Acta Agronomica Sinica

Table of Content

12 December 2008, Volume 34 Issue 12

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Association Analysis of Agronomic Trait QTLs with SSR Markers in Released Soybean Cultivars

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

Acta Agron Sin. 2008, 34(12): 2059-2069. doi:10.3724/SP.J.1006.2008.02059

Abstract ( 3211 )

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The genotyping data of 85 simple-sequence repeat (SSR) markers on released cultivar population (RCP) (a representative sample with 190 accessions) were obtained and analyzed for LD of pairwise loci and population structure, and then for association between SSR loci and 11 soybean agronomic traits under TASSEL GLM (General linear model) program. The results showed that: (1) LD was detected extensively not only among syntenic markers but also among nonsyntenic ones, while the loci pairs with D′>0.5 accounted for only 1.71% of the total ones. The syntenic D′ value attenuated fastly along with the increase of genetic distance. (2) Genetic structure analysis showed that RCP was composed of seven subpopulations. The 45 SSR loci with a total of 136 loci (time) were found to be associated with 11 agronomic traits in the RCP. Among those, 22 loci (times) were consistent with mapped QTLs from family-based linkage mapping procedure and 43 loci (times) were consistently detected in two experiment years. (3) There also found a certain number of loci associated simultaneously with two or more traits, which might be the genetic reason of correlation among traits as well as the pleiotropic effects of gene(s). (4) There found only a few association loci in released cultivar population coincided with those in landrace and wild populations, indicating the large difference of genetic structure between the populations. (5) The elite alleles of the agronomic traits along with their carriers were detected, such as the allele Satt347-300 for largest positive yield effect (+932 kg hm^-2 for Zhongdou 26)，Satt365-294 for biomass(+3 123 kg hm^-2 for Huangmaodou)，Be475343-198 for protein content (+0.41% for Huaidou 4)，Satt150-273 for oil content (+2.32% for Kefeng 15), and were used to illustrate their potential in breeding programs.

Expression of Protein Elicitor-Encoding Gene pemG1 in Tobacco (Nicotiana tobacum cv. Samsun NN) Plants and Enhancement of Resistance to TMV

MAO Jian-Jun;QIU De-Wen;YANG Xiu-Feng;ZENG Hong-Mei;YUAN Jing-Jing

Acta Agron Sin. 2008, 34(12): 2070-2076. doi:10.3724/SP.J.1006.2008.02070

Abstract ( 1957 )

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Protein elicitors are important signal molecules that trigger plants disease resistance. Defence responses will be induced once the elicitors are recognized by acceptors in plants. It is revealed that elicitor protein PemG1 from Magnaporthe grisea is able to increase hydrogen peroxide content of tobacco suspension cells. To study PemG1’s functions in plants, pemG1 gene was transferred into tobacco in the study. For this, plant expression vector pCAMBIA2300-Ubi-pemG1-Oc harboring elicitor-encoding gene pemG1 from Magnaporthe grisea was constructed. The maize ubiquitin promoter/octopine synthase terminator system and kanamycin-resistant gene npt II (neomycin phosphotransfers II) were used for constitutive expression systems. The vector was then introduced into Agrobacterium tumefaciens (strain AGL-1) by freeze-thaw method. Tobacco (Nicotiana tobacum cv. Samsun NN) primary transformants were produced by leaf disc transformation. The kanamycin-resistant regenerated plants were confirmed to be electropositive by PCR. Integration and expression of the pemG1 gene were further confirmed by Southern blotting and Western blotting, respectively. Then, transgenic tobacco plants of T₂ generation were inoculated with Tobacco Mosaic Virus (TMV) at two different virus concentration. In comparison with TMV-infected wild-type SNN plants, PemG1-expressed plants displayed reduced hypersensitive-response lesions in both treatments. Furthermore, accumulation level of pemG1 steady-state transcripts was examined at 24 h after inoculation. The results indicated that the reduction of lesions corresponded to the accumulation of pemG1 steady-state transcripts as monitored by Northern analysis. All these indicated that the expression of pemG1 in tobacco plants improved the resistance to TMV.

Development and Utilization of EST-derived Microsatellites in Sesame (Sesamum indicum L.)

