Table of Content

12 December 2018, Volume 44 Issue 12

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SPECIAL SECTION: GRAIN DEHYDRATION AND MECHANICAL GRAIN HARVEST OF MAIZE

Editorial: Strengthening the Research of Grain Dehydration and Lodging Characteristics to Promote the Application of Maize Mechanical Grain Harvest Technology

Shao-Kun LI,Rui-Zhi XIE,Ke-Ru WANG,Bo MING,Peng HOU

Acta Agronomica Sinica. 2018, 44(12):  1743-1746.  doi:10.3724/SP.J.1006.2018.01743

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Effects of Grain Moisture Content on Mechanical Grain Harvesting Quality of Summer Maize

Lu-Lu LI,Jun XUE,Rui-Zhi XIE,Ke-Ru WANG,Bo MING,Peng HOU,Shang GAO,Shao-Kun LI

Acta Agronomica Sinica. 2018, 44(12):  1747-1754.  doi:10.3724/SP.J.1006.2018.01747

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Broken grains, losing ears and grains always occur when maize is harvested by grain harvester, which is a hot topic. Studying grain mechanical harvesting quality and its affecting factors is of great significance for popularizing this technology, which provides a basis for finding out the best harvesting time and the direction of maize cultivar development. The experiments were conducted in Comprehensive Experiment Station of Chinese Academy of Agricultural Sciences located in Xinxiang city in 2015 and 2017. The dozens of popular cultivars grown in the Yellow-Huaihe-Haihe Rivers Plain summer maize region were harvested in different harvest times by a same grain combine harvester and a same driver. Indicators of grain moisture content, broken rate, impurity rate, grain loss rate and ear loss rate were measured to analyze their mutual relationships. With delaying harvest time, grain moisture content and impurity rate declined gradually, grain broken rate and grain loss rate decreased first and then increased, ear loss rate gradually rose. The grain moisture contents ranged from 9.68% to 41.36% in the two years. Its relationship with broken rate could be fitted by the equation y = 0.068x ²-2.743x+31.09 (R ²= 0.79 ^**, n = 140). Broken rate could be less than 5% when moisture content was 15.47%-24.78%. When moisture content was 20.05%, broken rate was the lowest. The relationship between impurity rate and moisture content could be fitted by the equation y = 0.0158e ^{0.1111 x}(R ²= 0.66 ^**, n = 140). Impurity rate decreased first and then tended to be stable with falling moisture content. Grain loss rate and moisture content could be regressed in the equation y = 0.006x ²-0.236x+3.479 (R ²= 0.42 ^**, n = 127). Grain loss rate was the lowest when moisture content was 20.37%. Ear loss rate and moisture content could be regressed in the equation y = 2578.7645/x ^2.2453 (R ²= 0.35 ^**, n = 140). Ear loss rate was more than 5% when moisture content was below 16.15%. We also found that harvesting qualities, especially broken rate, of different cultivars had significant differences while their grain moisture contents were the same. In conclusion, broken rate is the key factor that determined the quality of grain mechanical harvesting. The optimal grain moisture content interval of mechanical harvesting in Yellow-Huaihe-Haihe Rivers Plain summer maize region is 16.15%-24.78% at the standard of 5% broken rate and 5% ear loss rate. The harvesting quality would be the best when the moisture content is about 20%.

Relationship between Grain Dehydration and Meteorological Factors in the Yellow-Huai-Hai Rivers Summer Maize

Shang GAO,Bo MING,Lu-Lu LI,Rui-Zhi XIE,Jun XUE,Peng HOU,Ke-Ru WANG,Shao-Kun LI

Acta Agronomica Sinica. 2018, 44(12):  1755-1763.  doi:10.3724/SP.J.1006.2018.01755

