Table of Content

12 May 2013, Volume 39 Issue 05

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REVIEW

Improving Water Use Efficiency of Crops by Exploring Variety Differences

MEI Xu-Rong,ZHONG Xiu-Li,LIU Xiao-Ying

Acta Agron Sin. 2013, 39(05):  761-766.  doi:10.3724/SP.J.1006.2013.00761

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Improving water use efficiency (WUE) is considered to be an important measure for mitigating the conflict between water resource crisis and sustainable crop production. In this review, variety differences in WUE at different time-space scales, the scaling-up of WUE, and the association between WUE and yield are discussed. WUE_intrinsic (WUE_i) shows wide genotypic variability, in particular, under water deficit conditions. Variation in WUE_i seems to be associated rather with variation in stomatal conductance in cereals. WUE_plant (WUE_p) differed larger among genotypes under water deficit conditions, in contrast with the smaller difference under well-watered conditions. Stomatal conductance is a determinant trait affecting WUE_p based on the studies performed up to date. Genotypes differ largely in stomatal conductance in response to water deficit. Scaling-up of WUE between leaf level and field population level is limited by canopy and boundary layer resistances, partition of water use between soil evaporation and plant transpiration and the internal allocation pattern of biomass. High WUE_i associated with low stomatal conductance can result in a considerable yield gain in a dry, stored-moisture, environment but it is likely to be disadvantageous in terms of yield in more favorable growth environments.

Research Advance in Molecule Regulation Mechanism of Leaf Morphogenesis in Rice (Oryza sativa L.)

XU Jing, WANG Li, QIAN Qian, ZHANG Guang-Heng

Acta Agron Sin. 2013, 39(05):  767-774.  doi:10.3724/SP.J.1006.2013.00767

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Rice leaf morphosis is one of important components in the design of ideal plant architecture, and is the main focus in high-yield breeding of rice. The paper expounds the advance in the molecular genetics research of rice leaf morphosis (including leaf rolling, leaf angle, leaf drooping, and leaf width) by analyzing the leaf shape regulating genes that have been cloned. Comprehensive analysis reveals that the leaf rolling is controlled by related genes that regulate the development of leaf along the adaxial-abaxial axis, the development of bulliform cells, osmotic pressure or turgidity in bulliform cells, the formation of sclerenchymatous cells and the development of cuticle. Leaf inclination, which affects the plant space extension posture, is regulated by the development of phyllula which is controlled by genes conferring the biosynthesis or signaling of phytohormone brassinosteroids (BRs). The only cloned drooping leaf gene controlls the leaf shape by influencing midrib formation. Narrow leaf genes regulate the leaf width through controlling the synthesis of auxin and its polar transport,and the development and distribution of vascular tissues. However, the study on the relationship between regulation roles of these cloned leaf shape genes. is not profound enough to draw an outline of molecular regulation network fort rice leaf development and morphosis completely and clearly. Therefore, on the basis of current research findings, it is of great significance to further explore the rice leaf molecular regulation mechanism for establishing related regulation network and shaping ideal rice plant architecture.

CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Association Analysis between Agronomic-Processing Traits and SSR Markers and Genetic Dissection of Specific Accessions in Chinese Wild Soybean Population

FAN Hu, WEN Zi-Xiang, WANG Chun-E, WANG Fang, XING Guang-Nan, ZHAO Tuan-Jie,GAI Jun-Yi

Acta Agron Sin. 2013, 39(05):  775-788.  doi:10.3724/SP.J.1006.2013.00775

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Association analysis is potential in genetic dissection of germplasm accessions and breeding materials for designing crosses and improving selection efficiencies. The present study was aimed at finding elite QTLs/alleles as well as their carriers through genetic dissection of agronomic-processing traits in Chinese annual wild soybean (Glycine soja Sieb. et Zucc.) population for improvement and broadening the genetic background of modern soybean cultivars. The genotypic data of 204 simple-sequence repeat (SSR) markers on 174 wild accessions sampled from and evenly distributed in all the wild soybean eco-regions in China were used and analyzed for association with six agronomic and processing traits under TASSEL GLM (general linear model) program based on the population structure analysis. The QTLs significantly associated with the traits were analyzed further for their allele effects. The results showed: (1) Fifty-one SSR loci (times) associated with the six agronomic-processing traits were identified in the wild population. There were a few markers/loci associated with two or more traits simultaneously, which might be the genetic bases of correlation among the traits. Sixteen of fifty-one associated loci (times) were in agreement with mapped QTLs from linkage mapping procedure. (2)There existed only a few association loci in wild population coincided with those in landrace and released cultivar populations, indicating the difference of genetic structure among the three kinds of populations. (3) A set of elite alleles of detected loci and their carrier materials were screened out. Alleles for loci associated with several traits had different phenotypic effects in different traits, e.g. GMES5532a-A332 had positive phenotypic effect for both 100-seed weight and seedling death rate under submergence, while GMES5532a-A344 had negative effect on 100-seed weight but positive effect on seedling death rate under submergence. (4)There showed great difference of the genetic structure among the tested materials with extreme phenotypic value. The extreme accessions possessed the alleles with bigger effects, such as N23349 containing four alleles with bigger positive effects having its 100-seed weight as high as 9.08 g, while N23387 containing four alleles with bigger negative effects having its 100-seed weight only 0.75 g. The above results implied that association mapping could offer further genetic information complementary to linkage mapping, especially the information of multiple alleles of QTL on whole genome could be used in cross design for pyramiding elite alleles and marker-assisted selection in breeding for soybean.

