Table of Content

12 September 2014, Volume 40 Issue 09

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

An Evaluation System for Rice Black-Streaked Dwarf Virus Disease and Screening for Resistant Rice Germplasm

WANG Bao-Xiang,HU Jin-Long,SUN Zhi-Guang,SONG Zhao-Qiang,LU Bai-Guan,ZHOU Zhen-Ling,FAN Ji-Wei,QIN De-Rong,LIU Yu-Qiang,JIANG Ling,XU Da-Yong,WAN Jian-Min

Acta Agron Sin. 2014, 40(09):  1521-1530.  doi:10.3724/SP.J.1006.2014.01521

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Rice black-streaked dwarf virus disease (RBSDVD) is one of the most serious viral diseases. The absence of efficient resistance evaluation system for RBSDVD restricts the excavation of the resistance resource, thereby the resistance breeding and basal researches are limited. Here, we proposed that the appropriate density of small brown planthopper (SBPH) should be 8 million ha^-1 and the rate of RBSDV-carrying SBPH should be over 5% for RBSDVD evaluation in field condition. Further, we optimized the artificial inoculation evaluation system including circulative period, number of SBPH per plant, infestation time and age of SBPH. We evaluated 1240 varieties from 21 countries for RBSDV resistance by natural inoculation in 2010, 34 cultivars had the disease incidence less than 10%. The 34 cultivars were further evaluated by natural inoculation in three different locations in 2011 and 2012, respectively. Finally, only three varieties, Kanyakumari 29, Madurai 25, and Vietnam 160, which all came from Southeast Asia, had the consistent disease incidence less than 10% in different locations and years. To verify the resistance of the three varieties against RBSDVD, we carried out the interval sowing inoculation experiment in the three different locations in 2012. In the interval sowing experiment, the disease incidence of Kanyakumari 29 was less than 12%, whereas Madurai 25 and Vietnam 160 less than 9%. In addition, in the artificial field inoculation and artificial room inoculation experiments, the disease incidence of the three varieties was less than 9%. The above natural and artificial inoculation experiments showed that Kanyakumari 29, Madurai 25, and Vietnam 160 performed stable and high RBSDVD resistance. Taken together, the RBSDVD evaluation system combining field with artificial infestation identifications used in this study is accurate and reliable. This system could be used to widely screen RBSDVD resistance resources. The construction of RBSDVD evaluation system and the RBSDVD resistance resources identified in this study will provide the useful tools and materials for the identification of RBSDVD resistance gene(s) and development of RBSDVD resistance varieties.

Cloning and Expression Analysis of a Calcium-Dependent Protein Kinase Gene SiCDPK1 in Setaria italica

YU Qin-Yang,YIN Heng,AN Li-Jia,LI Wen-Li

Acta Agron Sin. 2014, 40(09):  1531-1539.  doi:10.3724/SP.J.1006.2014.01531

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CDPK (calcium-dependent protein kinase) is a kind of essential calcium sensors and calcium responders, which plays important roles in response to various abiotic stresses in plants. In this research, we cloned the abiotic stress response related CDPK gene with RT-PCR in Setaria italica, designated as SiCDPK1 (GenBank accession number KC249975.1). We predicted 28 CDPKs in the Setaria italica genome by using the known Arabidopsis CDPK sequences as query sequences. The phylogenetic analysis showed the SiCDPK gene family was divided into four subgroups, in which SiCDPK1 belongs to subgroup II. The ORF of SiCDPK1 contains 1596 bp, which encodes 531 amino acids. The predicted protein molecular weight is 59.5 kD and pI is 5.94. SiCDPK1 has conserved protein domains of CDPK. The regulatory element analysis of promoter in SiCDPK1 showed a lot of cis-acting elements associated with different abiotic stresses. The RT-PCR results showed that SiCDPK1 was induced by PEG, ABA, salinity and drought. The research on SiCDPK1 paves a way for unraveling the mechanism of abiotic stresses in plants.

Cloning, Expression, and Functional Analysis of GhMYB0 Gene from Cotton (Gossypium hirsumtum L.)

WANG Nuo-Han,YU Ji-Wen,WU Man,MA Qi-Feng1,LI Xing-Li,PEI Wen-Feng,LI Hai-Jing,HUANG Shuang-Ling,ZHANG Jin-Fa,YU Shu-Xun

Acta Agron Sin. 2014, 40(09):  1540-1548.  doi:10.3724/SP.J.1006.2014.01540

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MYB transcription factor, one of the most important protein families in plants, is involved in the regulation of secondary metabolism, morphogenesis of plant, responding to environment stress and plant hormone. In this study, we used D₅ genomic bank of Gossypium raimondii as the reference to AtMYB0 (GL1, NM_113708) protein, and cloned the full-length cDNA of a new MYB transcription factor gene GhMYB0 from cotton (Gossypium hirsutum L.). The open reading frame of GhMYB0 is 843 bp in length, which encodes 280 amino acid residues. GhMYB0 was confirmed as R2R3-MYB transcription factor via conserved structure analysis and subcellular localization. The qRT-PCR result indicated that GhMYB0 was highly expressed at the blossom day, its expresssion amount reached the peak after 20 days, with the most amount in flower, then in ovules. Transgenic funtion analysis indicated that GhMYB0 over-expressed in Arabidopsis lines, showing fewer trichomes in leaf epiderm than in that of the wild type, which suggests that the gene can restore the notrichome phenotype of gl-1 mutant of Arabidopsis. In addition, the transgenic lines had shorter plant heights, longer vegetative growth time, and pollen abortion.

