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12 September 2008, Volume 34 Issue 09

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Sudoku Square—A New Design in Field Experiment

MO Hui-Dong;XU Ru-Gen

Acta Agron Sin. 2008, 34(09):  1489-1493.  doi:10.3724/SP.J.1006.2008.01489

Abstract ( 1991 )   PDF (234KB) ( 1447 )   Save

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Sudoku is a game with incremental intelligence and is popularizing in many countries of Asia, Europe, and America. Its most common pattern is to fill the digits 1 through 9 into a square with 9 rows by 9 columns and subdivided 9 boxes, so that each digit appears once, and only once, in every row, column, and box. In the present paper, we investigated the basic properties of Sudoku in the general sense, and then make it a new design in field experiment.
A necessary condition for constructing a Sudoku square is k = pq and p, q ≥ 2, where k = number of rows, columns, and boxes in a k × k square, p = number of box-rows (the row consists of boxes) and q = number of box-columns (the column con-sists of boxes). Therefore, only non-prime number k can construct a Sudoku square and the prime number k can not. Table 1 lists 15 Sudoku squares in the case of k ≤ 20.
To design a Sudoku square, 4 steps are required as follows: (1) To write a k×k Sudoku square with restricted randomization , the procedure is to draw the random numbers of p or q sets each contains every number from 1 through k with no repeat, and then write down cyclically the first set numbers according to the order they appear into the first box-row or box-column, the second one into the second box-row or box-column, and so on and so forth. Note that any number must be shifted to the end of the series of random numbers if it has appeared in the column or row. (2) To randomize the order of box-rows and rows within each box-row. (3) To randomize the order of box-columns and columns within each box-column. (4) To assign randomly the k numbers to k treatments or k levels of a factor. Above mention indicates that a Sudoku square can layout k treatments with k replications and control 3-way (box, row, and column) soil-environment variations.
The linear model of data from a Sudoku square design is

where Y(ij)lm is an observed value of the plot in the lth row and mth column, subjected to the ith treatment and jth box; µ is the
overall mean; τi, βj, ρl, and γm are the main effects to the ith treatment, jth box, lth row, and mth column, respectively, and they
may be fixed or randomized; ε(ij)lm is random error and ε(ij)lm ~ N (0, ). Sudoku square can remove three sources of variation
from experiment error. Accordingly, the mean of treatment should be more precise with smaller error than that in Latin square.
Sudoku square design may be applied to multifactor experiments. The basic method is that the rows and/or columns may be substituted by experimental factors each consists of k levels, and hence the components ρl and γm in the model become main ef-fects of the factors. In such design, many effects and interactions have been confounded each other, but the main effects are or-thogonal and hence the estimate of one main effect is not influenced by the other main effects.

Identification and Mapping of a New Resistant Gene to Sugarcane Mosaic Virus in Maize

XI Zhang-Ying;ZHANG Shu-Hong;LI Xin-Hai;XIE Chuan-Xiao;LI Ming-Shun;HAO Zhuan-Fang;ZHANG De-Gui;LIANG Ye-Hong;BAI Li;ZHANG Shi-Huang

Acta Agron Sin. 2008, 34(09):  1494-1499.  doi:10.3724/SP.J.1006.2008.01494

Abstract ( 1931 )   PDF (434KB) ( 1377 )   Save

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Sugarcane mosaic virus (SCMV) causes considerable damage to maize (Zea mays L.) in China. Understanding the genetic of resistance gene(s) is the basis for effective selection in resistance breeding program. The objective of the present study
was to identify the new resistance gene to SCMV in China maize germplasm. Twenty-one BC₂F₃ populations derived from eight
maize intercross combinations were planted in field trials under artificial inoculation. The number of resistant and susceptible
plants in one BC₂F₃ population (Ye 478 ´ Hai 9-21) was found to be in accordance with the theoretical 1:3 ratio．A recessive gene
derived from the resistant parent Hai 9-21 was supposed to control the resistance to SCMV. With the aid of BSA (bulked segregant
analysis) and SSR marker analyses, a new recessive resistance gene to maize SCMV was identified, designated as scm3. The scm3 gene was located in the bin3.04/05, flanked by the SSR markers umc1965 and bnlg420 with the genetic distances of 45.7 and 6.5 cM, respectively. The other linked markers include umc1307, umc2265, bnlg2241, and umc2166. These linked markers are in the order of umc1965–scm3–bnlg420–umc1307–umc2265–bnlg2241–umc2166. Resistant germplasm to SCMV in maize was en-riched with the identification and mapping of scm3.

Genetic Dissection of Yield Potential in Rice (Oryza sativa L.) Using In-trogression Lines

KANG Le;LI Hong;SUN Yong;LU De-Cheng;ZHANG Fan;HUANG Dao-Qiang;XU Jian-Long;WANG Zhi-Dong;ZHU Ling-Hua;GAO Yong-Ming;FU Bin-Ying;LI Kang-Huo;ZHOU Yong-Li;ZHOU Shao-Chuan;LI Zhi-Kang

Acta Agron Sin. 2008, 34(09):  1500-1509.  doi:10.3724/SP.J.1006.2008.01500

Abstract ( 1928 )   PDF (253KB) ( 1258 )   Save

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To facilitate breeding for high grain yield potential in rice, two BC3F5 introgression populations, derived from two crosses between Fengaizhan (FAZ, the recurrent parent) and two donors (Khazar and IR64), were genotyped with 89 and 101 polymorphic SSR markers and evaluated in two environments (early and late seasons growing in Guangzhou) to identify and map QTL affecting grain yield (GY) and its components, panicle number per plant (PNP), filled grain number per panicle (GNP), and 1 000-grain weight (TGW). Regression analyses indicated that GY was largely determined by GNP followed by PNP in the early season, and by PNP in the late season. The contribution of TGW to GY was small in both seasons. ANOVA analyses revealed a total of 27 QTL regions associated with GY and its components across the rice genome, including 10 GY QTL, 9 PNP QTL, 9 GNP QTL, and 14 TGW QTL. Fifteen (35.7%) of the identified QTL mapped to the similar regions with previously reported QTL affecting the same traits, indicated the robustness of our results. The majority of the QTL were only detected in one of the envi-ronments, indicating a strong component of G × E interactions of the identified QTL. Three interesting genomic regions on chro-mosomes 3, 7, and 9 were noted, which were associated with GY and two of its components. Detailed analyses indicated that both pleiotropy and linkage might be responsible for the observed associations. Our results provided useful information to our current understanding of the genetic basis of GY in rice, and a new strategy of using IL populations for both QTL discovery and breeding.