Cloning and Analysis of MAPK7 Gene Family and Their Promoters from Brassica napus

ZHU Bin,LU Jun-Xing,PENG Qian,WENG Chang-Mei,WANG Shu-Wen,YU Hao,LI Jia-Na,LU Kun,LIANG Ying

Acta Agron Sin. 2013, 39(05):  789-805.  doi:10.3724/SP.J.1006.2013.00789

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Mitogen-activated protein kinase (MAPK) is a large family of serine/threonine protein kinase, containing 11 conserved subdomains. MAPK pathway play a central role in transferring information from diverse receptors/sensors to a wide range of cellular responses in plants. Signaling through MAP kinase cascade can lead to cellular responses including cell division, development, hormone, physiology, as well as the response to a broad variety of biotic and abiotic stresses. In this study, the full-length cDNA of MAPK7 gene family was isolated from Brassica napus. There were three members in this gene family, including BnMAPK7-1, BnMAPK7-2, and BnMAPK7-3. Standard mRNA lengths of these genes were 1 593, 1 434 and 1 547 bp. Phylogenetic tree showed that BnMAPK7 gene family was all originated from Brassica rapa, and BnMAPK7-1/-2 were generated from ancestral gene of Bra03723, while BnMAPK7-3 was evolved from ancestral gene of Bra03724. We also cloned promoters of BnMAPK7-1/-2, which contain some light responsive elements, hormone responsive elements and stress response elements. Quantitative real-time PCR (qRT-PCR) showed that BnMAPK7 gene family expressed in all organs tested, and could be induced by phytohormones (MeJA, ABA, and SA), signaling molecules (H₂O₂), stress (heat) and injury (wounding and Sclerotinia sclerotiorum). This study preliminarily proved that the BnMAPK7 gene family plays certain roles in plant stress responses. In addition, the recombinant BnMAPK7-1/-3 proteins were successfully expressed in Escherichia coli, but the main form of proteins was inclusion body, this result would contribute to further discuss in the future.

Cloning and Transcription Function Analysis of Cotton Transcription Factor GhGT30 Gene

LI Yue,SUN Jie,CHEN Shou-Yi,XIE Zong-Ming

Acta Agron Sin. 2013, 39(05):  806-815.  doi:10.3724/SP.J.1006.2013.00806

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Trihelix transcription factors play an important role in the regulation of plant growth and development, as well as in their response to many kinds of abiotic stress. According to expressed sequence tag (EST), full-length cDNA sequence of trihelix transcription factor was cloned from upland cotton (Gossypium hirsutum L.) using the methods of rapid-amplification of cDNA ends (RACE) and RT-PCR. Sequence analysis showed that the full-length of GhGT30 (GenBank accession No. JQ013098) was 2210 bp, containing a 2025 bp open reading frame which encoded a protein of 675 amino acids with predicted molecular weight of 76.26 kD and a isoelectric point of 6.21. SMART analysis showed GhGT30 with each trihelix domain at N-terminal and C-terminal, belonging to GT-2-type factors. Amino acid sequence alignment revealed that N-terminal of GhGT30 shared high degree of identity with other higher plant GT proteins. The phylogenetic tree showed that GhGT30 was located at the same branch with GmGT-2B. Transient expression of recombinant plasmid GhGT30/PBI221-GFP in Arabidopsis protoplasts showed that GhGT30 was located in cell nuclei. Real-time quantitative PCR (qPCR) showed that GhGT30 was expressed in a higher level in flower, fiber (12 DPA) than in root, stem leaf, and ovule (0 DPA). The gene was differentially respondes to various abiotic stresses (dehydration, high salinity, and low temperature) and ABA, indicating that it may play important roles in response of cotton plant to abiotic stresses.