Cloning, Expression, and Functional Analysis of an A Subfamily bZIP Transcription Factor Gene ZmbZIP81 in Maize

WANG Ce,YANG Yan-Ge,Lü Wei-Tao,ZHOU Chun-Ju,SUN Dong-Mei,DENG Xin

Acta Agron Sin. 2014, 40(09):  1549-1556.  doi:10.3724/SP.J.1006.2014.01549

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Basic leucine zipper (bZIP) proteins constitute a large family of transcription factors among eukaryotes, which plays important roles in gene expression regulation under abiotic stress in plants. In order to gain a better understanding of bZIPs in maize, we cloned ZmbZIP81 from maize, which encodes an A subfamily bZIP transcription factor. ZmbZIP81 is located on chromosome 6. The coding region of ZmbZIP81 is 2492 bp in length with four exons and three introns, which encodes 254 animo acid residues. Further study showed that the expression of ZmbZIP81 was induced by exogenous ABA, salt and drought treatments. The transgenic Arabidopsis plants overexpressing ZmbZIP81 were less sensitive to ABA, but more tolerant to salt, compared with the wild type. These results indicated that ZmbZIP81 may encode a transcription factor, regulate ABA signaling negatively and participate in abiotic stress tolerance regulation in maize.

Resistance of Slow Mildewing Genes to Stripe Rust and Leaf Rust in Common Wheat

LIU Jin-Dong,CHEN Xin-Min,HE Zhong-Hu,WU Ling,BAI Bin,LI Zai-Feng,XIA Xian-Chun

Acta Agron Sin. 2014, 40(09):  1557-1564.  doi:10.3724/SP.J.1006.2014.01557

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Pyramiding quantitative trait loci (QTLs) is an effective method to improve resistance to powdery mildew, stripe rust, and leaf rust in common wheat. We have developed 21 lines (F₆) carrying 2-5 slow mildewing QTLs by crossing slow powdery mildew cultivars Bainong 64 and Lumai 21 possessing four and three slow mildewing QTLs, respectively. These F₆ lines were evaluated in the field in Pianxian, Sichuan and Tianshui, Gansu for stripe rust resistance and in Baoding, Hebei and Zhoukou, Henan for leaf rust resistance during the 2012-2013 cropping season. According to the maximum disease severities (MDS) and the area under the disease progress curve (AUDPC), QTLs QPm.caas-4DL, QPm.caas-6BS and QPm.caas-2BL were highly resistant to stripe rust (P < 0.01), which explained 16.9%, 14.1%, and 17.3% of phenotypic variance, respectively. Locus QPm.caas-4DL also showed high resistance to leaf rust (P < 0.01) with phenotypic contribution of 35.3%. Lines that pyramided five (QPm.caas-1A/QPm.caas-4DL/ QPm.caas-2DL/QPm.caas-2BS/QPm.caas-2BL) and four (QPm.caas-1A/QPm.caas-4DL/QPm.caas-2BS/QPm.caas-2BL) QTLs exhibited higher resistance to both stripe and leaf rust compared with their parents. This result indicates that the combination of QPm.caas-4DL (from Bainong 64), QPm.caas-2BS and QPm.caas-2BL (Lumai 21) has a marked effect on improving adult resistance to powdery mildew, stripe rust and leaf rust, and the more QTLs are pyramided, the stronger slow disease resistance can be achieved. In breeding practice, the combination of 4-5 slow mildewing or rusting QTLs can result in durable resistance to multiple diseases.

Establishment and Application of Multiplex PCR System for Two Blast Resistance Genes Pi-ta and Pi-b in Rice

YAO Shu,LIU Yan-Qing,ZHANG Ya-Dong,ZHU Zhen,CHEN Tao,ZHAO Qing-Yong,ZHOU Li-Hui,ZHAO Chun-Fang,YU Xin,WANG Cai-Lin*

Acta Agron Sin. 2014, 40(09):  1565-1571.  doi:10.3724/SP.J.1006.2014.01565

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Rice blast is one of the important diseases in major rice producing areas of our country. The main blast resistance genes Pi-ta and Pi-b showed good resistance spectrum to rice blast in many rice growing areas of China, and has been utilized in rice breeding and commercial production. In this study, two sets of multiple PCR system for the two rice blast genes were established by selecting the functional markers of two resistance genes of Pi-ta and Pi-b and two susceptible genes of pi-ta and pi-b, respectively, based on the verification of the genotype of the two rice blast genes known in 22 rice varieties. System I could detect the two resistance genes of Pi-ta and Pi-b, while system II could detect the two susceptible genes of pi-ta and pi-b. Genotypes of the two rice blast genes in 336 new japonica lines were detected by using the two sets of multiple PCR system. The results were highly consistent with those tested by the conventional single mark detection method, indicating that the two multiplex PCR systems were stable, reliable and time-saving. They may serve as a rapid and efficient method to identify and screen rice germplasm resources and be applied in marker assistant selection for pyramiding multiple genes (QTLs) of rice blast resistance in rice breeding.

