Table of Content

12 July 2011, Volume 37 Issue 07

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Seedling and Slow Rusting Resistances to Leaf Rust in CIMMYT Wheat Lines

HAN Ye, HE Zhong-Hu, JIA Xian-Chun, LI Xing, LI Zai-Feng, LIU Da-Qun

Acta Agron Sin. 2011, 37(07):  1125-1133.  doi:10.3724/SP.J.1006.2011.01125

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CIMMYT wheat has played an important role in wheat breeding in China. Identification of leaf rust resistance genes in CIMMYT wheat is important for developing wheat cultivars with resistance to leaf rust in China. A total of 103 CIMMYT wheat lines and a set of 35 differential lines, mostly near-isogenic lines in the background of Thatcher with known leaf rust resistance genes were inoculated with 15 Chinese pathotypes of Puccinia triticina for postulating leaf rust resistance genes in CIMMYT wheats at the seedling stage. These genotypes were also planted in the field for characterization of slow rusting responses to leaf rust in the 2008–2009 and 2009–2010 cropping seasons.Four leaf rust resistance genes Lr26, Lr34, Lr42, and Lr47 were postulated in 46 genotypes through seedling test, pedigree analysis and molecular maker detection. Resistance gene Lr26 was present in nine accessions. Lr34 was identified in 28 lines. Lr42 was found in eleven lines and two lines might contain Lr47. Known resistance genes were not identified in the other 57 accessions and these lines were resistant to most of pathotypes tested. Forty-six genotypes showed slow leaf rusting resistance in the two cropping seasons. The results from seedling and field tests showed that CIMMYT wheats carry abundant effective seedling and adult plant resistance genes, and can be used in breeding resistant cultivars for durable control of wheat leaf rust in China.

Comparison of Floret Intact Chloroplast Proteome in Male Sterile Line induced by CHA-SQ-1, Cytoplasmic-Nuclear Sterile and Its Normal Fertile Lines in Wheat

LI Li, WANG Shu-Peng, ZHANG Gai-Sheng, WANG Liang-Ming, SONG Yu-Long, ZHANG Long-Yu, NIU Na, MA Shou-Cai

Acta Agron Sin. 2011, 37(07):  1134-1143.  doi:10.3724/SP.J.1006.2011.01134

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Weextracted floret chloroplast proteins from the genetic male sterile line ms(S)-1376, the physiological male sterile line ms(A)-1376 induced by chemical hybridizing agent SQ-1, and their counterpart maintainer line (A)-1376 (normal fertility). These proteins were separated via 2-D electrophoresis with immobilized pH 4–7 gradients as the first dimension and SDS-PAGE as the second one. We established a set of technique available for intact chloroplast isolation and 2-DE of proteins in wheat floret and compared the effect of intact chloroplast purification using two methods. Based on the 2-DE technique, we explored the difference of the floret chloroplast proteins among the three materials tested in their early uninucleate anther stage. The result showed that we obtained high purity of intact chloroplast using discontinuous sucrose density gradient centrifugation with three-step gradient densities of 30%, 45%, and 60%. Proteins were extracted from chloroplast by TCA-acetone and analyzed by PDQuest software, we got as much as 239 protein spots within pH 4–7 and with molecular weight of 14.4–66.2 kD on each 2-DE gel. We analyzed six differential expressed proteins by matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry (MS) and bioinformatical database, and found they were acyl-CoA dehydrogenase domain protein, calmodulin-binding protein phosphatase, multiple catalytic peptidase, heat-shock protein 60, light receptor protein 2 and a protein of unknown function. These proteins are involved in series of physiological reactions such as metabolism of energy substances, chloroplast defendance, chloroplasts signal transduction and plant growth, the differential expression of those proteins among the three materials tested is likely related to the male sterility in wheat.

Molecular Detection and Identification of TaPIEP1 Transgenic Wheat with Enhanced-resistance to Sharp Eyespot and Fusarium Head Blight

LIU Xin, CAI Shi-Bin, ZHANG Ba-Qiao, ZHOU Miao-Beng, LU Yan, TUN Ji-Zhong, DU Li-Pu, LI Shi-Shen, CANG Chu-Jiang, ZHANG Ceng-Yan