Cloning, Expression and Characterization of a Non-Specific Lipid Trans-fer Protein Gene from Potato

GAO Gang;REN Cai-Hong;JIN Li-Ping;XIE Kai-Yun;QU Dong-Yu

Acta Agron Sin. 2008, 34(09):  1510-1517.  doi:10.3724/SP.J.1006.2008.01510

Abstract ( 1840 )   PDF (592KB) ( 1396 )   Save

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Plant non-specific lipid transfer proteins (nsLTPs) are abundantlipid binding proteins with small molecules that play several biological roles including antimicrobial defense, signaling, cell wall loosening, proteinase inhibiting and so on. A new cDNA clone, named StLTPa1, corresponding to potato nsLTP gene was isolated from a cultivated potato (Solanum tuberosum) infected with Ralstonia solanacearum. The sequence analysis showed that the cloned cDNA contained 636 bp nucleotide which encoded a type I nsLTP of 91 amino acids. The StLTPa1 gene is well conserved in the coding region with 60–92% identity at the amino acid level, and 75–85% identity at the nucleotide sequence level compared with other Solanaceae nsLTPs. The transcripts of the gene accumulated in potato leaf and stem tissues induced by R. solanacearum and showed dominant differential expression between resistant and susceptible genotypes. In situ hybridization results showed that the StLTPa1 mRNA was localized in phloem cells of vascular tissues in potato leaf and stem tissues after pathogen infection. Salicylic acid, methyl jasmonate and abscisic acid induced StLTPa1 gene expression in different manners. These three signal molecules could produce a long-term effect on the StLTPa1 gene expression during the early stages of potato—R. solanacearum interaction. These results thus showed that the StLTPa1 may be pathogen-responsive gene in plant defenses and involve in a complex gene regulation network.

Genetic Diversity and Core Collection of Alien Pisum sativum L. Germ-plasm

ZONG Xu-Xiao; GUAN Jian-Ping;WANG Shu-Min;LIU Qing-Chang;Robert R Redden;Rebecca Ford

Acta Agron Sin. 2008, 34(09):  1518-1528.  doi:10.3724/SP.J.1006.2008.01518

Abstract ( 1939 )   PDF (356KB) ( 1664 )   Save

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China is the second producer of pea in the world with a collection of 5 000 accessions, around 20% of which were introduced from 70 foreign countries. It is essential to assess the genetic diversity among alien pea (Pisum sativum L.) germplasm accessions, to analyze their genetic relationships among various groups of gene pool from different geographical/ecological areas, and to constitute core collection of alien genetic resources of pea. The information generated from the study will be very helpful for the exploration and utilization of overseas pea genetic resources. For the purpose above, 21 SSR primer pairs with unambiguous unique polymorphic bands and their optimum annealing temperatures were successfully screened out from the 111 candidates. Pea’s SSR marker experimental system was optimized thereafter, and adopted for genetic diversity analysis and for constitution of a core collection among the 731 pea accessions from 67 countries of various continents. Using 21 SSR primer pairs, 109 poly-morphic bands were amplified, and 5.19 alleles were detected by each SSR primer pairs on an average. SSR alleles were not uni-formly distributed among continents, and the number of effective alleles and Shannon’s information index (I) were much varied among continental based groups of genetic resources. Significant difference appeared in the pairwise comparisons for genetic diversity between continental based groups of genetic resources. Asia group had the highest level of genetic diversity (I = 1.1753), followed by Europe (I = 1.1387), USSR (I = 1.0285), America (I = 1.0196), Africa (I = 0.9254), and Oceania (I = 0.8608) groups. Two large cluster groups and four cluster sub-groups were identified based on the dendrogram of pairwise Nei78 genetic distance. The clustering results of alien genetic resources revealed geographically broad correlation to their genetic diversity. Three types of population structure within 731 alien pea accessions were inferred by Structure analysis, which also broadly correlated to their geographic origins. A scientific and logical standard methodology for construction of core collection based on Structure analysis was designed and applied in this study, a subset (6.57% of the whole collection) of 48 accessions representing 84.4% of the whole allelic variability was proposed to be a core collection.

Genetic Diversity and Genetic Structure of Soybean Cultivar Population Released in Northeast China

ZHANG Jun;ZHAO Tuan-Jie;GAI Jun-Yi

Acta Agron Sin. 2008, 34(09):  1529-1536.  doi:10.3724/SP.J.1006.2008.01529

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There were 1 300 soybean cultivars released during 1923-2005 in China, of which 682 were from northeast China.
In the present study, 169 cultivars out of the 682 were analyzed with 64 SSR markers to reveal the genetic diversity of the north-
east China soybean cultivar population (NECSCP), the genetic diversity and marker allele complementarity among provincial
subpopulations (PSP) and released period subpopulations (RPSP), and the genetic structure of the population and subpopulations. The results showed that there existed a plenty of genetic diversity in NECSCP; with the period advance, some of the old alleles in earlier RPSP disappeared and some new alleles came out in later RPSP and the new ones were more than the old ones. Some mu-tual complementary alleles appeared among PSP, with the largest number of mutual complementary alleles between Heilongjiang subpopulation and Liaoning subpopulation. There also existed some specifically existent and specifically deficient alleles in PSP and RPSP. Significant relationship was found between SSR clusters and PSP as well as RPSP, indicating the sound genetic bases of the classification of PSP and RPSP. The NECSCP was traced to two model-based populations according to the Structure Analy-sis (Structure version 2.2). The two sources of germplasm accounted for the most part of Cluster I and II, and the most part of Cluster III and IV, respectively. The Heilongjiang subpopulation mainly contained both sources of germplasm, while Jilin and Liaoning subpopulations contained one of them, indicating the former possesed genetic base broader than the latter. In addition, all of the RPSP almost equally contained the two sources of germplasm. The results implied that germplasm exchange among PSP should be encouraged for broadening the genetic base in NECSCP.

