Table of Content

10 December 2009, Volume 35 Issue 12

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

  QTL Mapping of Protein Related Traits in Soybean[Glycine max (L.) Merr.]

LIU Shun-Hu,ZHOU Rui-Bao,YU De-Yue,CHEN Shou-Yi,GAI Jun-Yi

Acta Agron Sin. 2009, 35(12):  2139-2149.  doi:10.3724/SP.J.1006.2009.02139

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Soybean processing industry places emphasis on the quality of soybean protein which is related to the protein components, mainly 11S, 7S and 11S/7S, and their subunit constituents. In the improvement of soybean protein quality, the knowledge of genetic structure of the traits related to protein quality is of great importance. Therefore, the present paper was aimed at mapping QTLs of 16 traits, including protein content, protein plus fat content, fat content, 11S, 7S, 11S/7S, and subunit groups. Two populations, RIKY population with 184 recombinant inbred lines derived from Kefeng 1×Nannong 1138-2 and BIEX population with 114 BC₁F₂ lines derived from (Essex×ZDD2315) ×ZDD2315, were used to map QTLs with the softwares of composite interval mapping (CIM), multiple interval mapping (MIM) of WinQTL Cartographer Ver. 2.5 and the inclusive composite interval mapping (ICIM) of IciMapping. The results showed that there were totally 17⁺ QTLs detected with 11 for protein content, fat content and total content of protein and fat, and 1⁺ and 3⁺ for 11S subunit groups and 7S subunit groups, respectively, in RIKY, as well as totally 21⁺ detected with only 2⁺ for protein content, fat content and protein plus fat content, but 9⁺ and 6⁺ for 11S subunit groups and 7S subunit groups, respectively, in BIEX. There was no shared QTL detected for all 16 traits in both populations, indicating that the 16 traits between RIKY and BIEX have completely different genetic systems, and there existed obvious genetic differences between two parents of RIKY in protein content, fat content and protein plus fat content but less genetic differences in 11S subunit groups and 7S subunit groups, and those of BIEX were on the contrary. The group of protein content, fat content and protein plus fat content and the group of 11S, 7S and 11S/7S had common QTLs, showing their common genetic base, but there were no common QTLs in the groups of 11S subunit and 7S subunit. The results from QTL mapping and segregation analysis showed jointly that both major genes and minor genes contributed a large part of phenotypic variations for all 16 traits, suggesting that both major genes and minor genes should be considered in the breeding for protein-related traits.

Inheritance of DNA Methylation in Two Cotton Hybrid Dericed from CRI-12

ZHU Xin-Xia,WANG Bao-Hua,GUO Wang-Zhen,ZHANG Tian-Zhen

Acta Agron Sin. 2009, 35(12):  2150-2158.  doi:10.3724/SP.J.1006.2009.02150

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DNA methylation in the form of cytosine methylation is proposed as an evolutionary event, which contributes to genome evolution and plays an important role in maintaining genome integrity and controlling dynamics of gene activity. Hybridization and polyploidization play significant roles in the evolution of higher plants. Compared with animals, cytosine methylation is more abundant in plants, particularly at genomic regions containing transposons and their derivatives. Accumulated evidence had suggested that DNA methylation plays important roles in normal plant development. In different stages of plant growth, the changes in DNA methylation level play an important role in response to variations of its heredity and the environment. Notwithstanding these interesting findings, the causing factors for, and generality of, methylation dynamics in plants, particularly with hybrid formation and trans-generational heritability, remained largely vague. However, there is a paucity of evidence to support any direct link between the epigenetic phenomena of cytosine methylation alteration and gene silencing following hybridization and polyploidization. In this study, MSAP (methylation-sensitive amplified fragment length polymorphism) was used in this study to detect the DNA methylation patterns in the 5′-CCGG sites of two cotton hybrid derived from CRI-12 and their parents for understanding developmental stability and inheritance of cytosine methylation. It was found MSAP ratios, which were the ratios of MSAP type in the two cotton hybrids were 12.41%–20.05%, cytosine methylation profiles were variable, from increase to decrease during plant growth and development. Full methylation of internal cytosine (6.90%–11.47%) was the dominant in two cotton hybrids. Meanwhile, the MSAP profiles enable the monitoring of inheritance or variation of parental methylation patterns in hybrid progenies. It was found that a great majority (from 96.6 % to 98.86 %, depending on crosses) of the methylation profiles in cotton inbred lines transmitted to the inter-strain hybrids; however, from 1.14% to 3.39% of the profiles in the hybrids exhibited variation from the expected parental additivity. Both inherited and altered methylation profiles can be divided into distinct groups, and their frequencies are variable among the cross-combinations, and during plant growth and development. Bands in hybrids that appeared in both groups digested by Hpa II-EcoR I and Msp I-EcoR I, which were inherited from either or both of the maternal and paternal parent—this type apparently comprised the greatest majority, as all monomorphic bands belong to this type. In addition, sequencing of differentially methylated fragments and subsequent homology analysis of isolated bands that showed variation in hybrids indicated that diverse sequences were involved, including known-function cellular genes and mobile elements, Such as leucine-rich repeat family protein, PDR-like ABC-transporter, putative oligopeptide transporter, GTP-binding protein, similar to pathogenesis-related protein, DOMON domain-containing protein, putative adenosine phosphosulfate kinase, putative protein, RNA-directed DNA polymerase. The remaining 14 bands showed no homology to the database sequences. These results clearly demonstrated the power of the MSAP technique for large-scale DNA methylation detection in the cotton genome, and the complexity of DNA methylation change during plant growth and development. The different methylation levels may be induced by interspecific hybridization between two cotton hybrids, and indicated a direct relationship between cytosine methylation alteration and gene expression variation.