Acta Agron Sin. 2011, 37(07):  1144-1150.  doi:10.3724/SP.J.1006.2011.01144

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Wheat sharp eyespot, mainly caused by Rhizoctonia cerealis, and Fusarium head blight (FHB), primarily caused by Fusarium graminearum, are important diseases of wheat (Triticum aestivum L.) in China. We have isolated a pathogen-induced ERF gene from wheat, TaPIEP1, which encodes the ERF transcription factor TaPIEP1. TaPIEP1 localizes to the nucleus, binds to the GCC-box cis-element and possesses the transcriptional-activation activity. To study the roles of TaPIEP1 in wheat defense responses to the major pathogens of sharp eyespot and FHB, we characterized the TaPIEP1 transgenic wheat plants in T₄ and T₅ generations by PCR, Southern blot, RT-PCR, and Q-RT-PCR analyses. We also evaluated the disease resistance in these TaPIEP1 transgenic plants through inoculating R. cerealis and F. graminearum. The PCR and Southern blotting results showed that the alien TaPIEP1 was inherited stably in transgenic wheat plants, and was independently integrated with a single copy or two copies into seven transgenic wheat lines, suggesting that these transgenic wheat lines derived from seven transformants. The RT-PCR and Q-RT-PCR analysis results indicated that the alien gene TaPIEP1 was over-expressed in eight transgenic wheat lines. Compared with untransformed wheat host Yangmai 12, the eight transgenic wheat lines over-expressing TaPIEP1 showed significantly-enhanced resistance to R. cerealis infection. Out of them, some plants of three transgenic wheat lines displayed improved-resistance to both R. cerealis and F. graminearum infections. These results suggest that TaPIEP1 gene is involved in defense responses to attack with R. cerealis and F. graminearum, and TaPIEP1 is useful for improving wheat resistance to both diseases.

QTL Analysis of Root Traits of Soybean at Seedling Stage

ZHOU Rong, CHEN Hai-Feng, WANG Xian-Zhi, WU Bao-Duo, CHEN Shui-Lian, ZHANG Xiao-Juan, TUN Hua-Jun, YANG Zhong-Lu, QIU De-Zhen, JIANG Mu-Lan, ZHOU Xin-An

Acta Agron Sin. 2011, 37(07):  1151-1158.  doi:10.3724/SP.J.1006.2011.01151

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Root system plays important roles in plant growth and development, including uptaking water and nutrient, resisting biotic and abiotic stresses, and finally influencing yield and quality. A number of QTLs for shoot traits have been detected using different populations in soybean [Glycine max (L.) Merr], but rarely for root trait. The aim of the present study was to identify QTLs for some root traits at seedling stage in soybean. A total of 165 recombinant inbred lines (RILs) derived from the cross between Zhongdou 29 and Zhongdou 32 were used. Soybean seedlings were hydroponically cultured,root traits including main root length, number of lateral roots, root weight, root volume, and aerial part traits such as plant weight, shoot weight per plant, and ratio of root weight to shoot weight were measured at the stage of V2 (first trifoliolate leaf fully expanded). By composite interval mapping (CIM) method, twenty QTLs for roots and aerial part traits were mapped on eight chromosomes, including nine major-effect QTLs on chromosome 11 and 14 with 10.5–26.1% of the phenotypic variation. On chromosome 11 and 14, some QTLs for root traits and aerial part traits were clustered, which was consistent with the correlation analysis of phenotypic traits, indicating that the root traits are associated with the shoot traits.

Genetic Analysis and Gene Mapping of a Novel Narrow and Rolled Leaf Mutant nrl2(t) in Rice (Oryza sativa L.)

WANG De-Zhong, SANG Xian-Chun, LIU Xiao-Qiang, WANG Ceng, WANG Qiu-Shi, DIAO Fang-Meng, LING Yang-Hua, LI Yun-Feng, HE Guang-Hua

Acta Agron Sin. 2011, 37(07):  1159-1166.  doi:10.3724/SP.J.1006.2011.01159

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Study of the genes which regulate leaf development is significant in rice functional genomics research and molecular breeding. In the present study, a novel rolled and narrow leaf mutant was obtained from the rice (Oryza sativa L.) restorer line Jinhui 10 treated by ethyl methyl sulphonate (EMS), named nrl2_(t). The mutant exhibited narrow/semi-rolled and elongate leaves, earlier flowering, thinner stalk, higher pigment content and higher plant height compared with the control. The indole-3-acetic acid (IAA) content relatively reduced in the flag leaf compared to that of wild type, but increased in the young panicle at the heading stage. Genetic analysis indicated that the mutant was controlled by a single recessive gene, located on the chromosome 3 between SSR markers s3RM1 and s3RM3, delimiting to a 114 kb region. These results will lay a good foundation for molecular cloning and functional analysis of the NRL2_(t).

Analysis of Genes Resistance to Phytophthora Root Rot in Soybean Germplasm Imported from America

XIA Chang-Jian, ZHANG Ji-Qing, WANG Xiao-Ming, LIU Zhang-Xiong, SHU Zhen-Dong

Acta Agron Sin. 2011, 37(07):  1167-1174.  doi:10.3724/SP.J.1006.2011.01167

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Phytophthora root rot caused by Phytophthora sojae is a major constraint in soybean production in China. Breeding resistant cultivars is a most effective and economical method for the disease control. In this study, 85 soybean cultivars (lines) from America were inoculated with 13 strains of P. sojae using the hypocotyl inoculation technique and identified the reactions. The results showed that 72 cultivars (lines) were resistant to one or more P. sojae strains. Comparisons of reaction types of differential soybean cultivars (lines) and pedigree analyses allowed postulation of genes or combinations of genes for Rps1a, Rps1c, Rps1k, Rps2, Rps3c, Rps4, Rps5, Rps6,and Rps7 in 35 cultivars or lines. Of the 35 cultivars or lines, 14 carrying Rps1a, one carrying Rps1c and two carrying Rps1k could be used as resistant parents in soybean breeding programs.

