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    12 January 2020, Volume 46 Issue 01
    • CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS
      Establishment of screening method for salt tolerant soybean at emergence stage and screening of tolerant germplasm
      LIU Xie-Xiang,CHANG Ru-Zhen,GUAN Rong-Xia,QIU Li-Juan
      Acta Agronomica Sinica. 2020, 46(01):  1-8.  doi:10.3724/SP.J.1006.2020.94062
      Abstract ( 692 )   HTML ( 89 )   PDF (3749KB) ( 582 )   Save
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      Salinity is an important factor affecting crop production. Screening salt tolerant soybean germplasm is of great significance for the utilization of salinized soil in major soybean production regions. In order to select salt tolerant soybean, a screening method was developed by using six soybean accessions, including Zhonghuang 35, Zhonghuang 39, Williams 82, Tiefeng 8, Peking, and NY27-38. Seeds were grown in vermiculite and treated with 0, 100, and 150 mmol L -1 NaCl solution. Seedling rate (SR), plant height (H), fresh weight of shoot and root (FWS and FWR), dry weight of shoot and root (DWS and DWR) were decreased significantly under 150 mmol L -1 NaCl treatment, with significant difference among varieties. Therefore, 150 mmol L -1 NaCl was suitable to identify salt tolerant soybean at emergence stage. The salt tolerance index (SI) based on the growth and development of seedlings and the salt tolerance coefficient (ST) were significantly correlated with the salt tolerance. The method using salt tolerance index is non-destructive and does not require planting control, which could save time and labor in salt tolerant germplasm identification. Twenty-seven soybean resources were screened, in which three were highly tolerant (grade 1) and seven tolerant (grade 2) at emergence stage. Among them, Yundou 101, Zheng 1311, Wansu 1015, and Tiefeng 8 also showed salt tolerance (grade 1) at seedling stage. In summary, an effective method for screening salt tolerant soybean at emergence stage was developed, with vermiculite as the substrate, 150 mmol L -1 NaCl as suitable treatment solution, and salt tolerance index as the indicator. Four soybean accessions were found to be salt tolerant at both emergence and seedling stages. This screening method will be useful for identification of salt tolerant soybean germplasm.

      Mapping of QTLs for leafstalk angle in soybean
      WANG Cun-Hu,LIU Dong,XU Rui-Neng,YANG Yong-Qing,LIAO Hong
      Acta Agronomica Sinica. 2020, 46(01):  9-19.  doi:10.3724/SP.J.1006.2020.94056
      Abstract ( 583 )   HTML ( 24 )   PDF (4740KB) ( 224 )   Save
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      Leafstalk angle is one of the most important elements for shoot architecture of soybean, affecting canopy architecture, photosynthetic efficiency and final grain yield. Exploring genetic basis of soybean leafstalk angle is significant to improve soybean yield. In this study, two soybean accessions BLA and SLA, contrasting in leafstalk angle, and their derived RIL population were used for high resolution genetic map construction and QTL detection for leafstalk angle, further the near-isogenic lines (NIL) were constructed to validate partial QTLs. Genetic analysis results showed that values of leafstalk angle performed serial and normal distribution which coincides with genetic characteristics of quantitative traits. Additionally, a high resolution genetic map consisting of 859 bin markers was constructed by using GBS method. The linkage map covered 2326.9 cM of genetic distance and the average distance between two markers was 2.763 cM. A total of 14 QTLs for regulating leafstalk angle were detected, with explained 6.9%-12.4% of genetic variation, and their LOD values varied from 2.58 to 4.80, and five of them were clustered together on Chromosome 12. The phenotype of the NILs for qLA12 and qLA18 revealed that leafstalk angle performed significant difference between same pair of NILs which strongly suggested that qLA12 and qLA18 are two believable QTLs. In summary, our results lay a foundation for cloning functional genes of regulating leafstalk angle and provide genetic resources for breeding elite soybean varieties with ideal shoot architecture.