Relationship between Single Nucleotide Polymorphism of TaPK7 Gene and Drought Tolerance in Wheat

ZHANG Hong-Ying;MAO Xin-Guo;JING Rui-Lian;XIE Hui-Min;CHANG Xiao-Ping

Acta Agron Sin. 2008, 34(09):  1537-1543.  doi:10.3724/SP.J.1006.2008.01537

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Protein phosphorylation/dephosphorylation are major signaling events induced by abiotic stresses in higher plants. Sucrose nonfermenting1-related protein kinase2 (SnRK2), which belongs to serine-threonine protein kinase, plays an important role in the process of sugar signal transduction. It is reported that the gene family is activated by hyperosmotic stress and relays the stress signal via phosphorylation. TaPK7 gene, a member of SnRK2 gene family of wheat (Triticum aestivum L.), is involved in the response to osmostic stress, such as drought, high salt, low temperature, and ABA treatment in wheat seedlings. To investigate the relationship between single nucleotide polymorphism (SNP) in TaPK7 and drought tolerance, 45 hexaploid wheat accessions and 5 diploid species of wheat relatives were used to detect SNP of TaPK7 through sequencing. Sixty four SNP and nine InDel were detected in a total of 220 448 bp nucleotide acids, and the frequencies of SNP and InDel were 1 SNP /3 445 bp and 1 InDel /24 494 bp, respectively. The nucleotide diversity value in non-coding region was higher than that in coding region, which suggested that the coding region suffered stronger selection pressure than non-coding region. Ka/Ks value of TaPK7 was 0.415, which indicated that TaPK7 was a conservative gene. Sixteen SNPs were observed in coding region, and most of them happed in drought-tolerant accessions. A total of 21 haplotypes were identified from the plant materials. Among them, 7 haplotypes of TaPK7 were only related to accessions with drought-tolerant or drought-sensitive characteristics, 11 haplotypes contained me-dium-drought-tolerant accessions, but 3 haplotypes contained both types of accessions. SNPs in TaPK7 were correlative with drought tolerance, but it couldn’t explain the mechanism of drought tolerance completely in wheat.

Genetic Analysis and Mapping of Resistance Gene to Seed Coat Mottle in Soybean

LI Wen-Fu;LIU Chun-Yan;GAO Yun-Lai;LI Can-Dong;JIANG Hong-Wei; WANG Kun;CHEN Qing-Shan;HU Guo-Hua

Acta Agron Sin. 2008, 34(09):  1544-1548.  doi:10.3724/SP.J.1006.2008.01544

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Soybean mosaic virus (SMV) causes a worldwide disease in soybean, reducing yield and making mottling of soybean seeds, and so largely losing soybean economy value. Resistant variety breeding is the most effective way to protect against the seed coat mottle. In this study, an F_2:3 population, derived from Dongnong 3C624 (susceptible) × Dongnong 8143 (resistant), was used to study the genetic mechanism of the resistance, and map the resistant gene of seed coat mottle by simple sequence repeat (SSR) markers with bulked segregation analysis (BSA) method. Two parents and their F₂, F₃ population were inoculated with SMV strain No.1 in 2006 and 2007. Identification results in two years showed that resistance to SMV strain No.1 of Dongnong 8143 was controlled by one pair of dominant genes. Six hundred pairs of SSR primers were screened, and five SSR markers, Sat_297, Sat_229, Sat_317, Satt335, and Sct_188, were mapped near the resistance gene. Linkage analysis indicated that the resistance gene locus was located on the linkage group F. The order and genetic distance among the resistance gene and markers were Sat_297–12.4 cM–Sat_229–3.6 cM–SRSMV1–1.7 cM–Sat_317–2.4 cM–Satt335–13.8 cM–Sct_188. Sat_229, Sat_317, and Satt335 can be used for molecular assisted breeding.

Screening Parent Resources of Hybrid Rice in New Cytoplasm Male Ste- rile System (CMS-FA)

WANG Nai-Yuan;LIANG Kang-Jing;LI Yu;WANG Ying;WANG Hong-Fei;QIU Xiu-Li;WEI Xin-Yu;ZHANG Ying-Ying;KE Bei;ZHAO Jian-Ya

Acta Agron Sin. 2008, 34(09):  1549-1556.  doi:10.3724/SP.J.1006.2008.01549

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Jinnong 1A is a new type of cytoplasm male sterile (CMS) line in three-line hybrid rice (Oryza sativa L.). It is completely different from the sterile line of CMS-WA and CMS-HL types, and designated as CMS-FA type. In this study, Jinnong 1A, as the female parent, was crossed with 220 rice varieties originated from 10 countries and 13 provinces of China. The fertility of the F₁ generation was evaluated with F₁ pollen dye ability rate, bagged seed-setting rate, and natural seed-setting rate. The male parent was classified into maintainer or restorer lines when all the three fertility indices were ≤10% or ≥80% in the F₁ generation. Otherwise, it was regarded as non-parental variety for CMS-FA hybrid rice. In the total 220 varieties, 122 were identified as maintainer lines of Jinnong 1A, which accounted for 55.5%, but no varieties could be used as restorer lines. The other 98 varieties (accounting for 45.5%) were non-parent for CMS-FA hybrid rice. With regard to CMS-WA sterile line, Zhenshan 97A taken as the control in the study, the maintainer and restorer lines were 44 (20.0%) and 42 (19.1%), respectively. Compared with CMS-WA hybrid system, the CMS-FA system had a higher parent utilization rate by 16.4 percentile, especially the maintainer line utilization was higher by 35.5 percentile (up to 1.8 folds). Generally, the fertility abilities of domestic varieties were higher that those of in-troduced varieties in the F₁ generation.

Production and Characterization of Intergeneric Hybrids between Bras-sica Species (B. juncea, B. nigra) and Orychophragmus violaceus by Ovary Culture

WANG Ai-Yun;LI Xun;HU Da-You

Acta Agron Sin. 2008, 34(09):  1557-1562.  doi:10.3724/SP.J.1006.2008.01557

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Intergeneric hybridization is an available way to create new germplasm and enrich breeding materials. The reciprocal crosses have been made between Brassica species and Orychophragmus violaceus with the objective of carrying out desirable genes transfer from O. violaceus to B. juncea by ovary culture technique. The ovaries were cultured on 6 different culture media, and great differences on the intergeneric crossability were found among cross combinations, media and female parents. Hybrid plants were obtained through ovary culture, 9 of which were similar to female parent B. juncea or the intermediate type between male and female parents in morphology. Only one plant from Younensi × O. violaceus was completely male sterile, and showed significant variation for branching pattern and leaf morphology. Morphological and SSR molecular identifications showed these hybrids were truly intergeneric hybrids.