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There is a close relationship between maize grain dehydration and meteorological factors. Clarifying main meteorological factors and their influence on grain dehydration can better predict the dynamics of grain moisture content, and the rationally arrange the time of maize grain harvesting. The study was conducted in Xinxiang, Henan province from 2015 to 2017. Four main maize varieties Jingnongke 728 (JNK728), Zhengdan 958 (ZD958), Xianyu 335 (XY335), and Nonghua 816 (NH816) currently planted in local production were selected to continuously measure the changes of maize grain moisture content. The logistic power model was used for fitting the process of grain dehydration and the removing trend method was used for analysing the results. The actual moisture content of maize grain was divided into trend moisture content, meteorological moisture content, and random error. The relationship between meteorological moisture content and meteorological factors in the Yellow-Huai-Hai Rivers area was clarified. The main meteorological factors affecting grain dehydration before and after physiological maturity of maize grain were screened out stepwise regression and path analysis methods. The meteorological moisture content of maize grain had significant or extremely significant correlation with most meteorological factors which were average temperature (x₁), average wind speed (x₅) and evaporation (x₁₁) selected before physiological maturity, and the average temperature (x₁) and the average relative humidity (x₇) selected after the physiological maturity. The evaporation most contributed before the physiological maturity, while temperature and wind speed had indirect effect through evaporation. After physiological maturity, temperature and relative humidity were mainly direct effects, and the effect of relative humidity was slightly greater than that of temperature. The removing trend method used in this study is more scientific in both theoretical and practical operations. The results are also more credible and this method is of reference value to other similar researches.

Grain Dehydration Types and Establishment of Mechanical Grain Harvesting Time for Summer Maize in the Yellow-Huai-Hai Rivers Plain

Lu-Lu LI,Bo MING,Rui-Zhi XIE,Ke-Ru WANG,Peng HOU,Shao-Kun LI

Acta Agronomica Sinica. 2018, 44(12):  1764-1773.  doi:10.3724/SP.J.1006.2018.01764

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The wheat-maize double cropping system limits the heat resources of maize ripening and dewatering, which is the key factor to restrict the development of mechanical grain harvesting in the Yellow-Huai-Hai Rivers Plain. In this paper, methods of the optimum cultivar selection and harvesting time forecast were established to provide guidance for the promotion of mechanical grain harvesting in the double cropping system of the Yellow-Huai-Hai Rivers Plain. Twenty-seven main planting cultivars were selected and divided into four types by using the two-way average method. This method based on two parameters including the accumulated temperature from pollination to physiological maturity and the grain moisture content at physiological maturity. These four types were the later maturing and higher moisture content (I), the earlier maturing and higher moisture content (II), the earlier maturing and lower moisture content (III) and the later maturing and lower moisture content (IV). When grain moisture content reduced to 28% and 25% (suitable for mechanical grain harvesting) the cultivars’ active accumulated temperatures were simulated based on measurements of vegetative growth stage and dynamic change of grain moisture. According to the accumulated temperature and the historical meteorological data, the suitable days for mechanical grain harvesting of different cultivar types were estimated by using the geostatistical analysis method based on the starting points of normal sowing dates in the Yellow-Huai-Hai Rivers Plain, thus establishing the prediction method of optimum dates for mechanical grain harvesting. The accumulated temperatures from sowing to the time reaching grain moisture of 28% and 25% were 2982°C d and 3118°C d (I), 2770°C d and 2873°C d (II), 2729°C d and 2845°C d (III), and 2860°C d and 2980°C d (IV), respectively. The time for the type III cultivar with 28% and 25% moisture content respectively was two to three days and about two days earlier than that for the type II cultivar, seven to nine days and seven to ten days earlier than that for the IV type cultivar, and thirteen to seventeen days and sixteen to seventeen days earlier than that for the type I cultivar. All types of cultivar needed six to eight days to reduce grain moisture from 28% to 25%. Under the current maize cropping pattern and the sowing date of following wheat, all maize cultivars could be planted for mechanical grain harvesting in southern Henan and northern Anhui provinces in the southern Yellow-Huai-Hai Rivers Plain, while no cultivars could be used in the northern Yellow-Huai-Hai Rivers Plain, Guanzhong Area, and Shandong Peninsula where the mechanical grain harvesting of summer maize should be realized by selecting cultivar with the shorter maturing date and the rapid dehydration characteristic. In this study, the method to predict the dynamic change of grain moisture content and the optimum time of mechanical grain harvesting was established by the accumulated temperature. This method provides a feasible technical means for rationally distributing the grain harvesting cultivars and determining the suitable harvesting time.