Construction of Molecular Genetic Map and QTL Analysis of Fiber Quality in Cotton（Gossypium hirsutum L.）

YANG Xin-Lei,WANG Zhi-Wei,ZHANG Gui-Yin,PAN Yu-Xin,WU Li-Qiang,LI Zhi-Kun,

Acta Agron Sin. 2009, 35(12):  2159-2166.  doi:10.3724/SP.J.1006.2009.02159

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Cotton is a leading textile fiber crop in the world and a source of secondary products such as oil, live- stock feed (cotton seed cake) and cellulose. The improvement of cotton fiber quality is becoming extremely important with the innovation of spinning technology. A genetic map is necessary not only for the reliable detection, mapping and estimation of gene effects of important agronomic traits, but also for further research on the structure, organization, evolution and function of cotton genome. In the present study, simple sequence repeats (SSRs) and amplified fragment length polymorphism (AFLP)were used to assay anF₂ population from a cross between CRI8 (Gossypium hirsutum L.) and Pima90-53 (Gossypium barbadense L.). Two hundred and fourteen F₂plantswere used for map construction using 110 SSRs and 65 AFLPs. This map included 175 markers distributing on 42 linkage groups, covering 2030cM, accounting for 40.6% of the cotton genome, and with an average distance of 11.6 cM between two markers. The length of linkage groups ranged from 4.5to 147.3 cM and the markers on the groups ranged from 2 to 22. The linkage map waslocated on 10 chromosomes,which were Chr.4, Chr.8, Chr.9, Chr.10, Chr.12, Chr.14, Chr.15, Chr.18, Chr.21, and Chr.25.Based on composite interval mapping, five QTLs were identified for fiber length, distributing on Chr.21, Chr.15, LG2, and LG12, explaining 10.2%–35.8% of the fiber length variance. Four QTLs were identified for length uniformity, distributing on Chr.21, LG9, LG18, and LG12, explaining 12.6%–36.6% of the fiber length uniformity variance. Seven QTLs were identified for micronaire, distributing on Chr.9, LG1, LG9, LG20, and LG12, explaining 11.5%–26.1% of the fiber micronaire variance. Seven QTLs were identified for strength, distributing on Chr.21, Chr.12, Chr.8, LG1, LG4, and LG10, explaining 16.5%–52.8% of the fiber strength variance. Two QTLs were identified for fiber elongation, distributing on Chr.9 and Chr.21, explaining 18.1% and 27.1% of the fiber elongation variance.Assembledsection of QTLs existed in LG9, LG12, and Chr.21. The present map and QTL analysis may provide a useful tool for breeders to transfer desirable traits from G. barbadense to the mainly cultivated species, G. hirsutum.

Genetic Effects of 1BS Chromosome Arm on the Main Agrionomic Traits in Chuanmai 42

LI Jun,WEI Hui-Ting,YANG Su-Jie,LI Chao-Su,TANG Yong-Lu,HU Xiao-Rong,YANG Wu-Yun

Acta Agron Sin. 2009, 35(12):  2167-2173.  doi:10.3724/SP.J.1006.2009.02167

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Chuanmai 42 (Syn769/Sw3243//Chuan6415) is a non-1BL/1RS wheat (Triticum aestivum L.) cultivar with high-yield potential and good resistance to strip rust (Puccinia striiformis f. sp. tritici), which has been developed from an elite synthetic hexaploid wheat Syn769 (Decoy 1/Aegilops tauschii 188, 1BS/1BL). The 1BS chromosome arm of Chuanmai 42 is originated from Syn769 and carries a stripe rust resistance gene YrCH42. In purpose of understanding the genetic effects of 1BS and 1RS chromosome arm on yield-related traits in wheat, 127 recombinant inbred lines (RILs, F₈) derived from Chuanmai 42 and Chuannong 16 (1BL/1RS translocation cultivar) were evaluated in three years across four environments in Sichuan province from 2005 to 2008. A total of 16 traits of the two parents (Chuanmai 42 and Chuannong 16) and the RIL population, such as spike number, grain number per spike, thousand-grain weight, and grain yield, were investigated. 1BS chromosome arm lines derived from Chuanmai 42 and 1RS chromosome arm lines derived from Chuannong 16 were significantly different on six traits. The 1BS chromosome arm positively increased the ratio of spikes to summit population and harvest index, whereas the 1RS chromosome arm only had positive effect on tiller number per plant and spikelet number per spike. The average grain yield of RILs with 1BS chromosome arm was 2.91% higher than that of RILs with 1RS chromosome arm. Because the 1RS chromosome arm with Sec-1 gene significantly degrades the processing quality of wheat and the rust resistance genes are invalidated to rust races in China, it is suggested to replace the 1RS with the 1BS chromosome arm of Chuanmai 42.

Cloning and Characterization of GmTINY1 Gene in Soybean（Glycine max）

HUANG Fang,HE Hui,CHI Ying-Jun,GAI Jun-Yi,YU De-Yue*

Acta Agron Sin. 2009, 35(12):  2174-2179.  doi:10.3724/SP.J.1006.2009.02174

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Plant reproductive development involves the coordination of a lot of genes encoding transcription factors.The AP2 domain transcription factors have been proved with critical roles in plant reproductive development.By microarray analysis, we identified a gene which showed higher expression in pod as 500 folds as that in leaf of soybean. The Blast searches indicated this gene encodes a dehydration responsive element binding protein (DREB)-like protein showing highest similarity to Arabidopsis TINY, therefore named as GmTINY1. By searching soybean genome and EST databases, the putative full-length cDNA sequence for GmTINY1 was in silico assembled. The GmTINY1 gene was cloned from soybean seeds at 15 DAF (days after flowering) by RT-PCR. GmTINY1 contained a complete open reading frame (ORF) of 755 bp which encoded a peptide of 244 amino acids. The predicted molecular mass and isoelctric point of GmTINY1 are 26.76 kD and 5.12, respectively. An AP2 domain and a ser-rich domain were identified in GmTINY1 amino acid sequence by Motif Scan server. The GmTINY1 encoding product showed 59% and 62% sequence similarities with Arabidopsis TINY and TINY2, respectively. Multiple sequences alignment revealed that a highly conserved AP2 domain was present in each AP2 domain transcription factor. In this AP2 domain, it was found that a Ser⁶⁶ was specifically present in GmTINY1, DREB1B, TINY and TINY2 proteins but a Cys⁶⁶ in DREB1A and DREB1C proteins, indicating, like Arabidopsis TINY, TINY2 and DREB1B, GmTINY1 might be able to bind both the dehydration responsive element(DRE) and ethylene responsive element (ERE) motifs while DREB1A and DREB1C only bind DRE motif. Besides, it was found that a ser-rich domain probably involving translational modification on GmTINY1 protein was located close to AP2 domain. The neighbor-joining phylogenetic tree showed that the AP2 domain transcription factors were grouped into four subfamilies: DREB, ERF, AP2, and RAV; and GmTINY1, TINY, and TINY2 were grouped into a branch which attributed to the DREB subfamily. With an attempt to understand the biological role for GmTINY1 and to verify the microarray result, we used the Real-time quantitative PCR approach to analyze the expression pattern of GmTINY1 in various soybean organs. We found that expression of GmTINY1 was highest in pod, relatively lower in flower and root but undetectable in leaf, indicating GmTINY1 may play some roles in soybean reproductive organs and root, but not in leaf. The Blast search results against soybean EST database also supported the specific expression of GmTINY1 in soybean pod and root. We analyzed GmTINY1 expression during the course of seed development based on publicly available microarray data and found that GmTINY1 was expressed with a low level at the globular stage and heart stage but highly expressed in hilum at the cotyledon stage embryos. Taken together, it is suggested that GmTINY1 may play some regulatory role in soybean reproductive development, such as the formation of hilum in soybean.

