Table of Content

12 April 2016, Volume 42 Issue 04

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Cloning and Functional Analysis of a WRKY28-like Gene in Soybean

WANG Ting-Ting,CONG Ya-Hui,LIU Ju-Ge,WANG Ning,SHUAI Qin,LI Yan,GAI Jun-Yi

Acta Agron Sin. 2016, 42(04):  469-481.  doi:10.3724/SP.J.1006.2016.00469

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WRKY transcription factors play important roles in regulating plant growth and development, andparticipate in plant response to abiotic and biotic stresses.Arabidopsis WRKY28 is an essential transcription factor for plant response to necrotrophic pathogen and abiotic stress. To explore the function of the homologues gene of AtWRKY28 in soybean, we cloned GmWRKY28-like (Glyma.14G028900) and performed bioinformatics analysis. Its sub-cellular localization and tissue expression patternswere further investigated. We also analyzed the expression levels of GmWRKY28-like under ABA, PEG and NaCl stress treatments. Our results showed that the coding DNA sequence (CDS) of GmWRKY28-like gene is 1008 bp in length, encoding 335 amino acids. GmWRKY28-like contains a conserved WRKY domainwith22 serine, one threonine and two tyrosine, without any transmembrane domain or signal peptide. Phylogenetic analysis showed that the WRKY28 from Phaseolus vulgariswas most similar to GmWRKY28-like. GmWRKY28-like was verified to be located in the nucleus. This gene expressed at low levels in root and seed while high levels in true leaf, flower and shoot apical meristem. The 1500 bp upstream region of GmWRKY28-like contains a variety of cis-elements, such as MBS, W box, ABRE, and box-W1, which are involved in the response to biotic and abiotic stresses, andits expression was induced by ABA, PEG and NaCl treatments.In addition, overexpressing GmWRKY28-like in Arabidopsis thaliana enhanced plant tolerance to NaCl.This study would provide reference basis to further study the functions of GmWRKY28-like in soybean tolerance to abiotic stresses.

Identification of Heterotic Loci for Yield and Ear Traits Using CSSL Test Population in Maize

PENG Qian,XUE Ya-Dong,ZHANG Xiang-Ge,LI Hui-Min,SUN Gao-Yang,LI Wei-Hua,XIE Hui-Ling,TANG Ji-Hua

Acta Agron Sin. 2016, 42(04):  482-491.  doi:10.3724/SP.J.1006.2016.00482

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Heterosis plays an important role in enhancingcrop yield and quality.Dissecting the genetic basis of heterosis can promote hybrid maize selection, however that is unclear up to now. In this study, a set of chromosome segment substitution lines (CSSLs) population,which was constructed using the inbred line lx9801 as the receptor parent and the inbred line Chang7-2 as the donor parent, was crossed with the inbred line T7296 to construct the corresponding test population. The test population was used to identify the heterotic loci (HL) for grain yield and ear traits in maize,which showed significant difference inheterosisbetween the corresponding chromosomal region of the inbred line Chang7-2 and lx9801as well as the test inbred line T7296. A total of 64HL were identified for gain yield and ear traits, and among them 23 HL were identified at the two environments simultaneously, including 4 HL for ear length, 4 HL for ear width, 4 HL for row number, 7 HL for kernels per row, and 4HL for grain yield. Additionally, the HL for both grain yield and its components simultaneously were found on many chromosomal regions.This study could offer a basic material for thoroughly dissecting the genetic basis of heterosis for grain yield and its components in maize.