      Overexpression of OsMPK17 protein enhances drought tolerance of rice
      MA Jin-Jiao,LAN Jin-Ping,ZHANG Tong,CHEN Yue,GUO Ya-Lu,LIU Yu-Qing,YAN Gao-Wei,WEI Jian,DOU Shi-Juan,YANG Ming,LI Li-Yun,LIU Guo-Zhen
      Acta Agronomica Sinica. 2020, 46(01):  20-30.  doi:10.3724/SP.J.1006.2020.92007
      Abstract ( 598 )   HTML ( 14 )   PDF (2806KB) ( 260 )   Save
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      Mitogen-activated protein kinase (MAPK) highly conserved in eukaryotes plays important roles in stress responses in plant. In this study, full-length OsMPK17 gene was cloned and fusion protein was expressed. The purified protein was used as immunogen to generate monoclonal antibody. Western blot (WB) analyses were carried out for protein samples isolated from tissues under different abiotic stresses. The expression of OsMPK17 was induced by drought stress, suggesting that the OsMPK17 protein may play a role in drought stress response. Proteins isolated from leaves treated with abscisic acid (ABA) or methylene jasminate acid (MeJA) demonstrated a decrease of OsMPK17 protein abundance, suggesting that hormones may be involved in the function of the protein. The overexpression vector of OsMPK17 protein was established and transformed into TP309 via Agrobacteria-mediated protocol. Homozygous transgenic lines for overexpression of OsMPK17 protein were obtained. In the field planting experiment, the plant height and the spike length of transgenic lines shortened and the seed setting rate decreased. At seed germination stage, under the condition of PEG-6000 treatment, the seeds of overexpressed OsMPK17 protein lines grew better and the length of root and shoot was significantly longer than those of the wild type. At seedling stage, transgenic plants showed lower water loss rate when exposed in the air. The transgenic rice with overexpressed OsMPK17 protein grew better than the wild type in the experiment with soil drought stress and re-watering then. In conclusion, the overexpressed OsMPK17 protein enhances drought tolerance of rice. This study enhances the understanding for the function of OsMPK17 protein.

      Screening of NFR1α-interactive proteins in soybean using yeast two hybrid system
      KE Dan-Xia,PENG Kun-Peng
      Acta Agronomica Sinica. 2020, 46(01):  31-39.  doi:10.3724/SP.J.1006.2020.94036
      Abstract ( 663 )   HTML ( 32 )   PDF (3098KB) ( 226 )   Save
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      Soybean is the important plant protein crop and grain-bean intercropping crop. Exploring the biological nitrogen fixation potential of soybean is of far-reaching significance to promote the sustainable development of ecological agriculture. GmNFR1α, a soybean nod factor receptor protein, is very important for nodulation, but its specific regulatory mechanism is still unclear. Soybean mRNA was used as template to amplify the kinase domain of GmNFR1α protein (GmNFR1α-pk) by RT-PCR method and the pGBKT7-GmNFR1α-pk bait plasmid was constructed. Seventy-two positive clones interacted with GmNFR1α-pk were isolated through yeast two hybrid screening of soybean nodule AD-cDNA library from the library. Among them, 12 proteins including calcium ion binding chiral protein, hemoglobin, nodulin Nod44 and other proteins interacted with GmNFR1α-pk were screened by sequencing and homology analysis. The interaction between soybean hemoglobin and bait protein was verified by re-transforming in yeast and BiFC in tobacco. Comparison of homologous proteins and phylogenetic tree analysis were also done at the same time. The important function of GmLbc2 in nodulation process was clarified by hairy root transformation technology in Lotus japonicus. The results further complement and improve the signal transduction pathway mediated by GmNFR1α, and provide new molecular evidence for the symbiotic interaction mechanism between soybean and rhizobia.