WEI Li-Bin;ZHANG Hai-Yang;ZHENG Yong-Zhan;GUO Wang-Zhen;ZHANG Tian-Zhen

Acta Agron Sin. 2008, 34(12): 2077-2084. doi:10.3724/SP.J.1006.2008.02077

Abstract ( 2030 )

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The deficiencies of markers in Sesamum indicum L. that can be used at home and aboard seriously restrict its studies in molecular field. To accelerate the application of molecular markers in sesame, EST-SSR markers development and utilization using publicly available sesame EST data were performed. A total of 1 785 non-redundant EST sets were assembled among the 3 328 identified sesame EST. 148 microsatellites sequences containing 155 EST-SSR were detected from these EST. The total length of the non-redundant EST sequences was 774.266 kb, on average one EST-SSR each 4.99 kb. The distribution characteristics of the EST-SSR markers was analyzed. Among the SSR, dinucleotide AG/TC was the most abundant (occurring 58 times), with frequency of 37.42%. According to these EST sequences containing SSR, 50 primer pairs were designed and tested on 36 sesame accessions, 2 cotton accessions, 2 soybean accessions and 2 oil sunflower accessions to detect polymorphisms and transferability. With 44 EST-SSR, 108 loci were successfully amplified in sesame, with an average of 2.45 loci per primer pair. Of the 44 amplified primer pairs, 27(61.4%) primer pairs revealed polymorphisms in the 36 sesame accessions. The PIC (polymorphism information content) ranged from 0.105 to 0.844, with an average of 0.390. Based on genetic similarity coefficient, the UPGMA dendrogram grouped 26 of 36 accessions in to two sub-clusters (III and IV), but it revealed no association between genotypes and geographical sources. In addition, 2, 3 and 4 SSR markers could be transferred to the PCR of cotton, soybean and oil sunflower respectively. This study effectively proved that EST-SSR from sesame is valuable for genetic analysis, linkage mapping and transferability study among oil plants.

Genetic Evaluation of EST-SSRs Derived from Gossypium herbaceum

YU Yu;WANG Zhi-Wei;FENG Chang-Hui;ZHANG Yan-Xin;LIN Zhong-Xu;ZHANG Xian-Long

Acta Agron Sin. 2008, 34(12): 2085-2091. doi:10.3724/SP.J.1006.2008.02085

Abstract ( 1721 )

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Gossypium herbaceum (A genome) is generally regarded as the most closely relative of the progenitor at subgenomes of allotetraploid cotton, of which the evolution is necessary to study. In order to investigate the contribution of G. herbaceum to the tetraploid genome, EST-SSRs were isolated from 247 EST sequences of G. herbaceum documented in GenBank. Twenty-seven perfect SSRs were identified from twenty-five unique ESTs. These SSRs contained 1–6 bp nucleotide motifs with high frequency for 2-bp and 3-bp nucleotide motifs. A total of 25 primers were developed and 22 of them could amplify 24 cotton accessions including 7 diploids of A genome, 11 diploids of D genome and 6 allotetraploids of AD genome; only HAU217 could specifically amplified A genome and the other 21 primers could amplified both A and D genomes. The number of polymorphic fragments generated by each primer ranged from 1 to 9 with an average of 3.64. The PIC values ranged from 0.49 to 0.91 with an average of 0.81. Among the 25 EST-SSR primers, six primers revealed polymorphism between Emian 22 and Pima 3-79, and yielded seven polymorphic loci (five were codominant and two dominant) in the BC₁ [(Emian22 × Pima3-79) × Emian22] population. Only HAU230b showed distorted segregation in the BC₁ population. Six polymorphic loci were integrated into six chromosomes of our interspecific BC1 backbone genetic linkage map among which, four loci were mapped on four chromosomes of A sub-genome (Chr. 6, 10, 11, 12), and two loci on two chromosomes of D sub-genome (Chr. 19 and 20).

Expression Characteristics of Tobacco Tapetum-Specific Promoter pTA29 in Cotton

YIN Meng-Hui;DONG Jing;LI Xian-Bi;HUO Lei;LUO Ming;LI De-Mou;PEI Yan;XIAO Yue-Hua

Acta Agron Sin. 2008, 34(12): 2092-2098. doi:10.3724/SP.J.1006.2008.02092

Abstract ( 2317 )

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Tobacco tapetum-specific promoter pTA29 is widely used to create male sterile lines and to study pollen development in various plants. However, the pTA29 expression characteristics in cotton is still not elucidated. To determine the expression characteristics of pTA29 promoter in cotton, gus gene was fused downstream to pTA29, transformed into cotton. It was demonstrated that 10% alcohol suppressed the intrinsic GUS-like activity in cotton anther. GUS staining with modified solution showed that the GUS activity in the pTA29:gus transformants mainly exited in anthers with two peaks in the floral buds of 6 and 15 mm, while no GUS activity was detected in roots, stems, ovules, petals and bracts. Inconsistent with that in tobacco, the GUS activity was also detected in the leaf trichomes and pollens in pTA29:gus transformants. Real-time RT-PCR analysis indicated that the gus transcripts accumulated in a same pattern with the GUS activity. These results suggest that the tobacco tapetum-specific promoter pTA29 can drive the downstream genes to express preferentially in anthers of cotton. The application of pTA29 in cotton male sterility engineering was discussed.