Screening and Analysis of Mutiple Copy of Oleate Desaturase Gene (fad2) in Brassica napus

XIAO Gang;ZHANG Hong-Jun;PENG Qi;GUAN Chun-Yun

Acta Agron Sin. 2008, 34(09):  1563-1568.  doi:10.3724/SP.J.1006.2008.01563

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Rapeseed oil is primarily composed of palmitic, stearic, oleic, linoleic and linolenic fatty acids. Delta-12 desaturase (FAD2) in plants converts oleic acid (18:1) to linoleic acid (18:2) by inserting a double bond at the delta-12 position. Fatty acid desaturase-2 gene (fad2) encodes delta-12 desaturase that functions in the endoplasmic reticulum. Fifty-six fad2 DNA clones and nine fad2 seed cDNA clones of B. napus cv. Xiangyou 15 were randomly selected and sequenced in this study. These 56 DNA sequences share 91.0-99.9% identity in nucleotides. Through combination of identical sequences, 11 different sequences were found, of which each represented various copy of fad2 gene. Deduced amino acid sequences revealed that many stop codons occurred in the coding region of six copies, the other five copies shared 90.60-99.74% amino-acid identity. Two differential cDNA were found from nine fad2 seed cDNA sequence, no stop codons in the coding region, revealing that more than one fad2 gene express in developing seeds, and oleic acid content is controlled by multigene. The eleven copies in genome could be divided into two groups based on their homology, and designated as fad2I and fad2II, respectively. RT-PCR analysis in seeds at twenty-seven days after pollination showed that fad2I expressed strongly in seeds, and no expression of fad2II was found, but both of them expressed in leaves.

Analysis of rDNA Intergenic Spacer (IGS) Sequences in Oryza sativa L. and Their Phylogenetic Implications

DAI Xiao-Jun;OU Li-Jun;LI Wen-Jia;LIANG Man-Zhong;CHEN Liang-Bi

Acta Agron Sin. 2008, 34(09):  1569-1573.  doi:10.3724/SP.J.1006.2008.01569

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In plant unclear genome, the intergenic spacer region (IGS) is located on the region of 18S–28S and is often used in phylogenetic analysis among species, detecting intra-specific polymorphisms. Rice (Oryza sativa L.) is differentiated into not only some subspecies but also many ecotypes of these subspecies. Can the IGS region be a useful tool to study the phylogenetic relationships among these cultivars of Oryza sativa? In the study, a comparative analysis of the rDNA intergenic spacer entire sequences of thirteen cultivars in Oryza sativa L. was carried out with O. rufipogon as outgroup. In the cultivars used, there were six for typical O. sativa ssp. japonica, five for typical O. sativa ssp. indica, two for O. sativa ssp. javanica. The result indicated that the length range of IGS sequences was from 2 130 to 2 145 bp, the content of G+C varied from 74.59% to 75.29%, there were 229 variational loci which were 10.70% of entire bases and 76 informative loci which were 3.51% of entire bases in Oryza sativa. Thirty-eight indica and japonica specific loci were found in the IGS sequences of Oryza sativa, most of them were covered a about 400 bp segment located in the upstream of IGS sequence. The indica and japonica subspecies of Oryza sativa, as well as some closely related cultivars, can be discriminated clearly based on the phylogenetic tree constructed by IGS sequences. The study supported the opinion that the O.sativa ssp.javanica is a subspecies of Oryza sativa.

Cloning, Expression, and Mapping of Six Low-Molecular-Weight Heat- Shock Protein Genes in Cotton

HE Ya-Jun;GUO Wang-Zhen;ZHANG Tian-Zhen

Acta Agron Sin. 2008, 34(09):  1574-1580.  doi:10.3724/SP.J.1006.2008.01574

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Heat-shock proteins (HSPs), known as stress proteins, are created when cells are exposed to elevated temperatures, or to other kinds of environmental stress. Although HSPs were first characterized because their expression increased in response to elevated temperature, some of them are found in normal, nonstressed cells. HSPs have many biochemical functions in cell metabolism during plant developmental process. The objective of the study was to isolate low-molecular-weight HSP genes, further put a foundation to illustrate them function in cotton fiber developmental stages. Six low-molecular-weight HSP genes were isolated from cotton fiber cDNA library. Sequence analysis showed that they belong to three different types of low-molecular-weight HSP. RT-PCR analysis revealed that they exhibit different transcripional profile in cotton. The mitochondrial and cytoplasmic I HSP genes were regulateded by the fiber initiation; however, cytoplasmic II HSP genes were more closely correlated with the growth and development of cotton leaf. Using genetic map of the tetraploid cotton constructed by our laboratory, three of these genes, LMWHSP1, LMWHSP2, and LMWHSP3, were mapped on the cotton chromosomes A4, D8, and A6, respectively.

Cloning and Function Analysis of Gene SAMS from Glycine soja

FAN Jin-Ping;BAI Xi;LI Yong;JI Wei;WANG Xi;CAI Hua;ZHU Yan-Ming

Acta Agron Sin. 2008, 34(09):  1581-1587.  doi:10.3724/SP.J.1006.2008.01581

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Drought, salinity, and low temperature are the most severe natural disaster of many abiological adversities. They can make crop yield reduction, even to death. At present, biotechnology is an important way for crops to improve plant resistance. Glycine soja carrying tolerant genes in northeast of China was used as a material for cloning. Total RNA was extracted from the leaf, and the first strand of cDNA was synthesized with reverse transcription under low temperature (4℃), drought (30%PEG), and salinity (200 mmol L^-1 NaCl). S-adenosylmethionine synthetase gene (SAMS gene) was amplified by PCR with the first strand cDNA as template and a pair of primer based on constructed the cDNA library and ESTs sequence under salinity condition. Full-length SAMS gene sequence was obtained by Blast comparison. A expression vector based on pBI121 with CaMV35S promoter was constructed, and 180 transgenic tobacco plants transformed by Agrobacterium tumefaciens were obtained. Transgenic plants resistances to drought, salinity and low temperature were investigated. The gene function was analyzed via measuring the physiological stress indicators under different osmotic pressures. The results showed SAMS gene can improve tobacco resistance to lower temperature, drought, and salinity.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Impacts of Changes in Both Climate and Its Variability on Food Produc-tion in Northeast China