Analyses of QTLs for Rice Panicle and Milling Quality Traits and Their Interaction with Environment

HU Xia, SHI Yu-Min, JIA Qian, XU Qin, WANG Yun, CHEN Kai, SUN Yong, ZHU Lian-Hua, XU Jian-Long, LI Zhi-Kang

Acta Agron Sin. 2011, 37(07):  1175-1185.  doi:10.3724/SP.J.1006.2011.01175

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QTLs and their interactions with environments for yield-related traits—second branch number (SBN), spikelet number per panicle (SNP), filled grains number per panicle (FGN), 1000-grain weight (TGW) and panicle weight (PW); grain type traits—grain length (GL), width (GW) and thinkness (GT); and milling quality traits—brown rice percentage (BR), milled rice percentage (MR) and head rice percentage (HR) were identified and analyzed in the two environments, Nanning of Guangxi and Sanya of Hainan, using an introgression line population derived from the cross of recurrent parent Ce258 and a donor IR75862. There were significant differences in FGN, TGW, GL, GW and HR between the two parents. Significant correlations were found among the yield-related traits, and they were strikingly negatively correlated with TGW and GL. Most yield-related traits and grain type had no significant correlations with the three milling quality traits. A total of 57 QTLs were identified for yield-related traits, grain type and milling quality, including six for SBN, four for FGN, five for each of SNP, PW and TGW, nine for GL, seven for W, one for GT, four for BR, five for MR and six for HR, which distributed on all chromosomes except chromosome 11. Most QTLs affecting SBN, SNP and TGW clustered and distributed in the chromosomes independent of the QTLs for BR, MR and HR. Some important QTLs for the above traits were identified on chromosomes 2, 3, 4, 5, and 6 which had been previously detected many times in various genetic backgrounds and environments. One QTL affecting GL and GW in the region of RM152-RM310 on chromosome 8 was newly identified, which simultaneously increased GL and GW. The stable QTLs identified in this study are of importance for marker-assisted selection (MAS) in rice breeding programs. In addition, HR was largely affected by environment and the QTLs for HR had a significant interaction with environment. The interaction characteristics of QTL with environment and its application in MAS were deeply discussed in the paper.

Heterosis for Plant Height and Ear Position in Maize Revealed by Quantitative Trait Loci Analysis with Triple Testcross Design

SONG Fang-Wei, BANG Hui-Ru, LIU Ting, ZHANG Xi-Rong, SUN Ji-Shen, NI Zhong-Fu

Acta Agron Sin. 2011, 37(07):  1186-1195.  doi:10.3724/SP.J.1006.2011.01186

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In this study, the genetic basis of plant height and ear position for highly heterotic hybrid Yuyu 22 was analyzed by using TTC (triple testcross) genetic mating design, with a population including 270 testcross progenies. By using composite interval mapping, the number of detected QTLs for plant height and ear position was 20 and 17, respectively. These QTLs for plant height and ear position were classified as overdominant (11 and 8), additive (5 and 6), dominant (2 and 0) and partially dominant (2 and 3). Further analysis indicated that several QTL regions, including Bin1.06 (umc2151–umc1122), Bin3.05 (umc2127–umc2166–umc1539) and Bin7.03 (umc1865–umc1888), contributed to both plant height and ear position, which was consistent with the significant correlation between plant height and ear position. One-dimensional genome scan showed four and seven genome regions of QTL ´ genetic background interactions, 22 and 12 marker pairs with epistatic effects for plant height and ear height respectively and the contribution for phenotypic variation was 3.26–16.58% and 3.44–22.41%, which suggests that the contribution of epistasis to the heterosis of the two traits is important.