RNAi Vector Construction for Protein Disulfide Isomerase Gene and Seed Setting Characteristics in Offspring of Transgenic Rice under High Temperature Treatment

IU Guang-Kuai,CAO Zhen-Zhen,WEI Ke-Su,PAN Gang,SU Da,ZHANG Chun-Jiao,CHENG Fang-Min

Acta Agron Sin. 2013, 39(05):  816-826.  doi:10.3724/SP.J.1006.2013.00816

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To clarify the effect of PDI gene silence on rice yield traits and grain quality, we sub-cloned a 450 bp RNAi fragment from Nipponbare by RT-PCR, and successfully constructed a binary-vector pTCK303-RiOsPDI containing intron hpRNA (ihpRNA), then transformed it into the callus of wild type Nipponbare mediated by EHA105. The T-DNA region for PDI RNA interference in regenerating rice plants was integrated with rice genome via single copy in T₀ generation transgenic plants, and showed a 3:1 genetic mode in T₁ transgenic population, which could be conformed by PCR amplifying analysis and Southern blotting identification. The PCR and qRT-PCR for PDI gene expression in different organs showed that there were much lower level of PDI expression in grains, leaves, stem and sheath for transgenic plants compared with those for wild type Nipponbare, with almost 80% of the dropping in transgenic seeds. The influence of high temperature stress on seed setting traits, panicle agronomic traits and grain quality and also its relation to PDI gene expression in developing grains was further examined with T₁ generation of transgenic plants imposed to two temperature treatments under the controlled temperature chambers, the results indicated that PDI silence transgenic plants had a remarkable lower seed setting rate, somewhat lower grain weight compared with its wild phenotype under the high temperature treatment in despite of no obviously varying with its wild phenotype under normal developmental condition, suggesting that PDI gene should be  probably responsible for rice tolerance to high temperature stress. Moreover, there were lower translucence and higher chalky degree for transgenic plants than for Nipponbare, although no significant difference were observed in grain total protein and amylose content between PDI silence transgenic plant and its CK.

Specific Loci for Adult-Plant Resistance to Stripe Rust in Wheat Founder Parent Fan 6 and Their Genetic Dissection in Its Derivatives

CHEN Guo-Yue, LIU Wei, HE Yuan-Jiang, GOU Lu-Lu, YU Ma, CHEN Shi-Sheng, WEI Yu-Ming, ZHENG You-Liang

Acta Agronomica Sinica. 2013, 39(05):  827-836.  doi:10.3724/SP.J.1006.2013.00827

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Fan 6 is one of the most important founder parents of common wheat in China. The objective of this study was to reveal the genetic structureof Fan 6 and the transmission of its specific loci for adult-plant resistance to stripe rust (Puccinia striiformis f. sp. tritici, Pst) in 39 derivatives.The resistance was evluated using 80 SSR markers assocated with the consensus QTLs for adult-plant resistance to Pstand the phenotypic assessment was conducted at seedling and adult stages after mixed inoculation with Pst races CYR31, CYR32, and CYR33. Fan 6 and seven derivatives showed resistance to Pst in the whole growth stage. Nine SSR allelles, Xwmc631, Xgwm359, Xwmc407, Xgwm501, Xgwm148, Xgwm539, Xgwm533, Xgwm299, and Xgwm639,were identified to be specific to Fan 6, of which Xwmc631, Xgwm359, Xgwm501, Xgwm299, and Xgwm639 exhibited high inheritability in the four derivate generations of Fan 6. The result of marker–trait association analysis showed that six SSR loci were significantly correlated with adult-plant resistance to Pst in Fan 6 and its derivatives. Among them, alleles from Fan 6 on lociXgwm539 and Xgwm299 were responsible for disease severity, infection type, incidence, disease index, and area under the disease progress curve (AUDPC). These results indicated that the slow stripe-rusting resistance in Fan 6 has been intensively selected in breeding programs using Fan 6 as the founder parent, which will play an important role in Southwestern wheat area of China.

Functional Analysis of miRNA Resistant to Banded Leaf-Sheath Blight in Maize

LUO Mao,PENG Hua,SONG Rui,GAO Jian,PAN Guang-Tang,ZHANG Zhi-Ming

Acta Agron Sin. 2013, 39(05):  837-844.  doi:10.3724/SP.J.1006.2013.00837

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microRNAs (miRNAs) are an extensive class of endogenous, non-coding, short (19–24 nt) RNA molecules, which directly involve in regulating gene expression at the post-transcriptional level and play important roles in the regulation of plant growth and development, and in response to various abiotic and biotic stress. However, the miRNAs-regulated networks and function in response to BLSB are not very clear in Zea mays. In our previous studies, miRNAs and their target genes in maize were excavated by bioinformatic prediction, and a total of 23 conserved miRNAs and 89 miRNA targets were predicted and identified by a web-based integrated computing system and WMD 3. In this paper, based on previous studies, we profiled the responsive functions of miRNAs under BLSB stress, preliminarily identified the precursor of miRNAs in BLSB-stressed Zea mays (R15 and Ye478) by using semi-quantitative RT-PCR and detected the level of mature miRNAs under BLSB stress, showing that some miRNAs play very important roles in response to BLSB in Zea mays.