ZHU Da-Wei;JIN Zhi-Qing

Acta Agron Sin. 2008, 34(09):  1588-1597.  doi:10.3724/SP.J.1006.2008.01588

Abstract ( 1984 )   PDF (596KB) ( 1562 )   Save

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Northeast China abounds in soybean (Glycine max L.), maize (Zea mays L.), wheat (Triticum aestivum L.), and rice (Oryza sativa L.), and is one of the most susceptive regions to climate change in the country. It has been found an increase in mean annually temperature about 0.34℃ per 10 years in recent 50 years. The probabilities of meteorological disasters, such as drought, flood and cold damages also increase with increasing of climatic variability (CV), which has caused northeast China to be one of regions with the greatest fluctuation in grain yields in China. According to IPCC, the possible increase in mean earth temperature would be 1.8-4.0℃ from now up to the end of this century. Meanwhile, the mean temperature in northeast China would be obviously higher than that of the earth. The air temperature with a doubling of CO₂ concentration (555 mmol mol^-1) in future might be 6-7℃ higher than that at present time according to the predictions of 3 GCMs. Therefore, the possible effects of changes in both climate and it variability on food production in the studied region has drawn more attentions of Chinese government and scientists. In this study, 9 scenarios of (CC+ΔCV) involving both climate change (CC) and its variability (ΔCV) were generated at 19 sites in 3 agroecological zones in northeast China using the WGEN as a tool and based on the output of the 3 General Circulation Models (GISS, GFDL, and UKMO GCMs), the local current daily weather data from 1961 to 2000 (Baseline) at each site as well as the 3 hypotheses about the increase in CV in future. Then 4 crop models, i.e., SOYGRO, CERES-Maize, CERES-Wheat, and CERES-Rice in DSSAT were selected as the effect models and their parameter modification, validation and sensitivity analyses were done using the baseline weather, statistical yield data of the 4 crops and the local typical soil data. Finally, the potential impacts of changes in both climate and its variability on the food production in the studied regions with a doubling of CO₂ concentration doubled were assessed by running the effect models under both baseline and various (CC+ΔCV) scenarios, and by making comparison between the output simulated. The results showed that the 4 effect models were available in the studied regions and can be used as a tool in climate impact study. Climate change (CC) would be favorable for soybean and rice produc-tion in the studied region, especially in the northern cold zone and eastern wet zone, but unfavorable for both maize and spring wheat, the yields simulated, particularly the maize yield, reduced significantly under all the scenarios. With increasing of CV, not only the yields reduced compared with the control (ΔCV=0), but also the yield stabilities decreased for the rainfed crops, such as soybean, maize and spring wheat. However, there was no influence for the irrigated rice.

Effects of Nitrogen on the Antioxidant Enzyme Activities and Endogenous Hormone Contents of Cotton Leaf under Drought Stress and after Soil Re-Watering during the Flowering and Boll-Forming Stage

LIU Rui-Xian;GUO Wen-Qi;CHEN Bing-Lin;ZHOU Zhi-Guo

Acta Agron Sin. 2008, 34(09):  1598-1607.  doi:10.3724/SP.J.1006.2008.01598

Abstract ( 1918 )   PDF (721KB) ( 1400 )   Save

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The flowering and boll-forming stage is the key period for cotton yield. Short-term drought stress during this stage significantly inhibits cotton development and reduces final productivity. Nitrogen application plays an important role in alleviating the adverse effects of dry soil on plant development. The objective of this study was to investigate the effects of nitrogen on plant resistance to soil drought in terms of the changes of antioxidant enzyme activities and endogenous hormone contents in cotton leaf under short-term drought stress (withholding water for eight days then re-watering). Cotton plants were grown in pots with three N application levels (0, 3.73, and 7.46 g N pot^-1, equivalent to 0, 240, and 480 kg N ha^-1, respectively). Leaf water potential and soil relative water content decreased with increasing N supply at the end of soil drought stress period. At the same time, drought stress significantly increased SOD and POD activities, MDA and ABA contents in cotton leaf, but reduced CAT activity, soluble protein, ZR, and GA contents, as well as ZR/ABA, IAA/ABA, and GA/ABA. Under soil drought, CAT activity, soluble protein, ZR, IAA, and GA contents, ZR/ABA, IAA/ABA, GA/ABA, and net photosynthetic rate (Pn) in 240 kg N ha^-1 treatment were the highest among the three nitrogen treatments, but MDA content and ABA content in 240 kg N ha^-1 treatment was the lowest. These results suggested that 240 kg N ha^-1 was the optimal nitrogen application rate under short-term soil drought in this experiments, but deficient (0 kg N ha^-1) and excessive (480 kg N ha^-1) nitrogen supply were of disadvantage to the antioxidant enzyme activities, endogenous hormone contents and photosynthesis. Nitrogen affected antioxidant enzyme activities and endogenous hormone con-tents not only under water stress but also under re-watering after drought stress. At the 10th day after soil re-watering, there was no difference in SOD and CAT activities, MDA content and Pn between treatments with soil drought and well-watering. ABA content in drought treatment was significantly lower than that in well-watering treatment, but the trends of ZR, IAA, and GA con-tents, ZR/ABA, IAA/ABA, and GA/ABA were opposite. However, more N application was available to increase P_n through pro-moting antioxidant enzyme activities, decreasing lipid peroxidation and adjusting the balance of endogenous hormones (ZR/ABA, IAA/ABA, GA/ABA) in drought treatment after stress alleviation. So, the application of N should be reduced to decrease the ef-fects of stress when drought occurred, but after stress alleviation, farmers could apply additional N fertilizer to compensate for the loss of cotton growth.

Effects of Exogenous Nitric Oxide Donor Sodium Nitroprusside on β-Amylase and Its Subcellular Localization during Early Stage of Seed Germination in Wheat

SUN Yong-Gang;LING Teng-Fang;WANG Jia-Jie;XU Sheng;XUAN Wei;TANG Guo-Hui;SHEN Wen-Biao

Acta Agron Sin. 2008, 34(09):  1608-1614.  doi:10.3724/SP.J.1006.2008.01608

Abstract ( 1975 )   PDF (740KB) ( 1864 )   Save

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Nitric oxide (NO) is an important signaling molecule with diverse physiological functions in plants. NO can break dormancy of seeds, and promote seeds germination under various stresses and normal growth conditions. In this report, treatment with 0.5 mmol L^-1 sodium nitroprusside (SNP) promoted seeds germination by increasing β-amylase activity, while the application of α-cyclodextrin, a specific inhibitor of β-amylase, could apparently inhibit the process induced by SNP. Semi-quantitative RT-PCR analysis indicated that the application of SNP induced the free β-amylase activity, and up-regulated β-amylase transcript. West-ern-blotting result showed that SNP increased the protein level of β-amylase, whereas the cPTIO (a specific scavenger of NO) and actinomycin-D (a transcriptional inhibitor) reversed changes in transcriptional and the protein levels mentioned above. Subcellular localization studies of proteins via immunoelectron microscopy technique illustrated that SNP could increase the quantity of β-amylase which was predominantly located in protein storage vacuole, and adhered to starch granules. The above results suggest that SNP might not only enhance the activity of free β-amylase, but also induce the β-amylase synthesis de novo at the early stage of wheat seed germination.