Exploration and Transferability Evaluation of EST-SSRs in Quinoa

ZHANG Ti-Fu,QI Wi-Cong,GU Min-Feng,ZHANG Xiao-Lin,LI Tan,ZHAO Han

Acta Agron Sin. 2016, 42(04):  492-500.  doi:10.3724/SP.J.1006.2016.00492

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Quinoa draws more and more attentions from people, since quinoa seed as grain has comprehensive nutrients.But the fundamental research on quinoa just starts and remains in a moderated level. Simple sequence repeat (SSR) development in quinoa will enhance the resource for its genetic analysis. Here,the available RNA based sequencing (RNA-Seq) and expressed sequence tag (EST) data of quinoa deposited in the National Center for Biotechnology Information (NCBI) were engaged in EST-SSR development.Totally,1862 non-mononucleotide EST-SSRswere identified. Among the EST-SSRs, the dinucleotide type was the most abundant (38.3%), and the hexanucleotidewas the minimal(11.7%). The amount of the EST-SSR showed the declined trend along with the increase in its motif nucleotide length. Among 119 EST-SSR primersrandomly chosen for validation,66(55.9%) primers could give clearamplification bandsand 39 showed polymorphismsinfour quinoa accessions.Further analysis showed that the polymorphisms of EST-SSRs had no significant correlation with their motif nucleotide length. In addition, t-test demonstrated that the significant difference of EST-SSRpolymorphismswas not occurredbetween quinoa accessions and otherChenopodiaceae germplasm. These results indicating EST-SSRs developed in quinoa could be transferable in Chenopodiaceous genus and applied in genetic relationship analysis.

Isolation and Characterization of a Na⁺/H⁺Antiporter Gene from Sugarcane

LIU Feng**,SU Wei-Hua**,HUANG Long,XIAO Xin-Huan,HUANG Ning,LING Hui,SU Ya-Chun,ZHANG Hua,QUE You-Xiong

Acta Agron Sin. 2016, 42(04):  501-512.  doi:10.3724/SP.J.1006.2016.00501

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Salt overly sensitive 1(SOS1) gene, encoding a Na⁺/H⁺antiport protein, plays an important role in biological processes of plants against salt stress. Using a SOS1 mRNA sequence from Triticum aestivum (KJ563230) as the probe, the homologous ESTs of sugarcanewere obtainedfrom NCBI database. A sugarcane cDNA sequence of SOS1 gene was cloned by in silicocloning combined with RT-PCR,and named as ScSOS1 (GenBank accession number: KT003285). The bioinformatics analysis showed that ScSOS1 has a length of 1403bp witha complete open reading frame (ORF, 107 to 1423 bp), encoding a 423 amino acid residues of sugarcane SOS1 protein with an estimated molecular weight of 47.6 kD and a calculated isoelectric point (pI) of 9.12. The protein of ScSOS1 belongs to a conserved CAP_-ED superfamily. Yet the ScSOS1 protein has no signal peptide and belongs to hydrophilic protein with the main function forintermediary metabolism. The mainly secondary structure element of ScSOS1 protein is random coil. Real-time quantitative PCR (RT-qPCR) analysis revealed that ScSOS1was tissue-specificallyexpressed in leaf sheath, bark, pulp, bud and root of sugarcane,with the highest expression in leaf sheath and the lowest in root. Besides,the expression of ScSOS1gene could beregulatedby the treatments of NaCl, PEG, ABA, SA,and MeJA,and up-regulatedby the stresses of NaCland PEG, with the highest inducible expression levels of1.5 times and 4.0 times ashigh as those of control at 24 hours, respectively. This paper suggested that ScSOS1involves in sugarcane tolerance salt and osmotic stresses. It can set up a basis for the elucidation of sugarcane salt resistancemechanism.

Analysis of DNA Methylation Patterns in Resynthesized Brassica napus and Diploid Parents

XIE Tao,RONG Hao,JIANG Jin-Jin*,KONG Yue-Qin,RAN Li-Ping,WU Jian,WANG You-Ping

Acta Agron Sin. 2016, 42(04):  513-524.  doi:10.3724/SP.J.1006.2016.00513

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The genetic background of Brassica napus, one of the most important oil crops in China, is relatively narrow due to the short history of its polyploid origin. Resynthesized B. napus provides an optimal model for researches on plant polyploidization. In the present study, we compared the DNA methylation levels in synthesized B. napus (F₁ generation) and diploid parents using high-performance liquid chromatography (HPLC) and DNA methylation-sensitive amplification polymorphism (MSAP) analysis. HPLC analysis indicated methylation rates of 8.33% and 15.88% in B. rapa and B. oleracea, respectively. While the methylation rate of two hybrids was 10.29% and 12.83%, which werein-between of the parents’values. MSAP analysis proved the different methylation levels in F₁ generation and diploids, with the lowest and highest methylation levels identified in B. rapa and B. oleracea, respectively.Variance of the DNA methylation in F₁was 23.71%, among which 6.60% and 10.16% were inherited from A and C genome, respectively. Sequence analysis of MSAP polymorphic fragments indicated genes involved in multiple molecular functions were changed during polyploidization. Expression analysis of these genes agreed to the corresponding methylation changes. This study provides preliminary basis for understanding epigenetic variations during B. napus polyploidization.  