Microsatellite Molecular Marker Enrichment by Magnetic Beads in Flax

DENG Xin;CHEN Xin-Bo;LONG Song-Hua;WANG Xiao-Chun;GAO Yuan;HE Dong-Feng;WANG Jin;WANG Yu-Fu

Acta Agron Sin. 2008, 34(12): 2099-2105. doi:10.3724/SP.J.1006.2008.02099

Abstract ( 2092 )

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Flax (Linum usitatissimum L.) is one of the important oil and fiber crops in the world and can be used as a model plant for bast fiber genomics. The objectives of this study were to set up an efficient protocol to develop microsatellite markers for flax genetic linkage map construction, gene mapping, and marker-assisted selection (MAS). The 300–1 500 bp flax DNA fractions containing microsatellite sequences were captured by hybridizating the digested genomic DNA fragments with the oligonucleotide probes (CT)15 attached to streptavadin coated magnetic beads (Dynal). The enriched DNA fragments were ligated into pMD18-T vector and then transformed into E. coli Top 10 competent cells to form an enriched microsatellite sequence library. PCR screening using adaptor primer and VRV (CT)15 as primers identified 104 microsatellite clones from 422 transformants in the libraries. Sequence analysis of these positive clones confirmed 97 microsatellite sequences, with a high enrichment efficiency of 22.99% and PCR screening efficiency of 93.27%. Comparative analysis of the 97 microsatellite sequences showed that 51 among them were of high similarity for microsatellite sequences. PCR amplification using a pair of primers designed from these 51 sequences could successfully identify clones with these high similar microsatellite sequences before sequencing. This method can be used as an efficient tool to eliminate high copy microsatellite clones in screening microsatellite library.

Changes of Ca²⁺-ATPase in Photosensitive Genic Male-Sterile Rice Nongken 58S during Pollen Aborting

SHI Yin-Lian;DENG Fang;CAO Jian-Bo;YAO Jia-Ling

Acta Agron Sin. 2008, 34(12): 2106-2111. doi:10.3724/SP.J.1006.2008.02106

Abstract ( 2590 )

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TEM and lead nitrate were used to locate Ca²⁺-ATPase in the anther development of Photoperiod-sensitive Genic Male-sterile Rice Nongken 58S and normal fertile rice Nongken 58N. The results showed that the quantity and the producing time of Ca²⁺-ATPase in the anther wall, connective tissue and pollen of fertile and sterile rice were very different. Some of Ca²⁺-ATPase distributed on the epidermal cells of fertile anther at pollen mother cell stage. And there were some Ca²⁺-ATPase in different anther wall cells, the more on the Ubisch body during the development of the pollen. Comparatively, the less and the later-produced Ca²⁺-ATPase distributed in the different anther wall cells of the sterile anther at the same stage. There were visible Ca²⁺-ATPase in the vacuole membrane of epidermal cell, cytoplasm of remained tapetum cell and the surface of Ubisch bodies at the binucleate pollen stage. Abundant Ca²⁺-ATPase distributed on the exine, the intine, the membrane of the cytoplasm and the nucleus of fertile pollen at the late uninucleate pollen stage, but no Ca²⁺-ATPase distributed on the sterile pollen during the development of the anther except binucleate pollen stage. The quantity of Ca²⁺-ATPase in the sterile pollen was less than that in the fertile pollen at the binucleate pollen stage. There were most Ca²⁺-ATPase in the fertile connective tissue at pollen mother cell meiosis stage. Comparatively, a little Ca²⁺-ATPase distributed in the sterile connective tissue until the pre-uninucleate pollen stage. Based on the above results, we suppose that the reason of pollen abortion is the less and later-produced Ca²⁺-ATPase distribution on the sterile pollen wall and the plasma membrane during the sterile anther development. And Ca²⁺ pump does not work for little Ca²⁺-ATPase in the sterile rice, so that it makes pollen abortion with abundant Ca²⁺ in the cytoplasm.

Analysis of Indica-Japonica Characteristics in Thermo-Sensitive Genic Male Sterile Rice Line Zhu 1S

LIU Ping;DAI Xiao-Jun;YANG Yuan-Zhu;LI Wen-Jia;OU Li-Jun;LIANG Man-Zhong;CHEN Liang-Bi

Acta Agron Sin. 2008, 34(12): 2112-2120. doi:10.3724/SP.J.1006.2008.02112

Abstract ( 2136 )