Physiological Research on the Difference of Bentazon Tolerance in Wild Type Rice and Sensitive Lethal Mutants

WANG Yun-Sheng;LU Xu-Zhong;SUN Ming-Na;SONG Feng-Shun;LI Li;GAO Tong-Chun;YANG Jian-Bo

Acta Agron Sin. 2008, 34(09):  1615-1623.  doi:10.3724/SP.J.1006.2008.01615

Abstract ( 1938 )   PDF (541KB) ( 1530 )   Save

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Bentazon sensitive lethal (bsl) mutants can be applied in hybrid rice (Oryza sativa L.) breeding for improving seed production and quality. This study was to elucidate the physiological mechanism of bentazon tolerance in rice. Tolerant rice varieties (W6154s and Norin 8) as well as their corresponding mutants, sensitive to bentazon, were employed in this study. Plant net photosynthetic rate (P_n), chlorophyll fluorescence, and the level of superoxide radical ( ) as well as the contents of chlorophyll (Chl) and malondialdehyde (MDA), were analyzed for both tolerant and sensitive rice plants treated with bentazon. After treatment, the two sensitive mutants showed a significant reduction in Pn at 0.5 h. A continuous decrease of Chl contents was found over the first 3 d whereas a significant increase of MDA contents was noticed on the 3rd day and thereafter. Analysis of chlorophyll fluorescence revealed a bentazon-induced increase in the proportion of the reduced state of QA. In the early stage after bentazon treatment, wild types and their mutants showed no significant difference in the alteration of Pn and chlorophyll fluorescence. While these two parameters then increased progressively in both wild types and remained low in the mutants. A significant generation of was found over the 5 d period in the mutants. Both wild types and mutants contained the same level of bentazon after 2 h of treatment. Bentazon content dropped to barely detectable amount in the wild type varieties at 1 d. However, the mutants retained a substantial amount of the herbicide after 5 d. It is proposed that the herbicide might inhibit rice photophythesis and accumulation of oxidative stress with the treatment of bentazon in both lethal mutants. The damaging effect on PS II system can be significantly alleviated in the wild type varieties due to a higher rate of catabolism of the herbicide.

Response of Grain Yield of Different Japonica Rice Cultivars to Amount of Nitrogen Application in High-Fertility Paddy Field

WANG Dan-Ying;ZHANG Xiu-Fu;SHAO Guo-Sheng;XU Chun-Mei

Acta Agron Sin. 2008, 34(09):  1623-1628.  doi:10.3724/SP.J.1006.2008.01623

Abstract ( 1712 )   PDF (198KB) ( 1084 )   Save

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Nitrogen is the most important nutrition in rice production, and its function is affected by cultivar, fertilizer application and soil condition. In resent years, paddy field in Yangzi River has a trend of becoming fertile. In order to identify the optimal nitrogen application amount in high-fertility paddy field and to study the cultivar difference in nitrogen requirement, we planted 13 japonica rice cultivars with 5 nitrogen application levels in a high-fertility paddy field in China National Rice Research Institute, Zhejiang province. The results were as follows: (1) Rice yield was significantly increased by nitrogen, most japonica rice cultivars reached their highest yield when nitrogen was applied at 150–225 kg ha^-1. With the increase of nitrogen application amount, 1 000-grain weight and seed setting rate decreased, while grains per panicle and effective panicle number increased till nitrogen application amount reached 225 kg ha^-1. (2) There existed cultivar difference in optimal nitrogen application amount. According to the cultivar yield characteristics in none-nitrogen application treatment, low-yielding japonica rice cultivars were sensitive to N fertilizer, their yield increased largely even when small amount N fertilizer was applied, while the yield of high-yielding cultivars changed little when applied N fertilizer < 75 kg ha^-1; the optimal nitrogen application amount of cultivars with middle panicle number was larger than that with low (< 220×10⁴ per hectare) and high (< 220×10⁴ per hectare) panicle number. (3) Most of the cultivars released before 1980 had the highest yield when 225 kg ha^-1 nitrogen was applied, while the nitrogen needed for the highest yield in cultivars released after 1980 was different.

Effects of Source and Sink Reductions on Micronutrient and Protein Contents of Grain in Wheat

ZHANG Ying-Hua;ZHOU Shun-Li;ZHANG Kai;WANG Zhi-Min

Acta Agron Sin. 2008, 34(09):  1629-1636.  doi:10.3724/SP.J.1006.2008.01629

Abstract ( 1750 )   PDF (193KB) ( 1414 )   Save

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Micronutrient content in wheat (Triticum aestivum L.) grains directly affects human health. However, the regulatory mechanism of micronutrient in grains is not clear.The effect of source and sink manipulation on micronutrient content has not been reported. In this study, 9 winter wheat cultivars were selected to study the regulatory mechanism of micronutrient in wheat grains by reducing source (defoliation and spike shaded) or sink (50% spikelet removal) after anthesis. Changes of Fe, Zn, Mn, Cu, and protein contents in grains and grain weight at maturity were investigated. There were significant differences (P<0.001) on Fe, Zn, Mn, Cu, and protein contents in grains and grain weight among cultivars and among source and sink treatments. In the defoliation treatment, accompanied by the reductions of grain weight (31.9%) and protein content in grains (8.6%), the contents of Fe, Zn, Mn, and Cu in grains were reduced by 1.4%, 4.5%, 7.4%, and 3.7%, respectively. In the spike shaded treatment, grain weight decreased (22.8%) while grain protein content increased slightly (7.9%). The micronutrient contents in grains changed with culti-vars and elements, but the average contents showed increases in Fe (15.8%), Zn (7.1%), and Cu (4.2%) and a decrease in Mn (1.1%). In the treatment of 50% spikelet removal, grain weight was slightly increased by 2.6%, while the grain protein content and Fe, Zn, Mn, and Cu contents rose more obviously by 23.9%, 55.0%, 39.7%, 36.2%, and 13.3%, respectively. The contents of Fe, Zn, Mn, and Cu in grains were restricted by source supplies of the corresponding element, but the effects of the source supply were different across the elements and wheat genotypes. Correlation analysis showed that all coefficients of correlation (r) were significantly positive (r = 0.431-0.785, P<0.01) except that between grain weight and the contents of Cu (r = 0.291, P>0.05) and Fe (r = 0.255, P>0.05). This implies that the 4 micronutrients in grains can be adjusted accordantly and their contents are possibly increased with grain weight and protein content simultaneously.