Correlation Analysis between Total Catechins (or Anthocyanins) and Expression Levels of Genes Involved in Flavonoids Biosynthesis in Tea Plant with Purple Leaf

ZHOU Tian-Shan,WANG Xin-Chao,YU You-Ben,XIAO Yao,QIAN Wen-Jun,XIAO Bin,YANG Ya-Jun

Acta Agron Sin. 2016, 42(04):  525-531 .  doi:10.3724/SP.J.1006.2016.00525

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Flavan-3-ols (aka catechins) and Anthocyanins found in large amounts in tea plant with purple leaf are synthesized through flavonoids metobolic pathway. To investigate the metobolic flux of flavanoids biosynthetic pathway in tea plant with purple leaf, we employed a tea plant with purple leaf and a tea plant with green leaf both from Mei-Tang-Tai-Cha, to examine the expression profiles of related genes involved in flavonoids biosynthesis intensively and determine the concentrations of catechins and anthocynin. Then correlation between total catechin (or anthocyanin) and expression levels of related genes was analyzed. The results indicated that the expression levels of related genes (PAL, CHS, CHI, F3H, DFR, ANS, ANR1, ANR2, F3’H,and F3’5’H) were up-regulated in purple leaves as compared with those in the green leaves. The purple leaf also had higher concentration of anthocyanin than the green leaf, while the green leaf was richer in total catechines. In purple leaves, the expression levels of related genes (except LAR) were highly correlated with both concentrations of total catechines (r = 0.84–0.99) and anthocyanin(r = 0.72–1.00). By contrast, there was only a high correlation between the expression levels of related genes (except LAR and F3¢H) and the concentration of total catechines (r = 0.64–0.77) in green leaves.

DNA Methylation Dynamic Analysis of Self Compatible Line and Self-Incompatible Line of Brassica oleracea var. acephala at Seed Germination Stage

ZHANG Yang,HU Zhong-Ying,ZHAO Yue-Ming,LI Na,XIE Li-Nan

Acta Agron Sin. 2016, 42(04):  532-539.  doi:10.3724/SP.J.1006.2016.00532

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The seed of self-incompatible line often degraded. This studyaims to clarify the relationship between the degradation of the seeds and methylation. In this experiment, methylation sensitive amplification polymorphism (MSAP) was used to study the status and patterns of the DNA methylation at different periods in seed germination of self-incompatible line 9^# and self-compatible line 14^#.The improved CTAB method is adopted to extract seed germination in different periods of DNA, and then through the MSAP analysis, statistical amplification bands, compare the differences between 9^# and 14^#. The results are shown as follows: DNA methylation modification throughout the whole process of seed germination of 9^#, at the early stage of the germination (0 to 2 days) methylation sites continued to increase; at the later stage (2 to 8 days) demethylation increased apparently, and eventually the number of demethylation was 11 times more than methylation. It was proved that DNA methylation modification was an important way to regulate the gene expression during seed germination of self-incompatible line 9^#. Self-incompatible line 9^# and self-compatible line 14^# had different DNA methylation status clearly at the respectively periods of 0 and 2 days after seed germination.The proportion of total methylation, full-methylation and semi-methylation of 9^# was all higher than of 14^# at the same period. As seedings continued to grow after germination, in 9^#, the proportion of full-methylation increased clearly and almost that of semi-methylation did not change, while in 14^#, the proportion of semi-methylation increased clearly and almost that of full-methylation did not change.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

A Dynamic Model and Its Characteristics Analysis for Nitrogen Accumulation after Heading in Yongyou 538

WEI Huan-He,MENG Tian-Yao,LI Chao,ZHANG Hong-Cheng,SHI Tian-Yu,MA Rong-Rong,WANG Xiao-Yan,YANG Jun-Wen,DAI Qi-Gen,HUO Zhong-Yang,XU Ke,WEI Hai-Yan,GUO Bao-Wei