Differentially Expressed Protein Profiling during Ear Floral Development between Maize Hybrid and Its Parents

GUO Bao-Jian,SONG Fang-Wei,FENG Wan-Jun,SUI Zhi-Peng,SUN Qi-Xin,NI Zhong-Fu

Acta Agron Sin. 2013, 39(05):  845-854.  doi:10.3724/SP.J.1006.2013.00767

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To gain an insight into the molecular basis of heterosis related to kernel number per ear in maize, we established a differentially expressed protein profiling between highly heterotic hybrid Yuyu 22 and its parental lines Zong 3, 87-1 during ear floral development by using a combined methods of 2-DE and MALDI TOF MS. A total of 1290 protein spots were detected, among which 114 were found to be differentially expressed with a significant difference at P<0.05. The number of protein spots belongs to the models of expression in hybrid and uniparent but not in another parent (UPF1), hybrid is equal to the highly expressed parent (HDH), hybrid is equal to the mid-parent (MPE), hybrid is equal to the lowly expressed parent (LDH), up-regulated in hybrid (URH), down-regulated in hybrid (DRH), dominant expression of uniparental proteins but not in hybrids (UPnF1), hybrid-specific expressed protein spots (F1nBP) was 27, 25, 15, 13, 11, 11, 10, and 2, respectively. In addition, 104 proteins were identified by using MALDI TOF MS, which are involved in 12 functional categories, including metabolism, signal transduction, energy, gene transcription, protein synthesis, protein transport and storage, cell growth, cell division, cell structure, disease and defense, secondary metabolism, transposons, unknown and putative proteins. Taken together, expression differences between hybrid and its parents at protein abundances and multiple functions of in hybrid may contribute to the heterosis related to kernel number per ear.

Genetic Analysis and Molecular Mapping of Stripe Rust Resistance Gene in Wheat Cultivar Xiaoyan 9323

TANG Ming-Shuang,MA Dong-Fang,WANG Hai-Ge,YIN Jun-Liang,HOU Lu,YAO Qiang,JING Jin-Xue

Acta Agron Sin. 2013, 39(05):  855-861.  doi:10.3724/SP.J.1006.2013.00855

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Stripe rust, caused by Puccinia striiformis f. sp. tritici, is one of the most widespread and destructive wheat diseases worldwide. Resistance breeding is constantly pursued for decades to tackle the variations of prevalent Pst races. Xiaoyan 9323, the homology material of Xiaoyan 6, has early maturity, strong resistance, wide adaptability, higher resistance to stripe rust, excellent biological characteristics. To identify the resistance gene(s), we crossed Xiaoyan 9323 with susceptible genotype Mingxian 169, and tested F₁, F₂, F₃, and BC₁ progenies with Chinese race CYR32 at seedling stage in greenhouse. Then, SSR techniques were used to screen molecular markers linked to the gene conferring resistance to CYR32 in Xiaoyan 9323. The genetic analysis results showed that Xiaoyan 9323 displayed resistance to epidemic yellow rust races in China when tested with five races ofstripe rust and one recessive gene conferring resistance to races CYR32. The mapping population of F₂ generation was inoculated with CYR32. Six SSR markers, Xwmc807, Xbarc3, Xwmc684, Xwmc201, Xwmc553,and Xwmc179 were linked to the resistance gene, which were all located on chromosome arm 6AL. The closest flanking makers were Xwmc201 and Xwmc553 with genetic distances of 2.6 cM and 3.7 cM, respectively. According to SSR markers’ chromosome location, the gene was located at chromosome 6AL. Based on chromosomal location, reactions to various pathotypes andpedigree analysis, the gene may be a new one different from the known stripe rust resistance genes, designated as YrXY9323 temporarily. Two flanking SSR markers, Xwmc201 and Xwmc553, were used to test 42 wheat cultivars from Huang-Huai River Valleys wheat region. The results showed that 19% cultivars had the same polymorphic bands as YrXY9323, indicating that the polymorphic SSR markers can be useful in wheat molecular marker selection and breeding.

Identification and Gene Mapping of Rice Early Senescent Leaf (esl3) Mutant

MIAO Run-Long,JIANG Yu-Dong,LIAO Hong-Xiang,XU Fang-Fang,HE Guang-Hua,YANG Zheng-Lin,ZHAO Fang-Ming,SANG Xian-Chun

Acta Agron Sin. 2013, 39(05):  862-867.  doi:10.3724/SP.J.1006.2013.00862

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Leaf early senescence can directly decrease crop photosynthesis, yield and quality. Therefore, the identifications of mutants with early senescence and its gene function play key roles in crop genetic improvement. A mutant with early senescent leaf blades, named as esl3, was identified from a EMS-induced progeny in restorer line of Jinhui 10. The middle-upper leaf in mutation displayed a brown and withered phenotype from seedling stage to maturity. Correspondingly, the chlorophyll content and net photosynthetic rate declined in the abnormal leaves while enhanced in the normal green part of leaves compared with the wild type. Agronomic traits, such as panicle number, panicle length, grains per panicle, 1000-grain weight, plant height and weight of dry matter, were reduced significantly or very significantly except for seed setting rate as compared with those of wild type. Genetic analysis showed the senescence was controlled by a recessive nuclear gene. Using 391 mutation individuals in a F₂ generation of Nippomese/esl3, ESL3 was mapped between SSR marker RM19085 and Indel marker Ind05-2 on the chromosome 5 with physical distance 91 kb including 14 annotated genes. All of these results provide a foundation for the further gene cloning and functional analysis of ESL3 gene.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Responses of the Yield and the Grain Filling to Different Post-Anthesis Soil Drought Analyzed with Single Segment Substitution Line (SSSL) in Rice (Oryza sativa L.)