RNAi Vector Construction of AtDof1.7 Transcription Factors and Genetic Transformation into Arabidopsis thaliana

YIN Meng-Zhi, GUAN Mei, XIAO Gang, LI Quan, GUAN Chun-Yun

Acta Agron Sin. 2011, 37(07):  1196-1204.  doi:10.3724/SP.J.1006.2011.01196

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The Dof (DNA binding with one finger) transcription factorsare members of a family of plant-specific transcription factors that have a highly conserved DNA-binding domain, namely Dof domain which contains a single C2C2-type zinc-finger-like motif and specifically recognizes an (A/T)AAAG sequence as the recognition core. It suggests that the Dof transcription factors play diverse roles in specific biological processes in plants. Members of this protein family in plants are found to be involved in the gene regulation of many processes, but the roles in fatty acid metabolism are rarely reported. To investigate whether AtDof1.7 Dof transcription factor can regulate fatty acid metabolism, on the basis of the sequence of the gene (GenBank accession No. AT1G51700), we designed the specific primer containing different enzyme sites. With the template of Arabidopsis thaliana DNA, the AtDof1.7 gene fragment was isolated, which wasinserted into the expression vector by forward and reverse ways respectively. The RNA interference vector of pADOF1 containing AtDof1.7 gene fragment was constructed. By floral-dip method, pADOF1 was successfully transformed into wide-type Arabidopsis thaliana. Glyphosate resistance screening and PCR detection showed that five positive transgenic plants were obtained. The result of RT-PCR showed that transgenic plants had lower expression level of AtDof1.7 gene than the wild type. Fatty acid content was analyzed by gas chromatography which showed that the content of oleic acid increased and the content of linolenic acid decreased drastically in each transgenic plant compared with wide-type plants. These results indicated that AtDof1.7 transcription factor has certain relation with fatty acid metabolic pathway in Arabidopsis thaliana seed which provides a good foundation for further study on the function of AtDof1.7 transcription factor in fatty acid metabolic regulation.

Cloning and Activity Analysis of Soybean SACPD-C Promote

ZHANG Qiang-Lin, ZHAO Yan, LI Xiao-Wei, ZAI Ying, ZHANG Yan, WANG Yang, LI Jing-Wen, WANG Qiang-Yu

Acta Agron Sin. 2011, 37(07):  1205-1211.  doi:10.3724/SP.J.1006.2011.01205

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The SACPD-Cp promoter of soybean SACPD-C was isolated from the genomic DNA of soybean Jidou 2 by TAIL PCR. Promoter sequence analysis by PLACE showed that the cloned fragment contained a lot of the motifs that constituted the seed-specific cis-elements. Replacing CaMV35S promoter of pCAMBIA1301 with the SACPD-Cp fragment, the binary expression vector pCAM-SACPD-Cp was constructed. Transient expression by Agrobacterium tumefaciens mediated method, the histochemical GUS analysis and fluorometric GUS analysis were used for testing the expression of the GUS activity. The results indicated that GUS activity driven by SACPD-Cp fragment was 93.01% of that driven by CaMV35S promoter. The SACPD-Cp promoter did not have the homology compared with the reported promoters. GUS activity assays indicated that GUS was expressed only in seeds, but not in roots, stems and leaves, which suggests the SACPD-Cp is seed-specific promoter.

Proteomic Analyses of the Maize Cross Incompatibility Gene Ga1-S

LIU Fu-Hua, WANG Chi-Wen, LIU Xu, MA Xia, NING Li-Hua, ZHANG Hua, CUI De-Zhou, JIANG Chuan, CHEN Hua-Bang

Acta Agron Sin. 2011, 37(07):  1212-1218.  doi:10.3724/SP.J.1006.2011.01212

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The objective of this paper was to study the cross incompatibility gene Ga1-S in maize through proteomic approach. Near isogonic lines of Ga1-S gene, W22 (GG) and w22 (gg), were used to make the crosses of GG×GG, gg×GG,and GG×gg respectively. First，we observed the growth process of pollen tubes grown into silks in three crosses by fluorescence microscopy; second, total silk proteins were extracted from silks of the W22 (GG) at 10 h after pollination. Total proteins were extracted by TCA/Acetone, separated by two-dimensional gel electrophoresis (2-DE) and analyzed through MALDI-TOF-MS mass spectrometry. The results indicated that pollen tube couldn’t grow into silks base in the cross of GG×gg, but could in the other two crosses; In the silk proteome of GG×GG and GG×gg , there were 25 differentially expressed proteins, including 15 specifically expressed in GG×GG, and 10 specifically expressed in GG×gg. And 12 of them were annotated in various databases by MALDI-TOF-MS and MASCOT analyses. Proteins 11, 12, 14, 18, 22 and 24 presumably play important roles in the maize cross incompatibility.