      Cloning and functional analysis of promoter of potassium transporter gene GhHAK5 in upland cotton (Gossypium hirsutum L.)
      Mao-Ni CHAO,Hai-Yan HU,Run-Hao WANG,Yu CHEN,Li-Na FU,Qing-Qing LIU,Qing-Lian WANG
      Acta Agronomica Sinica. 2020, 46(01):  40-51.  doi:10.3724/SP.J.1006.2019.94066
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      Transcriptional regulation of KUP/HAK/KT potassium transporter gene is an important mechanism of plant response to low potassium stress. Cloning and analysis of promoter of potassium transporter gene in cotton is not only helpful to understand its expression pattern and regulation mechanism, but also important to improve the potassium absorption in cotton. Potassium transporter gene GhHAK5 is a highly expressed in roots and induced by low potassium stress in upland cotton, but the function of its promoter is still unclear. In this study, the 2000 bp promoter fragment of GhHAK5 was cloned from upland cotton variety Baimian 1 by using PCR amplification, and its function was analyzed by GUS histochemical staining and induced expression analysis of GUS under low potassium in pGhHAK5 transgenic Arabidopsis thaliana. In addition to TATA-box, CAAT-box and other basic cis-acting elements, pGhHAK5 also contained a number of cis-acting elements responsive to light, stress, phytohormone and circadian. pGhHAK5 was highly consistent with pGrHAK5 in the number and location of important regulatory elements, and had five root-specific expression regulatory elements (ATAAAAT) and an ARF transcription factor binding site (TGTCNN) involved in transcription regulation under low potassium conditions. GUS histochemical staining of transgenic Arabidopsis thaliana seedlings showed that the leaf veins and vascular tissue of hypocotyl were deeply stained, and the roots were shallowly stained. For mature Arabidopsis thaliana plants, enhanced GUS staining was observed in roots, leaf veins and the vascular tissue of calyx, and weakened GUS staining was observed in stem and pod skin, suggesting that pGhHAK5-driven GUS was mainly expressed in mature roots and vascular tissue of shoots. Induced expression analysis of GUS under low potassium in pGhHAK5 transgenic Arabidopsis thaliana showed that the expression of GUS driven by pGhHAK5 was weak in young roots of Arabidopsis thaliana seedlings, and its expression was not enhanced by low potassium stress. These results suggest that pGhHAK5 might be a potassium-deficient inducible promoter mainly in mature roots. Transcriptome and quantitative real-time PCR analysis showed that GhHAK5 expression in roots was affected by developmental stages, which was consistent with the results of GUS expression driven by pGhHAK5 in Arabidopsis thaliana. These results are helpful to understand the molecular mechanism of GhHAK5 expression regulation, and provide theoretical basis for improving potassium uptake efficiency and breeding potassium efficient varieties in cotton.

      CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS
      QTL mapping for total grain anthocyanin content and 1000-kernel weight in barley recombinant inbred lines population
      YANG Xiao-Meng, LI Xia, PU Xiao-Ying, DU Juan, Muhammad Kazim Ali, YANG Jia-Zhen, ZENG Ya-Wen, YANG Tao
      Acta Agronomica Sinica. 2020, 46(01):  52-61.  doi:10.3724/SP.J.1006.2020.91024
      Abstract ( 522 )   HTML ( 13 )   PDF (1408KB) ( 186 )   Save
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      In this study, 193 recombinant inbred lines (RILs) derived from a cross between Ziguangmangluoerleng (purple barley, endemic to Yunnan, China) and Schooner (yellow barley introduced from Australia), grown at three sites of Yunnan province of China for three consecutive years (2013-2015), were used to determine total grain anthocyanin content, 1000-kernel weight and their correlations, and mapped QTLs. There was a significant negative correlation between total grain anthocyanin content and 1000-kernel weight. Twelve QTLs for total grain anthocyanin content were located on chromosomes 1H, 2H, 4H, 6H, and 7H which showed 5.06% to 23.86% of phenotypic variation. Eight QTLs for 1000-kernel weight were located on chromosomes 2H, 4H, and 7H, which explained phenotypic variation from 4.67% to 42.32%. Ten QTLs had phenotypic variation ≥10% and five QTLs ≥ 20%, while the highest phenotypic variation was 42.32%. In addition, two QTLs for total grain anthocyanin content were repeatedly detected at two sites for two years, and located on 2H Bmag0125 to GBM1309 and 7H EBmatc0016 to Bmag0206 interval, respectively, which accounted for 13.66% to 17.76%, and 13.07% to 16.43% of the phenotypic variation, respectively. Two QTLs for 1000-kernel weight were repeatedly detected at three sites for three years and located on 2H scssr03381 to scssr07759 and 7H GBM1297 to GBM1303 interval, which showed 4.67% to 14.55% and 34.51% to 42.32% of phenotypic variations, respectively, and their contribution rates of additive effects were consistent. The common major QTLs for two agronomic attributes were mainly distributed on chromosomes 2H and 7H. These results provide a basis for further fine mapping, cloning and marker-assisted breeding of beneficial genes related to total grain anthocyanin content and 1000-kernel weight.

      CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS
      Evaluation of resistance to Fusarium head blight in Thinopyrum-derived wheat lines
      ZHANG Xiao-Jun,XIAO Jin,WANG Hai-Yan,QIAO Lin-Yi,LI Xin,GUO Hui-juan,CHANG Li-Fang,ZHANG Shu-Wei,YAN Xiao-Tao,CHANG Zhi-Jian,WU Zong-Xin
      Acta Agronomica Sinica. 2020, 46(01):  62-73.  doi:10.3724/SP.J.1006.2020.91015
      Abstract ( 595 )   HTML ( 8 )   PDF (2820KB) ( 228 )   Save
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      Fusarium head blight (FHB) caused by Fusarium graminearum is one of the most destructive fungal diseases in wheat production; however, only limited sources of resistance are available in wheat. In this study, we evaluated 119 lines derived from the crosses between wheat and wheat-Thinopyrum partial amphiploids for their resistance to F. graminearum isolate F0609 over six environments during 2016 to 2018 cropping seasons using single floret inoculation method. Among the wheat-Thinopyrum lines tested, 45 were moderately or highly susceptible, with 25%-50% or >50% of the average percentage of diseased spikelets (PDS), 61 were moderately resistant (MR) with 10%-25% of the average PDS, and 13 lines were identified as resistant (R), with the average PDS less than 10%. For the FHB resistance of the 13 resistant lines, CH16387 was superior to ‘Sumai 3’ and ‘Wangshuibai’, the most widely used source of resistance to FHB, CH16371 and CH16379 were superior to ‘Wangshuibai’, and the remaining ten lines were comparable to ‘Wangshuibai’ or ‘Sumai 3’, in terms of number of infected spikelets per spike and percentage of infected spikelets. Furthermore, the average PDS in these resistant lines over the six environments showed a similar distribution, suggesting a relatively stable FHB resistance. The donor parents, wheat-alien partial amphiploids, involved in development of these resistant derivatives, included wheat-Th. intermedium partial amphiploid TAI8045 and wheat-T.ponticum partial amphiploid TAP8430. As both TAI8045 and TAP8430 were resistant, but all the wheat parents were susceptible, it was likely that the resistance to FHB in these lines identified originated from TAI8045 and TAP8430. These derivatives can serve as novel sources to enhance resistance of wheat to FHB.

      TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY
      Current status and influencing factors of broken rate in mechanical grain harvesting of maize in Southwest China
      ZHAO Bo,LI Xiao-Long,ZHOU Mao-Lin,SONG Bi,LEI En,LI Zhong,WU Ya-Wei,YUAN Ji-Chao,KONG Fan-Lei
      Acta Agronomica Sinica. 2020, 46(01):  74-83.  doi:10.3724/SP.J.1006.2020.93026
      Abstract ( 456 )   HTML ( 13 )   PDF (587KB) ( 206 )   Save
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      Maize mechanical grain harvesting is the development direction of maize production in Southwest China. High grain broken rate is the main limiting factor for the development and application of this technology. It is of great significance to clarify the current status of broken rate of mechanical grain harvesting in Southwest China, to study the main influencing factors, so as to promote the development of mechanical grain harvesting in Southwest China. Using 788 sets of sample data of grain broken rate obtained from a series of multi-point and multi-variety grain harvesting experiments conducted in Southwest China from 2017 to 2018, the present situation of mechanical grain broken rate in Southwest China was analyzed. In 2018, the same machine and operator were used to carry out multi-variety, long-span and multi-harvest experiments to investigate the changes of grain broken rate, grain moisture content and grain mechanical strength in different harvest periods, and to analyze the relationship among grain moisture content, grain mechanical strength and broken rate. The broken rate of mechanically harvested grains was 0.54%-42.72% with the average of 8.34% in Southwest China. With the delayed mechanical grain harvesting, the moisture content of grains decreased, the crushing strength of grains increased, and the broken rate of grains decreased first and then increased. The relationship between broken rate (y) and grain moisture content (x) was in accordance with the equation y = 0.0329x 2- 1.3328x + 15.529 (R 2= 0.5467 **). The broken rate was the lowest when the moisture content of grains was 20.26%. The range of moisture content of the grains with a broken rate less than 5% was 10.76%-29.76%. The relationship between broken rate (y) and crushing strength of grain facade (xfacade) and side (xside) was in accordance with the equations of y = 0.0006xfacade 2 - 0.2692xfacade + 32.7030 (R 2 = 0.3138 **) and y = 0.0021xside 2 - 0.6092xside + 46.979 (R 2 = 0.3790 **), respectively. When the crushing strength of grain facade and side was 224.33 N and 145.05 N, the broken rate was the lowest. With delaying harvest time, the change of mechanical strength caused by the decrease of grain moisture content may be the main reason affecting the change of broken rate. Breeding and selecting varieties with strong standing pole ability and quick dehydration, making the moisture content of grain below 28%, is an important measure to reduce the broken rate of mechanical grain harvesting in Southwest China.

