avg. 9.93%) and Liansheng188 (avg. 16.31%) under N2 treatment. Also, high nitrogen application (N2) got lower nitrogen agricultural efficiency (NAE), nitrogen utilization efficiency (NUE) and nitrogen partial factor productivity (NPFP) than low nitrogen application (N1). The difference in grain yield and yield components was the result from the varieties, nitrogen regimes, and their interaction. Compared with salt-sensitive maize varieties, salt-tolerance maize varieties had greater grain yield, nitrogen absorption and use efficiency across same nitrogen regime. Specifically, the grain yield of salt-tolerance maize varieties were increased by 7.78%-27.63% (N0), 7.40%-24.87% (N1), and 0.32%-9.55% (N2), respectively, while the nitrogen utilization efficiency were increased by 26.65%-48.28% (N1) and 1.20%-24.87% (N2), respectively.【Conclusion】It was performance well for the salt-tolerances varieties than the salt-sensitive varieties on dry matter accumulation and nitrogen uptake and utilization. Low nitrogen application was beneficial for salt-tolerant maize variety getting higher grain yield and vice versa. The nitrogen utilization efficiency was affected by maize varieties, nitrogen regimes and its interaction, through affecting grain yield, dry matter accumulation, and nitrogen uptake and utilization. Thus, it would be an efficient strategy to achieve synergistic promotion of both maize grain yield and nitrogen use efficiency, through the coordination of nitrogen optimization with matched maize variety.

    Effects of Different Spring Nitrogen Topdressing Modes on Lodging Resistance and Lignin Accumulation of Winter Wheat
    DONG HeHe, LUO YongLi, LI WenQian, WANG YuanYuan, ZHANG QiuXia, CHEN Jin, JIN Min, LI Yong, WANG ZhenLin
    Scientia Agricultura Sinica. 2020, 53(21):  4399-4414.  doi:10.3864/j.issn.0578-1752.2020.21.009
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    【Objective】The purpose of this experiment was to explore the effects of different spring nitrogen topdressing modes on stem lodging resistance, lignin accumulation, grain yield of winter wheat, and to identify the appropriate spring nitrogen topdressing modes under the condition of high nitrogen application, so as to provide technical support for high and stable yield and stress-resistant cultivation of winter wheat.【Method】In the two wheat growing seasons of 2017-2018 and 2018-2019, the lodging sensitive variety Shannong 16 and the lodging resistant variety Jimai 22 were used as test materials, and the application rate was 1/3 under high nitrogen application rate of 300 kg·hm-2. There were four types of spring topdressing modes, which were equal amount of secondary nitrogen topdressing and remaining one-time nitrogen topdressing, namely the rising stage﹕booting stage 1/3﹕1/3 (T1), jointing stage: flowering stage 1/3﹕1/3 (T2), the remaining 2/3 nitrogen was applied at the booting stage (T3) and the remaining 2/3 nitrogen was applied at the jointing stage (CK). The effects of different nitrogen topdressing modes on stem resistance, lignin accumulation, expressive abundance of the key genes involving in lignin biosynthesis pathway and grain yield of winter wheat were studied.【Result】The total lignin accumulation and lignin monomers content of the lodging resistance wheat were both higher than those of the lodging sensitive wheat. The breaking strength under T1, CK was higher than that under T2 and T3, the lignin accumulation and monomer content were T1>T3>CK>T2 in two types cultivar, and the breaking strength, lignin accumulation, monomer content under all treatments at grain filling stage and maturity stage were T1>T3>T2>CK in two types cultivar. The breaking strength of Shannong 16 and Jimai 22 under T1 treatment were increased by 24.69%, 19.97%, 13.15% and 26.92%, 15.36%, 5.87%, respectively, compared with CK, T2, T3 at grain filling stage. The average lignin accumulation of Shannong 16 and Jimai22 under T1 at each growth stage was 21.71%, 15.45% , 8.85% and 25.19%, 21.75%, 15.83% higher than CK, T2, and T3, respectively. The average content of S monomer was 18.82%, 18.48%, and 8.39% higher than CK, T2 and T3 at maturity stage, respectively. The expressive abundance of key genes involved in lignin biosynthesis pathway (phenylalanine ammonia-lyase: PAL, caffeic acid3-o-methytransferase: COMT, coumarate-3-hydroxyl oxidase: C3H, innamoyl Co A reductase: CCR, cinnamate 4-hydroxylase: C4H etc.) decreased with the growth process, that tended to T1>T3>T2>CK under different stage of growth. The 1000-grain weight of the nitrogen topdressing remaining one-time at booting stage was higher than other treatments. T1 treatment could increase the spike number, grain number and yield. The lignin accumulation and monomer content of stem in different internodes during the same stage were I1>I2>I3>I4>I5.【Conclusion】Under the condition of high nitrogen application rate of 300 kg·hm-2 and basal application rate of 1/3, the same amount of secondary nitrogen topdressing modes treatment at the rising stage and booting stages significantly improved the breaking strength, lignin accumulation, lignin monomer content, the expressive abundance of key genes involved in lignin biosynthesis pathway and yield after anthesis stage, compared with other spring nitrogen topdressing modes. Therefore, the same amount of secondary nitrogen topdressing mode at rising stage and booting stage could be used as an appropriate spring nitrogen topdressing mode under the condition of high nitrogen application rate of 300 kg·hm-2 and basal application rate of 1/3 in Huang-Huai-Hai plain.