Dissecting and QTL Mapping of Component Traits of Resistance to Wheat Powdery Mildew at Early Infection Stage

WANG Hua-Zhong, ZHANG Zhen, HE Xiang, YUE Ji-Yu

Acta Agron Sin. 2011, 37(07):  1219-1228.  doi:10.3724/SP.J.1006.2011.01219

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Powdery mildew caused by Blumeria graminis f. sp. tritici (Bgt) is one of the major fungal diseases of wheat, and the use of resistant cultivars is the most effective disease control approach. Here, the International Triticeae Mapping Initiative (ITMI) W7984 × Opata85 wheat recombinant inbred population was used for powdery mildew resistance genetic study. Resistance complex trait was dissected into component traits as papilla index (PI), papilla scale (PC), haustorium index (HI) and secondary hypha index (SI) of several successive timepoint at early stage of Bgt infection. The change trends of PI and HI with time were both controlled by single main effect genes. With quantitative trait analysis, 34 resistance-related QTLs including 21 main effect QTLs were found and distributed in wheat 1B, 1D, 2B, 3A, 3B, 3D, 4A, 4B, 4D, 5B, 6A, 6B, 6D, 7B, and 7D chromosomes. QTL QPmPI16.tn-7B, which regulated the formation of papilla, had the largest effect, singly accounting for 48.69% of the phenotypic variance. Locus of QPmPI16.tn-7B promoting papilla formation was derived from the parent Opata85. Colocalized QTLs were found among different component traits. Component trait-specific QTLs may provide more information about the genetic mechanism of wheat powdery mildew resistance.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Yield Performance and Resource Efficiency of Double-Cropping Maize in the Yellow, Huai and Hai River Valleys Region

LI Li-Juan, WANG Mei-Yun, XUE Qiang-Lin, CUI Pan-Hong, HOU Hai-Feng, GE Jun-Zhu, ZHAO Meng

Acta Agron Sin. 2011, 37(07):  1229-1234.  doi:10.3724/SP.J.1006.2011.01229

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The winter wheat-summer maize relay system is the main cropping system in the Yellow, Huai and Hai River Valleys region. In recent years, because of climate changing, the winter freezing and drought have occurred frequently. To take full advantageof highphotosynthetic and high resourceutilization efficiencyof C₄crop, we explored the double-cropping maize system. The experiment was conducted in Xinxiang, Henan province in 2009 and 2010 growing seasons, comparing the grainyieldperformance andresource efficiency between double croppingmaize andthe winter wheat-summer maize cropping system. The results showed that the annual yield of double cropping maize was slightly high, the average yield of two years increased by 2.3%;annual light energy and temperature production efficiency increased by 26.1% and 6.5% respectively; the economic benefit increased by 1 628 Yuan ha^-1 and there was a farmland fallow of 140 days. It illuminated that the double-croppingmaize systems with facilitating soil fallow and avoiding winter freezing injure and drought were of high light and temperature efficiency, good economic efficiency, simplified planting patterns, and ecological security model, which will supplement winter wheat-summer maize model, and also remedy winter wheat loss in the Yellow, Huai and Hai River Valleys regions.

Characteristics of Photosynthesis and Matter Production of Rice with Different Planting Methods under High-Yielding Cultivation Condition

LI Jie,ZHANG Hong-Cheng,CHANG Yong,GONG Jin-Long,GUO Zhen-Hua,DAI Qi-Gen,HUO Zhong-Yang,XU Ke,WEI Hai-Yan,GAO Hui

Acta Agron Sin. 2011, 37(07):  1235-1248.  doi:10.3724/SP.J.1006.2011.01235

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To explore the characteristics of dry matter production and photosynthesis of rice under different planting methods in the rice-wheat cropping system in the lower Yangtze River, with early-maturing late japonica rice, late–maturing medium japonica rice and medium-maturing medium japonica rice (including japonica conventional rice and japonica hybrid rice) as materials, we compared the dry matter accumulation, distribution, translocation and leaf area, photosynthetic potential (PP), crop growth rate(CGR) and net assimilation rate (NAR) of rice by using precisionartificial transplanting with middle and strong seedlings grown in dry nursery (ATR), mechanical transplanting with small seedlings (MTR) and direct seeding (DSR). Results showed that: (1) Rice yield by using different planting methods was significantly positively correlated with totaldry matter accumulation at maturity, dry matter accumulationfrom headingto maturity, and dry matter accumulation from jointing to heading under the premise of ensuring the dry matter accumulation appropriate at heading, but not with dry matter accumulation from sowing to jointing and the harvest index. (2) For dry matter weight of population, there was no significant difference among the three planting methods before jointing, after jointing ATR was the highest, followed by MTR, DSR was the lowest, and the difference was increasing with the growing process. However, the dry matter weight per stem of ATR was the highest, while that of DSR was the lowest in the whole growth period. (3) For dry matter accumulation at different stages, there was no significant difference among the three planting methods from sowing to jointing, but ATR was significantly higher than MTR, MTR was significantly higher than DSR at the stages from jointingto headingand from heading tomaturity. The ratio to total dry matter weight increased in turn for ATR, MTR, DSR from sowing to jointing, there was no many difference among them from jointing to heading, and reduced in turn for them from heading to maturity. (4) For dry matter distribution, the dry matter weight ratio of panicle and stem to total plant at maturity reduced in turn for ATR, MTR, DSR, and that of leaf and sheath increased in turn for them. However,the ratio ofleaf at booting, heading and waxy ripe stages reduced in turn for them. (5) For dry matter export and transformation, the export rate and transformation rate of leaf and stem reduced in turn for ATR, MTR, DSR, and the matter was transportedback in stem after waxy stage, the amount of matter transportedback for ATR was most, while that for DSR was least. The export rate in sheath was no many difference in generally, but the transformation rate for ATR and MTR was lower than that for DSR. (6) For photosynthetic production, before jointing, the leaf area index was generally no many difference for three planting methods, the PPreduced in turn for ATR, MTR, DSR, and the CGR and NAR increased in turn. From jointing to heading, the PP also reduced in turn for ATR, MTR, DSR, but there was no significant difference for CGR and NAR. The leaf area rate of productive tillers at heading had no significant difference among different planting methods, but the leaf area rate from flag leaf to 3rd leaf of ATR was significantly higher than that of MTR, and MTR was significantly higher than that of DSR. After heading, the leaf area index, PP, CGR and NAR of ATR were the highest, while those of DSR were the lowest. The results suggested that dry matter and photosyntheticproduction of rice with different planting methods have their own characteristics. Compared to MTR and DSR, ATR has the advantages that the dry matter accumulation is appropriate in the early stage and significantly higher in the middle and late stage, so the total dry matter accumulation is significantly higher and its distribution is reasonable, the export and transformation rate is high, and the photosynthetic production capacity is great after heading.