      Interactive effects of liming and straw incorporation on yield and nitrogen uptake in a double rice cropping system
      LIAO Ping,LIU Lei,HE Yu-Xuan,TANG Gang,ZHANG Jun,ZENG Yong-Jun,WU Zi-Ming,HUANG Shan
      Acta Agronomica Sinica. 2020, 46(01):  84-92.  doi:10.3724/SP.J.1006.2020.92016
      Abstract ( 524 )   HTML ( 10 )   PDF (937KB) ( 267 )   Save
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      Soil acidification and low fertility limit crop productivity in red paddy soils. Liming and straw incorporation are effective practices to alleviate soil acidification and improve soil fertility, respectively, while their interaction is still unclear. A four-year field experiment was conducted in a double rice cropping system with red paddy soil in Jiangxi province to examine the interactive effect of liming and straw incorporation on rice yield and nitrogen (N) uptake from 2015 to 2018. Either liming or straw incorporation increased grain yield and N uptake in both early and late rice seasons. Lime application increased yield and N uptake by 10.7% and 15.5% under straw incorporation, while by 4.4% and 9.7% with straw removal in the early rice season, respectively. In contrast, liming enhanced yield and N uptake by 18.7% and 24.6% in the straw-incorporated treatments in the late rice season, respectively, whereas only by 10.5% and 5.7% in the straw-removed treatments. The effect of liming on enhancing grain yield, N uptake and soil pH for both early and late rice diminished in the present of time. Neither soil organic matter nor total N content was significantly affected by liming after the four-year experiment. Straw incorporation significantly increased soil organic matter, but had no effect on total N. Therefore, limes should be applied along with straw incorporation to simultaneously increase double rice yield, alleviate soil acidification, and improve soil fertility on acidic paddies. Besides, our results suggest that limes should be applied approximately every four years in the double rice cropping system with acidic red soil.

      Coordination of root growth and leaf senescence in cotton
      WANG Su-Fang,XUE Hui-Yun,ZHANG Zhi-Yong,TANG Ju-Xiang
      Acta Agronomica Sinica. 2020, 46(01):  93-101.  doi:10.3724/SP.J.1006.2020.94043
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      Two cotton cultivars, Baimian 1 and DP99B, were used to investigate the root growth and vigor, leaf senescence and yield in the field during 2011-2012. Baimian 1 produced higher cotton fiber yield than DP99B during two years. Baimian 1 had better leaf photosynthetic rate or performance index based on light energy absorption, higher root length density (RLD) and better root distribution, and higher root vigor than DP99B, evidenced by higher volume of bleeding sap, in which higher percentage of protein contents was contained. In 2012, DP99B had faster root growth with higher RLD at middle August and higher root vigor at late July than Baimian 1, and the total xylem sap amount of DP99B was 1.7 times that of Baimian 1. After bloom peaking, the higher density of root, more bleeding sap and slower leaf senescence showed the coordination to a great extent, confirming that leaf senescence is regulated by root growth and root vigor in later cotton growth season.