Cloning and Expression of Zinc Finger Protein Genetic ZF1 in Chickpea（Cicerone arietinum L.）

CHEN Chen,PENG Hui,GAO Wen-Rui,SHI Qing-Hua,ZHANG Hua,ZHANG Ju-Song,LI Jiang-Gui

Acta Agron Sin. 2009, 35(12):  2180-2186.  doi:10.3724/SP.J.1006.2009.02180

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Regulation of gene expression at the level of transcription controls many crucial biological processes including growth and development, stress response, signal transduction and disease resistance. A number of factors, such as C₂H₂ zinc finger protein, are required and factors play an important role in the transcription. Chickpea (Cicer arietinum L.) is the third important legume crop gown mainly in the arid and semi-arid regions in the world. Due to its taxonomic proximity with the model legume genome of Medicago truncatula and its ability to grow in soil with relatively low water content, chickpea is being investigated as a model legume crop for drought tolerance studies. In our laboratory, two cDNA libraries from the PEG-treated and non-treated seedling leaves of chickpea XJ209 were constructed and many genes were found to express differentially and involved in diverse biological processes, such as metabolism, transcription, signal transduction, protein synthesis and others. According to an EST in the cDNA libraries, a zinc finger protein gene ZF1 was cloned by RT-PCR and rapid amplification of cDNA ends (RACE). ZF1 did not include any intron, encoding a 26.33 kD protein with 244 amino acids, containing two typical C₂H₂ zinc finger domains. The deduced protein sequence had a potential nuclear localization signal (NLS). Meanwhile, transient expression of the ZF1-GFP protein in onion epidermal cells showed that ZF1 protein was localized in cell nuclei. Semi-quantitative RT-PCR analysis showed that ZF1 expressed in root, stem, leaf, flower, immature pod, and embryo of chickpea with different expression patterns. The expression of ZF1 investigated by semi-quantitative PCR had no obvious changes under stresses of cold, salt and wounding, while was increased under the treatments of heat and drought, as well as N-6-benzyl-adenine (6-BA), abscisic acid (ABA), ethephon (Et), gibberellin (GA₃), indole-3-acetic acid (IAA), methyl jasmonate (MeJA), salicylic acid (SA), and H₂O₂. These results from semi-quantitative PCR in several treatments were further confirmed to be mainly in accord with those from real-time quantification PCR. Our results suggest that ZF1 may play multiple roles in abiotic and biotic resistance pathways, as well as in plant growth.

Effects Contributed by Different Donor Parents and Backcross Times on R08 Improvement

WANG Yu-Hua,QIAO Shan-Bao,YANG Ke-Cheng,RONG Ting-Zhao,PAN Guang-Tang,

Acta Agron Sin. 2009, 35(12):  2187-2196.  doi:10.3724/SP.J.1006.2009.02187

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In this study, we usedR08 as the recurrent parent and 18 excellentinbreeding lines as the donor parents to improve R08 line through backcross and self-cross. A total of 18 BC₁F₃-derived lines and 18 BC₂F₂-derived lines with relatively diverse genetic background were obtained. Improving effects contributed by different donor parents and backcross times on R08 were analyzed by evaluation field trials, combining ability and SSR molecular markers of R08 improved lines. The results showed that 29 lines out of 36 BC-derived lines were resistant or high-resistant to northern leaf blight. General combining ability (GCA)of most yield traits in the majority of improved lines showed no decrease or a little increase compared with that of R08. BC₁F₃ (backcross once, self-cross twice) wasbetter than BC₂F₂ (backcross twice, self-cross once) in the improvement of disease resistance to northern leaf blightcompared with the lines which had same donor parents and different times of backcross, while the GCA of most yield traits in majority of the lines selected from the improved offspring was roughly the same. The results of SSR markers analysis showed that the genetic variation in the lines had no significant difference. On the contrary, there was a larger difference in disease resistance to northern leaf blight, GCA of the majority of yield traits and the results of SSR markersanalysis in the lines selected from different donor and same times of backcross. Donor parents Chang 7-2 and Chuan 321 played a larger role in improving R08’s disease resistance to northern leaf blight and most of yield traits’ GCA. Therefore, they are excellent donor parents. As a result, w4-1 and w10-1 are selected as elite lines of backcross-improving. Consequently, during the utilization of backcross in improving maize inbred lines, we could backcross once on the basis of selecting the right donor parents, and strengthen the identification and selection of target traits and the determination of GCA in self-cross process to improve the breeding efficiency of backcross improvement.