    Effects of Main Food Yield Under Straw Return in China: A Meta-Analysis
    YANG JunHao,LUO YongLi,CHEN Jin,JIN Min,WANG ZhenLin,LI Yong
    Scientia Agricultura Sinica. 2020, 53(21):  4415-4429.  doi:10.3864/j.issn.0578-1752.2020.21.010
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    【Objective】In order to provide scientific grounds for the implementation of grain crop straw return, this study quantified the yield effect of straw return.【Method】It was collected and sorted out the published Chinese literatures in the past 30 years (a total of 274 piece of literature and 1 930 pairs data until December 31, 2019). By using meta-analysis method, the comprehensive effect of straw returning on crop yield was clarified with the main analysis process, included calculation of effect value, heterogeneity test, meta-subgroup analysis and publication bias test. And then, the effects under different experiment region, average annual temperature, average annual precipitation, soil texture, soil pH, crop type, planting system, tillage method, fertilization method, experiment duration and return amount was further quantitatively analyzed.【Result】Compared with straw remove, straw return significantly increased crop yield, and the average increasing rate was about 8.06%, with a 95% confidence interval of 7.52%-8.60%. No publication bias was found in the result. The yield effect was the highest in the southeastern region, reaching 9.37% (95% CI: 8.11%-10.64%). The straw-return effect was higher when the average annual temperature was 5-10 °C and the average annual precipitation is more than 1 200 mm. In different soil texture, the yield effect of straw return was 8.13% in clay (95% CI: 6.80%-9.49%), 9.04% in loam (95% CI: 8.06%-10.01%) and 6.96% in sandy soils (95% CI: 5.18%-8.77%), respectively. Among the three types of grain crops, namely, wheat, corn, and rice, the increase rate of yield on maize reached 9.22% (95% CI: 8.38%-10.05%) by straw returning. Plowing and no-till was the best tillage methods exerting the yield effect of straw returning, the increasing rate of yield were 11.05% (95% CI: 10.05%-12.05%) and 8.98% (95% CI: 7.21%-10.79%), respectively. When the straw was returned to the field without fertilization, the crop yield was significantly increased with an increase rate of 25.66% (95% CI: 22.04%-29.38%), which was significantly higher than that of 8.08% (95% CI: 7.50%-8.68%) under normal fertilization, but the overall yield level was lower. The yield increase rate of straw mulching reached 9.56% and the yield increase effect of straw mulching over 20 years was significantly increased (yield increase rate: 15.42%, 95% CI: 11.05%-19.95%). In addition, the most suitable amount of straw was half of the ex-crop (increase rate of yield was 9.09%, 95% CI: 7.41%-10.79%).【Conclusion】Straw return could significantly increase crop yield in different agricultural production areas. Furthermore, the long-term implication of crop straw with no-till or plowing tillage, normal fertilization and appropriate amount, could maintain continuous increase in crop yield.

