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12 January 2010, Volume 36 Issue 1

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Comparative Study on Breeding Utilization Characteristics of the Isonuclear Alloplasmic Japonica CMS Lines Liuqianxin A with Four Different Cytoplasm Sources

ZHU Zheng-Bin,ZHANG Hong-Gen,LIU Chao,LI Peng,YI Chuan-Deng,TANG Shu-Zhu,

Acta Agron Sin. 2010, 36(1):  1-8.  doi:10.3724/SP.J.1006.2010.00001

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Aset of isonuclear alloplasmic Japonica CMS lines Liuqianxin A, constructed with four different cytoplasm sources from Hainan Male Sterile Wild Rice (WA type), Hainan Red Awned Wild Rice (HL type), Hunan Chaling Wild Rice (CL type) and India Chinsurah Boro II (BT type) respectively, together with their maintainer line Liuqianxin B, were applied to study their male sterile stability, flowering habits, outcrossingrate and restorable ability. The results showed: (1) Most pollen granules of BT, HL and CL Liuqianxin A were mainly stained-abortion, while those of WA Liuqianxin A weremainly typical-abortion. Selfed seed-setting rate ofBT Liuqianxin A was 0.60%, which would cause application risk in agricultural production. There were no selfed seeds in HL and CL Liuqianxin A,indicating that sterility of them wasbetter than that of BT type. (2) The length of 1st internode to the top was affected by the degree of abortive pollen, which influenced the plant height and the panicle exsertion (i.e. the length of panicle -neckabove the sheath of flag leaf). Namely the more serious abortive degree,the shorter panicle exsertion. Therefore, panicle was enclosed within the sheath of the flag leaf in WA Liuqianxin A, not in BT, HL and CL Liuqianxin A. (3) The flowering habits of WA Liuqianxin A presented assporadicflowering, distinctly lagged flowering time and stretched flowering duration, and were the worst in the four type CMS lines, thus its outcrossing rate was lower. Flowering habits and outcrossing rate between HL, CL CMS lines and BT CMS lines were not significantly different. However it was better in HL, CL CMS lines than in WA CMS lines. (4)BT Liuqianxin A showed the best restorable characteristic,HL was a little worse than BT,WA was the worst. And Japonica restorers for HL or CL CMS lines could be selected from the Japonica restorers for BT CMS lines. HL, CLCMS lines balanced above contradictions well, so an idea of substituting HL, CLCMS lines partly for BTtype was put forward, it can be used to solve the problems of single type sterile cytoplasm in current Japonica hybrid riceand fertility not stable in BTCMS lines.

Specific Loci in Genome of Wheat Milestone Parent Bima 4 and Their Transmission in Derivatives

YUAN Yuan-Yuan,WANG Qing-Zhuan,CUI Fa,ZHANG Jing-Tao,DU Bin,WANG Hong-Gang

Acta Agron Sin. 2010, 36(1):  9-16.  doi:10.3724/SP.J.1006.2010.00009

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Bima 4 is one of the most important milestone parents in China. The objective of this study was to reveal the genetic structure of Bima 4 and the transmission of its specific loci in descendents using molecular markers. A total of 1239 SSR, EST-SSR and STS markers covering the whole genome of wheat were screened with the four parents of the first progeny of Bima 4, i.e., Bima 4, Early Piemium, Jubileina 2, and Ckopocneлka JI-1. Thirty-three markers were effective to trace the specific loci of Bima 4 in the progenies. Seventy-six derivatives of Bima 4 were genotyped with the 33 markers. In the first and the second generations of Bima 4 derivatives, 32 markers, except for Xgwm577, could amplify the specific bands of Bima 4. The inheritable frequency of the specific loci were 7.1–92.6% in the first generation and 2.9–80.0% in the second generation, of which eight and ten loci showed the transmission percentage larger than 50.0% in the first and the second generations, respectively. In the third and the fourth generations, twenty-nine and twenty specific markers were observed, eight and four loci had the transmission rate higher than 50.0%, respectively. Among the specific loci, Xgwm261, Xedm80, SWES222, and CFE223 possessed the inheritable frequency higher than 50% in all four generations. Another 18 loci of Bima 4 were detected in the progenies with genetic contribution ratio higher than 25%. This indicates that some desirable traits, such as yield, grain quality, disease resistance, and adaptability might be associated with these loci or the nearby chromosome regions in Bima 4, and intensively selected in breeding programs. The important loci detected in this study provide the information for understanding the genetic basis of Bima 4 as a milestone parent in wheat breeding.