Effect of Lodging on Maize Grain Losing and Harvest Efficiency in Mechanical Grain Harvest

Jun XUE,Lu-Lu LI,Rui-Zhi XIE,Ke-Ru WANG,Peng HOU,Bo MING,Wan-Xu ZHANG,Guo-Qiang ZHANG,Shang GAO,Shi-Jie BAI,Zhen-Dong CHU,Shao-Kun LI

Acta Agronomica Sinica. 2018, 44(12):  1774-1781.  doi:10.3724/SP.J.1006.2018.01774

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Clarifying the effect of lodging on maize grain loss and harvest efficiency is important to propose adaptable measures developing maize grain harvesting technology in China. A number of sample data of field natural lodging rate, ear loss rate and kernel loss rate were obtained from experiments and demonstrations of maize grain harvesting. The lodging was also implemented by pushing down the maize plants artificially to analyze the quantitative relationship of lodging rate with grain loss and harvest efficiency in mechanical grain harvest. All of lodging rate, ear loss rate and kernel loss rate were higher in the Yellow-Huaihe- Haihe Rivers Plain summer maize region than in North and Northwest spring maize regions. Under natural lodging conditions, the ear loss was a major part of grain yield loss, which increased by 0.15% when lodging rate increased each 1%. As lodging rate increased each 1%, ear loss increased by 0.12% in spring maize region and by 0.15% in summer maize region. There were an exponentially increasing relationship for using whole feed type combine harvester and a linear increasing relationship for using half feed type combine harvester between lodging rate and ear loss rate, behaving a greater influence of lodging in Yellow- Huaihe-Haihe Rivers Plain summer region. Under lodging control conditions, the ear loss increased by 0.59% with each 1% increase in lodging rate, and the kernel loss was significantly and negatively correlated with lodging rate. This can be explained that more lodging plants have less ears entering the combine harvester and decreasing kernel loss rate. The harvest speed decreased exponentially with increasing lodging rate. Lowering the harvester header decreased ear loss rate but reduced the harvest speed. Common methods to prevent lodging and reduce grain loss should be breeding maize cultivars with lodging resistance, constructing high-quality maize populations and harvesting at optimal time.

Changes of Maize Lodging after Physiological Maturity and Its Influencing Factors

Jun XUE,Qun WANG,Lu-Lu LI,Wan-Xu ZHANG,Rui-Zhi XIE,Ke-Ru WANG,Bo MING,Peng HOU,Shao-Kun LI

Acta Agronomica Sinica. 2018, 44(12):  1782-1792.  doi:10.3724/SP.J.1006.2018.01782

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In view of the lodging problem during grain dehydration after physiological maturity in maize mechanical grain harvest, multi-sites experiments were conducted to investigate the lodging type and law and their influencing factors in summer maize and spring maize after physiological maturity. The increase of stalk lodging rate was the major reason for total lodging rate increase after physiological maturity. The stalk lodging rate increased as breaking force decreased. The stalk lodging rate was more than 5% when breaking force decreased to 14.3 N. All of height of gravity center, rind penetration strength (RPS) of the third internode, crushing strength (CS) of the fourth internode, and bending strength (BS) of the fifth internode gradually decreased after physiological maturity. Both dry weight per unit length (DWUL) and moisture content of the basal internode also gradually decreased. Stalk breaking force was significantly positively correlated with RPS, CS, BS, DWUL, and moisture content of the basal internode. RPS, CS, BS were significantly positively correlated with DWUL and moisture content. This study showed that natural senescence of maize after physiological maturity decreases the dry matter and moisture content, resulting in the decrease of stalk mechanical strength, and the increase of stalk lodging. The ability of stalk continuous standing after physiological maturity should be used as one of the important indices to measure which maize cultivar is fit for mechanical grain harvest. Harvesting at optimal time could prevent lodging after physiological maturity and reduce grain loss in mechanical grain harvest.

CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Cloning and Characterization of Brassinazole-resistant (BnaBZR1 and BnaBES1) CDS from Brassica napus L.

Tao FENG,Chun-Yun GUAN

Acta Agronomica Sinica. 2018, 44(12):  1793-1801.  doi:10.3724/SP.J.1006.2018.01793

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Brassinazole-resistant (BZR) is a key transcription factor in brassinosteroid signaling pathway of plants, containing brassinazole-resistant 1 (BZR1) and brassinazole-resistant 2 (BES1). In this study, three novel BZR1 coding sequences (CDSs) were isolated from cDNA of Brassica napus L. cv. Xiangyou 15 leaves, which were mapped on the chromosomes A07, A06, and A06, and designated as BnaBZR1_A07, BnaBES1_A06F, and BnaBES1_A06R, respectively. These three BnaBZR CDSs were 996, 993, and 996 bp in length and encoded predicted proteins with 331, 330, and 331 amino acid residues, respectively. BnaBZR proteins were predicted to be located on the cell nucleus and have a typical plant BZR/BES conserved domain. Multiple sequence alignments and phylogenetic analysis showed that the deduced amino acid sequences of BnaBZR were highly homologous to previously reported BZR/BES of Brassica oleracea, Arabidopsis thalian, and Eruca sativa. And the similarity of BZR1 or BES1 among different related species was higher than the similarity between BZR1 and BES1 in the same species or related species, indicating that BZR1 and BES1 differentiation is an early evolutionary event. The expression patterns of BnaBZR1_A07, BnaBES1_A06F, and BnaBES1_A06R in Xiangyou 15 were similar, whit high expression level at the seedling stage and flowering stage, while slightly lower level at the stage of bolting and podgrain ripening. The expression level of BnaBZR in the aerial parts such as leaves, stems, flowers and pods was higher than that in underground parts.