Fractal Analysis of Root System Architecture by Box-Counting Method and Its Relationship with Zn Accumulation in Rice (Oryza sativa L.)

WANG Hong;JIN Ji-Yun;YAMAUCHI Akira

Acta Agron Sin. 2008, 34(09):  1637-1643.  doi:10.3724/SP.J.1006.2008.01637

Abstract ( 1760 )   PDF (211KB) ( 1778 )   Save

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The analysis on the characterization of root system architecture would assist to better understand the functional and growth strategies of root systems of rice plants, which is closely related to rice plant’s adaptation to insufficient supply of soil water and nutrient. The fractal analytical method was used to examine the difference of the root systems of four rice genotypes (MADHUKAR, IR8192-200, IR26, and IR8192-31) and the relationship between root length and plant Zn uptake was explored. The root systems were grown for one month in root boxes with 25 cm in length, 2 cm in width and 40 cm in depth, which were filled with soil. The root systems were harvested following the needle-pinboard method, and then spread on the transparent plastic films with nets after carefully washing out the soils. The two-dimensional images of root systems were digitized by using a scan-ner. The digitized images were used for analysis based on fractal geometry with the box-counting method. The fractal parameters differed among the four selected rice genotypes. Variety of MADHUKAR had the greatest values of fractal dimension (FD) and fractal abundance (FA). IR8192-200’s roots had the smallest FD and FA. It was suggested that MADHUKAR had a higher capac-ity of root branch and a larger volume of soils explored by the whole root systems than other three rice genotypes. The FD and FA had significant correlations with total root length. Moreover, the correlation coefficient between FA and total root length was higher than that FD and total root length. The FD and the FA of rice roots were observed to positively correlate with shoot dry weight, shoot biomass per unit of Zn concentration, and Zn accumulation in shoot. However, shoot Zn concentration was negatively correlated with FD and FA. Root configuration changes might affect the growth of rice plants, plant Zn uptake and Zn use efficiency. The fractal analysis of root structure by box-counting method can be used to evaluate root system of different rice genotypes.

Relationship of Isozyme Genotypes of AGP with Activity of AGP and Starch Content in Wheat Grain

YUE Xiang-Wen;ZHAO Fa-Mao;LI Tian-Jiao;WANG Xian-Ze

Acta Agron Sin. 2008, 34(09):  1644-1649.  doi:10.3724/SP.J.1006.2008.01644

Abstract ( 2052 )   PDF (240KB) ( 1418 )   Save

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ADP-Glucose pyrophosphorylase(AGP) controls a rate-limiting step in the starch biosynthesis in developing wheat (Triticum aestivum L.) seeds, therefore, determinately affecting seed sink strength. Evidence is presented for the existence of AGP isozymes in common wheat endosperm. Following an approach already shown to be successful in maize (Zea mays L.), native polyacrylamide gel electrophoresis (native PAGE) was designed to identify AGP isozyme patterns from crude enzyme prepara-tions. To explore the relationship of isozyme genotypes with the starch content in wheat grains, activity of AGP and starch content were measured in 60 cultivars from 17 provinces in China. The results showed that there were four alleles, namely AGPa, AGPb, AGPc, and AGPd, with frequencies of 96.7%, 80.0%, 86.7%, and 16.7%, respectively. Five genotypes were determined in which AGPabc took on the highest frequency of 46.7% and AGPbc took on the lowest frequency of 3.3%. The activity of AGP and starch content in the cultivars with distinct genotypes were significantly different (P<0.05). The cultivars with genotype AGPabcd and AGPabc showed a high value of AGP activity and starch content. The lack of AGPa, AGPb, or AGPc in cultivars resulted in a low value of AGP activity and starch content. It indicated that different genotypes of AGP isozyme show distinct genetic impact on enzyme activity and starch content in common wheat.

Root Distribution and Competitive Ability of Summer Corn Denghai 3719

JIANG Wen-Shun;WANG Kong-Jun;WU Qiu-Ping;WANG Yong-Jun;DONG Shu-Ting;LIU Peng;ZHANG Ji-Wang

Acta Agron Sin. 2008, 34(09):  1650-1655.  doi:10.3724/SP.J.1006.2008.01650

Abstract ( 2186 )   PDF (263KB) ( 1416 )   Save

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Corn (Zea mays L.) plant density is known as a major factor determining the degree of competition between plants. Modern corn hybrids have several responses to light decline at large densities, such as keeping a erectophile plant type and elongating the maintenance of green leaves. Some researchers have pointed out that modern hybrids showed high levels in root vigor, ATPase activity, and soluble protein contents as well as the deep-vertical but narrow-horizontal distribution of roots in soils. However, the root competitive ability among cultivars that released in different years is little known. Denghai 3719 created a yield record of 21 t ha^-1 in 2005. To understand the root spatial distribution and competitive ability of Denghai 3719, an experiment was conducted in rectangle tanks for comparing the roots characteristics and the biomass of aboveground part between Denghai 3719 and Jinhai 5 (a hybrid widely cultivated in China as control). The cultivars were planted in two models, i.e., two plants per tank with the same cultivar and with each plant from both cultivars. Each model treated with two nitrogen levels (0 and 7.5 g N plant^-1). Under the nitrogen application condition, the two cultivars had a distinct biomass accumulation, but their root/shoot ratios were similar. Denghai 3719 took on superiority over Jinhai 5 both in the proportion and root vigor of shallow (0–20 cm) roots, as a result of an increase of nitrogen accumulation by 6% and biomass by 8% under competition, respectively. Under nitrogen deficiency, root/shoot ratio increased in both hybrids than that under nitrogen application, with Denghai 3719 and Jinhai 5 increased by 4% and 21%, respectively. Owing to the inferiority of Denghai 3719 over Jinhai 5 in respects of root/shoot ratio, and the proportion and root vigor of shallow (0–20 cm) roots under nitrogen deficiency, Denghai 3719 had a decrease in nitrogen accumulation by 8% and in biomass by 2% under competition, respectively. The results indicate that Denghai 3719 is more adapted to ni-trogen-efficient environment in view of root distribution and root vigor.

RESEARCH NOTES

Sexual Incompatibility between Maize and Its Wild Relatives Tripsacum L. and Coix L.