Acta Agron Sin. 2016, 42(04):  540-550.  doi:10.3724/SP.J.1006.2016.00540

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A field experiment was conducted using indica/japonica hybrid super rice Yongyou 538 as the material, conventional japonica rice Zhendao 18 and hybrid indica rice Zhongzheyou 1 as the check to study the characteristics of nitrogen accumulation after heading and compare the differences in characteristics of nitrogen accumulation after heading in different types of rice variety. Results followed that, on an average across two years, grain yield of Yongyou 538 was 12.5 t ha^-1, significantly higher than that of check varieties. Nitrogen accumulation at heading, at maturity, and from heading to maturity showed a trend of Yongyou 538>Zhendao 18>Zhongzheyou 1. Nitrogen absorption of 100 kg seeds of Zhendao 18 was the highest, followed by Zhongzheyou 1, and Yongyou 538, while opposite trends was observed for N partial factor productivity. Compared with the check, nitrogen output from stem and nitrogen increase in panicle of Yongyou 538 were consistently higher. Nitrogen accumulation in Yongyou 538 and Zhendao18 was both higher than that of Zhongzheyou 1 after heading, and Richards' equation was fit to simulate the relationship between nitrogen accumulation and days after heading for three types of rice variety (R²≥0.995). Maximum rate of nitrogen accumulation, mean rate of nitrogen accumulation, and days to maximum rate of nitrogen accumulation after heading in Zhendao 18 were the highest, while those in Yongyou 538 were the lowest. Effective nitrogen accumulation duration showed a trend of Yongyou 538> Zhendao 18>Zhongzheyou 1. Duration days, nitrogen accumulation rate, and nitrogen accumulation in early and late stage of Zhendao 18 were the highest, while those of Yongyou 538 were the lowest. Duration days and nitrogen accumulation in middle stage of Yongyou 538 was consistently higher compared with the check. Our results indicated that greater nitrogen uptake of Yongyou 538 was mainly occurred in the middle stage, which was 86.1% of the nitrogen accumulation from heading to maturity. And higher nitrogen uptake in middle stage after heading of Yongyou 538 was mainly attributed to the longer duration days in this stage.

Effects of the Mutant with Low Chlorophyll Content onPhotosynthesis and Yield in Rice

GU Jun-Fei*,ZHOU Zhen-Xiang,LI Zhi-Kang,DAI Qi-Xing,KONG Xiang-Sheng,WANG Zhi-Qin,YANG Jian-Chang

Acta Agron Sin. 2016, 42(04):  551-560.  doi:10.3724/SP.J.1006.2016.00551

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A chlorophyll-deficit rice mutant (YL) with ~51% chlorophyll of its wild type (WT) was 3.7%, 20.4%, and 39.1% higher in photosynthesisthan WT under saturating light condition,in treatments of0 kg N ha^-1, 120 kg N ha^-1, 240 kg N ha^-1, respectively. In the field and pot experiments, we studied leaf Rubisco content, stomatal conductance, expression levels of aquaporin genes, chlorophyll fluorescence, light and electron micrographs at different levels of N application. The results showed that the decreased level of chlorophyll content in YL was compensated by a relativelyhigher quantum yield of PSII. The electron micrographs of chloroplasts showed that there were no differences in chloroplast development between YL and WT. The stomatal conductance was much higher in the mutant than in wild type, and expression levels of the aquaporin genes suggested a higher mesophyll conductance in YL. The higherCO₂ conductance together with a higher Rubisco content in YL could be reasons for the higher photosynthetic rate. The yield of YL was similar to that of WT, but the growth duration in YL was much shorter, which could be caused by the different photosynthetic performance between YL and WT. All these results implicate that higher photosynthetic rate doesnot necessitate higher chlorophyll content. Moderate chlorophyll content will benefit the leaf photosynthesis. Decreasing N investment in chlorophyll synthesis and optimizing N distribution among different photosynthetic compounds could potentially improve photosynthesis and yield. The YL material used in this study could be potentially used to improve photosynthetic efficiency in breeding programmes.