Effects of Different Mulching Materials on Soil Water, Temperature, and Corn Growth

WANG Min, WANG Hai-Xia, HAN Qing-Fang, LI Rong, ZHANG Rui, GU Zhi-Kuan, YANG Bao-Peng

Acta Agron Sin. 2011, 37(07):  1249-1258.  doi:10.3724/SP.J.1006.2011.01249

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The study, with randomized block design, measured the effects of different mulching materials which included biodegradable film (S), plastic film (D), corn straw (J), liquid film (Y) and bare land on soil water, temperature and corn growth in Weibei rainfed tableland, which would be as the basis of mulching cultivation in this area. The results showed that soil moisture in different mulchings showed different characteristics after Heading and filling stage of corn, soil average moisture (40–60 cm) of J mulching was evidently (P<0.05) higher than that of control treatment and other mulchings; water deprivation of S and D mulchings was improved in the deeper soil layers (60–120 cm). ....

Responses of Corn (Zea mays L.) Nitrogen Status Indicators to Nitrogen Rates and Soil Moisture

ZHU Juan-Juan, LIANG Yin-Li, Tremblay Nicolas

Acta Agron Sin. 2011, 37(07):  1259-1265.  doi:10.3724/SP.J.1006.2011.01259

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Plants usually experience fluctuating water supply during their life cycle due to continuous changes in climatic factors. Soil water content (SWC) is one of the most critical factors affecting nitrogen (N) availability, movement, and uptake by crops. Consequently, SWC levels may confound the assessment of crop N status. The present study compared the sensitivity of tissue N concentration, SPAD readings, Dualex readings, and SPAD/Dualex ratios for assessing corn (Zea mays L.) N status under different water supply conditions. A greenhouse trial was conducted with four N fertilizer application rates (0, 50, 50+75, and 200 kg ha^-1) and three watering levels (drought, drought followed by rewatering, and fully-watered). Tissue N concentration, SPAD, Dualex, and SPAD/Dualex values were influenced significantly by N rates and by SWC. Tissue N concentration, SPAD, and SPAD/Dualex increased with N rates, whereas Dualex decreased. In the first phase of reaction to drought, tissue N concentration, SPAD and SPAD/Dualex decreased rapidly but Dualex increased; however, the opposite pattern of response was observed in the long term. Under rewatering, tissue N concentration, Dualex and SPAD/Dualex gradually recovered, whereas SPAD values did not change significantly as they did in the drought treatment. There were highly significant relationships between SPAD (r=0.92), Dualex (r= -0.86), or SPAD/Dualex (r=0.63) and tissue N concentration. However, SPAD and Dualex were better predictors of tissue N concentration under drought conditions (SPAD:r=0.90;Dualex:r= -0.83) than under fully-watered conditions (SPAD:r=0.39; Dualex:r= -0.44) at the end of the trial. Among the indicators, Dualex was better able to discriminate N treatments, with consistent results across SWC levels.