    PLANT PROTECTION
    Prediction of Suitable Area and Risk Analysis for Citrus Target Spot
    XU YongHong,CHEN Li,TANG Song,DING DeKuan,YANG YuHeng
    Scientia Agricultura Sinica. 2020, 53(21):  4430-4439.  doi:10.3864/j.issn.0578-1752.2020.21.011
    Abstract ( 372 )   HTML ( 24 )   PDF (2139KB) ( 688 )   Save
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    【Objective】Citrus target spot, a new disease reported in China, has caused serious economic losses in the local orchards. Therefore, it is necessary to carry out the prediction of the suitable area and risk analysis of the disease, so as to take timely and effective control measures for the disease, and finally achieve the purpose of reducing the risk level and preventing the spread of this disease.【Method】Combined the environmental data and the occurrence and distribution data of the disease areas, MaxEnt ecological niche models were used to predict the potential suitable area of citrus target spot pathogen (Pseudofabraea citricarpa) in China. The area under the curve (AUC) of receiver operating characteristic (ROC) was used to evaluate the accuracy of the prediction model, and the relationship between the climate factor and the distribution probability was obtained using the regularized training gain method. Additionally, the theory of pest risk analysis was used to explore the risk analysis system and calculation method of citrus target spot based on the prescribed procedures of pest risk analysis. Qualitative analysis of the evaluation indicators was conducted to quantify the evaluation values. Based on establishing a comprehensive evaluation model, the risk hazard value of citrus target spot was calculated, and finally the risk hazard value of the disease was evaluated.【Result】The average AUC value of the predicted result of MaxEnt model was 0.998, which indicated that the predicted result was highly accurate. The area of potential suitable areas for P. citricarpa accounts for 12.19% of the national area. Among them, the areas of high suitability, medium suitability, and low suitability account for about 2.85%, 3.99%, and 5.35% of the national area, respectively. The high and middle suitable areas are mainly concentrated in the citrus dominant area in the upper and middle reaches of the Yangtze River. Among them, high suitable area is mainly concentrated in Sichuan, Chongqing, southern Shaanxi, and a few areas in Guizhou and Hubei. The middle and low suitable areas are the peripheral expansion of the high suitable area. The analysis results of the importance of environmental variables obtained by the MaxEnt model normalization training gain knife-cut method show that the mean temperature in the coldest quarter (Bio11), the mean temperature in the driest quarter (Bio9), and the minimum temperature of the coldest month (Bio6) are the key factors affecting the distribution of P. citricarpa, which means that there is a high possibility of citrus target spot in low temperature and dry and cold seasons. The risk analysis finally created a multi-index comprehensive evaluation system of 5 criterion layers and 13 indicator layers, and quantitative and qualitative analyses of each indicator layer. The risk index value (R) of the disease was up to 2.08. This disease has the greatest potential harm to the two major citrus-producing areas in the Yangtze River Basin and in western Hubei and western Hunan.【Conclusion】In view of the high risk of citrus target spot, it is necessary to establish a monitoring system as soon as possible, and take effective control measures against the disease to prevent the spread between the citrus dominant area and adjacent citrus-producing areas in the upper and middle reaches of the Yangtze River.

    An in vitro Cap-Snatching System of Rice Stripe Tenuivirus Based on Crude Virion Preparations
    LIN WenZhong,WU Ran,JIN Jing,QIU Ping,ZHANG Jie,WU ZuJian,DU ZhenGuo
    Scientia Agricultura Sinica. 2020, 53(21):  4440-4448.  doi:10.3864/j.issn.0578-1752.2020.21.012
    Abstract ( 429 )   HTML ( 16 )   PDF (1219KB) ( 704 )   Save
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    【Background】Viruses of the order Bunyavirales and the family Orthomyxoviridae cleave host cellular mRNAs 10-20 nucleotides downstream of the cap structure and use the 5′ terminal cleavage product as a primer to initiate the transcription of their template RNAs. This process is called cap-snatching, the result of which is that all viral mRNAs contain a host-derived capped-RNA leader (CRL). Rice stripe tenuivirus (RSV) is a plant-infecting bunyavirus for which the mechanism of cap-snatching remains poorly characterized.【Objective】The objective of this study is to establish a convenient in vitro system to dissect the cap-snatching mechanisms of RSV, this study is designed to test whether crude preparations of RSV snatch CRLs from exogenously supplied mRNAs.