Cloning of Zoysiagrass CBF Gene and Validation of Cold Tolerance in Transgenic Arabidopsis

FENG Xun-Wei,CAI Hong-Wei

Acta Agron Sin. 2014, 40(09):  1572-1578.  doi:10.3724/SP.J.1006.2014.01572

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Zoysiagrass is recognized as an excellent warm-season turfgrass and mainly used in subtropical and tropical regions. Cold stress is a major constraint factor for the cultivation of zoysiagrass. In this study, according to the sequences of cold tolerance gene CBF had been reported in other plant species, we cloned the corresponding homologous of the ZjCBF gene by homology cloning method in Zoysia japonica using a material originated from the most northern area of Japan. Based on the alignment results compared with other reported CBF genes, we found the ZjCBF gene belongs to the CBF1 familiy. By semi-quantitative PCR and Real-time quantitative PCR, we analyzed the expression level of the ZjCBF gene in the cold condition and found that ZjCBF was induced by cold stress, and the ZjCBF expression reached peak after six hours at 4°C treatment. In addition, we also constructed ZjCBF over expression vector and generated transgenic Arabidopsis plants, with better cold tolerance than the wild-type, whether through cold acclimation or not.

EMS Induced HMW-GS Mutants from Soft Wheat Ningmai 9

ZHANG Ji-Yuan,ZHANG Ping-Ping,YAO Jin-Bao,YANG Dan,YANG Xue-Ming,MA Hong-Xiang

Acta Agron Sin. 2014, 40(09):  1579-1584.  doi:10.3724/SP.J.1006.2014.01579

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The objective of this study was to create a series of deletion lines of high molecular weight-glutenin subunit (HMW-GS) in similar backgrounds for wheat quality research and breeding. A total of 3781 M₁ plants of Ningmai 9 (a soft wheat cultivar) were obtained from 10000 seeds induced by 0.4% ethyl methane sulfonate (EMS). The HMW-GS compositions of these plants were identified via SDS-PAGE using half seed. Two hundred and ninety-nine lines with a mutation percentage of 7.91% were found to be HMW-GS mutants, including HMW-GS deletion and molecular weight mutation. Among them, 176 lines were HMW-GS deletion mutants, with a mutation percentage of 4.65% containing subunits Ax1, Bx7, By8, Dx2, and Dy12, with the mutation percentages ranging from 0.24% to 3.28%. The mutants of molecular weight were 130 lines with a mutation percentage of 3.44%. Each of the half M₁ seed with embryo was used to produce M₂ generation in greenhouse. Homozygous deletion lines of HMW-GS Ax1, Dx2, Bx7, By8, Dy12, and Ax1+ By8 were detected using SDS-PAGE and confirmed in M₃ generation. The content of glutenin macropolymer (GMP) and the ratio of glutenin-to-gliadin (GLU/GLI) ratio were determined using high performance liquid chromatography (HPLC). The results showed that all the deletion mutants had lower GMP content than Ningmai 9, particularly, the Bx7 deletion line had the reduced GMP content of 42%. The GLU/GLI ratio of the deletion lines was also smaller than that of Ningmai 9, and the lowest GLU/GLI ratio was found in Ax1+ By8 deletion line.

Identification, Classification, and Drought Response of F-box Gene Family in Foxtail Millet

HUO Dong-Ying,ZHENG Wei-Jun,LI Pan-Song,XU Zhao-Shi,ZHOU Yong-Bin,CHEN Ming,MA You-Zhi,MIN Dong-Hong,ZHANG Xiao-Hong

Acta Agron Sin. 2014, 40(09):  1585-1594.  doi:10.3724/SP.J.1006.2014.01585

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F-box proteins play critical roles in plant growth and development and respond to abiotic stresses, involving in cell-cycle regulation, cell apoptosis and signal transduction. Foxtail millet has a character with drought-tolerance. We identified 19 up-regulated F-box genes from 525 F-box families under stress in foxtail millet based on the transcriptome sequencing and divided them into six subgroups, and the genes in the same subgroup had the same intron-exon structure. These genes were unevenly distributed on eight foxtail millet chromosomes, and there were six genes on chromosome 2, that gene number was more than that contained on other chromosomes. The analysis of conserved domain of 19 genes showed that all the protein sequences had a conserved F-box motif, and several other domain also existed in C-terminal including FBD, WD40, FBA, ZnF, and Kelch LRR. Putative cis-acting elements showed that the number of MYB and MYC was the most, which ranged from 9 to 78. Transcriptome sequencing showed that SiF-box18 was more hypersensitive to the drought stress than other F-box members and response to drought, salt, ABA, GA, SA and JA based on the real time PCR. The transient expression in Arabidopsis protoplasts displayed that SiF-box18 protein was localized in nuclear section. This study provided experimental data for further studying the functions of the SiF-box18 gene.