Evaluating Uniformity and Stability of Wheat Cultivars Based on Ratio of Homozygous DNA Locus

WANG Li-Xin,JI Wei,LI Hong-Bo,GE Ling-Ling,Xin Ai-Hua,WANG Li-Xia,CHANG Li-Fang,

Acta Agron Sin. 2009, 35(12):  2197-2204.  doi:10.3724/SP.J.1006.2009.02197

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Evaluation of the uniformity and stability is of great importance in the determination of cultivar release. The homozygous DNA locus ratio is one of the main factors affecting the uniformity and stability of wheat (Triticum aestivum L.) cultivars. To figure out the feasibility of molecular markers in testing the uniformity and stability of wheat cultivars based on the homozygous DNA locus ratio, we examined each 50 individuals of every line of 10 F₄, 10 F₅ lines and 511 cultivars with 172 pairs of SSR, 99 pairs of EST-SSR, and 76 pairs of AFLP-SCAR primers. The homozygous DNA locus ratio was 82.1–94.5% in the F₄ lines and 95.7–99.4% in the F₅ lines, and the predicted homozygous DNA locus ratio was 98–100% in the F₆ generation according to the homozygous DNA locus ratio of 500 individuals from F₅ lines. In the 136 released cultivars and 375 cultivars from the National Regional Trials, 10% were observed with the homozygous DNA locus ratio less than 95%, including 11 released cultivars. Thirteen out of 129 cultivars from the 2007–2008 National Regional Trial for Winter Wheat had the homozygous DNA locus ratio less than 95% according to the test result at 84 loci. Compared with the cultivars whose homozygous locus ratio was higher than 95% (control), eight of the 13 cultivars showed obviously segregation in major agronomic traits, such as plant height, plant type, spikelet number per spike, spike length, spike type and grain color, another five with 94% of the homozygous locus ratio had similar trait variations to the control. The test result of 375 cultivars from the National Regional Trials indicated that cultivars with the homozygous DNA locus ratio less than 90% did not have the uniformity and stability; whereas the most of cultivars with the homozygous DNA locus ratio higher than 95% and part of cultivars with the ratio ranging from 90% to 95% possessed the characteristics of uniformity and stability. The results indicated that molecular markers can be a great supplemental tool in the evaluation of uniformity and stability of new cultivars. Thereby, it is feasibly to be evaluated the uniformity and stability of wheat cultivars based on the homozygous DNA locus ratio. Fifty pairs of SSR, EST-SSR and AFLP-SCAR primers were recommended for testing the homozygous DNA locus ratio and at least two kind of molecular markers were advisable to be used in evaluating the uniformity and stability of wheat cultivars. In this study, the method and practical details were explained with the sample size of 20 individual plants and the test locus number of 50.

Genetic Diversity in Naked Oatmeal（Avena nuda） Germplasm Revealed by AFLP Markers

XU Wei,ZHANG Zong-Wen,WU Bin,CUI Lin

Acta Agron Sin. 2009, 35(12):  2205-2212.  doi:10.3724/SP.J.1006.2009.02205

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Oat (Avena L.) is one of the most important cereal crops in the world, ranked at the sixth top place in planting area and yield among all cereal crops, and possesses high values in food and nutrition, health protection and feeding livestock. Naked oat (A. nuda) is an endemic type in China. However, a few studies on naked oat germplasm at molecular level have been reported. The aim of this study was to evaluate the genetic diversity of core collection of naked oat using AFLP markers. A total of 281 accessions of naked oat were analyzed using 20 AFLP primer combinations. Selective amplification created 1 137 bands, of which 260 were polymorphic, accounting for 22.96% of the total bands. The mean polymorphism information content (PIC) was 0.0326. For different geographic groups, Simpson’s index ranged from 1.235 to 1.495, and Shannon’s index varied from 0.1558 to 0.4437. The majority (83.45%) of the AFLP variation resided within accessions of each group, and the rest (16.55%) existed among accessions between groups. The sample size of geographic groups was significantly associated with the number of polymorphic loci, proportion of within-group variation, Simpson’s index and Shannon’ s index. Accessions from Inner Mongolia and Shanxi were most diverse, and those from northeastern China were most distinct. Genetic resemblance was found within accessions from western China. Germplasm from East Europe was genetically close to that from Inner Mongolia, China. The genetic diversity of Chinese accessions was significantly higher than that of exotic accessions. Compared with breeding cultivars, landraces presented a higher proportion of within-group variation. Naked oat landraces were suggested to be collected in the regions where are not well represented by the current collections, and collecting activities should be continuous in the diversity-rich areas such as northwestern and southwestern China in order to enrich naked oat gene pool in China.

Detection of QTL for Resistance to Rice Black-Streaked Dwarf  Disease

PAN Cun-Hong,LI Ai-Hong,CHEN Zong-Xiang,WU Lin-Bo,DAI Zheng-Yuan, HUANG Nian-Sen

Acta Agron Sin. 2009, 35(12):  2213-2217.  doi:10.3724/SP.J.1006.2009.02213

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The rice black-streaked dwarf viral disease (RBSDV), transmitted by the planthopper Laodelphax striatellus Fallèn, was one of the most serious diseases in rice in south China. Breeding of RBSDV resistance variety using marker-assisted selection was effective measure to reduce the disease damage. For achieving this aim, QTL mapping of resistance to RBSDV was studied using a recombinant inbred line (RIL) population from the cross between Zhenshan 97B and Minghui 63. Reactions of 242 RILs to RBSDV were investigated by natural infection method in Agricultural College of Yangzhou University and Lixiahe Agricultural Research Institute, and scored by the incidence of RBSDV. The trait of RBSDV incidence was normally distributed and marked bias towards the resistant parent, which implied that they were controlled by quantitative trait loci. Six QTLs for resistance to RBSDV were detected by WinQTLcart 2.5 software. Two adjacent QTLs were mapped on chromosome 6, two on chromosome 11, one on chromosomes 7 and 9, respectively. Four QTLs on chromosomes 6, 7, and 9 could be detected in two locations, and were stably expressed across the two environments. There had not been any reports about location of QTL for resistance of rice stripe virus and planthopper, which suggested that six QTLs in this study were really resistant to RBSDV. Two QTLs on chromosome 6 were with main effect, and their contributions to the total variation were 20.20% and 18.68% with LOD scores of 12.09 and 9.77 respectively, moreover, they had high value for study on genetics of RBSDV and should be useful in marker-assisted selection for resistance to RBSDV.