【Method】Crude preparations of RSV were obtained by PEG precipitation combined with differential centrifugation. The protein components of the preparations were analyzed by SDS-PAGE and mass spectrometry. After adding rabbit reticulocyte lysate (RCL) rich in globin mRNAs, the preparations were used to establish an in vitro cap-snatching reaction mix. Total RNA was extracted from the reaction mix at the end of the reaction. RSV mRNAs with CRLs obtained from globin-α mRNAs were detected using nested RT-PCR. The products of the nested RT-PCR were cloned, and the sequences were analyzed.【Result】Two mL of crude RSV preparations was obtained from 100 g of virus-infected rice. The preparations contain chloroplast proteins including ribulose-1,5-bisphosphate carboxylase/oxygenase in addition to RSV virions. A 20 μL reaction system containing 2 μL RSV crude preparations, 8 μL RCL, 4 mmol·L-1 MgCl2, 2 mmol·L-1 of each NTP and 0.8 U·μL-1 RNase inhibitor was prepared and incubated at 30℃ for 1.5 h. Clearly discernable bands with expected sizes were obtained in the nested RT-PCR, indicating that RSV crude preparations can cleave globin-α mRNAs and use their CRLs. After adding the cap analogue m7G (5′) ppp (5′) G, the brightness of the bands was decreased and the extent of the decrease correlated with the concentration of the cap analogue, indicating that cap binding is essential for the cleavage. PCR bands with expected sizes were recovered and sequenced after cloning. Sequence analysis revealed a scenario reminiscent of that seen in vivo: RSV cleaves globin-α mRNAs after A or C to obtain CRLs capable of base-pairing with its template RNAs. In initiating transcription with these CRLs, RSV uses the prime-and-realign mechanism frequently and has a greater tendency to use this mechanism in synthesizing nucleoprotein gene (NP) than in synthesizing non-capsid protein gene (NCP) mRNAs.【Conclusion】The crude preparations of RSV can snatch CRLs from exogenously added mRNAs and use the CRLs to prime transcription in a way just like it does in vivo. Therefore, RSV crude preparations can be used to dissect the cap-snatching or the transcription of RSV.

    SOIL & FERTILIZER·WATER-SAVING IRRIGATION·AGROECOLOGY & ENVIRONMENT
    Soil Texture Classification of Hyperspectral Based on Data Mining Technology
    ZHONG Liang,GUO Xi,GUO JiaXin,HAN Yi,ZHU Qing,XIONG Xing
    Scientia Agricultura Sinica. 2020, 53(21):  4449-4459.  doi:10.3864/j.issn.0578-1752.2020.21.013
    Abstract ( 316 )   HTML ( 18 )   PDF (2104KB) ( 837 )   Save
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    【Objective】 The aim of this study was to find the reflection law of Vis-NIR spectra of different soil texture types in red soil region, and to quickly and accurately predict the soil texture type by the spectrum. 【Method】 Taking the north of Fengxin County in Jiangxi Province as the research area, 245 soil samples were taken as the research objects. Under the 4 groups and 12 levels of international soil texture classification standards, the spectral reflectance of different soil texture types was analyzed first, then the data mining models combining 9 mathematical transformation methods and 5 machine learning algorithms were used to classify the soil texture, and finally analysis of the confusion matrix with the highest modeling accuracy and the triangular coordinate distribution map of prediction results. 【Result】 (1) There were many overlaps and overlaps in the spectral reflectance between different soil textures, and the law between the soil texture and the spectral reflectance was more complicated. (2) Fractional derivative transformation was an extension of the integer derivative, which was helpful for the classification of soil texture, but the original spectral data had more abundant feature information and was more suitable for the classification of soil texture. (3) Both ensemble learning methods and neural network methods were good choices when modeling unbalanced data sets. (4) It was difficult to distinguish the categories near the boundary of soil texture by using the model. Among them, clay loam group was the most likely to be predicted wrongly under the four classification standards, and clay loam and loamy clay were the two most likely to be predicted wrongly under the 12 classification standards. (5) Among the four groups of classification standards, the highest prediction accuracy (at 0.68) was obtained by the combination of normalization treatment and MLP model, and the prediction accuracy of clay loam group could reach 0.84. After subdivision to 12 levels classification, the best classification result came from combination of original data and MLP model, and the classification accuracy of loamy clay was 0.89. 【Conclusion】 The results of this study could provide a reference for soil texture classification by using hyperspectral data.