Effects of Ethylene-Chlormequat-Potassium on Characteristics of Leaf Senescence at Different Plant Positionsafter Anthesis under Different Planting Densities

LU Lin,DONG Zhi-Qiang*,DONG Xue-Rui,LI Guang-Yan

Acta Agron Sin. 2016, 42(04):  561-573.  doi:10.3724/SP.J.1006.2016.00561

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In order to explore the effects of ethylene-chlormequat-potassium(ECK) on leaf aging and early senescence in summer maize, and provide a theoretical basis for high and stable yields of summer maize under high planting density by chemical regulation technology in North China Plain,a field experimentwas conducted using two types of maize hybrids (Zhongdan909 and Xundan20)with treatments of ethylene-chlormequat-potassium under different planting densities. The results showed that the increased planting density significantly decreased leaf area (LA) per plant and increased LA reduction rate. With the increase of planting density decreased SPAD value, soluble protein content, and activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) of ear leaf, the third leaf above ear, and the third leaf below ear,while malondialdehyde (MDA) content increased. The above indexes had differences among varieties andleaf positions. ECK treatment significantly increased activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD), SPAD value and soluble protein content in leaves at different positions, decreased LA reduction rate, delayedand alleviatedleaf senescence. Under the density of ≥7.5×10⁴ plant ha^-1, the yield of Zhongdan909 and Xundan20, compared with their own controls, increased by 5.59%−6.63% and 6.73%−8.10%, respectively. ECK treatment significantly prevented early senescence under higher planting densities, therefore increased yield. Thus, adopting an appropriate planting density combined with ECK application could be an important technique for achieving high grain yield in summer maize production in North China Plain.

Characteristics of Photosynthesis and Antioxidation in Rice Photo-oxidation Mutant 812HS

XU Jin-Gang,Lü Chuan-Gen,LIU Li,Lü Chun-Fang,MA Jing,XIA Shi-Jian,CHEN Guo-Xiang,GAO Zhi-Ping

Acta Agron Sin. 2016, 42(04):  574-582.  doi:10.3724/SP.J.1006.2016.00574

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To reveal the physiological mechanism of leaf photo-oxidation in a rice mutant 812HS, we compared and analyzed differences of photochemical activity, antioxidative enzyme activities between 812HS and its wild type 812S grown in the field.  Results showed that chlorophyll content, PSII activity, photophosphorylation activity, net photosynthetic rate (P_n) and antioxidative enzymes activities as well as active oxygen contents in 812HS were similar to those in 812S before exposed to high intensity of sunlight. However, all above indexes were affected by a period of high intensity of sunlight. The decreased degree of chlorophyll content, PSII activity, non-cyclic photophosphorylation (NCPS) activity and P_n in 812HS were significantly higher than those in 812S. Besides, high intensity of sunlight led to a lower increase rate of POD and CAT activities in 812HS. Therefore, the contents of O₂^?, H₂O₂, and MDA in 812HS became higher than those in 812S. The result implied that the leaf photo-oxidation of mutant 812HS mainly results from higher sensitivity of PSII activities and lower CAT, POD activities under high intensity of sunlight.

Effects of Meteorological Factors on Stalk Elongation in New-planting and Ratooning Sugarcane