Characterization of Evolution and Tissue-Expression of Rice （Oryza sativa L.） α-Amylase Genes

LIAO Deng-Qun,ZHANG Hong-Liang,LI Zi-Chao,John BENNETT

Acta Agron Sin. 2010, 36(1):  17-27.  doi:10.3724/SP.J.1006.2010.00017

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α-amylases play an important role in starch degradation in plants, especially in cereal germinating seeds. Existing reports on structural organization and evolution of rice α-amylase family mainly focus on members of subfamilies OsAmy1 and OsAmy3 and their expression in germinating seeds, however, it is not known whether the putative α-amylase genes else exist in rice genome and what their structural organization, evolution and expression profiling look like especially among subfamilies. Via TblastN search and conservative domain analysis, we revealed that there were 11 putative α-amylase genes in rice genome. Through tools of bioinformatics, phylogenetic reconstruction and semi-quantitative RT-PCR, we studied the structural evolution among these 11 α-amylase genes and their spatial-temporal expression profiling. The results showed that there was a distinctly divergent and ranked gene structure among members of this family. OsAmy5A and OsAmy4A were the most primitive genes, and other ones were evolved from them mainly through loss of introns and fixed more conserved domains and sequences. These genes were also divergent in expression and function. The more primitive the genes are the less spatial-temporal specificity in gene expression they have. OsAmy5A, OsAmy4A, and OsAmy2A were expressed in all tissues, however, the rest were expressed spatially and temporally. OsAmy1A, which was expressed at the beginning of seed germination but not all during the grain filling stage, should serve to control energy supply between generations. OsAmy3A, both expressed dramatically at the end of grain filling and the initiation of seed germination, should be related to sustaining life activities in embryos of dormancy seeds. OsAmy3D and OsAmy3E were regulated at the gene expression level by sugar concentration during seed germination, and may play an important role in stable and continuous energy supply during seed germination.

Direct Selection Response for Flowering Traits in Four Tropical and Subtropical Maize Populations by Mass Selection

ZHANG De-Gui,LI Xin-Hai,LI Ming-Shun,XIE Chuan-Xiao,HAO Zhuan-Fang,BAI Li

Acta Agron Sin. 2010, 36(1):  28-35.  doi:10.3724/SP.J.1006.2010.00028

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Selection responses were characterized among 4 circles in 2 tropical populations and 2 subtropical populations at two locations during 2006–2007. Analysis of variance indicated that the difference for most flowering traits was not significant among different cirles in the same population in Hainan, while significant progress (P<0.05) was available among populations for flowering traits under evaluation in Beijing. The mean days to silking for tropical POB43 and SUWAN-1 advanced respectively from 99.2 and 90.7 to 79.5 and 76.2, with average of 4.9 and 3.6 in advance per circle, days to anthesis advanced respectively from 90.8 and 77.8 to 76.7 and 74.7, with average of 3.5 and 0.8 in advance per circle, and the mean ASI advanced respectively from 8.3 and 12.8 days to 2.8 and 3.5, averaged 1.4 and 2.3 days in advance per circle. The mean days to silking for subtropical POB69 and POB70 advanced respectively from 78.3 and 81.8 to 69.2 and 69.0, with average of 2.3 and 3.2 in advance per circle, days to anthesis advanced respectively from 71.0 and 72.5 to 67.5 and 68.0 with average of 0.9 and 7.0 days in advance per circle, and the mean ASI advanced respectively from 7.3 and 9.3 days to 1.7 and 2.7 days, averaged 1.4 and 1.7 days in advance per circle. The selection responses obtained in this paper indicated that controlling bi-parental mass selection effectively improved the adaptability of the four tropical and subtropical maize populations.

Density-Enhanced Genetic Linkage Map of RIL Population NJRIKY and Its Impacts on Mapping Genes and QTLs and QTLs in Soybean

ZHOU Bin,XING Han,CHEN Shou-Yi,GAI Jun-Yi

Acta Agron Sin. 2010, 36(1):  36-46.  doi:10.3724/SP.J.1006.2010.00036

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A high-density genetic linkage map with informative markers is essential for plant genome analysis, including gene mapping, identification of quantitative trait locus (QTL), map-based cloning, and physical map construction. Though four genetic linkage maps for the recombinant inbred line population NJRIKY derived from (Kefeng 1×Nannong 1138-2) have been established already, there are still problems of precision and accuracy in mapping genes and QTLs due to insufficiency of genetic information and number of markers. A total of 401 polymorphic SSR markers were screened out from 967 ones for density-enhancement of the previous maps. Along with other marker data, a new genetic linkage map was constructed by using Mapmaker/Exp 3.0b, with 553 markers, including 316 SSR, 197 RFLP, 39 EST and one morphologic markers, spanning 25 linkage groups, covering total length 2 071.6 cM of the soybean genome, with an average marker interval distance of 3.70 cM. In comparison with the old map, the number of gaps larger than 20 cM decreased from forty-two to two on the enhanced map. Using this map to relocate the seven SMV resistant genes, Rsc-3, Rsc-7, Rsc-9, Rsc-13, Rsa, Rn1 and Rn3 were mapped on LG D1b again with distances to the flanking markers all less than 6 cM, among them, Rsc-9, Rn1 and Rsa less than 1 cM and Rsc-13 co-segregating with EST-SSR marker GMKF168a. After re-mapping the QTLs for eight agronomic traits, 42 QTLs were detected on 12 linkage groups, with 20 of them accounted for more than 10% of the total variation, respectively, and their marker intervals obviously shortened.