DUAN Tao-Li;MU Jin-Yi;TANG Qi-Lin;RONG Ting-Zhao;WANG Pei

Acta Agron Sin. 2008, 34(09):  1656-1661.  doi:10.3724/SP.J.1006.2008.01656

Abstract ( 2037 )   PDF (634KB) ( 1800 )   Save

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Pollens of Tripsacum L. could germinate on the stigmas of maize (Zea mays L.). After extending in maize style, the pollen tubes reached the top of ovary and released androgamete into embryo sac. But the normal hybrids of maize × Tripsacum L. were not obtained because of embryo sac incompatibility or hybrids abortion. Pollens of Coix L. could also germinate on the stigmas of maize, and the pollen tubes of C. lacryma-jobi L. var. frumentacea could reach the base of maize style, but the pollen tubes of Coix lacryma-jobi L. stopped growing at maize pistil. This indicated that there was a strict reproductive isolation between maize and Coix L. and style or embryo sac incompatibility was the crossing barrier between maize and Coix L. The ratio of the abnormal pollen tubes in the cross between maize and Coix L. was higher than that between maize and Tripsacum L., suggesting that maize has a closer relationship to Tripsacum L. than to Coix L.

Effects of High Temperature on Chlorophyll Fluorescence, Active Oxygen Resistance Activity, and Grain Quality in Grain-Filling Periods in Rice Plants

TENG Zhong-Hua;ZHI Li;ZONG Xue-Feng;WANG San-Gen;HE Guang-Hua

Acta Agron Sin. 2008, 34(09):  1662-1666.  doi:10.3724/SP.J.1006.2008.01662

Abstract ( 1964 )   PDF (259KB) ( 1987 )   Save

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The synthesis of assimilate such as starch, protein and lipid depends on the photosynthesis. Under stresses, the pigments, primary reaction and electronic transport chain which have relations with photosynthesis are hurt or inhibited. The effect of high temperature caused by “Greenhouse Effects” becomes more and more frequent. To elucidate the injury mechanism under high temperature in rice plants, the dynamic changes of chlorophyll content, chlorophyll fluorescence parameters and active oxygen resistance activity were measured and the grain quality indices including starch, protein, and chalkiness were also analyzed in rice plants of cultivars Xinongyou 30 and Fuyou 1 during grain-filling period under high temperature treatment in climatic cabinets. The results showed that under high temperature (33℃), chlorophyll content of leaves decreased, initial fluorescence (F_o) increased obviously, maximal photochemical efficiency of PS II (F_v/F_m) and the potential photochemical efficiency of PS II (F_v/F_o) decreased, F_v/F_o and F_v/F_m declined faster during the whole grain-filling period, especially in late period. Meanwhile, active oxygen resistance activity (AORA) lowered by 45.16 and 35.99% as compared with the control in the late grain-filling period; under high temperature condition, the total starch and amylose contents of grains were lower than those of control, the protein contents increased to a different degree, and chalkiness and 1000-grain weight changed significantly in two cultivars. The main reason of degeneration of grain quality under high temperature stress is related to the inhibition of primary reaction of photosynthesis, drop of active oxygen resistance activity and contraction of functional period in leaves of rice plants.

Function Verifying of Darkness Inducing Motif YTCANTYY in Pib Pro-moter via Rice Transformation

SHAO Ke-Qiang;YANG Shi-Hu;YU Li;WAN Jian-Min

Acta Agron Sin. 2008, 34(09):  1667-1672.  doi:10.3724/SP.J.1006.2008.01667

Abstract ( 1947 )   PDF (494KB) ( 1642 )   Save

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By using transgenic rice plants of 5′ deletion Pib promoter fragment-gus constructions, the relationships between the copy number of motif YTCANTYY in Pib promoter and activity of Pib promoter and its darkness induction attribute were systematically analyzed. The results from GUS histochemistry analysis revealed, after darkness induction the transgenic rice calli of Pib promoter fragments harboring 6, 3, or 1 copy of YTCANTYY motif were developed GUS blue to a different degree in X-gluc solution, but the 5′ deletion Pib promoter fragment without any YTCANTYY was unable to drive gus gene to show any GUS blue. Fluorescence quantitative analysis results showed that Pib promoter sequence had strong organ specificity. Even for the 222 bp fragment of 5′ deletion Pib promoter, which does not contain YTCANTYY motif, in its transgenic rice plants the Pib promoter activity of root was higher than that of above ground organs. But the activities of promotion and darkness inducing were increased with the increase of promoter fragments in length and the increase of this motif copy. These results indicated that YTCANTYY in Pib promoter is a functional motif for darkness induction and in other words this motif confers the darkness induction on Pib promoter. At least within 6 copies, the activity of darkness induction was positively correlated with the copy number of YTCANTYY. And the activity of darkness induction for each individual YTCANTYY motif seemed to be additive.

Effects of Brassinosteroid on Photosynthetic Characteristics in Soybean under Aluminum Stress

DONG Deng-Feng;LI Yang-Rui;JIANG Li-Geng

Acta Agron Sin. 2008, 34(09):  1673-1678.  doi:10.3724/SP.J.1006.2008.01673

Abstract ( 1931 )   PDF (363KB) ( 1380 )   Save

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Al sensitive soybean genotype BD2 was pretreated by soaking seeds with two kinds of brassinosteroids, 24-epibrass-
inosteroid (EBR) and long-effective brassinosteroid (coded as TS303), and then hydroponically cultured with 1/5 strength Hoagland solution with or without 1 mmol L^-1 Al. Root elongation, root tip Al and callose concentrations were determined to find the optimal applicative concentration of BRs. Effects and mechanisms of EBR and TS303 on photosynthetic characteristics were subsequently investigated at optimal applicative concentration. The results showed that EBR and TS303 enhanced soybean toler-ance to Al, as indicated by increased root elongation and in accordance with decreased Al and callose concentrations in root tips. The optimal effects occurred at concentration of 0.1 mg L^-1 for both EBR and TS303, and TS303 showed a better effect than EBR. The results also showed that 0.1 mg L^-1 of EBR and 0.1 mg L^-1 of TS303 both ameliorated the decrease in leaf area and net pho-tosynthetic rate caused by Al stress, indicating an enhancement in photosynthetic capacity. EBR and TS303 could counteract, at least in part, the decrease in chlorophyll content, maximal PS II efficiency (F_v/F_m), stomatal conductance, carbonic anhydrase activity, concentration and activity of RuBPCase caused by Al stress. The results suggested that, under Al stress, the increased net photosynthetic rate of soybean caused by EBR and TS303 was due to the increase in light energy harvest and transfer, and CO₂ transportation and fixation as well.