Functional Analysis of Hypocotyl Phototropism Modulated by RPT2-Interacting Protein RIP1 in Arabidopsis thaliana L.

Xiang ZHAO,Zi-Yi ZHU,Xiao-Nan WANG,Shi-Chao MU,Xiao ZHANG

Acta Agronomica Sinica. 2018, 44(12):  1802-1808.  doi:10.3724/SP.J.1006.2018.01802

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The rpt2-2 single mutant lost phototropism, but phot1 rpt2-2 double mutant shows phototropic response, indicating that PHOT1 has a function in inhibiting hypocotyl phototropism, and RPT2 maybe play vital role in these prosses. Here, we used RPT2 as bait protein to screen yeast library and successfully obtained six proteins interacted with RPT2 including JAC1 and PHOT1. Yeast hybridization verified that four of these proteins could interact with RPT2. Phenotypic analysis of two mutants of gene RIP1 showed that the single mutant rip1-1 and rip1-2 had normal phototropism in response to high blue light, but rpt2-2 rip1-1 and rpt2-2 rip1-2 double mutant were defective in phototropism, similar with the phot1 rpt2-2 double mutant. These results suggested that this protein may modulate PHOT1-mediated high blue light inhibitory response. Functional analysis of this protein will be helpful to promote the discovery of the mechanism of phot1-mediated inhibitory response.

Analysis of SNP and Allele-specific Expression in Transcriptome of Sorghum bicolor × Sorghum sudanense and Their Parents

Jing DONG,Xiao-Ping LU,Kun-Ming ZHANG,Chun-Lei XUE,Rui-Xia ZHANG

Acta Agronomica Sinica. 2018, 44(12):  1809-1817.  doi:10.3724/SP.J.1006.2018.01809

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Taking root, stem and leaf tissues of S. sudanense hybrids and their parents as test materials, Illumina Hiseq 2000 was used to analyze the transcriptome to explore the relationship between single nucleotide variation and heterosis in the hybrids of Sorghum bicolor × S. sudanense and their parents. About 58 000 SNP loci were detected from the sequencing samples with an average length of 58 122 160 bp. The number of genic SNP was significantly more than that of intergenic SNP. The frequency of SNP was 1/741 bp, and the conversion ratio of the average conversion was 1.00:1.53. Among all the types of variation, C/T and G/A had the highest frequency. After screening, 198 (21%) extremely significant biased alleles were expressed in bias SNP, and 65% of them were biased towards paternal white shell S. sudanense, and many of the transcriptional copies with high level gene expression in the white shell S. sudanense were also expressed in the Sorghum bicolorss × S. sudanense hybrid. The two parental alleles with 79%, 78%, and 82% transcripts showed a stable level of expression in the three tissues. It is suggested that the trans-acting may affect the specific expression of the allele more than the cis-acting. Six highly-biased SNP-unigene alleles were selected for qRT-PCR validation. The differential gene expression pattern of these genes was consistent with that of RNA-Seq analysis. Illumina sequencing technology was used to study allelic expression in this study, provides a basis for heterosis analysis of Sorghum bicolor × S. sudanense and also a theoretical reference for related studies of other forage crops.