Primary Mapping of QTL for Dehydration Rate of Maize Kernal after Physiologyical Maturing

LIU Xian-Jun,WANG Zhen-Hua,WANG Xia,LI Ting-Feng,ZHANG Lin

Acta Agron Sin. 2010, 36(1):  47-52.  doi:10.3724/SP.J.1006.2010.00047

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The aim of this study was to identify QTL for dehydration rate of maize kernel after physiological maturing using 232 recombinant inbred lines derived from a cross between line Ji846 (more faster kernel dehydration rate, 1.18% d^-1) and line Ye3189 (more slower kernel dehydration rate, 0.39% d^-1). Dehydration rate of maize kernel of this population and two parents were evaluated according to the method of Wang et al.(2001) and Jin et al. (1997) at tested locations Shuangcheng and Harbin in 2007, respectively. A molecular genetic map including 10 linkage groups was constructed, covering 1 941.7 cM with mean distance 19.22 cM using 101 SSR markers. A total of nine QTLs were identified through software WinQTL2.5, which were located on chromosomes 2, 3, 4, 5 and 6, respectively. Additive effect of these QTLs was derived from line Ji846. Of them, two QTLs (qKdr-2-1 located in bnlg198-umc1516 of chromosomes 2, qKdr-6-1 located in phi126-phi077 of chromosomes 6) were repeatedly found in two environments, which explained 15.49% of total phenotypic variation. Since beneficial alleles were from line Ji846，it was concluded that these QTLs would have the greatest potential value for marker assisted selection for high kernel dehydration rate of maize after physiological maturing.

QTL Mapping of Seed Physical Traits in Upland Cotton (Gossypium hirsutum L.)

LIU Da-Jun,ZHANG Jian,ZHANG Ke,Wang Wei,ZHANG Zheng-Sheng

Acta Agron Sin. 2010, 36(1):  53-60.  doi:10.3724/SP.J.1006.2010.00053

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Cotton is a leading natural fiber crop in the world, and also provides important plant oil and protein. Cotton fiber is developed from a single cell of seed epidermis, so QTL mapping of seed traits is important to reveal the genetic characteristics of seed traits and to understand the genetic relationship among seed, yield and fiber quality traits. Six seed physical traits of upland cotton recombinant inbred line population identified in three environments presented continuous segregation, and the significant variances existed in the six physical traits were affected by environments. The linkage map constructed from the upland cotton recombinant inbred line population (T586 × Yumian1) F_2:7 were used to map QTLs for six seed physical traits by MQM method, and thirty-four QTLs were detected, including nine QTLs for seed weight (qSW), five QTLs for fuzz weight (qFW), three QTLs for fuzz percentage (qFP), eight QTLs for kernel weight (qKW), six QTLs for seed hull weight (qHW), and three QTLs for seed kernel percentage (qKP), with explained phenotypic trait variance rangingfrom 4.6% to 80.1%. Out of thirty-four QTLs, nine QTLs were identified in two or three environments, and they included two large-effect QTLs controlling fuzz weight and fuzz percentage at N₁ locus on chromosome 12, and other seven small-effect QTLs. A total of 34 QTLs were mapped on 15 chromosomes, and among them 20 QTLs distributed on A sub-genome and 14 QTLs distributed on D sub-genome. Twelve chromosome regions have two or more QTLs for seed physical traits in each region, and directions of most QTLs for different seed physical traits, which originated from the same parent in the same chromosome region, were consistent with the correlation coefficients of traits.

Mapping QTLs for Uppermost Internode Diameter and Thickness and Area of Culm Wall with Doubled-Haploid Population in Wheat 

SANG Yun,ZHAO Liang,ZHANG Kun-Pu,TIAN Ji-Chun, YE Bao-Xing

Acta Agron Sin. 2010, 36(1):  61-67.  doi:10.3724/SP.J.1006.2010.00061

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A population of 168 doubled haploid derived from two elite Chinese wheat (Triticum aestivum L.) cultivars Huapei 3 and Yumai 57, grown in two continuous cropping seasons in Tai’an, Shandong province, was used to investigate the genetic basis of uppermost internode diameter (UID) and thickness (CWT) and area (CWA) of culm wall in wheat. The quantitative trait loci (QTLs) for each trait were analyzed based on the constructed molecular linkage map of this population, including 324 SSR markers covering the whole wheat genome. The additive effects, epistatic effects, and their interactions with environment were identified by using the mixed linear model approach. A total of ten additive QTLs and six pairs of epistatic QTLs were detected. Among the ten QTLs, three had interactions with environment. For UID, four QTLs were detected on chromosomes 2D, 3D, and 5D (two regions), and explained 14.98% of phenotypic variation. Three QTLs for CWT were identified and accounted for 14.41% of the variation in the same or close region chromosome of UID, which showed pleiotropisms or tight linkages. Three QTLs on chromosome 3D, 4B and 5D controlling CWA explained 19.03% of the variation. Two intervals of XCFD53–XWMC18 and XWMC215–XBARC34 on chromosomes 2D and 5D for thickness and area of culm wall explained 11.37% and 10.98% phenotypic variation, respectively. They could be used in marker-assisted selection. For the six epistatic QTLs, the epistatic effects were not significant and without epistatic × environment interactions. These QTLs accounted for 19.01% of the observed phenotypic variation, without any additive effects (except qCWA-3D) of their own but involved in epistatic interactions. Such loci might play the role of modifying agents that tend to activate other loci or modify the action of other loci.