    Effect of Long-Term Fertilization on Nutrient Distribution of Fluvo-Aquic Soil Profile
    WEN YanChen,LI HaiYan,YUAN Liang,XU JiuKai,MA RongHui,LIN ZhiAn,ZHAO BingQiang
    Scientia Agricultura Sinica. 2020, 53(21):  4460-4469.  doi:10.3864/j.issn.0578-1752.2020.21.014
    Abstract ( 332 )   HTML ( 16 )   PDF (498KB) ( 558 )   Save
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    【Objective】Based on the long-term positioning monitoring platform of fertilization experiment, the effects of different fertilization patterns on the soil fertility and spatial distribution of nutrients were studied in fluvo-aquic soil, so as to provide a basis for rational fertilization and scientific fertilization of farmland in the North China Plain. 【Method】 Taking no fertilization (CK) as a control, three treatments with equal nitrogen rate (N 180-225 kg·hm-2) was conducted since 1986, including chemical fertilizer (F), organic manure (M), and combination of organic manure with chemical fertilizer (MF). Soil pH, organic matter, nitrogen, phosphorus, potassium of and its spatial distribution were analyzed for every 20 cm depth of soil till 200 cm. 【Result】 After 31 years of continuous fertilization, soil organic matter, total nitrogen, alkali-hydrolyzed nitrogen, nitrate nitrogen, available phosphorus, and available potassium all decreased with the increase of soil depth. As to the equal nitrogen application, the organic matter content under F, M and MF in 0-40 cm was 14.2, 25.6 and 18.2 g·kg-1, respectively. Compared with F, the organic matter under M and MF were increased by 80.3% and 28.2%, respectively. The total nitrogen content under F, M and MF in 0-40 cm was 0.93, 1.67, and 1.21 g·kg-1, respectively. M and MF increased total nitrogen by 79.6% and 30.1%, respectively, compared with F. The alkali hydrolysable nitrogen content under F, M and MF in 0-40 cm was 80.2, 120.7, and 83.3 mg·kg-1, respectively. And compared with F, the growth ratio of alkali hydrolysable nitrogen for M and MF was 50.5% and 3.9%, respectively. The 0-200 cm nitrate nitrogen content of F (21.1 mg·kg-1) was 3.4 times and 1.8 times as much as that of M (6.2 mg·kg-1) and MF (11.9 mg·kg-1), respectively. The available phosphorus of 0-60 cm for M (134.3 mg·kg-1) and MF (60.5 mg·kg-1) was 7.2 times and 3.3 times than that of F (18.6 mg·kg-1), respectively. The available K content under F, M and MF in 0-40 cm was 90, 163, and 89 mg·kg-1, respectively. Compared with chemical fertilizer, the pH of 0-200 cm soil of long-term application of cattle manure or combination of organic manure with chemical fertilizer showed no significant difference.【Conclusion】 Long-term application of chemical fertilizer had high risk of nitrate leaching, and the content of nitrate nitrogen in the 0-200 cm soil layer was 21.1 mg·kg-1 under the F treatment, which increased the risk of nitrate nitrogen leaching. Long-term application of organic manure had high risk phosphorus leaching. Although the soil phosphorus concentration was mainly above 60 cm, the available phosphorus content of the 20-40 cm soil was as high as 115 mg·kg-1and 70 mg·kg-1 under M and MF treatment, leading to the high potential leaching risks. Combination of organic manure with chemical fertilizer could ensure high yield, and reduce the risk of environmental pollution of nitrogen and phosphorus.

    Analysis of Suitable Irrigation Schemes with High-Production and High-Efficiency for Spring Maize to Adapt to Climate Change in the West of Northeast China
    HUANG QiuWan,LIU ZhiJuan,YANG XiaoGuang,BAI Fan,LIU Tao,ZHANG ZhenTao,SUN Shuang,ZHAO Jin
    Scientia Agricultura Sinica. 2020, 53(21):  4470-4484.  doi:10.3864/j.issn.0578-1752.2020.21.015
    Abstract ( 339 )   HTML ( 11 )   PDF (6043KB) ( 1349 )   Save
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    【Objective】 The three provinces of Northeast China are not only an important grain production commodity in the country, but also the most sensitive areas to climate change. Thus, it is critical to clarify the suitable irrigation schemes for spring maize in arid areas of the west of Northeast China, which may be benefit on spring maize yield and its stability with higher water use efficiency under climate change. 【Method】 Based on the accumulated temperature and water deficit rate (k) during the growing season in 1981-2017, the potential planting areas of spring maize in Northeast China were divided into 10 climate zones (CZs). Five of them (k>0) in the west portion were selected as research areas. With meteorological data, experimental data, and soil data, maize yield potential was assessed by the well-calibrated and validated agricultural production system model (APSIM-Maize) in each CZ under different irrigation scenarios. According to the comprehensive analysis of both yield and water use efficiency, the suitable irrigation measures and the yield increment in different decades in each CZ were identified. 