CHEN Yan-Li,FENG Li-Ping,DING Mei-Hua,KUANG Zhao-Min

Acta Agron Sin. 2016, 42(04):  583-590.  doi:10.3724/SP.J.1006.2016.00583

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Sugarcane stalk elongation is the most important factor for the development evaluation and yield estimation, on which meteorological factors have significant effects. Differences between new planting sugarcane and ratooning sugarcane in development and response to meteorological factors need to be analyzed for promoting agricultural production. In this paper, taking new-planting sugarcane and ratooning sugarcane of Guangxi as the research materials, observedsugarcane agronomic data and meteorological information at four agro-meteorological experimental stations from 2000 to 2011 were used to analyze the relationship between stalk elongation and meteorological factors that were precipitation, relative humidity, maximum temperature, minimum temperature, mean temperature, air pressure, and sunshine hours at different stages. The results show that there was an obvious difference between new-planting sugarcane and ratooning sugarcane in stalk height. During the sugarcane stem elongation, compared with ratooning sugarcane, new-planting sugarcane had a higher stalk height with a lower background in most of years, besides, its total stem elongation amount was much more but elongation duration was short. There was a significant correlation between stalk elongation and most meteorological factors in both new-planting sugarcane and ratooning sugarcane. The effect of most meteorological variables was larger in new-planting sugarcane than in ratooning sugarcane. The correlation between new-planting sugarcane and meteorological factors are obviously higher than that of ratoon sugarcane. Minimum temperature, relative humidity and maximum temperature played a direct positive role on stalk elongation in both new-planting sugarcane and ratooning sugarcane, and average temperature and air pressure played a direct negative role, meanwhile, accumulated temperature and rainfall play a significant indirect effect through other meteorological factors. There was a significant lag in the response of stem elongation to rainfall for both new-planting sugarcane and ratooning sugarcane. Compared with ratooning sugarcane, lag of new-planting sugarcane was longer. The total lag time was about 20 days for new-planting sugarcane and 10 days for ratooning sugarcane. There was also a lag in response to sunshine hours for new-planting sugarcane, but no lag to temperature for both sugarcanes.

RESEARCH NOTES

Effect of Symbiosis Periods and Plant Densities on Growth and Yield of Rapeseed Intercropping Cotton

KUAI Jie,DU Xue-Zhu,HU Man,ZENG Jiang-Xue,ZUO Qing-Song,WU Jiang-Sheng,ZHOU Guang-Sheng

Acta Agron Sin. 2016, 42(04):  591-599.  doi:10.3724/SP.J.1006.2016.00591

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To explore the effect of symbiotic periods and densities on the growth and yield of rapeseed intercropping cotton, a split-plot experiment with three symbiotic periods [10 d (T10), 20 d (T20), and 30 d (T30)] and four levels of densities [30×10⁴ (D1), 45×10⁴ (D2), 60×10⁴ (D3), and 75×10⁴ plants ha^–1 (D4)] was designed. The results showed that: (1) Prolonging symbiotic periods was favorable for rapeseed growth in terms of the number of green leaves, LAI, root biomass, aboveground biomass, root-shoot ratio, plant height, crown diameter all increased, whereas angle of stem lodging decreased. These led to increase in yield both single plant and unit hectare. (2) The effects of plant density on rapeseed growth and yield depended on the symbiotic period. The number of green leaves, root biomass, aboveground biomass decreased with plant densities, which resulted in decreased yield per plant. At T30, the maximum LAI was observed under D3, while it was increased with plant density at T20 and T10. The population yield had the same trend with LAI. The yield reached the maximum when the symbiosis period was 30 days and the plant density at 45×10⁴ plants ha^–1,whereas the angle of stem lodging reached the minimum at T30D3. (3) Based on the regressions, for Wuxue sites, the optimum symbiotic period was 29.8 days and the optimum plant density was 48.8×10⁴ plants ha^–1 while these for Tianmen were 29.7 days and 57.6 plants ha^–1. Under these arrangements, Wuxue and Tianmen could achieve the yield about 3243.0, 3082.8 kg ha^–1,which were increased by 23.5%, 17.4%, respectively, when compared to the traditional arrangement (the symbiotic period was 15d, the plant density was 15.0 to 22.5×10⁴ plants ha^–1 and the average yield was about 2625 kg ha^–1).

Photosynthetic Characteristics of Transgenic Wheat Expressing Maize C₄-Type NADP-ME Gene