CAI Yi-Xia,HUANG Ze-Shuang,ZHU Hai-Tao,CHEN Jian-Jun,DENG Shi-Yuan,WANG Wei

Acta Agron Sin. 2013, 39(05):  868-877.  doi:10.3724/SP.J.1006.2013.00868

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To explore the physiological mechanisms of the yield and the grain filling in rice affected by post-anthesis soil drought, we analyzed the characters of grain filling and the activities of enzymes involved in sucrose metabolism and starch synthesis in the single segment substitution line (SSSL) and its receptor parent Huajingxian 74 under normal (CK), moderate deficit (SD) and severe deficit (MD) water conditions after flowering were analyzed. The result showed that the SSSL, containing the resistance gene segment provided by Brazil upland rice, presented higher drought resistance than its receptor parent Huajingxian 74 under the MD and SD treatments. The yield reduction in SSSL was much less than that in Huajingxian 74. SPAD values and net photosynthetic rate of flag leaf in SSSL under the MD and SD treatments applied at 7 day after anthesis (DAA) were less than its receptor parent during mid and late grain-filling period, and the activities of sucrose synthase (SS), acid invertase (AINV), ADP glucose pyrophosphorylase (AGPP), soluble starch synthase (SSS), and Q enzymes in SSSL grains were elevated remarkably, resulting in the enhancement of grain sink activities under MD and SD at early and mid grain-filling stages. Although the activities of the above mentioned enzymes were descended much quickly during late grain-filling period under the continuous drought stress, which could shorten the duration of active grain-filling significantly, the average and the maximum grain-filling rates of SSSL under MD and SD were increased much more those that of the receptor parent during mid and early filling period, which could compensate for the loss of assimilate accumulation in grain by the abatement of active grain-filling duration, consequently the yield of SSSL under drought stress was higher than that of receptor parent, especially under SD.

Cytochemical Observation of Fertile and Sterile Anthers of Thermo-Sensitive Genic Male-Sterile Wheat

LI Dong-Xiao,LI Gan,FENG Su-Wei,RU Zhen-Gang

Acta Agron Sin. 2013, 39(05):  878-884.  doi:10.3724/SP.J.1006.2013.00878

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Cytochemical observation of fertile and sterile anthers of thermo-sensitive genic male-sterile wheat (Triticum astivum L.) indicated that lipids in both fertile and sterile anthers were very few during their development. Starches in both anthers were few too before microspore division. In fertile anthers, after microspore division and forming a bi-cellular pollen grain, the big vacuole in vegetative cell of pollen was disintegrated and disappeared, and the cytoplasmic inclusion and starch grains increased persistently. The mature pollen accumulated many starch grains. In sterile anthers, the structure of pollen was similar to that of fertile pollen before microspore division, without much difference between them. After forming a bi-cellular pollen, however, the big vacuole in vegetative cell was not disintegrated and disappeared, the cytoplasmic inclusion decreased, and the accumulated starches in pollen also disappeared. Finally, the pollen grains aborted with its cytoplasmic inclusion disintegration in bi-cellular state. Pollen abortion in this male sterile wheat is related to starch metabolism.

Effect of Number and Interspace of Planting Rows on Population and Individual Quality of Strip-Drilling Wheat

ZHENG Ting,FAN Gao-Qiong,CHEN Yi,LI Jin-Gang,RONG Xiao-Jiao,LI Guo-Rui,YANG Wen-Yu