Isolation and Characterization of IbNPR1 Gene from Sweet Potato（Ipomoea batatas）

CHEN Guan-Shui,ZHOU Yi-Fei,LIN Sheng,ZHANG Zheng,PAN Da-Ren

Acta Agron Sin. 2009, 35(12):  2218-2224.  doi:10.3724/SP.J.1006.2009.02218

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NPR1 (non-expressor of pathogenesis-related genes 1) protein is a key regulator of salicylic acid (SA)-mediated gene epression in systemic acquired resistance (SAR). By using homologous cloning and RACE (rapid amplification of cDNA ends) techniques, a full-length cDNA of IbNPR1 (Ipomoea batatas non-expressor of pathogenesis-related genes 1) was isolated from sweet potato var. Qingnong 2. The full length cDNA was 2 353 bp, including an ORF (open reading frame) putatively encoding a polypeptide of 586 amino acids residues with a predicted molecular mass of 64.851 kD. The deduced amino acid sequence shared structural features with known NPR1 (-like) proteins: ankyrin repeat and BTB/POZ. Furthermore, phylogenetic analysis showed IbNPR1 had the closest association with LeNPR1 from Lycopersicon esculentum. Southern-blot analysis revealed that the IbNPR1 belonged to low-copy gene family in sweet potato. Semi-quantitative RT-PCR analysis indicated that IbNPR1 was constitutively expressed in roots, stems and leaves. In addition, IbNPR1 could be induced by salicylic acid. The results suggest that IbNPR1 plays an important role in the response to pathogen infections in sweet potato.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Post-Anthesis Changes in concentrations of Polyamines in Superior and Inferior Apikelets and Their Relation with Grain Filling of Super Rice

TAN Gui-Lu,ZHANG Hao,FU Jing,WANG Zhi-Qin,LIU Li-Jun,YANG Jian-Chang*

Acta Agron Sin. 2009, 35(12):  2225-2233.  doi:10.3724/SP.J.1006.2009.02225

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Success in super rice breeding has been considered a great progress in rice production in China. However, many unfilled inferior spikelets limit the realization of great yield. As polyamines have been frequently described as endogenous plant growth regulators or intracellular messengers mediating physiological processes, this study investigated whether and how polyamines are involved in the regulating post-anthesis development of rice spikelets. Four super rice cultivars, Liangyoupeijiu and II you 084 (indica hybrids), Huaidao 9 and Wujing 15 (japonica), and two high-yielding check cultivars, Shanyou 63 (indica hybrid) and Yangfujing 8 (japonica), were field grown. Concentrations of putrescine (Put),spermidine (Spd) and spermine (Spm)in both inferior and superior spikelets during the grain filling period and grain filling rate were determined. The relationship between polyamine concentrations and grain filling rate were analyzed, and chemical regulators were applied to verify the roles of polyamines in grain filling. The results showed that the maximum grain filling rate, mean grain filling rate, and brown rice weight for superior spikelets showed small difference between the super rice and check rice, but those of inferior spikelets were significantly lower for super rice than for check rice cultivars. Changes in concentrations of polyamines in grains exhibited single peak during the grain filling period. The peak and mean concentrations of Put were greater in inferior than in superior spikelets. The peak and mean concentrations of Spd and Spm were greater in the superior than in the inferior, and greater in the check rice than in the super rice. The mean grain filling rate and brown rice weight were negatively and very significantly correlated with the Put concentrations, and positively and very significantly correlated with Spd and Spm concentrations, Spd/Put, and Spm/Put. Application of Spd or Spm to panicle at the early grain filling stage significantly enhanced activities of sucrose synthetase, adenine diphosphoglucose pyrophosphorylase, and soluble starch synthetase in inferior spikelets, and significantly increasedgrain filling rate, seed setting rate and grain weight of inferior spikelets. Application of Put or methylglyoxal-bis (guanylhydrazone) (MGBG, an inhibitor of S-adenosyl-L-methionine decarboxylase) exhibited an opposite effect. The results suggest that polyamines play a role in regulating grain filling. Low concentrations of Spd and Spm and low Spd/Put and Spm/Put may be an important physiological reason for the small grain filling rate and low grain weight of inferior spikelets in super rice.

Fertilization Process in Sorghum and Its Performance Time for Each Stage

LI Ran-Li,SHEN Jia-Heng,JIA Yuan,LI Wei,WANG Li-Ming

Acta Agron Sin. 2009, 35(12):  2234-2242.  doi:10.3724/SP.J.1006.2009.02234

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Sorghum (Sorghum bicolor L. Moench) grows widely in the world as the fifth biggest crop in use for food, feed and raw material in brewing industry. Great achievements have been taken in routine breeding, and also in apomixis in sorghum. Reports on sorghum embryology mainly focused on the morphological structure and development of flower, megasporogenesis, microsporogensis, megagametophyte and so on. The objective of this study was to explore the fertiligation process of sorghum by routine paraffin-embedded section technique to offer some information for its genetic breeding, gene engineering and reproductive biology. The results showed that pollen grains germinated immediately when they fell on stigma in self-pollinated sorghum, then pollen tubes grew into the intercellular space of branched structure of penniform stigma, entering and penetrating ovary, and growing into micropyle. Pollen tube entered and destroyed one synergid and released successive round staff between egg and central cells. One sperm nucleus entered egg and the other entered central cell. Male and female nucleoli were fused at last. The performance time was as follows: pollen tube grew into micropyle and entered one synergid to release two sperms at 0.5–3 h after flowering; fusion of sperm-polar nucleus and egg-sperm nucleus took place at about 1–3 h after flowering; primary endosperm nucleus divided at about 4 h after flowering; zygote divided at 14 h after flowering; the dormancy stage of zygote was about 4–14 h after flowering, which is the proper time for transgenic operation with pollen-tube pathway technology and other physic-chemical mutagenesis.