【Result】 (1) In the past 37 years, the water limitation on spring maize yield in CZ1 and CZ3 were less than that in three other CZs, with a range of 0-27% and 0-9%, respectively. Irrigation contributed little to yield increase, but it could improve the yield stability. The coefficient of yield variation reduced from 0.24 to 0.11 in CZ1, respectively, and reduced from 0.14 to 0.12 in CZ3, respectively. In CZ5, CZ7 and CZ9, more water limitation was found on maize yield, with a range of 27%-69%, 15%-35%, and 31%-51%, respectively. Moreover, irrigation also reduced the coefficients of yield variation by 0.39, 0.33 and 0.52 in the three CZs. The results indicated that irrigation could lead to a high and stable maize yield in the arid areas of Northeast China. (2) The suitable irrigation amount was 40 mm, which could produce high spring maize yield with high water use efficiency in CZ1 and CZ3. However, irrigation time had a little influence on the yield and water use efficiency of spring maize. Meanwhile, the suitable irrigation amounts for high yield and high water use efficiency were 60-80 mm in CZ5, CZ7 and CZ9, and the suitable irrigation times were from silking to 20 days after silking, jointing to 10 days after jointing and jointing to 10 days after jointing. (3) Compared with the rain-fed conditions, the yield increments varied in different CZs under suitable irrigation measures, which ranged from 33% to 86%, 24% to 46% and 50% to 77% in CZ5, CZ7 and CZ9, respectively. Lower yield increments were found in CZ1 and CZ3, with ranges of 5% to 43% and 9% to 19%, respectively. 【Conclusion】 The suitable irrigation amount for spring maize decreased with the latitude increased, and the suitable irrigation time delayed with the increased latitude. In addition, the suitable irrigation time in each CZ advanced because of warming climate. Compared with the rain-fed conditions, spring maize yield could be increased by 0-86% under suitable irrigation measures in each CZ. In particular, the yield increments in CZ5, CZ7 and CZ9 were greater than those in CZ1 and CZ3.

    HORTICULTURE
    Pedigree Analysis and Breeding Inspiration of Apple Cultivars in China
    DONG ZhiDan,SONG ShangWei,SONG ChunHui,ZHENG XianBo,JIAO Jian,WANG MiaoMiao,YAN ZhenLi,ZHANG RuiPing,BAI TuanHui
    Scientia Agricultura Sinica. 2020, 53(21):  4485-4496.  doi:10.3864/j.issn.0578-1752.2020.21.016
    Abstract ( 602 )   HTML ( 50 )   PDF (1238KB) ( 1241 )   Save
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    In order to comprehensively summarize the apple breeding achievements in the past 70 years since the founding of the People’s Republic of China, the information on the parent composition, parent selection and characteristics of 273 apple cultivars (excluding rootstock) in China from 1951 to 2019 were collected and systematically analyzed, and the pedigree diagram of these cultivars was drawn. Among 273 apple cultivars, most were obtained by hybridization (145, 53.11%), followed by bud sports (111, 40.65%), seedling selection (15, 5.50%) and mutation (2, 0.73%). According to the skin color, the cultivars with red skin were the most (240, 87.91%), the number of green and yellow skin were 19 (6.96%) and 14 (5.13%), respectively. According to the average fruit mass, the percentages of big size (≥200 g), middle size (100-200 g) and small size (≥100 g) fruits were 57.14%, 35.53% and 7.73%, respectively. The percentages of the early, middle and late maturity were 24.54%, 32.97% and 42.49%, respectively. Among the 273 apple cultivars, 83 (30.40%) were long-storage, 78 (28.57%) cold-resistant, 34 (12.45%) spur-type, 8 (2.93%) columnar and 4 (1.47%) red-flesh cultivars. 262 apple cultivars with known parents were bred from 103 parents, including 3 local, 63 abroad and 37 derived cultivars. Pedigree analysis revealed that Fuji, Golden Delicious, Delicious and Gala were backbone parents used for apple breeding, with 104, 64, 36 and 24 cultivars, respectively. Hybridization and bud mutation were the main methods to apple breeding and the combinations with both parents from different geographical area or having great botanical characteristic difference always had strong heterosis. On the basis of these, the problems in apple breeding were analyzed, and the application of biotechnology in pedigree analysis was also prospected. This paper provided a useful reference for making the breeding plan and selecting parents of apple in the future.