Acta Agron Sin. 2013, 39(05):  885-895.  doi:10.3724/SP.J.1006.2013.00885

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Winter wheat is widely planted in the hilly regions in southwest china, mainly in strip-relay-intercropping system. Wheat land is traditionally prepared in strips containing five equidistant rows. The objective of this study was to optimize the number and interspace of planting rows for land preparation using machines in the hilly regions in Sichuan Province, China. A two-year field experiment was carried out, using two plant-type cultivars, Chuannong 27 of the compact-short type and Mianmai 367 of the intermediate type. Under fixed strip width (2m) and planting density (150×10⁴ha^-1), six planting patterns were compared, which were traditional pattern (CK), three-row with 30cm+30cm intervals (F3-1), three-row with 35cm+35cm intervals (F3-2), three-row with 40cm+40cm intervals (F3-3), four-row with 20cm+20cm+20cm intervals (F4-1), four-row with 20cm+30cm+20cm intervals (F4-2), and four-row with 20 cm+40 cm+20 cm intervals (F4-3). The field aeration light transmission condition and quality of population and individual were surveyed at different growth stages.The results indicated that reduction of row number per strip and increase of row spacing resulted in higher light transmission rate at the top and basal parts of plant population at booting stage, and the circulation of air reinforced. With the improved aeration and light transmission condition, quality of population and individual and yield significantly increased, but those of edge row almost remained unchanged, thus the border advantage was cut down. Meanwhile, the related quality index of inner row showed that, spike setting rate and effective spike number increased, furthermore, the decline rate of leaf area greatly decreased from booting to milky stage, besides, the accumulation of dry weight increased, and then, grain per spike, spike weight and yield increased. Finally,higher yields were obtained in treatmentsF3-3 and F4-3 compared to CK. Therefore, treatments F3-3 or F4-3 had the optimum number and interspace of planting rows for mechanical sowing strip wheat in these regions. In addition, the yield of F3-2 and F4-2 was equivalent to that of CK, but most indexes of individual quality of inner rows were better than those of CK, so F3-2 and F4-2 could replace the traditional double-three-zero strip planting pattern, too.

Effects of Paddy Soils from Different Parent Materials on Yield and Nutrient Uptake Characteristics of Double-Cropping Rice

YU Tian-Yi,PANG Huan-Cheng,TANG Hai-Ming,YANG Guang-Li,LI Yu-Yi,XIAO Xiao-Ping,TANG Wen-Guang,CHEN Fu,REN Tian-Zhi

Acta Agron Sin. 2013, 39(05):  896-904.  doi:10.3724/SP.J.1006.2013.00896

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Parent materials of paddy soils are various in double-cropping paddy fields of Hunan Province. Investigation of the effects of paddy soils from different parent materials on yield and nutrient uptake characteristics of double-cropping rice will provide references for rational regional distribution and high yield cultivation of double-cropping rice in Hunan Province. Yield and nutrient uptake characteristics of double-cropping rice were analyzed using paddy soils from different parent materials in a 7-year experiment in Changsha, Hunan. The results indicated that, different paddy soils had very significant influence (P<0.01) on yield of early rice and total yield of double-cropping rice, but no significant influence on yield of late rice. Yields of early rice and double-cropping rice were higher in red yellow clayey soil and alluvial sandy soil, with average yields (2009–2011) of 6896.9 kg ha^-1 and 6908.3 kg ha^-1 for early rice and 14 308.0 kg ha^-1 and 14 446.3 kg ha^-1 for double-cropping rice, respectively. Grey clayey soil and purple clayey soil were not beneficial to increasing yields of early rice and double-cropping rice. Average yields of early rice for the two treatments were only 6217.0 kg ha^-1 and 6180.2 kg ha^-1, and those of double-cropping rice were 13 635.4 kg ha^-1 and 13 274.5 kg ha^-1, respectively. The nutrient uptake traits of double-cropping rice varied with different paddy soils. Nitrogen uptake of double-cropping rice was higher in red yellow clayey soil, yellow clayey soil and alluvial sandy soil. Grey clayey soil was not beneficial to phosphorus uptake. Correlation analysis indicated that, nitrogen and potassium uptake of early rice had a positively significant correlation (P<0.05) with yield of early rice, and nitrogen uptake of double-cropping rice had a significantly positive correlation (P<0.05) with yield of double-cropping rice. Differences of physical and chemical properties in paddy soils from different parent materials were the main reason caused differences of yield and nutrient uptake in double-cropping rice.

Effect of Potassium Application Rate on Cotton (Gossypium hirsutum L.) Biomass and Yield

YANG Guo-Zheng,WANG De-Peng,NIE Yi-Chun,ZHANG Xian-Long

Acta Agron Sin. 2013, 39(05):  905-911.  doi:10.3724/SP.J.1006.2013.00905

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Cotton production in China is recently confronted with either yield loss by plant early senescence resulted from potassium (K) deficit, or cost rise and nutrients leaching by K excess use. However, the optimal K rate in term of cotton biomass production and yield remains uncertain to make a recommendation for the farmers. Both field with random block design and outdoor pot trials were carried out to determine how cotton (Gossypium hirsutum L. vs. Huazamian H318) biomass and yield were affected by K rates. The result showed that K2 (225 kg ha^–1) harvested the highest yield (1 341 kg ha^–1) and bore the most bolls (74 bolls per square meter) in the field trial, with a similar trend for the pot trial. As expected, cotton biomass of K2 was the highest at each of the sampling stages, especially for reproductive organs. Cotton biomass initiated simultaneously the fast accumulation period (FAP), but terminated the period differently among five K rates (0–450 kg ha^–1). During the period, K2 had the highest biomass accumulation rate both on an average and in the maximum, and for vegetative and reproductive organs. It suggests that K rate of 225 kg ha^–1 be optimal to produce a favorable yield in the field of medium fertility when N 300 kg ha^–1 and P₂O₅ 90 kg ha^–1 are applied in the Middle Reaches of Yangtze River, in which condition cotton plants accumulate greater amount of biomass with a higher accumulating rate.