Quantitative Trait Loci of Major Fatty Acid Components in Soybean

ZOU Xiao,HAN Fen-Xia,CHEN Ming-Yang,SUN Jun-Ming,NAN Jin-Ping,YAN Shu-Rong,YANG Hua

Acta Agron Sin. 2014, 40(09):  1595-1603.  doi:10.3724/SP.J.1006.2014.01595

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The mapping population with 100 BC₂F₂ lines of soybean backcross from Zhonghuang 13 × Zhonghuang 20 was developed and tested for its genetic variation. A linkage map with a total distance of 2157.3 cM was constructed with an average distance of 16.5 cM using 131 polymorphism SSR markers. Five kinds of fatty acid components were measured by GC in three years. The QTLs of major fatty acid components were analyzed with ICIM by IciMapping 3.3. The results showed that 26 QTLs associated with five fatty acid components were detected, including five QTLs for palmitic acid, five QTLs for stearic acid, seven QTLs for oleic acid, five QTLs for linoleic acid and four QTLs for linolenic acid. There were three intervals related to the same component detected in different years. The interval of sat_294–satt228 related to palmitic acid was detected in three years, the intervals of sat_253–satt323 and sat_292–satt397 related to oleic acid were detected in two years. Four intervals were identified to be related to two different components. The intervals of sat_294-satt228 related to palmitic acid and oleic acid, satt308–sat_422 related to stearic acid and linoeic acid, sat_292–satt397 related to oleic acid and linoeic acid, and satt374–satt269 related to linoeic acid and linolenic acid were detected.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Effects of Alkali Treatment on Component and Structure and Enzyme Saccharifying Efficiency of Sweet Sorghum Bagasse

MA Qiang,DUN Bao-Qing,XI Ya-Jun,WANG Zhi,CHEN Chao-Ru,LU Ming,LI Gui-Ying

Acta Agron Sin. 2014, 40(09):  1604-1611.  doi:10.3724/SP.J.1006.2014.01604

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Sweet sorghum variety M81 was used as the experimental material, the sweet sorghum bagasse (SSB) was treated under four conditions (lime at room temperature, lime with microwave treatment, lime with autoclave treatment and sodium hydroxide at room temperature) with the washed and untreated SSB as control. The changes of lignocellulose structure and the cellulase saccharifying efficiency of SSB under different conditions were investigated. The results showed that four treatments effectively changed the lignocellulose component of sweet sorghum bagasse, especially in the case pretreated by sodium hydroxide under room temperature for two weeks, and lime played an important role in hemicellulose dissolution too. Scanning electron microscopy (SEM) observation indicated that the lignocellulose structure was different in two treatments of lime with autoclave treatment and sodium hydroxide at room temperature. The surface of lignin in the treatment of lime and autoclave was eroded seriously and its fragments adhered to the surface of cellulose, but the internal fiber structure still arranged tightly; in the treatment of NaOH at room temperature the lignocellulose beam structure was swelled and degraded, and the cellulose fiber net appeared due to the surface component of lignin removed a lot and many small holes appeared. By using the four pretreated methods, the cellulose and hemicellulose of sweet sorghum bagasse were enzymatically saccharified, the concentrations of glucose and xylose increased 1.5, 2.1, 1.9, 4.2 times and 3.1, 5.0, 4.9, 2.4 times, respectively as compared with the control. The direct conversion rate and the relative conversion rate of cellulose and hemicellulose are different, but have a significant guiding function for the choose of treatment methods and the effect of comprehensive evaluation, in addition, also an instructive function for the breeding and cultivating of sweet sorghum with high yield and good energy productive factors in the practical production.

Sugar Metabolism and its Relationship with Fiber Strength Affected by Waterlogging during Flowering and Bolling Stage in Cotton

YANG Chang-Qin,LIU Rui-Xian,ZHANG Guo-Wei,YANG Fu-Qiang,ZHOU Zhi-Guo

Acta Agron Sin. 2014, 40(09):  1612-1618.  doi:10.3724/SP.J.1006.2014.01612

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The experiments were conducted using a cotton cultivar NuCOTN 33B with pool culture under different waterlogging treatments in 2007 and 2009 to study effects of waterlogging on carbohydrate metabolism and its relationship with fiber strength during flowering and bolling stage in Nanjing, China. The results showed that the mean values of sucrose and β-1,3-glucan contents decreased by 24.86% to 81.30% and 8.59% to 36.30% respectively at 17 to 38 days after anthesis under waterlogging. The maximum rate of cellulose accumulation increased in response to mild waterlogging conditions, decreased in response to serious conditions, but the duration of maximum cellulose accumulation shortened, which resulted in the decrease in cellulose content. The value of fiber strength at mature period decreased by 3.57% to 10.03% under waterlogging. The mean values of SS and SPS activities increased by 8.45% to 24.59% and 12.79% to 18.20% respectively in response to mild waterlogging conditions, but decreased by 7.06% to 8.16% and 11.40% to 11.64% respectively at 17 to 38 days after anthesis in response to the serious waterlogging conditions, which were due to enhanced metabolic demands. Waterlogging decreased the activities of sucrase and β-1,3-glucanase at 17 days after anthesis. Therefore, insufficient carbon source, together with the increased carbon consumption or the inhibited sugar metabolism were potential factors contributing to low fiber strength for waterlogging plants.