WANG Yong-Xia,DU Xin-Hua,XU Wei-Gang,QI Xue-Li,LI Yan,WANG Hui-Wei,HU Lin

Acta Agron Sin. 2016, 42(04):  600-608.  doi:10.3724/SP.J.1006.2016.00600

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To explore the physiological characteristics of the transgenic wheat expressing maize C₄-type NADP-ME, we introduced NADP-ME into the C₃ crop wheat by using particle bombardment transformation. Two transgenic wheat lines (10T(9)-1-1, 10T(9)-225-4) and parental control (Zhoumai 19)were used to study molecular characteristics and photosynthesis property, to reveal the mechanism. The results showed that the NADP-ME sequence was integrated into wheat genome, and the transcription and translation were exactly same as expect. The enzyme activity of NADP-ME in flag leaf in transgenic plants were increased significantly than untransformed plants, for instance it was increased 1.33 and 1.13 times on the 7th day after flowering. Net photosynthetic rate (P_n) of flag leaf in transgenic plants obviously decreased when compared to the untransformed plants. On the 7th day after anthesis, P_n of transgenic wheat decreased by 17.26% and 10.35%. The yield and 1000-grain weight were decreased than the control. Utilization efficiency on strong light utilizing and ability of CO₂ assimilation in transgenic line 10T(9)-225-4 were significantly declined, photosynthesis rate was also decreased. stomatal opening rate and stomatal conductance were significant decrease, malic acid content of transgenic wheat reducing 5.6% while pyruvate level is raised by 17.1%, and P_n of transgenic wheat can be restored by feeding with exogenous malate. Those results indicated that the transgenic wheat expressing maize NADP-ME gene showed lower photosynthetic characteristics than the control, the reason was maybe the decrease of stomatal aperture caused by decline of malic acid content.

Critical Index Analysisof Safe Over-wintering Rate ofWinter Rapeseed (Brassica rapa) in Cold and Arid Region in North China

SUN Wan-Cang1,**,LIU Hai-Qing1,**,LIU Zi-Gang1,*,WU Jun-Yan,LI Xue-Cai,FANG Yan,ZENG Xiu-Cun,XU Yao-Zhao,ZHANG Ya-Hong,DONG Yun

Acta Agron Sin. 2016, 42(04):  609-618.  doi:10.3724/SP.J.1006.2016.00609

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To research the safe over-wintering rate of winter rapeseed (Brassica rapa) in different ecological areas in North China, to confirm the critical value of over-wintering rate, and to clarify the main factors affecting over-wintering rate, we collected the data of long term multi-location field experiments at 48 ecological sitesin 13 provinces and cities and areas in 2011–2014 with winter rapeseed varietyLongyou 7, Longyou 6, Longyou 8, Longyou 9, Tianyou 4, Tianyou 2 toanalyzethe over-wintering rate and yield and the correlations between them. The results indicated that there were significant differencesof over-wintering rate in different ecological areas, which ranged from 10% to 99% and the yield also had significant difference in different locations.Theover-wintering ratesof varieties with strong cold resistance were over 70%.Regression analysis showed a significant linearcorrelation between over-wintering rate and yield,with the regression equation ofy=ax+b.The yield increased with the increase of over-wintering rate when the over-wintering rate <70%, and tended to stable when the over-wintering rate was 70%, butdidn’t had significant influence on yield when >70%.In conclusion, variety is one of the key factors affecting the over-wintering rate of winter rapeseed.The critical value of safe over-wintering rate in north Chinais 70%, and the corresponding planting conditionsare the strong cold resistant varieties,the extreme lowest temperature–31.79°C, the temperature of winter–7.20°C,annual average temperature 6.38°C, negative cumulative temperatures in winter–997.57°Cin planting areas, latitudebelow 44.83°and longitude over 80.34°.

Effects of Nitrogen Forms and Its Application Time on Plant Growth and Tuber Yield of Potato

SUYALA Qi-Qige,QIN Yong-Lin,JIA Li-Guo,FAN Ming-Shou

Acta Agron Sin. 2016, 42(04):  619-623.  doi:10.3724/SP.J.1006.2016.00619

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The effects of nitrogen form on potato plant growth, tuber formation and tuber yield were studied under sand cultural condition using cultivars Kexin 1 and Favorita in 2013 and 2014. The results showed that there were no significantly different influences on plant height, leaf area, leaf SPAD value, plant dry matter accumulation and tuber weight when applied nitrite (NO₃-N) or ammonia (NH₄-N) before tuberization. However, there were higher leaf SPAD value，faster plant growth and higher tuber yield under application of NH₄-N after tuberization compared with that of NO₃-N. Moreover, no significant effect was detected on tuber dry matter distribution under different forms of nitrogen applied. Thus, potato nitrogen management including N fertilizer form and its application time should be adjusted according to the aim of commercial potato production or seed potato propagation.