Relationship of Ear Differentiation with Kernel Development and Barrenness in Maize (Zea mays L.)

MENG Jia-Jia,DONG Shu-Ting,SHI De-Yang,ZHANG Hai-Yan

Acta Agron Sin. 2013, 39(05):  912-918.  doi:10.3724/SP.J.1006.2013.00912

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Two cultivars ZD958 and DH661 were used to analyze the effect of different planting densities (45 000 plant ha^-1, 75 000 plant ha^-1, 10 5000 plant ha^-1) on kernel development and barrenness in maize (Zea mays L.). The results showed that increasing plant density had little effects on the time of ear primordia differentiation (the ear primordia presented at 28–29 days after sowing under different densities) and the total number of floret primordia during silking. However, the differentiation of ear was postponed under high density, the number of abortive florets and unfertilized florets increased with the increase of plant density. Compared with low-density, the high density reduced number of normal florets per ear by 100.0 for DH661 and by 76.4 for ZD958. Additionally, the anthesis-silking interval (ASI) was elongated, the ratio of the silked-plants was decreased (ratio of DH661 was 93.64% and that of ZD958 was 81.80% under high density), the time of silking was delayed, the number of silked florets per ear was reduced and the pollen shedding duration was shortened with increasing plant density, which results in the increment of abortion after fertilization. Interestingly, kernel abortion would also occur during grain-filling, especially in 10 days after anthesis. The kernel number per ear had a positive correlation with the bottom transmittance at silking, 10 d after silking and 20 d after silking, while the ratio of abortive floret was negatively correlated with the bottom transmittance before flowering significantly.

Effects of Meteorological Factors at Different Growth Stages on Yield Traits of Maize (Zea mays L.) in Heilonggang Basin

MING Bo,ZHU Jin-Cheng,TAO Hong-Bin,XU Li-Na,GUO Bu-Qing,WANG Pu

Acta Agron Sin. 2013, 39(05):  919-927.  doi:10.3724/SP.J.1006.2013.00919

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Sowing date affects the phenology of crop through adjusting meteorological factors at different growth stages, which plays an important role on development and yield in maize. A two-year field study was conducted to assess the effects of meteorological factors on summer maize yield and its components under various sowing dates in Heilonggang basin in 2009 and 2010.Zhengdan 958 (ZD958), a popular cultivar in the region, was sown at five sowing dates (20 April, 5 May, 20 May, 4 June, and 18 June) in 2009 and three sowing dates (30 April, 21 May, and 11 June) in 2010, respectively, and harvested atphysiological maturity (R6) stage. Meteorological factors, including maximum temperature, minimum temperature, temperature range, growing-degree day, precipitation, wind speed, maximum wind speed,relative humidity and sunshine duration, maize yield and yield components including ear number (EN), kernel number per ear (KNE) and 1000-kernel weight (KW), as well as the relationship between meteorological factors and yield components were analyzed. Partial correlation analysis was used to estimate the effect of agro-meteorological variables on maize yield. The results showed that due to the annual difference of meteorological conditions, yield traits were not changed with sowing date. At the density of 8.25 plants ha^-1, multiple linear regressions between yield and its components suggested that a high KW combined with a stable KNE was important to increase yield. Yield traits were closely correlated with various meteorological factors at different growth stages. The light condition affected KNE and yield significantly during ear formation stage and anthesis stage. Daily temperature range was significantly correlated with yield at seedling and vegetative growth stage. Daily maximum temperature and daily minimum temperature significantly affected KNE from tasseling to silking. Effective precipitation of whole growth period influenced the increment of KW and KNE. The above factors are important in sowing period adjustment and choosing cultivation methods. Therefore, a technique could be applied in this area with earlier sowing date and delayed harvest, so that stress from adverse weather conditions could be avoided and kernel filling duration could be extended to achieve maximum yield.