      Effects of precision leaf age fertilization on yield and nitrogen utilization of
      japonica rice
      WANG Yan,YI Jun,GAO Ji-Ping,ZHANG Li-Na,YANG Ji-Fen,ZHAO Yan-Ze,XIN Wei,ZHEN Xiao-Xi,ZHANG Wen-Zhong
      Acta Agronomica Sinica. 2020, 46(01):  102-116.  doi:10.3724/SP.J.1006.2020.92009
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      The japonica rice cultivar Jigeng 88 (14 leaves), Shennong 265 (15 leaves) and Shennong 1401 (16 leaves) with different main leaf ages were used to analyze the effects of different source-sink nitrogen fertilizer application models on agronomic traits, yield and nitrogen utilization characteristics of rice grown in the field-tube condition. Two kinds of fertilizer proportions (base fertilizer: panicle fertilizer was 6:4 and 8:2) were set under 225 kg hm -2 of nitrogen application based on the light and simple fertilization model (basal fertilizer, tillering fertilizer, panicle fertilizer). The tillering fertilizer was applied at the stage of source construction, and panicle fertilizer was applied at stage of sink formation. The precise nitrogen application combined different nitrogen fertilizer modes for tillering and panicle fertilizers with different leaf ages. Number of differentiated spikelets, effective panicles, yield, and nitrogen use efficiency, were significantly higher by using the 6:4 fertilizer proportions than by using 8:2 under all nitrogen fertilizer application models in these cultivars. Under different nitrogen fertilizer regimes, the 8 leaves of Jigeng 88 (leaf age index was 57.1%), 9 leaves of Shennong 265 (leaf age index was 60.0%), and 10 leaves of Shennong 1401 (leaf age index was 62.55%) were the best stage to apply tillering fertilizer. It means that the leaf age index about 60% is better to protect the more panicle formation. The 11 leaves of Jigeng 88 (leaf age index was 78.6%), 12 leaves of Shennong 265 (leaf age index was 80.0%), 13 leaves of Shennong 1401 (leaf age index was 81.3%) were the best stage to apply panicle fertilizer. It means that leaf age index about 80% is better to promote spikelet differentiation. The yield, nitrogen accumulation, nitrogen uptake and utilization, agronomic efficiency, and partial productivity were significantly higher in 6:4 (8, 11) of Jigeng 88, 6:4 (9, 12) of Shennong 265, 6:4 (10, 13) of Shennong 1401 than in other treatments. Therefore, the delayed leaf age of tillering nitrogen fertilizer application (leaf age index was about 60%), ahead of applied the panicle fertilizer (leaf age index was about 80%), and increasing the ratio of nitrogen fertilizer application not only significantly increase nitrogen accumulation, nitrogen absorption and utilization, nitrogen agronomic utilization rate and partial productivity but also promote number of differentiated spikelets and the percentage of effective panicle number, achieving the dual role of protecting and promoting spikelets, and high yields.

      Effect of nitrogen application on yield and rice quality of mechanical transplanting high quality late rice
      TANG Jian,TANG Chuang,GUO Bao-Wei,ZHANG Cheng-Xin,ZHANG Zhen-Zhen,WANG Ke,ZHANG Hong-Cheng,CHEN Heng,SUN Ming-Zhu
      Acta Agronomica Sinica. 2020, 46(01):  117-130.  doi:10.3724/SP.J.1006.2020.92010
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      The experiment was conducted by using four high quality late rice varieties, including Taiyou 398, Huanghuazhan, Tianyouhuazhan, and Meixiangxinzhan under four nitrogen treatments of 0, 135, 180, and 255 kg hm -2 to select the optimum nitrogen application rate for the coordination of high quality and high yield. The appropriate increase of nitrogen application improved the yield of high quality rice, which reached maximum under the nitrogen treatment of 180 kg hm -2. When the nitrogen application was 180 kg hm -2, the indicators such as the brown rice rate, milled rice rate and head milled rice rate for all varieties reached maximum except for the head milled rice rate of Huanghuazhan. As more nitrogen was gradually applied, there were growing length-width ratio, protein content and gel consistency of double-season high-quality late rice while in contrast reduction in chalky grain percentage, chalkiness degree and amylose content, which also brought about a steady drop in peak viscosity, trough viscosity, breakdown, final viscosity while a rise in setback and pasting temperature. To sum up, the appropriate increase of nitrogen application can improve the processing quality, appearance quality, cooking and nutritional quality while deteriorate the RVA characteristics. The nitrogen application of 180 kg hm -2 facilitates a better coordination between quality and yield in high quality double-season late rice under mechanical transplanting.