Development of Cytoplasmic Male Sterile Line A2Sx3197 with Resistance to Head Smut （Sphacetheca reliana clint） and Pollen Abortion in Sorghum vulara

CHENG Qing-Jun,ZHANG Fu-Yao*,LI Tuan-Yin,LIU Qing-Shan,DU Zhi-Hong,PING Jun

Acta Agron Sin. 2010, 36(1):  68-75.  doi:10.3724/SP.J.1006.2010.00068

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The sorghum cytoplasmic male sterile (CMS) line A₁Tx3197 was used widely in China. At the end of 1970s, this line and its hybrids gradually lost resistance to sorghum head smut because of race shift. Meanwhile, the floret abortion of this line led to low yield. Since the maintainer of A₂ type CMS can restore the fertility of A₁ type CMS, to improve the head smut resistance and floret fertility of A₁Tx3197, BV₄ with the genes conferring the head smut and floret abortion resistances was used as a donor, and A₁Tx3197 was used as a recurrent parent. After five generation backcrossing, a intermediate material BSx3197 carrying head smut and floret abortion resistance genes, a maintainer for A₂-CMS, was acquired. Then BSx3197 was used to replace the karyon of A₂ type CMS line. Finally a novel A₂ type CMS line A₂Sx3197 with its maintainer BSx3197 (MS₁MS₁ms₂ms₂) was bred. The line A₂Sx3197 was restorable in A₁ and A₅ cytoplasmic background, but sterile in A₂, A₃, A₄, A₆, 9E cytoplasmic background. The average disease incidence of A₂Sx3197 was 0–0.8%, and the average abortion incidence was 0–8.4%. A₂Sx3197 had significantly higher resistance to the head smut and floret abortion than A₁Sx3197, which was similar with BV₄. The main agronomic traits of A₂Sx3197 and A₁Tx3197 were not significantly different such as days of heading, plant height, spike length, spike width, 1000-grain weight, grain weight per spike, grain color, shell color, spike shape and spike type.

Effects of Improvement by Mass Selection on the Different Maize Synthetic Populations

ZOU Chao-Ying,LI Lu-Jiang,YANG Ke-Cheng*,PAN Guang-Tang,RONG Ting-Zhao

Acta Agron Sin. 2010, 36(1):  76-84.  doi:10.3724/SP.J.1006.2010.00076

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On the basis ofstatistical analysis offield test and genetic parameters evaluation by Simple Sequence Repeat (SSR) markers, the experiment was conducted with three maize synthetic populations GP3, GP4 and GP5 with mass selection for 4 cycles. The results showed that there existed genetic differences in most traits for the different populations and cycles, and the significant interaction effects between populations with cycles. The genetic gain was GP3<GP5<GP4in kernel depth and GP3> GP5>GP4 in rows per ear. After 4 cycles of mass selection, there was an obvious increase in the mean kernel depth and rows per ear, which displayed significant direct responses. Plant height and ear height exhibited an increase with selection, and the increase in GP4 was significantly higher than that in GP3 and GP5. The genetic gain of GP4 in yield per plant and ear diameter was higher than that of GP3 and GP5. Compared the cycle C4 with C0, most yield traits were improved for all the populations, which implied asignificant correlated response. Excluding plant height and ear height, the differences in GCA were significant for the other traits. The GCA effects of GP5 in most yield traits were higher than those of GP3 and GP4. The population improvement by mass selection resulted in an increase in the GCA effects of most yield traits. Most test-cross combinations, with more than 8% of yield per plant over the check, were derived from the cycle C4 of all the populations, which displayed significant indirect responses to mass selection. For the coefficients of variation in phenotypic traits, there were no obvious changes. For the genetic similarity coefficients of intrapopulation, there were a gradual increase in the derivatives of GP3 and GP4 and no changes in those of GP5. The genotype number in the derivatives of GP3 and GP4 showed a decreasing tendency while a little increases in those of GP5. The results above indicated that populations might be improved effectively and retained a high genetic diversity by mass selection. However, there existed different effects of genetic improvement on different populations and traits.

Molecular Cloning and Characterization of Two Fiber Elongation Genes Using a Cotton Fiber Developmental Mutant (Gossypium hirsutum L.)