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Zhu 1S is an early indica thermo-sensitive genic male sterile (TGMS) rice line widely used in hybrid rice production. In this study, with typical indica and japonica cultivars as control, the DNA polymorphism of Zhu 1S was analyzed by using three molecular markers of ISSR, SRAP, and TRAP. The results showed that the nuclear genome of Zhu 1S was mainly indica-derived, but it contained some japonica-specific DNA fragments and had certain japonica consanguinity. The specific molecular fingerprint of Zhu 1S could be established by using any of the three molecular markers. Moreover, the analysis of ORF100, ORF29–TrnC^GCA, TrnT^UGU–TrnL^UAA, intron sequences of rps16 gene in chloroplast DNA of Zhu 1S showed that the chloroplast genome of Zhu 1S was indica-type, while the chloroplast genomes of Pei’ai 64S and Zhun S were japonica-type. There were two base substitutions in TrnT^UGU–TrnL^UAA fragment of Zhu 1S. It should be applicable approach for breeding two-line early hybrid rice combination with high and stable yield by using dual-purpose genic male sterile lines with indica-type cytoplasm and appropriate japonica consanguinity in double-cropping rice area around the middle and lower reaches of the Yangtze river. Hence, the results have some instructions for the breeding of high quality dual-purpose genic male sterile lines and the rice combinations.

Expression Pattern of Special Genes Resistant to Powdery Mildew (Blumeria graminis f. sp. tritici) in SSH-cDNA Library of Wheat

WU Jin-Hua;HU Yin-Gang;WANG Xin-Ru;ZHANG Hong;WANG Chang-You;WANG Qiu-Ying;JI Wan-Quan

Acta Agron Sin. 2008, 34(12): 2121-2125. doi:10.3724/SP.J.1006.2008.02121

Abstract ( 3037 )

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Powdery mildew, caused by Blumeria graminis f. sp. tritici, is one of the most important fungal diseases of common wheat (Triticum aestivum L.) worldwide and causes severe yield losses. Wheat germplasm N9436, developed by our research group, is a resistant material to powdery mildew. In the present study, a suppression subtraction hybridization (SSH) cDNA library was constructed with cDNA from N9436 leaf inoculated by Blumeria graminis as the tester and cDNA from N9436 healthy leaf as the driver. A total of 140 positive clones were randomly chosen from the SSH-cDNA library and were amplified with sp6 and t7 primers to examine the insert size, which ranged from 200 to 1 000 bp with an average of 238 bp. After screening repeat and redundancy sequences, 94 expressed sequence tags (ESTs) were acquired. Protein homology search in nr-protein database revealed that 49 ESTs were highly homologous with known proteins functioning in primary metabolism (2%), energy metabolism (24%), cell structure (2%), transcription (2%), protein synthesis and processing (16%), transport (4%), signal transduction (4%), and disease resistance and defenses (30%). Compared with the EST sequences among the SSH-cDNA library, 2 ESTs (GenBank accession number: EX567369 and EX567360) were highly similar to pathogenesis-related protein (Z25-1) and glutathione-S-transferase (Z440-1), respectively. On the basis of the EST sequences, 2 pairs of primers were designed and used to detect the expression differences of the 2 genes when inoculating with powdery mildew by Reverse Transcriptase PCR (RT-PCR). Z25-1 and Z440-1 were both expressed under inoculation. Their expression amounts were the largest in 72 h after inoculation with powdery mildew. But their expression trends were different. At early stage of inoculation (24 h after inoculation), the expression amount of Z440-1 was very a little, then increased in 72 h, and finally decreased in 96 h. The expression amount of Z25-1 increased from 24 h to 72 h after inoculation and decreased after 96 h. It suggests that pathogenesis-related protein and glutathione-S-transferase belong to inducible expression genes and are involved in the resistance to powdery mildew.

Gene Expression Profiling in Roots of Wheat Cultivar “Luohan 2” under Water Stress

LI Yong-Chun;MENG Fan-Rong;WANG Xiao;CHEN Lei;REN Jiang-Ping;NIU Hong-Bin;LI Lei;YIN Jun

Acta Agron Sin. 2008, 34(12): 2126-2133. doi:10.3724/SP.J.1006.2008.02126

Abstract ( 2252 )

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High-through microarray technology is a powerful tool for analyzing gene expression profiles of plants exposed to abiotic stresses. To investigate the molecular mechanisms of water-stress response in wheat (Triticum aestivum L.), the transcript profiles in 20% PEG 6000 treated roots and control roots of a wheat cultivar ‘Luohan 2’ were comparatively studied using the Affymetrix wheat GeneChip. Analysis of the microarray data showed that there were 3 743 genes (4 074 probe sets) induced and 4 573 genes (5 043 probe sets) repressed in roots under water-stress. Generally, the down-regulated genes were greater in quantity than up-regulated genes. Among these differentially expressed genes, 1 593 and 2 238 genes (1 716 and 2 451 probe sets) were up- and down-regulated exceeding 2 folds, respectively. Through the sourcing annotations directly from Affymetrix website (www.affymetrix.com/analysis/) in tandem with BLASTX analyzing using the Affymetrix probe set sequences, 619 candidate genes were annotated. The functional classification of annotated genes were performed based on literature searches of the functional categories described in the MIPS database and the 619 annotated genes were classified into 10 functional categories, involving in metabolism, stress response, biogenesis of cellular components, protein synthesis, cellular communication, cellular transport, transcription, cell division, protein processing, and others. Thirty-two up- or down-regulated genes with over 16-fold change ratios were annotated. A half of them belonged to the stress response category, and another five were associated with metabolism. In addition, the differential expression patterns of eight representative candidate genes were confirmed by real-time quantitative RT-PCR and the results showed that the expression changes of these candidates were generally consistent with the microarray results detected by Affymetrix GeneChip.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Effect of Heat-Stress during Meiosis on Grain Yield of Rice Cultivars Differing in Heat-Tolerance and Its Physiological Mechanism