RESEARCH NOTES

Functional Characterization of Isochrysis galbana Δ5 Desaturase Gene IgD5 in Arabidopsis thaliana

LIU Jiang,SUN Quan-Xi,LI Xin-Zheng,QI Bao-Xiu

Acta Agron Sin. 2013, 39(05):  928-934.  doi:10.3724/SP.J.1006.2013.00928

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We have isolated a Δ5 desaturase gene from the alga Isochrysis galbana, namely IgD5. Phylogenetic analysis showed that it shared the highest homology with a functionally characterized Δ5 desaturase from Pavlova salina. Previously, we demonstrated that IgD5 has activity towards the omega-6 fatty acid substrate by heterologous expression of IgD5 inSaccharomyces cerevisiae. However, whether IgD5 also has activity towards the potential omega-3 fatty acid substrate has not been verified. In this study, we transformed IgD5 into a double transgenic Arabidopsis thaliana (TMA2)that can already synthesize di-homo-γ-linolenic acid (DGLA, 20:3Δ^8,11,14) and eicosatetraenoic acid (ETA, 20:4Δ^8,11,14,17). Triple transgenic plants were identified by PCR and RT-PCR. The total fatty acids composition of the transgenic lines was determined by gas chromatography. Novel fatty acids, arachidonic acid (AA, 20:4Δ^{5, 8,11,14}) and eicosapentaenoic acid (EPA, 20:5Δ^5,8,11,14,17) were detected and accounted for 7.44% and 2.07% of total fatty acids, with a conversion rate of 68% and 60%, respectively, which are much higher than those in yeast. In addition, IgD5 did not show a preference for either ω3 or ω6 substrate. Furthermore, IgD5 has strong substrate specificity as no fatty acid products were detected except for AA and EPA. These new findings further confirmed that IgD5 is an excellent gene for the production of fish oil in plants due to its high enzyme activity coupled with substrate specificity.

Identification of Low Phytic acid Maize Germplasm and Primary Screening of Its Molecular Markers

GAO Qing-Hua,MENG Yi-Jiang,ZHANG Cui,JIA Meng,LIU Zhao,HOU Ming-Ming,JIN De-Min,LI Xue-Jiao,NIU Dong-Dong,MIAO Liu-Yang,GUO Le-Qun,DOU Shi-Juan,LIU Li-Juan,LI Li-Yun,ZHAI Wen-Xue,LIU Guo-Zhen

Acta Agron Sin. 2013, 39(05):  935-942.  doi:10.3724/SP.J.1006.2013.00935

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Reducing the content of phytic acid (PA, myo-inositol-1,2,3,4,5,6-hexakis phosphate) is important for improving the nutritional value of maize (Zea mays L.). The identification and application of low phytic acid (lpa) maize germplasm is an economical and effective approach in breeding program. In our previous study, Qi319 was identified as a low phytic acid inbred line. In this study, we found that the content of phytic acid phosphorus in Qi319 kernels is about one fourth of normal maize inbred lines based on quantitative analysis. The characterization of agronomic traits revealed that the germination rate of Qi319 was 75.5%, lower than that of normal inbred lines, however, Qi319 plants grew normally in the field. F₂ population was generated by crossing between Qi319 and Lpa241, segregation was found for the content of phytic acid among F₂ populations. The segregation ratio of 3:1 confirmed that the lpa trait was determined by a single recessive gene. We then identified two molecular markers (IDP7818 and IDP7635) located on the long arm of chromosome 2 that were co-segregated with low phytic acid loci. This result provides a fundamental basis for marker-assisted maize lpa selection process.

Yield Trends of Double Rice under Long-Term Fertilizations in Southern China

LI Zhong-Fang,XU Ming-Gang,ZHANG Hui-Min,SUN Nan,LOU Yi-Lai

Acta Agron Sin. 2013, 39(05):  943-949.  doi:10.3724/SP.J.1006.2013.00943

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Four long-term field experiments conducted in Baisha Fujian, Jinxian Jiangxi, Nanchang Jiangxi, and Wangcheng Hunan of Southern China, were selected to assess dynamic characteristics of double-rice grain yield under different nutrient strategies. For each experiment, there were five treatments of chemical fertilizer NPK (NPK), manure combined with chemical fertilizer NPK (NPKM), chemical fertilizer NP (NP), chemical fertilizer NK (NK), and control (CK). The results showed that rice yield in the treatments of NPKM, NPK, NP, and NK increased by 84.3%, 68.1%, 42.9%, and 39.9%, respectively on average compared with the CK, and was remarkably higher in the NPKM than in the NPK treatment. Rice yield change as a whole showed increasing or stable trend for the NPKM and NPK treatments, especially for late-rice. Rice yield showed a decreasing trend in the NK treatment, but stable in other treatments. The early-rice was declined with lasting planting years than the late-rice. The significantly positive correlations were found between the yield trends and phosphorus application rate across the sites. There were a relative stable yield trend in Nanchang due to the higher phosphorus application (52 kg ha^-1 yr^-1), and the negative trends in Baisa due to the low phosphorus application (24 kg ha^-1 yr^-1). The deficiency of phosphorus fertilizer makes rice yield decreasing. The yield-declining trends were observed in rice especially in early-rice with no fertilizer or chemical fertilizers alone. The results suggest that manure application combined with chemical NPK fertilizers should be encouraged for increasing yield and sustainability. Phosphorus should be appropriately applied at 50.0–63.9 kg ha^-1 yr^-1, especially for early-rice.