WANG Lei,ZHU Yi-Chao,CAI Cai-Ping,ZHANG Tian-Zhen,GUO Wang-Zhen

Acta Agron Sin. 2010, 36(1):  85-91.  doi:10.3724/SP.J.1006.2010.00085

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Cotton fibers are single-celled seed trichomes of major economic importance. Many important genes are expressed during cotton fiber development and fiber developmental mutants can be used to preferentially detect the genes controlling fiber development. The Ligon lintless mutant (Li₁li₁) is a fiber elongation developmental mutant with a dominant monogenetic mutation characterized by short fibers and distorted leaf, stem and flower growth, and the recessive pure line (li₁li₁) exhibits normal fiber developmental characteristics. The objectives of this study were to isolate genes preferentially or specifically expressed in fiber elongation stage by comparing gene expression differences between Li₁li₁ and li₁li₁. RNA isolated from 10 days post anthesis (DPA) fibers and ovules mixture in Li₁li₁ and li₁li₁ were used to screen differential gene expression in fiber development using differential display reverse transcriptase polymerase chain reaction (DDRT-PCR). Two differential expression cDNA segments were isolated, the corresponding full-length cDNAs were cloned and their primary function was analyzed. The two genes encoded 542 and 667 amino acid residues and functioned as glutamate decarboxylase (GhGAD) and vacuole-pyrophosphatase (GhVP1), respectively. Transcriptional level assays showed the two genes were constitutively expressed in tested tissues with higher expression levels during the fiber elongation stage. Further, a BC₁ mapping population derived from hybridization between G. hirsutum acc. TM-1 and G. barbadense cv. Hai 7124, and TM-1 as the recurrent parent, was used for the location of GhGAD and GhVP1 on chromosomes 12 and 8, respectively, using cleaved amplified polymorphic sequences (CAPs).

QTL Mapping for Photosynthetic Gas-Exchange Parameters in Soybean

YIN Zhi-Tong,SONG Hai-Na,MENG Fan-Fan,XU Xiao-Ming,YU De-Yue

Acta Agron Sin. 2010, 36(1):  92-100.  doi:10.3724/SP.J.1006.2010.00092

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Photosynthesis plays an important role in determining crop’s yield. Photosynthetic gas-exchange parameters have been widely used to reflect the photosynthetic capacity of plant. The present study was conducted to identify QTLs associated with gas-exchange parameters in soybean. Pot experiments were carried out in two successive years to evaluate 184 recombinant inbred lines (RILs) derived from a cross between Kefeng 1 and Nannong 1138-2 for photosynthetic rate, stomatal conductance, intercellar CO₂ concentration and transpiration rate at R6 growth stage. The RILs showed transgressive segregation for these parameters, their broad heritability was lower-middle, ranging from 0.48 to 0.60, and significant correlations were observed among them. In total, fifteen QTLs located on seven linkage groups (LG) were identified, six of which expressed stably in two environments. The percentage of variation explained by these QTLs ranged from 4.80% to 12.30%, and with LOD scores from 2.25 to 6.31. Three QTLs for photosynthetic rate were placed on LG C1, E and O respectively, among which the QTL qPnC1.1 (flanked by markers sat_311 and sct_191) was detected in both years; four QTLs for stomatal conductance were placed on LG C1, D2, E and I, respectively, among which QTLs qSCD2.1 (flanked by sat_296 and sat_277) and qSCI.1 (flanked by satt726 and satt330) expressed stably in both years; five QTLs for intercellular CO₂ concentration were placed on LG C1, D2, E, I and O, respectively, among which QTLs qCiI.1 (flanked by satt726 and satt330) and qCiO.1 (flanked by satt94 and sat_291) were detected in both years; three QTLs for transpiration rate were placed on LG C2, H and O, respectively, among which QTL qTrO.1 (flanked by BE801128 and satt345) was detected in both years. It was found that in many cases some QTLs for different traits were located in the same regions of LG. A total of four genomic regions were detected controlling different parameters: the marker interval sat_311–sct_191 on LG C1 for photosynthetic rate and stomatal conductance simultaneously, with positive alleles from Nannong 1138-2; the marker interval sat_172–satt268 on LG E for photosynthetic rate, intercellular CO₂ concentration and stomatal conductance simultaneously, with positive alleles from Kefeng 1; the marker intervals sat_296–sat_277 on LG D2 and satt726–satt330 on LG I for stomatal conductance and interncellular CO₂ concentration simultaneously, with positive alleles from Nanong 1138-2 for the former marker interval, while from Kefeng 1 for the latter one. Compared with other studies, we did not find common QTL that could express stably across different genetic materials, which suggested that the genetic mechanism of photosynthetic gas-exchange parameters is complex in soybean, and further studies need to be performed with more soybean mapping populations in the future.