Correlation between Na⁺ Contents in Different Organs of Soybean and Salt Tolerance at the Seedling Stage

LIU Guang-Yu, GUAN Rong-Xia, CHANG Ru-Tian, QIU Li-Juan

Acta Agron Sin. 2011, 37(07):  1266-1273.  doi:10.3724/SP.J.1006.2011.01266

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Salinity is recognized as one of the abiotic stresses negetively affecting crop productivity worldwide, which is mainly introduced by the consequence of Na⁺ toxicity. Great advances have been made in screening methodologies for salt tolerant soybean [Glycine max (L.) Merr.] in recent years. But few studies have focused on the evaluation of the relationship of soybean salt tolerance with Na⁺ content in different organs. The objective of our study was to develop a steady, measurable and effective method for salt tolerance evaluation of soybean germplasm based on measuring Na⁺ content in soybean. Twenty nine cultivars were grown in 1/2 Haogland nutrient solution, in which 100 mmol L^–1 NaCl was added when the second pair of simple primary leaves fully expanded. The visual foliar symptom was used to evaluate the scale of the salt tolerance. Roots, stems, leaves, and cotyledons were sampled at eight days after salt treatment. Different parts of the plant were measured by the atomic absorption spectrophotometer. Na⁺ content was extremly correlated with the scale of salt tolerance content in stem, leaf and cotyledon but not in root. Clustering for salt tolerant (including scale of 1 and 2) and salt sensitive (including scale of 3, 4, and 5) soybean cultivars at seedling stage based on Na⁺ contents in stem, leaf and cotyledon. The average Na⁺ contents of leaf and cotyledon from the tolerant cultivars were significantly lower than those from the sensitive culitvars. There was significant difference of Na⁺ contents in roots but there was not in stem between tolerant and sensitive soybean. Therefore, Na⁺ content in leaf and cotyledon can be used for evaluation of salt tolerance in cultivated soybean at the seedling stage. The results indicated that the possibility evaluating salt tolerant soybean cultivars at the seedling stage by Na⁺ content of leaf and cotyledon in hydroponics provides a method for germplasm identification, gene cloning and cultivar development of salt tolerance in soybean.

Image Segmentation of Cotton Based on YCbCcr Color Space and Fisher Discrimination Analysis

LIU Jin-Shuai, LAI Hui-Cheng, JIA Zhen-Hong

Acta Agron Sin. 2011, 37(07):  1274-1279.  doi:10.3724/SP.J.1006.2011.01274

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For cotton harvesting robot, the cotton image segmentation is one of the key technologies. In this paper, under HSV, HIS, and YCbCr color spaces respectively, according to the difference between cotton color and background color, the various objects(cotton batting, cotton branches, soil etc.)in the sample images were classified, and then the pixel value of every category in different samples was extracted based on the classification result. In the following, the rule that the dispersion is biggest between different classes and smallest within the same class was used to calculate the Fisher discrimination vector and the center of mass in every class. Finally, image segmentation was carried out based on the criterion of pixel value close to the center of mass. The result showed that the least segmentation noise was obtained in the YCbCr color space, in which the method of labeling for self-adapting denoising was need. The simulation showed that the cotton could be separated exactly from the background by the above algorithm whether the cotton was exposed to the sunlight or the shadow. A total of that 136 cotton images were segmented with an accuracy of 90.44% in YCbCr color space.

Observation of Differentiation and Pigment Deposition Process in Colored Cotton Fibers

ZHANG Mei-Ling, SONG Xian-Liang, SUN Xue-Zhen, WANG Zhen-Lin, ZHAO Qiang-Long, LI Zong-Tai, JI Gong, XU Xiao-Long

Acta Agron Sin. 2011, 37(07):  1280-1288.  doi:10.3724/SP.J.1006.2011.01280

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To further know the differentiation differencesand the process of pigment deposition between colored cotton fibers and normal white cotton fibers as well as in colored cotton fibers, morphological changes of ovule epidermal cells, fibers early development, and the process of pigment deposition were investigated inthree cotton (Gossypium hirsutum L.) cultivars (colored cotton Zongxu 1 (ZX1), Longlümian 2 (G-7), and white cotton Lumianyan 28 (LMY28)) using optical microscopy, scanning electron microscopy and transmission electron microscopy. The results showed that the central part of the ovule epidermal cells was began to differentiate at –1 DPA (days post anthesis, DPA). There were protuberances of ovule fiber cells at 0 DPA. The number and volume of protuberances increased at 1 DPA, when the fiber cells of LMY28 had the elongated trends. In addition, fiber cells already elongated at 3 DPA.In summary, it showed that LMY28 was the best, followed by ZX-1, and G-7 was the worst in the degree of differentiation, the number of protuberance, as well as, the level of development and elongation. Pigment forming time and depositing position showed signification differences in the fibers development process of ZX-1 and G-7’s. That is to say, the pigment formation of G-7 is earlier than that of ZX-1, and the pigment of G-7 deposited in both lumen and the inner secondary wall, while the pigment of ZX-1 only deposited in lumen. In conclusion, the poor quality of ZX-1 and G-7 is probably in relation to the later differentiation processes, the smaller numbers of ovule epidermal cells, as well as pigment deposited in fiber development process.