      Chemical compositions of cuticular waxes on stems and leaves of three legume green manure crops
      LI Yang,YAO Lu-Hua,GUO Xin,ZHAO Xiao,HUANG Lei,WANG Deng-Ke,ZHANG Xue-Feng,XIAO Qian-Lin,YANG Rui-Ji,GUO Yan-Jun
      Acta Agronomica Sinica. 2020, 46(01):  131-139.  doi:10.3724/SP.J.1006.2020.94048
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      Cuticular waxes are hydrophobic compounds covering plant surfaces and play vital roles in protecting plants from various biotic and abiotic stresses. However, less is known as related to the cuticular wax on leaves or stems of summer legume green manures. In the current study, stems and leaves from three summer legume green manure crops grown in the fields were sampled, including Crotalaria juncea, Sesbania cannabina, and Phaseolus calcaratus Roxbwere. Using gas chromatography-mass spectrometer (GC-MS), we identified most of the chemical compounds on these plant species. In total, eight classes of wax compounds were identified, including fatty acids, primary alcohols, aldehydes, alkanes, alkyl esters, diols, terpenoids and sterols. Among these compounds, fatty acids, primary alcohols, aldehydes and alkanes with serial homologs could be observed in stems and leaves of all tested plant species excepting fatty acids in leaves of C. juncea, with their weight proportions accounting for more than 60% in total wax. This suggested that alkane forming and alcohol forming pathways were two major biosynthesis pathways in these plants. In stems of S. cannabina, two compounds were identified as diols with the functional hydroxyl group located at 1,18 and 1,16 positions. Using gas chromatography with flam ionized detector (GC/FID), we quantified the total wax and wax compounds. Total wax coverage differed among three plant species and between two organs. The total stem wax coverage was the highest in C. juncea (16.33 μg cm -2), followed by S. cannabina (6.45 μg cm -2) and P. calcaratus (0.72 μg cm -2). The total wax coverage on stems of C. juncea was significantly higher than that on leaves, whereas no significant difference in total wax coverage between stems and leaves was observed in S. cannabina and P. calcaratus. The predominant wax class differed in plant species and organs. For C. juncea, alkanes were the predominant composition in stems accounting for 57.38% of total wax, whereas primary alcohols were the predominant composition in leaves accounting for 50.12%. For S. cannabina, both stems and leaves were dominated by primary alcohols, accounting for 30.12% and 71.21% of total wax, respectively. For P. calcaratus, both stems and leaves were dominated by alkanes, accounting for 40.79% and 39.27% of total wax, respectively. We further analyzed the chain length distributions of the wax classes in stems and leaves. Generally, fatty acids, primary alcohols and aldehydes were consisted of serials of even carbon number homologs, whereas alkanes were consisted of both even- and odd-carbon number homologs with odd number predominance over even number. The predominant compound in each wax class also differed between plant species and organs. The dominant fatty acids on stems and leaves in C. juncea, S. cannabina, and P. calcaratus were C30, C30 and C26, and C28, respectively; the dominant primary alcohols were C28, C30, and C28 and C32 respectively; the dominant aldehydes were C32 and C30, C30, and C30 and C28, respectively; while the dominant alkanes were C31, C29, and C31, respectively. The terpenoids identified in current study were β-amyrin, α-amyrin and lupenol. The variations of predominant wax class and wax compound between plant species and organs implied that genes involved in wax biosynthesis might also be different. These results provide basic knowledges in studying the molecular mechanisms of cuticular waxes in legume green manure crops fronting biotic and abiotic stresses.