Cloning and Tissue Expression of Acting1 Gene in Different Fiber Development Phases of Ramie [Boehmeria nivea (Linn.) Gaud]

MA Xiong-Feng,YU Chun-Ming,TANG Shou-Wei,ZHU Ai-Guo,WANG Yan-Zhou,ZHU Si-Yuan,

Acta Agron Sin. 2010, 36(1):  101-108.  doi:10.3724/SP.J.1006.2010.00101

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Ramie [Boehmeria nivea (L.) Gaud] is an important natural fiber crop, and its quality improvement is a challenge for ramie breeders in breeding program. Plant fiber development is a complex process, which involves many genes and enzymes. Actin protein cytoskeleton plays a significant role in cytomorphology including cell elongation of ramie fiber. It is promising for ramie quality improvement by purposely regulating Actin gene expression with gene engineering technique. In the present study, the full-length cDNA sequence of Actin1 gene from ramie cultivar Zhongzhu 1 was cloned (GenBank accession number: DQ665832) by usingdegenerate primer RT-PCR method, RACE technology and screening with a full-length cDNA library. The full-length cDNA was composed of 1 782 bp sequences including an open reading frame (ORF) of 1 134 bp region which encoded 377 amino acids. Bioinformatic analysis showed that the conserved motifsof Actin1gene contained six ATP binding sites, six profilin binding sites and nine gelsolin binding sites. The cDNA sequence of Actin1 shared high sequence homology with that from other crops previously reported, which was close to that from Morus alba (GenBank accession number: DQ785808), Ricinus communis (AY360221) and Gossypium hirsutum (AY305723-305736). Gene sequence analysis showed that the putative amino acid sequence and Gossypium hirsutum Actin (AAP73451.1, AAP73457.1) were gathered to a same group. Degenerate primer RT-PCR method was used to clone18S rRNA and Histone3 genes and establish the fluorescence quantitative PCR system. The system was used to study the expression of Actin1 gene in different fiber development phases by using 18S rRNA and Histone3 genes as inner references. The results showed that Actin1 could express in all kinds of ramie fiber development phases, and the mRNA was 230 times higher in 97 cm of plant height than 11, 150 and 220 cm, 20 times higher than in 47 cm. The BnACTIN1 gene expression increased slowly in 11 to 47 cm of plant height, the peak in the plant height from 47 to 97 cm, in then rapidly declined in 150 cm of plant height, and kept the lowest level till the plant height was up to 220 cm. The high expression of BnACTIN1 gene presented at the beginning of the rapid elongation of the fiber cell, but slightly earlier than the peak period of fiber development. We speculated that ramie actin cytoskeleton plays a important role in the process of phloem fiber elongation.

Characterization of Wheat Stripe Rust Resistance Genes in Shaanmai 139

ZHANG Hong,REN Zhi-Long,HU Yin-Gang,WANG Chang-You,JI Wan-Quan

Acta Agron Sin. 2010, 36(1):  109-114.  doi:10.3724/SP.J.1006.2010.00109

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Stripe rust, caused by Puccinia striiformis West. f. sp. tritici, is one of the most damaging diseases of wheat (Triticum aestivum L.) worldwide. Application of resistant varieties has been considered as the most economical and environment-friendly approach to control the disease. Resistance to stripe rust is frequently overcome by the pathogendue to the emergence of new virulent races. Wheat cultivarShaanmai 139 is resistant to allcurrent Chinese epidemic races of P. striiformis f. sp. tritici, CYR29, CYR30, CYR31, CYR32, and CYR33. Based on the monosomic genetic analysis, here, we reported the characterization and molecular marker of stripe rust resistance genes to CYR32 in Shaanmai 139. We screened 442 F₂ plants derived from two crosses between Shaanmai 139 and two susceptible cultivars Abbondanza and Huixianhong, respectively. The results showed the ratios of the resistant to the susceptible of F₂ population from Shaanmai 139´Abbondanza and Shaanmai 139×Huixianhong were 203:16 and 210:13 respectively, corresponding to 15:1 (χ² is 0.26 and 0.02, χ²_{0.05, 1} = 3.84). Monosomic analysis showed the ratios deviated from 15:1 in the F₂ plants of Shaanmai 139×Abbondaza 1BN and Shaanmai 139×Abbondaza 2DN, while the others ratios corresponded to 15:1. Thus, two resistance loci in Shaanmai 139 were found on chromosomes 1B and 2D, tentatively designated YrSM139-1B and YrSM139-2D, respectively, according to the analysis of 21 monosomic and nullsomic lines of the cultivar Abbondanza and SSR mappingresults. One SSR marker, Xgwm273, was closely linked toYrSM139-1B in the F₂population. SSR mapping results showed that YrSM139-1B derived from a T. dicoccoides accession,AS846.

Identification of Quantitative Trait Loci for Alkali Digestion Value in Japonica Rice

LI Mao-Mao,XU Lei,REN Jun-Fang,CAO Gui-Lan,YU Li-Qin,HE Hao-Hua，HAN Long-Zhi,

Acta Agron Sin. 2010, 36(1):  115-120.  doi:10.3724/SP.J.1006.2010.00115

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Using an F₂ population including 200 individuals derived from a cross combination between two japonica rice DL115 with large grain and XL005 with small grain, which were significantly different on alkali digestion value (ADV), the quantitative trait loci for ADV were identified by composite interval mapping with SSR markers.The results showed that ADV exhibited a normal continuous distribution in F₂ population, indicating that ADV is a quantitative trait controlled by multiple genes. A total of three QTLs conferring ADV were detected in intervals of RM14870–RM1284, RM3838–RM3351, and RM1812–RM332 on chromosomes 3, 5, and 11, and explained 6.5%, 10.3% and 8.1% of the observed phenotypic variance, respectively. The allele of qADV5 was derived from XL005 with less ADV, and the alleles of qADV3 and qADV11 were derived from DL115 with bigger ADV. The gene action was controlled by dominance and over-dominance.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Analysis of Physiological and Biochemical Characteristics of Six Mutants with Stable High Percentage of Chalkiness in Rice Grains