    Rapid Determination of RAA and GBC in Broccoli by Near Infrared Spectroscopy
    LIU QianNan,HUANG Wei,DING YunHua,WANG YaQin,HU LiPing,ZHAO XueZhi,HE HongJu,LIU GuangMin
    Scientia Agricultura Sinica. 2020, 53(21):  4497-4506.  doi:10.3864/j.issn.0578-1752.2020.21.017
    Abstract ( 277 )   HTML ( 17 )   PDF (1752KB) ( 711 )   Save
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    【Objective】Broccoli is a cruciferous vegetable with high glucosinolates content. A large number of medical and nutritional studies have shown that regular consumption of broccoli can effectively reduce the incidence of a variety of cancers. It has been confirmed that the anticancer characteristics of broccoli are mainly related to the degradation products of glucosinolates, especially the degradation products of 4-methylthiobutyl-thioglucoside (RAA) and 3-methylindolythioglucoside (GBC). The aim of this study was to establish a rapid method for the determination of anticancer glucosinolates in broccoli by near infrared spectroscopy.【Method】In this study, the content of RAA and GBC in broccoli was determined by high performance liquid chromatography (HPLC). Based on the partial least squares (PLS), the spectral files obtained by NIRS scanning and chemical analysis results were progressed by different scattering methods (SNV, detrend, and SNV + detrend) and different derivative treatment (FD and SD). After the spectral data were preprocessed, the calibration equation was obtained and the model was verified.【Result】RAA and GBC were the main glucosinolates in broccoli, accounting for more than 60% of the total content. The results of 90 broccoli samples showed that the average content of RAA was the highest, the range of change was the largest, the average content was 6.20 μmol?g-1, and the range of change was 0.66-14.54 μmol?g-1; the average content of GBC was 4.43 μmol?g-1, and the range of change was 0.25-10.79 μmol?g-1. After screening, the correlation coefficients of calibration set and prediction set of RAA prediction model with SNV + SD treatment were 0.867 and 0.912, respectively; the correlation coefficients of calibration set and prediction set of GBC prediction model using SNV + SD treatment were 0.918 and 0.960, respectively. 【Conclusion】In this study, the rapid detection model of RAA and GBC was established, which laid a foundation for the rapid detection of the nutritional quality of broccoli and the rapid detection and utilization of superior broccoli germplasm resources.

    ANIMAL SCIENCE·VETERINARY SCIENCE·RESOURCE INSECT
    A Survey on Distribution of Arsenic Contents in Feedstuffs for Livestock and Poultry in China
    ZHANG TieYing,ZHANG LiYang,LIU JunLi,LIAO ChaoYong,LÜ Lin,LIAO XiuDong,LUO XuGang
    Scientia Agricultura Sinica. 2020, 53(21):  4507-4515.  doi:10.3864/j.issn.0578-1752.2020.21.018
    Abstract ( 374 )   HTML ( 24 )   PDF (420KB) ( 703 )   Save
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    【Objective】 The aim of this survey was to study the arsenic (As) contents in various feed ingredients from different provinces in China, providing a scientific basis for controlling As contents in the feed ingredients, and even for guiding feed companies to establish a scientific process on As detection. 【Method】A total of 40 types of 4 054 feed samples were collected from 31 provinces, municipalities and regions, and then the As contents of them were measured by Ion chromatography-inductively coupled plasma mass spectrometer (IC-ICP-MS). 【Result】The results showed that the average As contents of these 40 kinds of feed ingredients ranged from 5.21 to 13 292.0 μg·kg-1, and the distribution of As contents in different species of feed ingredients was as follows: mineral ingredients (5 018.6 μg·kg-1)>animal ingredients (1 704.8 μg·kg-1)>straw ingredients (1 239.0 μg·kg-1)>pasture ingredients (500.3 μg·kg-1)>cereal by-products (329.24 μg·kg-1)>plant protein ingredients (72.99 μg·kg-1 )>cereals (38.07 μg·kg-1 ). Meanwhile, the distribution of As contents of cereals, cereal by-products and straw ingredients was as follows: corn straw>corn by-products (corn gluten meal, spray corn cortex and corn DDGS)>corn; wheat straw>wheat by-products (wheat bran, wheat DDGS and wheat middling)>wheat; rice straw>rice by-products ( rice bran and defatted rice bran)>rice>broken rice, which concerned the capacities of different parts of cereals gathering As from soil and water, root>leaf>stem>chaff>grain . The results in comparison with As contents of corn, wheat or soybean meal from different provinces (regions) are extremely significant (P<0.01) respectively, demonstrating As contents among same type of samples from different regions are significant also. Moreover, the ratios of As contents exceeding the limit standard, based on hygienical standard for feeds, have been calculated among the 40 kinds of feed ingredients. As contents in cereals, plant protein ingredients and pasture ingredients were under the limit standard. Nevertheless, As contents of only defatted rice bran in cereal by-products presented the over-limit ratio of 2.8%; As contents of only fish meal in animal ingredients showed the over-limit ratio of 5.3%; The over-limit ratio of rice straw in straw ingredients was 27.4%; Both limestone and dicalcium phosphate in mineral ingredients were with high over-limit ratios 30.8% and 60%, respectively. Over-limit ratios of As contents in different kinds of feed ingredients were as follows: dicalcium phosphate>limestone>rice straw>fish meal>defatted rice bran.【Conclusion】 The above results showed that the As contents in feed ingredients varied greatly in different kinds and regions. The As contents of those cereals relatives ingredients presented a common rule, that is, As contents of straw ingredients were highest, successively, cereals by-products and cereals. Especially, As contents of dicalcium phosphate, limestone, rice straw, fish meal and defatted rice bran were above the limit standard sometimes, which could be considered as high risk feed ingredients. Therefore, the As content in basal diets from different types and regions should be considered in the preparation of diets. It is necessary to improve As detection frequency to make sure of the As contents in animal diets under the safe limits according to the GB 13078-2017 strictly.