Effects of Endogenous Hormone Balance on Dormancy and Germination of Tiller Bud

LUO Bao-Jie**,XU Jun-Xu**,DING Yan-Feng,LI Gang-Hua,LIU Zheng-Hui,WANG Shao-Hua

Acta Agron Sin. 2014, 40(09):  1619-1628.  doi:10.3724/SP.J.1006.2014.01619

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The objection ofthis experiment was to study the changes of contents of CTK, IAA and the ratio of CTK/IAA during heading stage , and to investigate the regulation of endogenous hormones in rice tiller. Exogenous 6-BA and IAA were used to regulate the development of tiller buds, establish the transfer between dormancy and germination, and measure the contents of CTK and IAA in elongated nodes and tiller buds located at the elongated nodes. The exogenous 6-BA Increased the CTK contents in nodes and tiller buds, decreased the IAA content in nodes had little effect in the content of IAA in tiller buds, significantly increased ratios of CTK/IAA in both nodes and tiller buds, and promoted the transfer from dormancy to germination. External IAA after removing panicle decreased CTK contents in nodes and tiller buds, which were maintained at a low level, increased the IAA content in buds, and significantly decreased the ratio of CTK/IAA in nodes and tiller buds, causing the transfer from germination to dormancy. Tiller development is determined by the balance between CTK and IAA, higher CTK/IAA ratio is benefit to the transfer from dormancy to germination, while lower CTK/IAA ratio inhibits the transfer. The ratios of CTK/IAA at 2.6–2.8 in nodes, 4.8–5.0 in tiller buds can be considered as the critical exponent of the transfer between dormancy and germination.

Effect of Reduced N Application on Crop Yield in Maize-Soybean Intercropping System

LIU Xiao-Ming,YONG Tai-Wen,SU Ben-Ying,LIU Wen-Yu,ZHOU Li,SONG Chun,YANG Feng,WANG Xiao-Chun,YANG Wen-Yu

Acta Agron Sin. 2014, 40(09):  1629-1638.  doi:10.3724/SP.J.1006.2014.01629

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Maize-soybean strip relay intercropping pattern is widely adopted in Southeast China. Whereas the traditional fertilized measures used by farmers are not good for high yield of soybean. In order to get high yield for both maize and soybean in this system, a field experiment was conducted to investigate the effect of reduced N application on photosynthetic characteristics and dry matter accumulation of soybean, and the system crop yield. The experiment included three planting patterns (maize monocropping, soybean monocropping and maize-soybean relay strip intercropping) and three rates of N fertilizer application (0, 180, 240 kg ha^–1). The results demonstrated that, the net photosynthetic rate (P_n), transpiration rate (G_s), stomatal conductance (C_i), photosynthetic capacity (T_r), dry matter accumulation of soybean increased initially and then decreased in the later stage. Compared with soybean monocropping, the P_n, G_s, and T_r of intercropped soybean decreased significantly in the intergrowth stage (V5), but had no significant differences at R2, R4, and R6 stages. Although the below-ground, above-ground and total dry matter accumulation of soybean significantly decreased during the whole growth period, the crop growth rate from R4 to R6 stages and economic coefficient significantly increased. In the maize-soybean relay strip intercropping system, N application significantly enhanced the P_n, G_s, T_r, dry matter accumulation, pod number per plant, and grain yield of soybean. Compared with the conventional N application (240 N kg ha^–1), P_n of soybean under the reduced amount of N application (180 N kg ha^–1) increased by 3.57% and 11.82% at R4 and R6 stages, respectively. Furthermore, the total dry matter accumulation increased by 5.06% and 10.21% at R6 and R8 stages, and pod number per plant and grain yield increased by 8.30% and 10.15%, respectively. Finally, the maize-soybean relay strip intercropping system possessed the highest yield under the N application rate of 180 N kg·ha^–1, with the economic coefficient and land equivalent ratio (LER) of 0.49 and 2.17, respectively. Taken together, the reduced N application in maize-soybean relay strip intercropping system can increase the yield of soybean and whole the system through improving soybean photosynthetic characteristics and enhancing dry matter accumulation.

Effects of Water-Nitrogen Management Patterns on Nitrogen Utilization Characteristics and Yield in Rice Cultivars with Different Nitrogen Use Efficiencies