Characterization and Regulatory Roles in Thermotolerance of Wheat Heat Shock Transcription Factor Gene TaHsfA2e

Yu-Jie ZHANG,Yuan-Yuan ZHANG,Hua-Ning ZHANG,Ning QIN,Guo-Liang LI,Xiu-Lin GUO

Acta Agronomica Sinica. 2018, 44(12):  1818-1828.  doi:10.3724/SP.J.1006.2018.01818

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As key regulatory genes in the signal pathway responsive to heat stress, plant heat shock transcription factors (Hsfs) can enhance plant thermotolerances by triggering hsp or other relative genes to express. Plant Hsfs belong to multi-genes family, the members are different among varieties. Based on the phylogenetic tree of Hsf proteins from wheat (Triticum aestivum), rice (Oryza sativa) and Arabidopsis, we isolated the TaHsfA2e (GenBank accession number MG700614) from wheat young leaves treated with 37°C for 1.5 h using homologous cloning methods. Sequence analysis showed that the coding sequence (CDS) of TaHsfA2e is 1026 bp in length and encodes 341 amino acid residues. The TaHsfA2e protein was predicted to contain a DNA-binding domain (DBD), a nuclear localization signal (NLS) of KRRRP peptide, a nuclear export signal (NES) of LENLAMNI peptide and an aromatic, large hydrophobic and acidic amino residues (AHA) of CCFWEELLSE peptide, and localized in the nuclei under normal growth conditions. TaHsfA2e shared 96%, 94%, and 94% identities with HsfA6f and HsfA2d from wheat and HsfA2d from Aegilops tauschii, respectively. TaHsfA2e was lowly expressed in majority of tissues and organs but highly expressed in mature seeds of wheat, and the gene expression in leaf was up-regulated by heat shock at 37°C, with the peak value at 60 min after treatment, but down-regulated by salicylic acid or H₂O₂. TaHsfA2e could be induced by Gal in yeast (Saccharomyces cerevisiae), and yeast overexpressing pYES2-TaHsfA2e showed stronger growth potential than the controls expressing pYES2 after heat shock at 50 °C for 45 min, though all of the yeast growth potential were also decreased after treatment. Both of basal and acquired thermotolerances of transgenic Arabidopsis plants that overexpressed TaHsfA2e were improved, and the expressions of Hsp genes were up-regulated to different degrees. These results are essential for deep understanding biological functions and regulatory mechanism of subclass A2 Hsf members in plants.

Spatio-temporal Expression of Bt Protein and Stem Borer Resistance of Transgenic Early Japonica Rice with cry1C* or cry2A* Gene

Rong-Tian LI,Xin-Yu WANG,Chong-Bing TIAN,Qing ZHOU,Chang-Hua LIU

Acta Agronomica Sinica. 2018, 44(12):  1829-1836.  doi:10.3724/SP.J.1006.2018.01829

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The early japonica rice Kongyu 131 (Oryza sativa) was transformed with cry1C* or cry2A* gene driven by ubi promoter using Agrobacterium tumefaciens mediated method to create the transgenic early japonica rice Kongyu 131 (cry1C*) and Kongyu 131 (cry2A*). The experiments were conducted by transplanting the different lines of Kongyu 131 (cry1C*) and Kongyu 131 (cry2A*) from independent transformation events in the field to detect Bt protein content (BPC) of organs of the transgenic rice at different growth stages with enzyme-linked immune sorbent assay (ELISA) and resistance to rice striped stem borer as evidenced by insect feeding bioassays. The BPC of cry1C* gene was always lower than that of cry2A* in early japonica rice. There was a difference in BPC at different growth stages of transgenic rice, displaying tillering stage < heading stage < filling stage in leaf blade or sheath-stem and heading stage > filling stage > maturity in young panicle or brown rice. BPC of organs of transgenic rice was different at every stage, the order of BPC from high to low was leaf blade and sheath-stem at tillering stage, leaf blade, young panicle and sheath-stem at heading stage, leaf blade, sheath-stem, young panicle and brown rice at filling stage and maturity. There were some obvious differences in BPC of leaf blade, sheath-stem and young panicle at heading stage or brown rice at maturity and in borer-resistant property among transgenic lines with cry1C* or cry2A*. Correlations between BPC of each organ at heading stage and borer-resistant property or BPC of brown rice were not found in transgenic rice lines with cry1C* or cry2A*. The BPC increased in vegetative organs while descended in reproductive organs in the process of growth and development, and BPC of vegetative organs was usually higher than BPC of reproductive organs in both of Kongyu 131 (cry1C*) and Kongyu 131 (cry2A*). All transgenic early japonica rice showed effective resistance to stem borer in the experiment, though there was significant difference in BPC either between cry1C* and cry2A* genes or among transgenic rice lines.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Morpho-physiological Responses of Cotton Shoot Apex to the Chemical Topping with Fortified Mepiquat Chloride