    Effects of Dilute Sulfuric Acid Pretreatment on Chemical Composition and Characterization Structure of Hybrid Pennisetum (Pennisetum americanum×P.purpureum) Lignocellulose
    GAO FengQin,JING YuanYuan,DE Ying,WAN QiHao,LIU YingHao,
    Scientia Agricultura Sinica. 2020, 53(21):  4516-4526.  doi:10.3864/j.issn.0578-1752.2020.21.019
    Abstract ( 316 )   HTML ( 13 )   PDF (1255KB) ( 607 )   Save
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    【Objective】 Study the effects of H2SO4 concentration, solid-liquid ratio, treatment time and temperature on lignocellulose degradation efficiency of hybrid pennisetum under dilute sulfuric acid pretreatment, analyze the mechanism of dilute sulfuric acid on lignocellulose degradation, and screen the best pretreatment process.【Method】 Four single factors: H2SO4 concentration (0.5%, 1.0%, 1.5%, 2.0%, 2.5%), solid-liquid ratio (1﹕6, 1﹕8, 1﹕10, 1﹕12, 1﹕14), time (15, 30, 45, 60, 90 min) and temperature (80, 100, 110, 120, 125℃) were tested. Five levels of each factor were selected and repeated three times to analyze the effects of single factor on solid decomposition rate, cellulose degradation rate, hemicellulose degradation rate, lignin removal rate and hydrolyzed sugar. On the basis of single factor experiment, L8 (24) orthogonal test with 4 factors and 2 levels was used to determine the main influencing factors, and SEM and XRD analysis were carried out for the hybrid pennisetum under the optimal processing conditions. 【Result】 The results of single factor test showed that the degradation rate of hemicellulose was higher than that of lignin under all factors. With the increase of H2SO4 concentration, the degradation rate of cellulose and hemicellulose increased, and the lignin removal rate decreased; the yield of glucose produced by cellulose hydrolysis increased with the increase of concentration, but the content of xylose decreased gradually. The low concentration of H2SO4 (0.5%-1.5%) promoted the degradation and digestion of solid substances of hybrid pennisetum, increased concentration (>1.5%) further did not significantly change the solid degradation. The influence of solid-liquid ratio on each index was small,and when the solid-liquid ratio increased to 1﹕10, the solid decomposition rate, hemicellulose and lignin removal reached the maximum. The pretreatment time had no obvious effect on solid decomposition rate, hemicellulose and lignin degradation, but promoted hemicellulose degradation and glucose production. Temperature has obvious effects on solid decomposition rate, degradation of cellulose, hemicellulose and lignin, and yield of hydrolyzed sugar, and 100℃ is an important critical value, and effective degradation of lignocellulose need temperature above 100℃. The orthogonal test results showed that the factors affecting hemicellulose degradation were temperature - concentration - time - solid - liquid ratio. After pretreatment with dilute sulfuric acid, the structure of lignocellulose collapsed, non-cellulose was removed, cellulose bundles were exposed (SEM), and the degree of crystallization and polymerization of cellulose was increased (XRD). 【Conclusion】 Hemicellulose was mainly degraded by dilute sulfuric acid pretreatment, but lignin was poorly degraded. Temperature is the most important factor, followed by H2SO4 concentration. Under the influence of four factors, the optimum technological conditions are as follows: concentration 1.5%, solid-liquid ratio 1﹕6, time 15 min, temperature 120℃.