SUN Yong-Jian,SUN Yuan-Yuan,XU Hui, LI Yue,YAN Feng-Jun,JIANG Ming-Jin,MA Jun

Acta Agron Sin. 2014, 40(09):  1639-1649.  doi:10.3724/SP.J.1006.2014.01639

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The optimal water-nitrogen (N) managements and the selection of genotypes with high nitrogen utilization efficiency (NUE) play a vital note in rice production aiming at high yield, high NUE and water-saving irrigation. In order to elucidate effects of water-nitrogen management patterns on N utilization characteristics, grain yield and its physiological basis in rice cultivars with different NUEs. Two different NUE rice cultivars with high-yield and high N-efficiency (Dexiang 4103) as well as medium-yield and low N-efficiency (Yixiang 3724), were used with three water-nitrogen management patterns, including standing irrigation and optimized N application (W1N1), alternate irrigation and optimized N application (W2N1), and dry cultivation and optimized N application (W3N2). The relationship between yield or N utilization characteristics and glutamine synthetase (GS) activity, photosynthetic rate (P_n) and root activity was investigated. The results showed that rice cultivars with different NUEs and water-nitrogen management patterns significantly affected N utilization characteristics, irrigation water use efficiency, physiological characteristics and grain yield. The regulation effects of water-nitrogen management patterns on NUE indexes (physiological efficiency, agronomy efficiency, and N recovery efficiency) were lower than those of rice cultivars with different NUEs, while the effects of water-nitrogen management on irrigation water use efficiency, total N accumulation, N dry matter production efficiency, and N production efficiency were significant. Compared with W1N1 and W3N2, W2N1 could promote the N uptake from elongation to maturing stages, enhance activity of GS, P_n, and root activity, and then improve grain yield and NUE of two different NUE rice cultivars, being the best model in this experiment. Moreover, the regulation effects of water-nitrogen management patterns on the cultivar with medium-yield and low N-efficiency were significantly higher than these with high-yield and high N-efficiency rice cultivars. The results also showed that average total spikelet number, N accumulation from elongation to heading stages, GS activity and P_n of leaves, and root activity of high N-efficiency rice cultivar were higher than those of low N-efficiency rice cultivar. Especially, during filling stage compared with medium-yielding and low N-efficiency cultivar, the high-yielding and high N-efficiency rice cultivar was more beneficial to higher metabolism and assimilation capacity of leaves and roots, which is the important reason for high-yielding and high N-efficiency rice cultivar further to increase yield and NUE. Correlation analysis indicated that there existed significantly positive correlations of GS activity and P_n of leaves, and root activity in the two N-efficiency rice cultivars with indices of N uptake and utilization and yield, furthermore, the maximum correlation coefficients of GS activity of leaves and root activity with yield or NUE were observed at heading stage.

Effects of Shading on Grain-Filling Properties and Yield of Maize at Different Growth Stages

CHEN Chuan-Yong,WANG Rong-Huan,ZHAO Jiu-Ran,XU Tian-Jun,WANG Yuan-Dong,LIU Xiu-Zhi,LIU Chun-Ge,PEI Zhi-Chao,CHENG Guang-Lei,CHEN Guo-Ping

Acta Agron Sin. 2014, 40(09):  1650-1657.  doi:10.3724/SP.J.1006.2014.01650

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 The objective of this study was to explore the effect of shading at different growth stages on grain filling properties and yield of maize (Zea mays L.). The Field experiments were carried out using maize cultivars (Jingke 968, Zhengdan 958) with shading of 50% at the 13th leaf fully expanded (T1), the silking (T2) and the15th day after silking (T3) for seven days in 2012–2013. The natural light condition without shading was used as the control. The Logistic equation was used to analyze the grain filling process. The results showed that grains per ear, 1000-kernel weight and yield were all decreased to a different degree under shading conditions at different growth stages, and the decrease rate of grain yield was increased with lasting shading duration. The yield was significantly different under different shading treatments. The duration of the maximum grain filling and active grain-filling period (P) were shortened, the maximum and mean grain-filling rate (G_max) decreased and the final grain weight (A) reduced under shading conditions. The relation among grain weight, grain number per ear and grain yield was determined by characteristics of maize cultivar. The grain weight of the same cultivar was significantly positively correlated with grain weight with the maximum grain-filling rate (W_max), and the grain weight of different maize cultivars was determined by active grain-filling period (P). The grain number per ear of the same maize cultivar was significantly positively correlated with G_max, and the grain number per ear of different maize cultivars was determined by W_max. It is an important way to keep a high or stable yield by selecting the suitable cultivar, improving W_max and G_max and prolonging active grain-filling period (P) under weak light stress.

Impact of IAA, GA3, and ABA on Negative Root Phototropism and Root Growth of Rice

LIU Da-Tong,JING Yan-Ping,SHI Hai-Xiang,ZHONG Ting-Ting,WANG Zhong*

Acta Agron Sin. 2014, 40(09):  1658-1666.  doi:10.3724/SP.J.1006.2014.01658

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The objective of this research was to investigate the relationship between rice roots negative phototropism and endogenous plant hormone levels, as well as the impact of exogenous hormones on rice root growth. The adventitious roots and primary roots of conventional cultivars Yangdao6 (indica), Nipponbare (japonica), Zhonghua11 (japonica) and its OsPIN1a over expressed transgenic seedlings were used to observe the process of root negative phototropism, measure contents of endogenous auxin (IAA), gibberellin (GA₃) and abscisic acid (ABA) in the bending part of root tips, and investigate the impact of exogenous hormones to rice root morphology and anatomy. Results indicated that seedling roots of both Yangdao6 and Nipponbare had negative phototropism, and the lateral roots and adventitious roots of Yangdao6 showed stronger negative phototropism. Plant hormones and negative phototropism of rice root and root development are closely linked. Under unilateral illumination, endogenous IAA, GA₃ and ABA levels declined. The content of these phytohormones in the irradiated side was lower than that in the shaded side. The treatment of unilateral light and exogenous IAA induced a large number of root hairs in Yangdao6. Compared with conventional rice, the angel of negative phototropism was lager in OsPIN1a transgenic plant. There was no direct relationship between exogenous GA₃ and ABA treatments and root negative phototropism of rice. Exogenous ABA inhibited root growth obviously. The total absorption surface area, root number and root length per plant were significantly reduced by ABA treatment. The treatment of 10 μmol L^-1ABA not only caused a dysplasia of both meristematic and elongation zone but also promoted the development of the central vascular tissue in root tips.