Jing AN,Fang LI,Chun-Jiang ZHOU,Xiao-Li TIAN,Zhao-Hu LI

Acta Agronomica Sinica. 2018, 44(12):  1837-1843.  doi:10.3724/SP.J.1006.2018.01837

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The plant growth regulator mepiquat chloride (1,1-dimethyl piperidinium chloride, DPC) has been successfully and worldwide used in cotton production. Fortified mepiquat chloride is a type of aqueous formulation containing 25% DPC (referred to DPC ⁺ hereafter), which can slightly damage young tissues of epidermis. DPC ⁺ has shown potential in cotton chemical topping in China, and may replace the conventional manual topping in future. In order to investigate the mechanism of cotton chemical topping with DPC ⁺, this field study was conducted in 2015. DPC ⁺ (1125 mL ha ^-1) was applied after peak blooming stage on 24 July, with water as a control (CK). DPC ⁺ application significantly decreased plant height and reduced the nodes above the last white flower (NAWF) as compared with CK. After three days of DPC ⁺ treatment, cotton shoot apical meristem (SAM) became flatter than CK, and the ratio of height/length of SAM was significantly less than that of CK. With respect to redox status at shoot apex, O₂ ^-production rate, H₂O₂ generation and MDA content were significantly increased at six hours after DPC ⁺ application. In addition, the expression of GhSPL3 (a SPL transcription factor, which might play an important role in bud differentiation, the transition of growth phase and flower formation), GhV1 (a B3-domain containing transcription factor, which potentially involved in floral initiation), and GhREV3 (a class III homeodomain-leucine zipper transcription factors, which has key roles in meristem and organ development) were down-regulated by DPC ⁺ also at six hours after application. In conclusion, DPC ⁺ application during later flowering period can implement cotton chemical topping by inducing short-time oxidative stress at cotton apex, down-regulating genes involved in SAM development, flower bud differentiation, and reducing cotton shoot growth.

Leaf-age-model Parameters and Characteristics of High-yield Cultivars of Machine-transplanted Double Cropping Rice

Wei-Sheng LYU,Yong-Jun ZENG,Qing-Hua SHI,Xiao-Hua PAN,Shan HUANG,Qing-Yin SHANG,Xue-Ming TAN,Mu-Ying LI,Shui-Xiu HU,Yan-Hua ZENG

Acta Agronomica Sinica. 2018, 44(12):  1844-1857.  doi:10.3724/SP.J.1006.2018.01844

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The aim of this study was to provide references for the breeding and precise quantitative cultivation of high-yielding cultivars of machine-transplanted double cropping rice. Therefore a two-year field experiment was conducted with 19 early rice cultivars and 20 late rice cultivars to determine the leaf-age-model parameters and characteristics of high-yielding cultivars of machine-transplanted double cropping rice by using clustering and variance analysis methods in double-cropping rice areas (Shanggao of Jiangxi) in the middle reaches of the Yangtze River. The average total number of leaves (N) in the main stem of the early rice was 10.7 to 12.2, the number of leaves varied from 10 to 13, the average number of internodes (n) was four and the stage of tiller equal panicle was N-n+1. For machine-transplanted late rice, N was ranged from 14.4 to 15.2, the number of leaves varied from 14 to 16, n was five, and the stage of tiller equal panicle was N-n. Machine-transplanted double cropping rice with high-yield ability had the basic characteristics of medium tillering ability, greater grain-leaf ratio, higher panicle-bearing tiller rate, ear size, total spikelets, daily production, biomass accumulation per stem and leaf area index (LAI) as well as higher leaf area per stem in mid and latter stages. While there were some differences in population quality between early rice and late rice. For high-yielding cultivars of machine-transplanted early rice, the growth duration, daily yield, tillering ability, grains per spike and 1000-grain weight were 110-113 d, 75-79 kg ha ^-1 d ^-1, 2.6-3.4 spikes per plant, 115-135 and 26-28 g, respectively. The corresponding value of machine-transplanted late rice were 115-120 d, 78-82 kg ha ^-1 d ^-1, 4.2-4.8 spikes per plant, 130-150 and 24-27 g, respectively.