CAO Yun-Ying;DUAN Hua;YANG Li-Nian;WANG Zhi-Qing;YANG Jian-Chang

Acta Agron Sin. 2008, 34(12): 2134-2142. doi:10.3724/SP.J.1006.2008.02134

Abstract ( 2727 )

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Meiosis is the most stress-sensitive period in reproduction of rice plants. However, little is known how heat-stress during meiosis affects grain yield of rice. This study investigated the development of anthers and pollens, yield components, and some physiological parameters under the heat-stress during meiosis. Two indica rice cultivars with different heat-tolerance, Shuanggui 1 (heat-sensitive) and Huanghuazhan (heat-tolerant), were pot-grown and subjected to treatments of heat-stress (the mean temperature during the day >35℃) and natural temperature (the mean temperature during the day <33℃, CK). The results showed that the heat-stress significantly reduced anther dehiscence and pollen fertility rate of Shuanggui 1, while it much less affected those of Huanghuazhan. The number of spikelets per panicle, seed-setting rate, and 1000-grain weight were significantly decreased under the heat-stress for both cultivars, leading to a significant reduction in grain yield, with a more reduction in Shuanggui 1 than in Huanghuazhan. The heat-stress treatment significantly decreased grain width of Shuanggui 1 and obviously increased ratio of length to width of grain, whereas it less affected those of Huanghuazhan. The heat-stress significantly reduced root oxidation activity and ribonucleic acid (RNA) content of young panicles, and significantly increased malondialdehyde (MDA) content of leaves and ethylene evolution rate of young panicles, and the extent of the decrease or increase was more in Shuanggui 1 than in Huanghuazhan. The heat-stress treatment significantly increased activities of peroxidase, superoxide dismutase and catalase of leaves in Huanghuazhan, while it much less affected those in Shuanggui 1. The results indicate that stronger root activity and antioxidative defense system, greater RNA content, and less ethylene synthesis and lower MDA content in rice plants during meiosis would be physiological mechanisms in maintaining a higher grain yield for a heat-tolerant cultivar under high-temperature stress.

Physiological Mechanism of Sucrose Metabolism in Cotton Fiber and Fiber Strength Regulated by Nitrogen

MA Rong-Hui;XU Nai-Yin;ZHANG Chuan-Xi;LI Wen-Feng;FENG Ying;QU Lei;WANG You-Hua;ZHOU Zhi-Guo

Acta Agron Sin. 2008, 34(12): 2143-2151. doi:10.3724/SP.J.1006.2008.02143

Abstract ( 2026 )

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Fiber strength is one of the important criteria of cotton (Gossypium hirsutum L.) quality. Two cotton cultivars (KC-1, average fiber strength is 35 cN tex^-1; AC-33B, average fiber strength is 32 cN tex^-1) were used, with three nitrogen application rates (0, 240, 480 kg ha^-1), standing for low, moderate and high nitrogen levels respectively in field experiments in Nanjing (118º50′E, 32º02′N, middle lower reaches of Yangtze River Valley) and Xuzhou (117°11’ E, 34°15’ N, Yellow River Valley), Jiangsu province, which stand for the different ecological conditions. The results showed that the changes of nitrogen concentration in the subtending leaf of cotton boll followed the equation: [YN is nitrogen concentration in the subtending leaf of cotton boll (%); t is boll age (d); a and b are the parameters]. “a” was significantly high under high-nitrogen level, which, to a great extent, led to the decreases of sucrose inversion amount and activity of the enzymes (invertase, sucrose synthetase, and phosphate sucrose synthetase) before the 24th day post anthesis (DPA), as well as the maximal speed of cellulose accumulation in cotton fiber and fiber strength at the 24th DPA. “b” was significantly high under low-nitrogen level , which made negative effects on sucrose metabolism after the 24th DPA, shorten the duration for cellulose rapid accumulation in cotton fiber and reduced the increment of fiber strength from the 24th DPA to boll opening. The changes under high or low-nitrogen levels described above were important physiological responses of cotton fiber development to nitrogen concentration in the subtending leaf of cotton boll, and ultimately resulted in lower final fiber strength, and the changes showed similar trends in KC-1 and AC-33B. The results indicated that, in the subtending leaf of cotton boll, the 24^th DPA was a transition point of sucrose metabolism in cotton fiber and fiber strength regulated by nitrogen.