JIN Tian-Yun,LI Hui,GUO Tao,LIU Xiao-Lu,SU Ning,WAN Jian-Min

Acta Agron Sin. 2010, 36(1):  121-132.  doi:10.3724/SP.J.1006.2010.00121

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Chalkiness is an important quality character in rice, which is affected by comprehensive effects of genetic and environmental factors. Furthermore, the environmental factors affect the formation of chalkiness through the physiological and biochemical processes. Here, we screened six mutants with stable severe chalky rice grains from the T-DNA insertion mutant pool of cultivar Nipponbare. The changes in activities of the key enzymes associated with starch synthesis, including sucrose synthase, adenosine diphosphoglucose pyrophosphorylase (AGPase), starch synthase, starch branching enzyme and starch debranching enzyme in grains during the filling period, could impact the starch synthesis, the shape and fine structure of the starch granule, thus result in the formation of chalkiness. Temperature condition during grain filling is one of the most important environmental factors affecting the quality of rice. But high temperature stress did not take place during this experiment. To explain the mechanism of the formation of chalkiness from the physiological and biochemical aspects, we analyzed the fluctuation of the key enzyme activities associated with starch synthesis, sucrose content, starch content, and the ratio of amylose to total starch in mature grains. The results suggest that physiological studies of grain development are essential to reveal the formative mechanism of chalky rice.

Changes in Grain Yield and Morphological and Physiological Characteristics during 60-year Evolution of Japonica rice Cultivars in Jiangsu Province,China

ZHANG Hao,TAN Gui-Lu,XUE Ya-Guang,LIU Li-Jun,YANG Jian-Chang

Acta Agron Sin. 2010, 36(1):  133-140.  doi:10.3724/SP.J.1006.2010.00133

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Great progress has been made in japonica rice breeding. However, little is known about physiological and agronomical features responsible for the improvement. In this study, 12 typical japonica rice cultivars (including super rice) applied in the production in Jiangsu province during the last 60 years were used, and classified into six types of 1950s, 1960s, 1970s, 1980s, and 1990s in the 20th century and since 2000 according to their application times. All the tested cultivars were grown in the field and the evolution characteristics of grain yield and its components, source-sink relationships, morphology and physiology were investigated. Results showed that the grain yield was progressively increased with the evolution of the cultivars. Increase in grain yield was attributed mainly to the increase in total number of spikelets, which resulted mainly from large panicles. The percentage of filled grains was increased for cultivars from 1950s to 1980s in 20th century, whereas it was decreased for those at 1990s in 20th century and since 2000. There was no significant difference in 1000-grain weight among the six types of cultivars. With the improvement of rice cultivars, biomass, especially after heading, and harvest index were simultaneously increased. At main growth stages, with the improvement of rice cultivars, root dry weight, root-shoot ratio, root oxidation activity and leaf photosynthetic rate were increased significantly, but root oxidation activity and leaf photosynthetic rate during grain filing for super rice were declined rapidly. Improvement of rice cultivars significantly increased total, effective, high-effective leaf areas and grain-leaf ratio (the ratio of total spikelet number to leaf area) at heading, and increased panicle length, number of primary and secondary panicle branches greatly. From 1950s to 1990s in the 20th century, plant height was reduced, while it was increased significantly for super rice since 2000, with a plant height of about 120 cm. The leaf angle of the top three leaves on stems were significantly decreased with the improvement of rice cultivars. The results indicate that agronomical and physiological characteristics of japonica cultivars are improved during the evolution, and low percentage of filled grains limits grain yield potential in super rice cultivars.

Spatial Variability of Polyphenol Content of Flue-Cured Tobacco in Yunnan Province,China