Relationship between Leaf Photosynthetic Parameters and Drought Resistance at Silking Stage in Maize Inbred Lines

CHEN Chun-Mei,GAO Ju-Lin*,SU Zhi-Jun,YU Xiao-Fang,HU Shu-Ping,ZHAO Xiao-Liang

Acta Agron Sin. 2014, 40(09):  1667-1676.  doi:10.3724/SP.J.1006.2014.01667

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 To explore drought resistance of maize inbred lines, based on leaf photosynthetic parameters at silking stage, we treated 51 maize inbred lines with drought stress at silking stage in Humochuanpingyuanguanqu and Hetaopingyuanguanqu in 2012 and 2013 to analyze response of leaf photosynthetic parameters to drought stress and the relationship between photosynthetic parameters and drought tolerance. The result indicated that at silking stage, no matter under drought and the condition of irrigation, P_n, T_r, G_s, C_i, F_v/F_m, Φ_PSII, and SPAD had a significant and positive correlation with drought resistance coefficient, WUE had a significant and negative correlation with it, while qN and qP had no correlation with it. Stepwise regression analysis on the eight leaf photosynthetic parameters above showed that P_n, WUE, F_v/F_m, Φ_PSII, and SPAD significantly correlated with drought resistance coefficient at P < 0.01. P_n, WUE and SPAD directly contributed to drought resistance coefficient, while F_v/F_m and Φ_PSII contributed indirectly. Thirty-two maize inbred lines were classified into three groups based on different drought resistance, group 1 with the highest drought resistance contained eight inbred lines (H201, H21, Ying 64, Ji 842, Zao 49, Ji 8415, Dong 46, and Shen 137), group 2 with the higher drought resistance contained fifteen lines and group 3 with the lowest drought resistance contained nine lines. The grouping result was consistant with that of yield classification.Therefore, at silking stage, P_n, WUE, F_v/F_m, Φ_PSII, SPAD, and drought resistance coefficient can be used as drought resistance evaluation indexes established for the three groups of maize inbred lines. Regression relationship was between P_n, WUE, F_v/F_m, Φ_PSII, SPAD, and drought resistance coefficient at silking stage, and the threshold values were confirmed.

Effects of Plastic Film Mulching Cultivation on Young Roots Growth Development, Tuber Formation and Tuber Yield of Sweet Potato

WANG Cui-Juan,SHI Chun-Yu,WANG Zhen-Zhen,CHAI Sha-Sha,LIU Hong-Juan,SHI Yan-Xi

Acta Agron Sin. 2014, 40(09):  1677-1685.  doi:10.3724/SP.J.1006.2014.01677

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A two-year trial and a one-year pot experiment were performed to investigate growth and development and absorbing ability of young roots, endogenous hormones content of differentiated roots at early growing stage using variety Jixu 23 with two types of plastic film mulching cultivation, and no plastic as control (CK). The tuberous root fresh weight per plant at 50 days after planting was determined, and its relationship with tuberous root yield at harvest time was analyzed. The results showed that, at 10 and 20 days after planting, the number, total length, fresh weight, and volume of young roots significantly increased compared with control, and the differences in activity, total absorption area and active absorption area of young roots between two plastic film mulching treatments were significant (P<0.05), showing the black plastic film mulching (BF) superior to the transparent film mulching (TF). Besides, zeatin riboside (ZR) content of differentiated roots (at 10 and 20 days after planting) was significant improved, which was in favor of procambium activity and tuberous roots formation. On the other hand, at early expansion period of tuberous roots, plastic film mulching cultivation increased abscisic acid (ABA) content and decreased gibberellin (GA) content in differentiated roots, as well as improved the secondary cambium activity, starch accumulation and differentiated root expansion. Meanwhile, abscisic acid (ABA) content and gibberellin (GA) content under the black film mulching significantly changed. Film mulching cultivation increased the number and fresh weight of tuberous roots per plant at 50 days after planting, which contributed to higher fresh yield of tuberous root at harvest time. In the two year experiment, two treatments significantly enhanced the valid tuber number and fresh tuber yield compared with CK. The average increments were 10.71% and 5.76% in 2011, and 12.99% and 7.45% in 2012, respectively.

Effect of Nitrogen Fertilization Timing on Lignin Synthesis of Stem and Physiological Mechanism of Lodging Resistance in Wheat 

LU Kun-Li,YIN Yan-Ping,WANG Zhen-Lin*,LI Yong,PENG Dian-Liang,YANG Wei-Bing,CUI Zheng-Yong,YANG Dong-Qing,JIANG Wen-Wen