Evaluation of Phosphorus Efficiency in Rapeseed (Brassica napus L.) Recombinant Inbred Lines at Seedling Stage

ZHANG Hai-Wei;HUANG Yu;YE Xiang-Sheng;XU Fang-Sen

Acta Agron Sin. 2008, 34(12): 2152-2159. doi:10.3724/SP.J.1006.2008.02152

Abstract ( 2006 )

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Phosphorus (P) is one of the necessary mineral nutrients for plants. Despite high concentrations of total P in soil, its bio-available concentration is very low compared to the requirement of plants and soil organisms. P deficiency is a major factor limiting plant growth and productivity worldwide. The plant species or cultivars show significant difference in accumulation and utilizing soil P, thus, developing P-efficient crops has been proposed as an available strategy to improve the fertilizer use efficiency or to obtain high yields in low input agricultural systems. The aim of the study was to evaluate P efficiency of 135 recombinant inbred lines (RIL) derived from a cross between P-efficient cultivar and P-inefficient cultivar of rapeseed (Brassica napus L.) through investigating shoot dry weight (SDW), root dry weight (RDW), root/shoot-ratio (R/S), average maximal root length (AMRL), shoot phosphorus uptake (SPU), total phosphorus uptake (TPU) and P use efficiency (PUE) at the seedling stage in a solution culture experiment with low P (P1, 5 μmol L^-1) and normal P treatments (P2, 1 000 μmol L^-1). The correlation between the tested traits and P efficiency among the RIL was analyzed. The results showed that 1) low-P stress limited seriously plant growth at seedling stage, and there existed significant differences among the genotypes of the RIL compared with normal P treatment; 2) all of the four traits, SDW, RDW, R/S, and AMRL, showed normal distribution in the RIL under both P treatments and presented significant transgressive segregation; and 3) the correlation among the seven traits investigated in the study indicated that relative SDW and RDW could be used as available evaluation indices for P efficiency but the effect of genetic factor should be considered at the same time; 4) on the basis of the screening indexes, genotypes with extremely high P efficiency were screened from the population, but they should be identified on low-P soil further.

HMW-GS Accumulation and GMP Size Distribution in Grains of SN12 Grown in Different Soil Conditions

LIANG Tai-Bo;YIN Yan-Ping;CAI Rui-Guo;YAN Su-Hui;LI Wen-Yang;GENG Qing-Hui;WANG Ping;WU Yun-Hai;LI Yong;WANG Zhen-Lin

Acta Agron Sin. 2008, 34(12): 2160-2167. doi:10.3724/SP.J.1006.2008.02160

Abstract ( 2375 )

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Glutenin macropolymer (GMP), the important component of wheat (Triticum aestivum L.) glutenin polymer, consists of high molecular weight gultenin subunits (HMW-GS) and low molecular weight gultenin subunits (LMW-GS). Accumulations of HMW-GS and GMP play key roles in grain quality of wheat. According to recent studies, GMP is a particle network in endosperm of wheat. The content of GMP is affected by HMW-GS accumulation and environment factors. But to date, there are few reports about the relationship between HMW-GS accumulation and GMP particle distribution. To study the HMW-GS accumulation and its relation to GMP particle distribution, a pool experiment was carried out with wheat cultivar Shannong 12 grown under three soil textures. Forty spikes was sampled at 7, 14, 21, 28, and 35 d after anthesis, and partitioned into two groups, superior grain (the 2nd grain from the basal part of a spikelet) and inferior grain (the 4th grain from the basal part of a spikelet). HMW-GS was separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The result showed that all HMW-GS already formed at 14 d after anthesis both in superior grain and inferior grain. Higher HMW-GS content showed that superior grain had strong HMW-GS accumulating ability than inferior grain. HMW-GS accumulation and GMP content of wheat grown in clay loam soil were higher than those in sandy and loam soil, which indicated that clay loam soil was suitable for accumulating of HMW-GS. The diameter of GMP particle was in 0.37–245 μm, it changed in the pattern of two-peak curve in volume and surface area distribution, while single-peak curve in number distribution of GMP particle. The percentages of number and volume of >100 μm GMP particle were higher in superior grain than in inferior grain. The contents of HMW-GS and GMP were negatively correlated with GMP particle volume of <10 μm and <100 μm, but positively correlated with that of >100 μm. It is suggested that larger GMP particle has more HMW-GS content.