Photosynthetic Characteristics of Flag Leaf in Rice Genotypes with Different N Use Efficiencies

WEI Hai-Yan,ZHANG Hong-Cheng,MA Qun,DAI Qi-Gen,HUO Zhong-Yang，XU Ke，ZHANG Qing

Acta Agron Sin. 2009, 35(12):  2243-2251.  doi:10.3724/SP.J.1006.2009.02243

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N is yet the most important and largest input required in rice production although over use of N causes so many environment problems. N use efficiency is different in different rice genotypes. Therefore it is necessary to identify the physiological mechanism of N absorption and utilization in different rice genotypes. In this research, field experiment with 225 kg ha^-1 N fertilizer application was carried out in 2006 on the farm of Yangzhou University, Jiangsu province, China. Twelve rice genotypes (six N-efficient and six N-inefficient) selected from one hundred and twenty rice cultivars grown in Yangzhou during 2004 and 2005 were adopted to investigate the photosynthetic characteristics of flag leaf in rice genotypes with different N use efficiencies. Relationships between photosynthetic physiological characteristics of flag Leaf and N use efficiency as well as seed setting abilities were also analyzed. Results showed that, during the period of grain filling, the photosynthetic indexes of flag leaf including chlorophyll content, nitrogen content, net photosynthetic rate, the photosynthetic function duration, the maximum photochemical efficiency (F_v/F_m), the potential photochemical efficiency of photosystem II (F_v/F_o), the actual photochemical efficiency of photosystem II (Φ_PSII), the photochemical quenching coefficient (q_P) and the non-photochemical quenching coefficient (q_N) of N efficient genotypes were obviously higher than those of N inefficient genotypes. All photosynthetic indexes of flag leaf above positively correlated to N use efficiency and seed setting abilities. And it could be concluded that, for N efficient genotypes, they had better characteristics of photosynthesis and longer photosynthetic function duration. Meanwhile, the PS II of N efficient genotypes was steady which had larger potential to convert light energy into electrochemical energy, and the non-photochemical quenching could protect the photosynthetic apparatus further. Therefore, the accumulation of photosynthate and the seed setting abilities of N efficient genotypes were better than those of N inefficient genotypes. And the N absorption and utilization of N efficient genotypes were also enhanced through the feedback regulation of root and shoot.

Distribution of Sugar Content in Corn Stalk

BIAN Yun-Long,DU Kai,WANG Yi-Jun,DENG De-Xiang

Acta Agron Sin. 2009, 35(12):  2252-2257.  doi:10.3724/SP.J.1006.2009.02252

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Increasing the sugar content in silage corn stalk will improve the forage quality and palatability, the study on which can provide valuable information for silage corn breeding on stalk high sugar content. Three different genotypes, normal corn “Suyu 16”, sweet corn “05-8” and super sweet corn ‘Yangtian 1’, were investigated in this study. The sugar content (Brix values) of corn stalk was evaluated at seven stages using the pocket refractometer PAL-1. Results of two-year experiment were as follows: (1) Sugar content of corn stalk increased with the position of internodes from bottom to top, usually with the highest in ear internode or the internodes immediately above or below it. The relationship between sugar content and internode position varied from different genotypes and were modeled using the following three nonlinear equations: Y = 5.0277 exp(0.020564X - 0.017816X²) for Suyu 16, Y = 8.8489 exp(0.05949X - 0.006454X²) for 05-8 and Y = 9.6652 exp(0.06944X - 0.009475X²) for Yangtian 1, respectively. (2) The stalk sugar content of “Suyu 16” changed in a single peak curve, decreased at late growing stage. However, the stalk sugar content of “05-8” and “Yangtian 1” was increased at late growing stage. The difference of stalk sugar content may be related to the grain filling characteristics of the three genotypes. (3) Results of variance analysis of nested design indicated highly significant variation for sugar content of stalk among three corn genotypes, the total sugar content was the highest in super sweet corn, and the second highest in sweet corn. Moreover, sugar contents significantly varied depending on different internodes and different measurement stages. (4) Removing ear resulted in the increased sugar content in corn stalk. Additionally, the kernel sink-potential may influence the accumulation of sugar in corn stalk.

Dynamic Analysis on Response of Dry Matter Accumulation and Partitioning to Nitrogen Fertilizer in Wheat Cultivars with Different Plant Types

LI Guo-Qiang,TANG Liang,ZHANG Wen-Yu,CAO Wei-Xing,ZHU Yan*

Acta Agron Sin. 2009, 35(12):  2258-2265.  doi:10.3724/SP.J.1006.2009.02258

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Biomass accumulation and partition in different plant organs affect the grain yield in cereal crops. Many investigators have established equations to simulate the dynamic growth and biomass accumulation of crops in various experiments using polynomial, Expolianear, Logistic, and Richard models. However, these models have limitations in some extent. The vapor pressure (VP) model has been used to quantitatively simulate the dynamic accumulation of dry matter in maize (Zea mays L.) roots and the branch number of princess flower. In this study, the VP model was introduced in wheat (Triticum aestivum L.) to test its applicability in simulating accumulation and partitioning of biomass. Four wheat cultivars with four plant types, respectively, were planted in 2006–2007 and 2007–2008 growing seasons under the nitrogen application levels of 75, 150, and 225 kg ha^-1. Based on the dry weights of various organs at main growth stages, the Richards and VP equations tested the fitness of the biomass accumulation and partitioning in relation to accumulated growing-degree days. The results showed that with increasing nitrogen rate, the average dry matter growth rate (R_a), maximum growth rate (R_max) and duration of the third phase (D₃) increased, while the time reaching to R_max was shortened consistently in four cultivars. In Aikang 58 (compact-short type), Huaimai 17 (loose type) and Yangmai 12 (intermediate type), the initial growth potential (R₀) increased with the promotion of nitrogen rate, while the duration of early increment phase (D₁) and the dry matter accumulation at R_max (W_Rmax) decreased. In contrast, the R₀, W_Rmax, and D₁ of Ningmai 9 (compact-high type) exhibited an opposite pattern. In Aikang 58 and Ningmai 9, the second phase duration (D₂) decreased when the nitrogen rate increased, and Yangmai 12 and Huaimai 17 had the smallest D₂ value under the medium nitrogen rate. With the increase of nitrogen rate, the maximum dry matter partitioning percentage (P_max) of leaf and spike in Huaimai 17 and Yangmai 12 as well as the maximum dry matter partitioning percentage of stem and sheath (P_Smax) in Aikang 58 and Ningmai 9 decreased. In contrast, the P_max of leaf and spike in Aikang 58 and Ningmai 9, and the P_Smax in Huaimai 17 and Yangmai 12 increased accompanying with the increase of nitrogen rate. In terms of the maximum decreasing rate of dry matter partitioning percentage (MDRP) to leaf, Ningmai 9, Huaimai 17 and Yangmai 12 showed a decrease trend when nitrogen rate increased, while Aikang 58 was in an increase tendency. For the maximum increasing rate of dry matter partitioning percentage (MIRP) to spike, Aikang 58 and Ningmai 9 had a negative response to nitrogen rate and Huaimai 17 and Yangmai 12 had a positive response. Excessive application of nitrogen had negative effects on the promotion of MDRP to spike in Ningmai 9 and the reduction of MIRP to spike in Yangmai 12. No consistent effects were observed on the maximum changing rate of dry matter partitioning percentage to stem and sheath (R_Simax and R_Sdmax). Thereby, plant types of wheat cultivars should be considered in the nitrogen application regime in practical system of cultivation techniques.