Effects of Split Application of Nitrogen Fertilizer on Yield, Quality and Nitrogen Use Efficiency of Sweet Potato

Jian-Gang AN,Fu JING,Yi DING,Yi XIAO,Hao-Hao SHANG,Hong-Li LI,Xiao-Lu YANG,Dao-Bin TANG,Ji-Chun WANG

Acta Agronomica Sinica. 2018, 44(12):  1858-1866.  doi:10.3724/SP.J.1006.2018.01858

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To explore the optimal split nitrogen fertilizer application methods for high yield and quality sweet potato production in intercropping, we conducted a field experiment using two sweet potato cultivars Yuzi 7 and Wanshu 10 with single N application, 2-split and 3-split N application, and measured the yield, quality, and nitrogen use efficiency in monocropping and interplanting in 2015-2016. The yield, single storage root weight, soluble protein content, soluble sugar content of storage root, apparent nitrogen use efficiency and partial nitrogen productivity were significantly increased in the two tested cultivars under 2-split and 3-split N application in monocropping and interplanting. Under interplanting, commodity rate was not significantly different in the two cultivars among the three N application treatments, however, the highest commodity rate was obtained under 3-split N application in monocropping. The highest content of β-carotene in the storage root was obtained when 3-split N application was used in Wanshu 10, and the highest content of anthocyanin in the storage root was obtained when 2-split N application was used in Yuzi 7, but the highest starch content of storage root was obtained when non-split N application was used in the two cultivars. All of the quality traits except soluble protein content of storage root, and yield and nitrogen use efficiency reduced in intercropping, but these traits were equal or better in 2 or 3-split N application when compared to those in monocropping. In conclusion, non-split N application could be used to increase the starch content of storage root, and 2 or 3-split N application could be used to increase other quality traits, yield and nitrogen efficiency of sweet potato.

Effects of Light Intensity on Photosynthetic Characteristics and Assimilates of Soybean Leaf

Ya-Jiao CHENG,Yuan-Fang FAN,Jun-Xu CHEN,Zhong-Lin WANG,Ting-Ting TAN,Jia-Feng LI,Sheng-Lan LI,Feng YANG,Wen-Yu YANG

Acta Agronomica Sinica. 2018, 44(12):  1867-1874.  doi:10.3724/SP.J.1006.2018.01867

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Light intensity plays a significant role in determining the growth and seed yield of crops under the sheltering of intercropping systems. By setting different light intensities, the photosynthetic characteristics, assimilate metabolism and the diurnal variation of chloroplast ultrastructure in leaf of different soybean cultivars to clarify the effect of light intensity on the structure of soybean leaf and the accumulation of carbohydrate, in order to provide a theoretical basis for improving soybean yield and quality. A pot experiment was carried out with three light intensities treatments, including CK (normal light, shading 0), A1 (black shading net, shading 10%) and A2 (two black shading nets, shading 36%) of two soybean cultivars (shade-resistant cultivar Nandou-12 and shade susceptible cultivar Guixia-3). With increased shading, net photosynthetic rate, stomatal conductance, transpiration rate and biomass decreased while intercellular carbon dioxide concentration and chlorophyll b increased in all treatments. There was a significant difference in the diurnal variation of sucrose and starch contents in soybean leaf under the same treatment. The diurnal variation of sucrose content in soybean leaf showed a bimodal curve with the peaks at 16:00 and next day 6:00 respectively under CK and A1 treatment. Under A2 treatment, the highest diurnal sucrose content was 32.80 μg g ^-1 in Nandou 12 and showed a unimodal changing trend with the peak at 16:00. The diurnal variation of starch content showed a single-peak curve and the highest value appeared at 21:00. Compared with the shade sensitive cultivar, the shade-tolerant soybean had greater diurnal variation of sucrose content and starch content under A2 treatment. The chloroplast structure of soybean leaf was intact and unbroken under the low light treatment. The diurnal variation of the cross-sectional area ratio of starch grain to chloroplast in the same cultivar changed significantly under the same treatment, showing a trend of decreasing after increasing. The changing rate was greater in shade-tolerant cultivar than in sensitive cultivar, and the maximum value appeared at 21:00. Therefore, biomass accumulation of soybean leaves and photosynthesis decreased with increasing shading. However, shade-tolerant cultivar maintained a good photosynthesis by adjusting the diurnal variation of photosynthetic organ structure, thus better adapting to the moderate shading condition.