Effects of Nitrogen on Starch Accumulation and Activities of Enzymes Involved in Starch Synthesis in Rice Caryopsis

ZHANG Jun;LI Yun-Xiang;LIU Juan;WANG Zhong;CHEN Gang;XIONG Fei

Acta Agron Sin. 2008, 34(12): 2168-2175. doi:10.374/SP.J.1006.2008.02168

Abstract ( 2070 )

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Starch accumulation is the main event in the developing rice grain, and the activities of key enzymes involved in starch synthesis are the important factors affecting the grain filling. N-fertilizer can regulate the plant growth, flower emergence, grain yield and quality, while the effects of N-fertilizer on starch accumulation and the activities of key enzymes in rice grains are rarely known. In this study, two rice cultivars, Yangdao 6 and Jingdao 941, were used as materials to study the effects of nitrogen on starch accumulation and the activities of related enzymes involved in starch synthesis. The results indicated that increased panicle N-fertilizer could significantly decrease the soluble sugar in the developing caryopsis, while the starch content reduced slightly. The amylose and amylopectin contents in the caryopsis increased synchronously with the raising of grain weight. When the panicle N-fertilizer was added, the amylose content in caryopsis as well as the content ratio of amylose to total starch decreased observably. During the development of rice caryopses, the activities of ADP-glucose pyrophosphorylase (AGP), granule-bound starch synthase (GBSS), soluble starch synthase (SSS) and starch branching enzyme (SBE) in endosperm changed as single peak curve. That was, the enzyme activities increased at the early stage of grain filling, till their peak at 10–15 d after flowering, then depressed. Application of nitrogen fertilizer could improve the activities of AGP, SSS, and SBE in rice caryopsis at middle and late filling stages, while decrease GBSS activity at early and middle filling stages. And the effect of the N fertilized at the booting stage was superior to that at the tilling stage.

Effect of Panicle Fertilizer Application Rate on Morphological, Ecological Characteristics, and Organ Temperature of Rice

YAN Chuan;DING Yan-Feng;WANG Qiang-Sheng;LI Gang-Hua;LIU Zheng-Hui;MIAO Xiao-Jian;ZHENG Yong-Mei;WEI Guang-Bin;WANG Shao-Hua

Acta Agron Sin. 2008, 34(12): 2176-2183. doi:10.3724/SP.J.1006.2008.02176

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Using 2 japonica and indica rice cultivars with three panicle fertilizer application rate treatments and a control, different populations of rice were constructed, and the effect of panicle fertilizer application rate (PFAR) on morphological, ecological characteristics and organ temperature of rice were studied. The results showed that PFAR had a significant effect on length of panicle, panicle camber, length of leaf and leaf angle. It was also observed that air temperature, humidity, light intensity and content of CO2 were also affected by different PFAR treatments, medium PFAR was proved to be best for microclimate within rice population. Besides, there were felicitous leaf area index, length of second leaf, photosynthetic rate, transpiration and lower canopy temperature at medium PFAR. The temperature of plant organs was significantly affected by PFAR, the more the PFAR, the lower the temperature of panicle and leaf. The organ temperature was significantly different at the 0.05 level between medium PFAR and lower PFAR, control treatments, while not significantly between medium PFAR and higher PFAR. This study clearly showed that appropriate agronomic practices, such as PFAR, have a significant effect on the temperature of plant organs and canopy, and also enhance the resistance to heat stress.

Effect of Panicle Nitrogen Fertilizer on Concentrations of Cytokinin and Auxin in Young Panicles of Japonica Rice and Its Relation with Spikelet Development

WANG Xia-Wen;WANG Shao-Hua;LI Gang-Hua;WANG Qiang-sheng;LIU Zheng-Hui;YU Xiang;DING Yan-Feng

Acta Agron Sin. 2008, 34(12): 2184-2189. doi:10.3724/SP.J.1006.2008.02184

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Panicle N fertilizer, which is nitrogen fertilizer applied at panicle development stage, has great influence on the development of rice panicle. Studies have revealed that the beneficial response of nitrogen fertilizer on spikelet development is associated with the increase of spikelets number per panicle. However, little is known concerning the effect of panicle N fertilizer on endogenous hormones in rice young panicle. In the present study, two japonica rice cultivars (Wuyujing 3 and 2401) were used, and two panicle N fertilizer treatments, 120 kg N ha^-1 as high nitrogen (HN) and 0 kg N ha^-1 as low nitrogen (LN), were conducted to investigate the relationship between spikelets number and hormonal changes during rice panicle differentiation. The results showed that zeatin + zeatin riboside (ZRs), isopen-tenyl adenine (iPAs), and indole-3-acetic acid (IAA) concentrations were the highest at spikelet differentiation stage, sharply declined and remained almost static till heading, and recovered slightly after heading. Panicle N fertilizer treatment resulted in higher concentrations of ZRs and iPAs, especially at the spikelet differentiation stage. Whereas, IAA displayed lower concentration in HN as compared to LN. Moreover, there were higher ratios of ZRs/IAA and iPAs/IAA for HN as compared to LN during the panicle differentiation stage. The difference between them was the maximum at the spikelet differentiation stage and then declined to the minimum before heading, while there was no significant difference between two cultivars. The results suggested that the effect of panicle N fertilizer on spikelet differentiation and numbers per panicle could be associated with the changes of endogenous hormones such as ZRs, iPAs and IAA, either in their concentrations or in their ratios.