Effect of Nitrogen Fertilizer Application on Development of Boll and Fiber Quality in High Fiber Quality Cotton

CHEN Yuan,WANG Yong-Hui,YANG Zhao-Hua,XIAO Jian,LUAN Na,ZHANG Xiang, CHEN De-Hua

Acta Agron Sin. 2009, 35(12):  2266-2272.  doi:10.3724/SP.J.1006.2009.02266

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The objective of this study was to investigate the extent of the yield increase and fiber quality improvement with nitrogen fertilizer application at different developing periods for high fiber quality cotton. Two cultivars of high quality cotton, hybrid Kemian 1, and conventional Kemian 4, were used to study the effect of nitrogen application on boll weight, boll volume and fiber quality. The five experiments were conducted on the farm of Jiangsu Provincial Key Laboratory of Crops Genetics and Physiology of Yangzhou University from 2003 to 2005, the first experiment was the ratio of nitrogen fertilizer at transplanting, flowering and boll setting, peak boll setting period of 20:60:20, 10:60:30, 25:65:10 for Kemian 1, and 20:60:20, 15:70:15, 10:75:15 for Kemian 4, the second was the basic nitrogen fertilizer at transplanting of 10%, 20%, 30% for Kemian 1, and 10%, 15%, 20% for Kemian 4, the third was 0, 20%, 30%, 40% of the nitrogen fertilizer at early floweringperiod for both cultivars, the fourth was the nitrogen fertilizer applied at 17,19,21 leaf age on main stem, and the fifth was the nitrogen fertilizer at peak boll setting period of 10%, 20%, 25% for Kemian 1, and 10%, 15%, 20% for Kemian 4. The results showed that bigger boll and better fiber quality were gotten under the application of 208.5 to 243.0 kg nitrogen per hectare, and the treatment of nitrogen fertilizer 20%, 60%, 20% for Kemian 1, and 15%, 70%, 15% for Kemian 4, respectively in the first experiment. 30% of nitrogen fertilizer applied at early flowering was optimal for the development of bigger boll and better fiber quality, 15%–20% of nitrogen fertilizer applied at the peak boll setting period was best for development of the late boll in autumn. The nitrogen fertilizer application at peak flowering period was earlier at 17 leaf age, later at 21 leaf age, and optimal at 19 to 20 leaf age on the main stem. The correlation analysis indicated further that there were positive correlation between boll size, boll weight and yield, fiber quality. The nitrogen fertilizer application at the early flowering period was beneficial to develop bigger boll, higher yield and better fiber quality. These results suggest that the key of the high lint yield and good fiber quality is to develop big boll for the high fiber quality cotton.

Responses of Flour Quality and Dough Rheological Properties to Stiobion avenae F. Inoculated in Spring Wheat

SHI Gui-Ying,SHANG Xun-Wu,WANG Hua-Jun,MA Xiao-Le,HU Bing-Fen,LI Chang-Sheng

Acta Agron Sin. 2009, 35(12):  2273-2279.  doi:10.3724/SP.J.1006.2009.02273

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Sitobion avenae F., one of the important aphid species infesting spring wheat (Triticum aestivum L.) in western China, causes not only yield loss but also quality degradation of wheat flour. In the authors’ earlier studies, two wheat lines with high resistance to S. avenae, 04-9284 and C272 were screened out from 521 accessions. Another five highly susceptible cultivars (lines) were also identified, including a specific cultivar “Guanchun 20” for Lanzhou hand-stretched noodles. The aims of the present study were to compare quality differences of resistant and susceptible wheat lines inoculated with aphids, and to assess the contributions of grain hardness and gliadin to aphid resistance. The lines 04-9284 and C272 (soft grain) were used as resistant lines, and four cultivars (lines), Ganchun 20 (hard grain) as well as Ganchuan 18, C162, and C167 (soft grain with specific ω gliadin in grains after aphid infecting) were susceptible to S. avenae. After artificial inoculation with S. avenae on 5 June, the density of aphid population was measured from 15 June to 20 July at an interval of 6–7 d. Flour quality and dough rheological properties were determined after grain maturing. The mean density of aphid population at peak occurrence was 4.3-fold higher in susceptible lines than in resistant lines. Aphid infecting resulted in no significant change in flour granule (t = 0.4312, P = 0.68), but induced significant increase in ash content (t = 2.9207, P = 0.03) and reductions in protein content (t = 2.5444, P = 0.05), SDS sedimentation value (t = 4.5736, P = 0.01), strength (t = 4.2517, P = 0.01), swelling (t = 6.6691, P = 0.00), extensibility (t = 3.1826, P = 0.02), tenacity (t = 3.6653, P = 0.01), and index of elastic (t = 2.8750, P = 0.03). In susceptible lines Ganchun 18, C162, and C167, aphid infecting significantly reduced quality parameters mentioned above excluding flour gradual and ash content. Ganchun 20 showed less influence than the other three susceptible lines,its protein content, swelling, and extensibility reduced insignificantly, and the other parameters decreased slightly. In resistant lines 04-9284 and C272, there were significant variations after aphid infecting only in strength and extensibility with much smaller values than those in the three susceptible lines. Correlation analysis showed that the peak aphid density in the five lines with soft grain was positively correlated with the decrease percentages of quality parameters, such as swelling (r = 0.9968,P<0.01), tenacity (r = 0.9619,P<0.01), SDS sedimentation, strength (r = 0.9108,P<0.05), and protein content (r = 0.8886,P<0.05). With respect to the hard-grain cultivar Ganchun 20, the flour quality was still qualified for processing hand-stretched noodles even at the high density of 214.67 aphids per tiller. Field investigation showed that the peak density of S. avenae on Ganchun 20 was 122.36–154.33 heads per tiller in common years, which is much fewer than that in this study. Therefore, Ganchun 20 is not degraded seriously in flour quality under normal occurrence of S. avenae and possesses a relative stability of quality in response to the infecting of aphid.