RESEARCH NOTES

Genetic Mapping of Bruchid Resistance Gene in Mungbean V1128

Chang-You LIU,Qiu-Zhu SU,Bao-Jie FAN,Zhi-Min CAO,Zhi-Xiao ZHANG,Jing WU,Xu-Zhen CHENG,Jing TIAN

Acta Agronomica Sinica. 2018, 44(12):  1875-1881.  doi:10.3724/SP.J.1006.2018.01875

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It is an urgent research topic to map the bruchid resistance gene and to carry out bruchid resistance breeding using molecular marker-assisted method in mungbean. This study was carried out to identify a F₂ isolated group formed by the hybrid of a bruchid-resistant cultivar “V1128” and a bruchid-susceptible cultivar “Jilyu 7”, and to analyze the genetic regularity of V1128 in resistance to bruchids. The bulked segregant analysis (BSA) method was used for screening the polymorphic markers. Genetic linkage map construction and quantitative trait locus (QTL) mapping were conducted using software QTL IciMapping 4.0. The results showed that the bruchid resistance of V1128 was controlled by a dominant gene with main effect. According to previous naming rules, the bruchid resistance gene of V1128 was temporarily named as “Br3”. When we treated bruchid-resistance as a quality trait, Br3 was used as a marker for linkage map construction and was positioned between the markers DMB158 and VRBR-SSR033 (VRID5, VRBR-SSR032, and VRBR-SSR033 are located at the same map position). The genetic distances of Br3 away from the two markers were 4.4 cM and 5.8 cM, respectively. Br3 was positioned on chromosome 5 in the physical range of about 288 kb. By using the inclusive composite interval mapping (ICIM) to locate the seed damage rate, a main QTL locus with LOD score of 38.04 was identified in the marker intervals from DMB158 to VRBR-SSR033, contributing 71.64% of the observed phenotypic variation. The allele of male parent V1128 had a significant effect on reducing the rate of seed damage. The results can provide useful information for the molecular marker-assisted breeding of mungbean, and the fine localization and cloning of Br3.

Cloning of RuBisCo Subunits Genes rbcL and rbcS from Winter Rapeseed (Brassica rapa) and Their Expression under Drought Stress

Chao MI,Yan-Ning ZHAO,Zi-Gang LIU,Qi-Xian CHEN,Wan-Cang SUN,Yan FANG,Xue-Cai LI,Jun-Yan WU

Acta Agronomica Sinica. 2018, 44(12):  1882-1890.  doi:10.3724/SP.J.1006.2018.01882

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In this study, we used the two-dimensional gel electrophoresis (2D-DIGE) technology combined with the liquid chromatography-mass spectrometry (LC-MS) technology to filtrate the differential protein small subunit of RuBisCo which was related to photosynthesis in winter rapeseed (Brassica rapa) under drought stress. According to the published Brassica rapa RuBisCo subunit conserved sequences of rbcL and rbcS, we designed the primers and used the reverse transcription-polymerase chain reaction (RT-PCR) technology to amplify the cDNA sequence in Longyou 7. We obtained the open reading frame (ORF) of the RuBisCo subunit rbcL and rbcS, which had the length 1095 bp and 549 bp, and encoded the proteins contains 364 and 181 amino acids, respectively. The results of bioinformatics analysis showed that compare with Brassica rapa subsp. chinensis and Brassica rapa, the protein homology of rbcL and in Longyou 7 was above 99%, with the conserved domain sequence belonging to RuBisCo large superfamily. The theoretical relative molecular mass and isoelectric point of rbcL were 40.29 kDa and 6.70, respectively. And the instability index was -41.67 (II> 40 was considered as unstable protein), showing that it was an unstable protein. The aliphatic index was 83.63 and the grand average of hydropathicity was 0.232, which indicated that it was a hydrophilic protein. The secondary structure included 38.74% alpha helix, 10.99% extended strand and 50.27% random coil. And the tertiary structure contained five differential activity pockets. The protein homology of rbcS and Brassica oleracea in Longyou 7 was 99%, that conserved domain sequence was contained the rbcS superfamily and the RuBisCo Small like superfamily, which theoretical relative molecular mass and isoelectric point were 20.32 kDa and 8.23, respectively. The instability index was 33.66, showing that was a stable protein, and the aliphatic index was 74.86, the grand average of hydropathicity was -0.142, showing a hydrophilic protein. The secondary structure included 16.02% alpha helix, 28.37% extended strand and 55.25% random coil. And the tertiary structure contained four differential activity pockets. Real-time quantitative and semi-quantitative results showed that, the expression of rbcL and rbcS in winter rapeseed leaves under drought stress was down-regulated, which was the reason of decreasing photosynthesis. In addition, the decreased net photosynthesis rate (P_n) in winter rapeseed leaves was related to the inhibited RuBPCase expression and decreased RuBPCase activity, and the non-stomatal limitation was the main factor of declined P_n.