Space-Time Dynamics of Heterodera glycines in Soybean Roots

LI Xiu-Xia;WANG Zhen-Hua;SHI Li-Bo;WU Hai-Yan;BI Jian-Jie;LI Duo-Chuan

Acta Agron Sin. 2008, 34(12): 2190-2195. doi:10.3724/SP.J.1006.2008.02190

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Population of Heterodera glycines fluctuations in the fields during growth of soybean. In order to investigate dynamics of Heterodera glycines in soybean roots, and provide more information of effective control for soybean cyst nematode, distribution and dynamics of soybean cyst nematode (SCN, Heterodera glycines, race 4) in the soybean roots were monitored during the period of 7–37 d after seedling emergence in 2006 and 2007. The results indicated that distribution of SCN population closely related to the growth of roots. Nematodes invaded the roots at 7 days after seedling emergence, and nematode density and population increased with the growth of soybean roots, the fluctuation of nematodes per centimeter root showed a sigmoid curve. The changed of nematodes per cm root showed an inverse trend with the age of seedlings between taproot and lateral root. Nematode density in taproot had a declining trend, when that in lateral root increased to a stable value. Difference of nematode density between taproot and lateral root decreased with deepening the soil layer, number of nematodes per cm root and percent to total nematodes reached the ultimate number in the 5–15 cm soil, suggesting that most of the nematodes distributed in lateral root and at the 5–15 cm soil layer during the soybean seedling stage.

Characteristics of Photosynthesis in Different Wheat Cultivars under High Light Intensity and High Temperature Stresses

QI Xue-Li;HU Lin;DONG Hai-Bin;ZHANG Lei;WANG Gen-Song;GAO Chong; XU Wei-Gang

Acta Agron Sin. 2008, 34(12): 2196-2201. doi:10.3724/SP.J.1006.2008.02196

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High light associated with high temperature has strong effects on photosynthesis in wheat (Triticum aestivum L.) and results in grain yield loss at maturity. To explore the photosynthetic responses of different wheat cultivars to high light and high temperature (HLHT), we measured the photosynthetic and chlorophyll fluorescence characteristics of flag leaves of four cultivars under the high light intensity of 1 900 μmol m^-2 s^-1 and high temperature of 35ºC. Under natural groth condition (control), both photosynthetic rate under saturated light and saturated light intensity for photosynthesis in Zhengmai 9405 and Zhou 18 were higher than those in Gaocheng 8901 and Yumai 49, and the apparent quantum yield of Zhengmai 9405 was the maximal among the four cultivars. Compared with the control, after the HLHT treatment, the net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs) in Gaocheng 8901, Yumai 49 and Zhou 18 were significantly reduced, whereas these parameters changed slightly in Zhengmai 9405 with a rather steady P_nvalue of 11.6 μmol CO₂ m^-2 s^-1 in flag leaves. In the four cultivars, the intercellular CO₂concentration (Ci) showed no significant changes compared with the control, the maximum photochemical efficiency (F_v/F_m), the efficiency of open centers of photosystem II (F_v’/F_m’), the actual photochemical efficiency of photosystem II (Ф_PSII), and the photochemical quenching (q_P) decreased while non-photochemical quenching (NPQ) increased significantly, and each of the five chlorophyll fluorescence parameters in Zhengmai 9405 was the highest. The results mentioned above indicated that different cultivars had notable differences in the adaptability to high light intensity and high temperature, Zhengmai 9405 was more adaptable than Gaocheng 8901, Yumai 49, and Zhou 18. The higher Tr and NPQ of Zhengmai 9405 may be one of the reasons for its higher photosynthesis rate.

Modeling with Climatic Factors and Analysis on Ecological Characters for Grain Weight Dissected Factors of Two-line Hybrid Rice, Liangyoupeijiu

LÜ Chuan-Gen;ZONG Shou-Yu;HU Ning;ZOU Jiang-Shi;YAO Ke-Min;TANG Wei-Ya

Acta Agron Sin. 2008, 34(12): 2202-2209. doi:10.3724/SP.J.1006.2008.02202

Abstract ( 1936 )

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