      RESEARCH NOTES
      Identification of rice chromosome segment substitution Line Z747 with increased grain number and QTL mapping for related traits
      WANG Da-Chuan,WANG Hui,MA Fu-Ying,DU Jie,ZHANG Jia-Yu,XU Guang-Yi,HE Guang-Hua,LI Yun-Feng,LING Ying-Hua,ZHAO Fang-Ming
      Acta Agronomica Sinica. 2020, 46(01):  140-146.  doi:10.3724/SP.J.1006.2020.92022
      Abstract ( 483 )   HTML ( 8 )   PDF (1154KB) ( 214 )   Save
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      Increasing grain number per panicle is important for rice breeding for high yield. Its inheritance is very complex and controlled by many genes. Chromosome segment substitution lines can dissect complex traits controlled by many genes, and thus are ideal genetic research materials. Here, an excellent rice chromosome segment substitution line Z747 with increased grain number was identified from recipient Nipponbare and donor Xihui 18 through advanced backcrossing and inbreeding combined SSR marker-assisted selection. Z747 carried fifteen substitution segments with 4.49 Mb of average length. Compared with Nipponbare, Z747 had significantly increased spikelet number per panicle, number of primary branches, number of secondary branches, panicle length and grain length, and decreased grain width and seed setting rate. However, the seed setting rate in Z747 was still up to 81%. Furthermore, secondary F2 population from crosses between Nipponbare and Z747 was used to map QTL for related traits. A total of 46 QTLs distributed on chromosomes 1, 2, 3, 5, 6, 9, 11, and 12 were detected. Among them, 12 QTLs such as qGPP12, qPH-3-1, and qPH-3-2 etc. might be alleles of cloned genes, and the remaining 34 QTLs such as qSPP9 etc. might not be identified in the past. The spikelet number per panicle of Z747 was mainly controlled by two QTLs (qSPP3 and qSPP5) with effects of increasing spikelet number and one (qSPP9) with decreasing effects. These results are important for fine mapping and cloning of major QTL, and developing single-segment substitution lines carrying favorable QTLs.

      Genome-wide association study of seed number per silique in rapeseed (Brassica napus L.)
      SUN Cheng-Ming,CHEN Feng,CHEN Song,PENG Qi,ZHANG Wei,YI Bin,ZHANG Jie-Fu,FU Ting-Dong
      Acta Agronomica Sinica. 2020, 46(01):  147-153.  doi:10.3724/SP.J.1006.2020.94060
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      Seed number per silique (SSN) is a key component of seed yield in rapeseed, increasing SSN can improve the seed yield of plants. A collection of 496 representative rapeseed accessions was genotyped by the Illumina 60K SNP array and phenotyped for SSN in two environments. The genome-wide association study (GWAS) of SSN was performed via the MLM (Mixed linear model) and GLM (General linear model). The broad-sense heritability of SSN was 57.7%. Nine and twenty loci were detected with MLM and GLM, respectively, and all loci detected by MLM were included those by GLM. Six loci were overlapped with reported QTLs, and two of them were validated by two independent researches, and the rest 14 loci were new. We identified plausible candidate genes nearby seven loci, and the reported rapeseed SSN gene BnaC9.SMG7b was found near the locus Bn-scaff_15576_1-p74980 on C09 chromosome detected in this study. Besides, six candidates orthologous to documented Arabidopsis SSN genes, like GRDP1, SPATULA, HVA22D, and DA2, were found near our GWAS loci. The results provide an insight into the genetic basis of seed number per silique and lay a foundation for further mechanism exploration and breeding for this trait in B. napus.

Co-sponsored:
the Crop Science Society of China
the Institute of Crop Science, CAAS
China Science Publishing & Media Ltd.
Published: Science Press
Editor-in-chief: Wan Jian-min
Associate Editors-in-Chief:
Chen Xiao-ya Yang Jian-chang Zhang Xian-long Wang Jian-kang Xu Ming-liang Liu Chun-ming Wang Dao-wen Sun Chuan-qing Ding Yan-feng Jin Wei-wei Chu Cheng-cai Cheng Wei-hong
Director of the editorial department:
Cheng Wei-hong
CN 11-1809/S
ISSN 0496-3490
Post subscription code: 82-336

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  • Started in 2013
  • Covered by SCIE
  • Open access in ScienceDirect

Editor in chief: Wan Jian-min
CN 10-1112/S
ISSN 2095-5421, 2214-5141(online)
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