Acta Agron Sin. 2014, 40(09):  1686-1694.  doi:10.3724/SP.J.1006.2014.01686

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For understanding the effects of nitrogen management on lignin synthesis in wheat stem and plant lodging resistance, a field experiment was conducted, using the lodging resistant cultivar Jimai 22 and the lodging sensitive cultivar Shannong 16, in 2011–2012 and 2012–2013 growing seasons. The lignin accumulation in stem, activities of enzymes related to lignin synthesis, lodging resistance index, and grain yield were evaluated under four nitrogen treatments. All treatments received 240 kg ha^–1 nitrogen during the whole growth period, in which 80 kg ha⁻¹ was applied before sowing. The remaining nitrogen was applied at pseudo stem erection and booting stages (1:1) for N1, at jointing stage for N2, at jointing and anthesis stages (1:1) for N3, and at booting stage for N4 treatment. Compared with N2 and N3, N1 and N4 were superior in lignin content, stem mechanical strength, and lodging resistance. Nitrogen fertilization timing had significant effects on activities of phenylalanine ammonia-lyase (PAL), tyrosine ammonia-lyase (TAL), and peroxidase (POD). Under N1 condition, the three key enzymes were in high activity. PAL, TAL and POD activities were higher in N2 treatment than in other treatments at 0–7 d after emergence of the second internode (ESI), and dropped rapidly at 21 d after ESI. Under N3 condition, the PAL, TAL and POD activities were low at 0–21 d after ESI, and the activity decline was alleviated by the nitrogen supplement at anthesis stage (21 d after ESI). Under N4 condition, the activities of these enzymes were increased after 14 d of ESI. At milk and dough stages, both cultivars had higher snapping resistance of the basal stem in N1 and N4 than in N2 and N3 treatments. Besides, the lodging resistance index and grain yield were also significantly higher in N1 and N4 than in N2 and N3. These results indicated that nitrogen applied at booting stage (N1 and N4 treatments) is propitious to increase PAL, TAL, POD activities and lignin content in stem, leading to the improved stem mechanical strength and decreased lodging area and lodging degree of wheat.

RESEARCH NOTES

QTL Mapping for Arabinoxylans Content and Its Relationship with Processing Quality in Common Wheat

ANG Li,HUANG Yu-Lian,CHANG Ping,YAN Jun,ZHANG Ye-Lun,XIA Xian-Chun,TIAN Yu-Bing,HE Zhong-Hu,ZHANG Yong

Acta Agron Sin. 2014, 40(09):  1695-1701.  doi:10.3724/SP.J.1006.2014.01695

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Arabinoxylans (AX) are the hydrophilic nonstarch polysaccharides in wheat grain, and they play a critical role in food processing and nutrition quality. Quantitative trait loci (QTLs) for water-extractable (WE-AX) and total AX (TOT-AX) contents were identified and mapped using 240 recombinant inbred lines (RILs, F_2:6) derived from the cross between PH82-2 and Neixiang 188. Besides, relationships between WE-AX and TOT-AX contents and protein content, Mixograph and Rapid Viscosity Analyzer (RVA) parameters were evaluated. Inclusive composite interval mapping identified five QTLs for TOT-AX content on chromosomes 1B, 4B, 5B, 5D, and 6B, which explained 5.6–18.7% of the phenotypic variations. Five QTLs associated with WE-AX content were mapped on chromosomes 1A, 1B, 5B, 6B, and 7A, explaining 4.3–34.9% of the phenotypic variation. QTLs for TOT-AX content on chromosomes 1B, 5B, and 6B shared identical marker intervals with those for WE-AX content. 1BL/1RS translocation affected both TOT-AX and WE-AX contents, whereas, grain hardness only affected WE-AX content. TOT-AX content had significant correlations with RVA parameters including peak viscosity, breakdown, final viscosity, setback, and Chinese White Salted Noodle quality traits (springness and flavor), but the correlation coefficients were influenced by 1BL/1RS translocation and the type of grain hardness.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Molecular Cloning and Expression of a bZIP Transcription Factor Gene CsbZIP1 in Tea Plant (Camellia sinensis)

CAO Hong-Li,YUE Chuan,ZHOU Yan-Hua,WANG Lu,HAO Xin-Yuan,YANG Ya-Jun*,WANG Xin-Chao*

Acta Agron Sin. 2014, 40(09):  1702-1709.  doi:10.3724/SP.J.1006.2014.01702

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The basic leucine zipper proteins (bZIP) are one of the most extensive and conserved transcriptional factors families in eukaryotes, and plant bZIPs play important roles in many biological processes, especialy for resisting abiotic stresses. In this study, a bZIP full-length cDNA sequence was cloned using RACE and reverse transcription-PCR(RT-PCR) techniques from tea plant (Camellia sinensis). The obtained full-length cDNA was named CsbZIP1 with GenBank accession number JX050148.1. It is 1515 bp in length, containing a 813 bp open reading frame (ORF), encoding 270 amino acid residues with 29.484 kD molecular weight, and containing a typical BRLZ motif (basic region domain and leucine zipper domain) of B-zip1 family. The phylogenetic tree analysis revealed that CsbZIP1 belongs to F subfamily of bZIP. The subcellular location showed that CsbZIP1 protein is located in nucleus. The qRT-PCR analysis indicated that the expression level of CsbZIP1 was up-regulated by cold (4℃) and salt (NaCl) treatments, and both expression amounts increased at first, then declined after 24 hours. However, the expression pattern was down-regulated by ABA treatment within 24 hours. These results demonstrated that CsbZIP1 could be associated with cold and salt stresses in tea plant.