Difference of Ion Accumulation in Wild Soybean (Glycine soja) under High Saline-alkali Stress

XIAO Xin-Hui, LI Xiang-Hua, LIU Xiang, ZHANG Ying, WANG Ke-Jing

Acta Agron Sin. 2011, 37(07):  1289-1300.  doi:10.3724/SP.J.1006.2011.01289

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We usedpot cultivation with coastal soil containing total 3% salinity to identify the salt tolerance of 895 wild soybean plants collected in the Tianjin and Tangshan region of China, and to determine Na⁺, Cl^–, K⁺, Ca²⁺, Mg²⁺ contents in the stems and leaves of 203 plants that died at different stages and at maturity. The aim was to evaluate the differences of ion accumulations in the dead and survival wild soybean plants, and to discuss the mechanism of salt tolerance. The results showed that there were no significant differences in the content of every ion (Na⁺, Cl^–, K⁺, Ca²⁺, Mg²⁺) among these plants with a different survival time during the vegetative growth period. When the content of Na⁺ or Cl^– was accumulated to a certain high level in plants, the low salt-tolerant plants would be dead. Wild soybean individuals could die when their stems accumulated Na⁺ and Cl^– to the range of 3.239–4.682% and 4.639–6.328%, and their leaves accumulated Na⁺ and Cl^– to the range of 1.754–2.349% and 4.126–5.073%, respectively. The salt-tolerant plants could be divided into three types of low, moderate, and high levels in ion accumulations. The contents of Na⁺ and Cl^– in the stems and leaves of the high salt-tolerant plants were less than those of the low salt-tolerant ones. With survival time prolonging, the contents of K⁺ in the stems and Ca²⁺and Mg²⁺ in the leaves were increased. There were two types for the content levels of Na⁺ and Cl^– ions in stems and leaves of the survival plants, i.e. a low-level accumulation and a high-level accumulation, suggesting that the salt-tolerant wild soybean lines may have two kinds of mechanisms for the salt tolerance: one is high bearing and another is low absorption.

RESEARCH NOTES

Effect of Plant Density on Grain Yield Dry Matter Accumulation and Partitioning in Summer Maize Cultivar Denghai 661

LIU Wei, ZHANG Ji-Wang, LV Peng, YANG Jin-Sheng, LIU Peng, DONG Shu-Ting, LI De-Hai, SUN Qiang-Quan

Acta Agron Sin. 2011, 37(07):  1301-1307.  doi:10.3724/SP.J.1006.2011.01301

Abstract ( 2506 )   PDF (216KB) ( 1921 )   Save

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The effects of plant density on the dry matter accumulation and distribution were studied under high yield condition hoping to provide a scientific basis for the cultivation and breeding of high-yielding maize, using summer maize cultivar Denghai 661 and Nongda 108 were used as the experimental material and planted with different planting densities. The results showed that, population grain yield and dry matter accumulation increased significantly with the increasing of plant density, while the per plant were decreased.Denghai 661 had a high growth potential at 90 000 plant ha^-1, whichwas the optimum plant population for the maximal grain yield. At anthesis and milking stages, the decreaserateof stem dry matter accumulation was greater than that of leafwith increasing plant density,which was on the contrary at maturity stage. So the effects of plant density on stem dry matter accumulation were significantly stronger than that before milking stage, which was on the contrary after milking stage. After milking stage,the transportation efficiency of both stem and leaf reduced significantly with the increasing of plant density, the contribution rate of stem also reduced significantly, leaf increased. The stem dry mattertransportation contributed more than leaf’s to the grain yield under the density from 30 000 to 90 000 plant ha^-1, butthe leaf dry matter transportationcontributed more than stems to the grain yield under the density from 105 000 to 135 000 plant ha^-1.

Comparison of Effects of Sorghum bmr-6 and bmr-12 Genes on Yield and Quality Traits

WANG Li-Hua, LI Jie-Qin, LIN Ping, WANG Pei, YOU Zhen-Wen, and ZHAN Qiu-Wen

Acta Agron Sin. 2011, 37(07):  1308-1312.  doi:10.3724/SP.J.1006.2011.01308

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This research aimed to compare the impact of bmr-6 and bmr-12 on yield and quality traits in five sorghum genetic backgrounds: Atlas, Early Hegari-Sart, Kansas Collier, Rox Orange and Wheatland. The results showed that bmr-6 and bmr-12 generally made a shorter plant height and bigger stem diameter. However, bmr-6 and bmr-12 had little effects on tiller number and leaf number.Bmr-6 and bmr-12 had negative effects on yield traits, but the effects were different in different genetic backgrounds. As for the quality traits, bmr-6 generally decreased the contents of NDF (Neutral Detergent Fiber) and ADF (Acid Detergent Fiber) and bmr-12 had no impact on the two traits. Both bmr-6 and bmr-12 decreased the contents of ADL (Acid Detergent Lignin) and ADF (Acid Detergent Lignin) in the five genetic backgrounds. Considering all factors, bmr-12 is more useful in breeding than bmr-6.