RESEARCH ACTIVITIES

Ultra-Structural Changes of the Vascular Bundles and CaM Immuno-Gold Localization at Phloem Cells among Different Positional Rachillae within a Rice Panicle

ZHANG Qi-Fang,LIU Yi,HUANG Fu-Deng,HU Dong-Wei,CHENG Fang-Min

Acta Agron Sin. 2009, 35(12):  2280-2287.  doi:10.3724/SP.J.1006.2009.02280

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The ultra-structure of the vascular bundle phloem in rice rachilla and its time-course during grain filling period were observed for different positional rachillae within a rice panicle by using low-temperature embedding and electron microscopy technique, and CaM distribution in sieve element (SE) and companion cells (CC) of the central vascular phloem was investigated by immuno-gold localization. The results showed that there were obvious difference in the anatomical structure of the vascular bundle between different positional rice rachillae, with the relative large total vascular area, phloem area and vessel area in central vascular bundle for superior positional rachilla within a panicle, indicting that the superior rachilla had better structure for the assimilate transport compared to the inferior positional rachilla; the similar time-course in the degradation pattern of some organelles of SE and CC in central vascular phloem was observed in different positional rachillae at grain filling stage, with the relative delaying degradation and disintegration of SE,CC and phloem parenchyma cells for inferior positional rachilla; the abundant mitochondrion, chloroplast, starch granules and plasmodesmata, and numerous CaM labeling density were found in SE and CC of superior rachilla compared to inferior positional rachilla at beginning filling stage, while no significant differences between two types of rachilla at middle and late filling stages, implying that superior postional rachilla had relatively better transporting function at initial filling stage relative to inferior rachilla.

Effects of Planting Density on Photosynthetic Characteristics and Assimilate Accumulation of Leaves in Different Positions in Flue-Cured Tobacco

WANG Rui,LIU Guo-Shun,NI Guo-Shi,BI Qing-Wen,YANG Li-Bo,ZHEN Cai-Hong

Acta Agron Sin. 2009, 35(12):  2288-2295.  doi:10.3724/SP.J.1006.2009.02288

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The leaves in threepositions(leaf 5, 11, 17 from bottom to top) of flue-cured tobacco Yunyan 87 with four planting densities (16 665, 15 150, 13 875, and 12 825 plants ha^-1)were tested in the field experiment in Liangfeng Village, Xuanen County, Chinain 2008. The results indicated thatthe net photosynthetic rate (P_n), specific leaf weight and carbohydrate content exhibited significant difference under various planting densities in mature period (60 days after transplanting), and the impact of plant density increased in the process of leaf development. With the decrease of planting density, the decline rate of P_n was reduced, photosynthetic function decline was delayed, and the accumulating time of assimilate was prolonged. The lower leaf did not appear photosynthetic midday depression under three planting densities except under the lowest density (12 825 plants ha^-1). The upper leaf appeared photosynthetic midday depression under all the planting densities. Degree of photosynthetic midday depression for the middle leaf was lightened under lower densities. Under planting density of 15 150 plants ha^-1, the middle leaf had higherdaily photosynthesis and assimilate, and the photosynthesis and transpiration achieved the most coordinate state, exhibiting higher single-leaf WUE.

Evaluation of Drought Tolerance and Fertility Traits for Rice Maintainer Lines Extensively Used in China

TAO Long-Xing,FU Guan-Fu,SONG Jian,LE Ming-Kai,WANG Xi

Acta Agron Sin. 2009, 35(12):  2296-2303.  doi:10.3724/SP.J.1006.2009.02296

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By monitoring soil moisture using both soil moisture meter and soil sampling method, we evaluated the drought tolerance of maintainer lines at panicle stage. Results showedthat: (1) the maintainer lines K22-B, Jin 23-B, and II-32-B were drought-insensitive at panicle stage, while Zhenshan 97-B, Zhong 9-B, and Xieqingzao-B were drought-sensitive; (2) the tested maintainer lines were more sensitive to drought stress at flowering stage (from pollen filling stage to spikelets filling stage) than at booting stage (from meiosis stage of pollen mother cell to pollen filling stage); (3) drought stress at booting stage mainly injured the spikelet fertility and there was a positive correlation between stress index and percentage of unfilled grains (r = 6988^**), and drought stress at flowering stage injured both the fertility and plumpness of spikelets, the percentage of unfilled grains and the percentage of non-fully filled grains exhibited a positive correlation with stress index (r = 0.7660^** and r = 0.5230 respectively); (4) there was no correlation between drought tolerance at panicle stage and grain setting characteristics under normal condition．

Characteristics of Photosynthesis in Two Leaf Color Mutants of Rice

Lü Dian-Hua,ZONG Xue-Feng,WANG San-Gen,LING Ying-Hua,SANG Xian-Chun,HE Guang-Hua

Acta Agron Sin. 2009, 35(12):  2304-2308.  doi:10.3724/SP.J.1006.2009.02304

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Two leaf color mutants, ygl5 and pygl1, were identified from the progeny of Jinhui10 treated with EMS, and Jinhui10 was an excellent restorer line bred in the Rice Research Institute of Southwest University. This paper reported their photosynthetic parameters and ultra-structure of chloroplast. Compared with the original parent, both mutants had a decline content of chlorophylls significantly, especially in total chlorophylls for ygl5 and in chlorophyll b for the pygl1. Photosynthetic and chlorophyll fluorescence parameters were determined by LI-6400, the results showed that the net photosynthetic rate (P_n), transpiration rate (T_r) and stomatal conductance (G_s) were higher in the mutants, with higher light compensation point (LCP) and lower light saturation point (LSP) as well as lower CO₂ compensation point (CCP) and CO₂ saturation point (CSP). Compared with Jinhui 10, the mutants displayed less chloroplast grana and higher optional maximal photochemical efficiency of PSII (F_v/F_m), actual photochemical efficiency of PSII (Φ_PSII), and photochemical quenching (q_P), suggesting that the mutants have higher light energy capture and conversion efficiencies as well as the electron transport efficiency.