WU De-Chuan,ZHOU Ji-Heng,FAN Zai-Dou,LI Wen-Bi,ZHANG Yi-Yang,YANG Cheng

Acta Agron Sin. 2010, 36(1):  141-146.  doi:10.3724/SP.J.1006.2010.00141

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Flue-cured tobacco in Yunnan plays an important role in formula of Chinese cigarette. Polyphenol is one of the main aroma precursors in tobacco leaf, so researchers highly focus on polyphenol compound. The objective of the study was to investigate spatial distribution of polyphenol content in flue-cured tobacco in Yunnan, and to provide references for layout of tobacco planting and using of tobacco leaf. The tobacco planting areas in Yunnan were selected as the experiment sites. 1410 flue-cured tobacco samples of C3F grade in 2007 and 2008 were collected from 705 sites via Global Position System (GPS). Polyphenol contents of tobacco samples were determined, and the original data of tobacco polyphenol contents were taken from the samples mean in every site. The original data, data of logarithmic transformation and data of Box-Cox transformation were tested for normal distribution. Surface trend and spatial distribution of tobacco polyphenol content were analyzed by Geostatistics Analyst. The results showed that the data of logarithmic transformation showed normal distribution. The integrative comparisons of semi-variogram parameters of the ordinary kriging prediction with different trends and theoretical models indicated that 0-order trend effect and gaussian model were preferable. There was moderate spatial correlation (C₀/C₀+C=35.71%) and no surface trend (0-order)for tobacco polyphenol content in Yunnan. In most tobacco growing areas of Yunnan, the tobacco polyphenol content ranged from 3.50% to 4.00% (acted as background value). The growing areas that the polyphenol content was over 4.00% were mainly located in the west, centre and east of Yunnan. The growing areas that polyphenol content was over 4.50% were sporadically distributed in the areas, with polyphenols contents of 4.00–4.50%. Polyphenol content showed gradient-like distribution with high-to-low trend from center to surroundings in the growing areas. The areas with polyphenol contents of 5.50–6.73% were located in Nanjian county, the northern Yongping county, the north-west of Longling county and the western Wuding county, and the area in Nanjian county was the biggest one among them.

Response of PvP5CS1 Transgenic Arabidopsis Plants to Drought-and Salt-Stress

CHEN Ji-Bao,ZHAO Li-Ying,MAO Xin-Guo,WANG Shu-Min,JING Rui-Lian

Acta Agron Sin. 2010, 36(1):  147-153.  doi:10.3724/SP.J.1006.2010.00147

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Under adverse environment, many plants increase their cell osmotic potential through accumulation of intracellular organic osmolytes-proline. The proline accumulation in plants can not only increase cell osmotic potential but also stabilize proteins, membranes, and subcellular structures as well as protect cells against oxidative damage by reactive oxygen species. Pyrroline- 5-carboxylate synthetase (P5CS), a rate-limiting enzyme involved in the biosynthesis of proline in higher plants, is encoded by P5CS gene. The full length cDNA sequence of PvP5CS1 gene was subcloned into pCHF3 vector and transformed into wild Arabidopsis via Agrobacterium tumefaciens. A total of six positive transgenic plants were obtained. The result of RT-PCR showed that the PvP5CS1 gene was normally expressed in transgenic plants. The T₄ generation purified lines of transgenic plants and wild Arabidopsis were used for osmotic stress experiment. Seed relative germination rates of transgenic plants under treatment or non-treatment conditions were all significantly higher than those of wild plants under stress conditions (P<0.001). The average seed relative germination rate of transgenic seedlings was 1.62 times and 1.6 times higher than those of wild plants treated with 150 mmol L^-1 mannitol and 150 mmol L^-1 NaCl, respectively. Proline content, conductivity rate and root length of eight-day transgenic seedlings under osmatic stress were determined. The results showed that introduction of PvP5CS1 gene into Arabidopsis resulted in significant accumulation of proline. The relative proline content in transgenic plants under stress non-treated conditions were all significantly higher than those in wild type plants (P<0.05). Under four treatments (CK, 150, 250 mmol L^-1 mannitol and 150 mmol L^-1 NaCl), the average relative proline contents in transgenic plants were 1.38, 2.68, 1.30 and 1.30 times of those in wild type plants. The transgenic plants had longer root and less cell damage than wild plants under osmotic stress conditions. Under 150, 250 mmol L^-1 mannitol- and 150 mmol L^-1 NaCl-stress conditions, average relative conductivity rate in transgenic plants were 85%,77%, and 85% of that in wild type plants, respectively. The average relative root length in transgenic plants was 1.2,1.3, and 1.2 times of that in wild type plants, respectively. After 300 mmol L^-1 NaCl treatment for 15 days, the seedling death rate was 42% and 90% for transgenic and wild type plants, respectively. In the condition of drought stress for 25 days and following by re-watering for 5 days, the seedling death rate of transgenic plants was also significantly lower than that of wild types (P<0.05), which was 56% for transgenic plants and 70% for wild plants. These results indicated that over-expression of PvP5CS1 in transgenic Arabidopsis plants increased plants tolerance to salt and drought stresses.

Effects of Phosphorus on Growth and Uptake of Heavy Metals in Plants Grown in the Soil Contaminated by uranium Tailing

XIANG Yan-Ci,GUAN Chun-Yun,HUANG Huang,YAN Ming-Li,PENG Xiu-Hua

Acta Agron Sin. 2010, 36(1):  154-162.  doi:10.3724/SP.J.1006.2010.00154

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The uranium tailing contains uranium and other heavy metals like lead, cadmium and zinc, which usually makes the surrounding soil and water bodies seriously polluted with contaminated rain and dust. There is a potential threat to human’s health because the heavy metals can be absorbed and accumulated by the crops grown in the polluted areas, and then possibly transferred to human body by an environment-crop-food chain. The development of an economical and effective remediation method for the heavy-metal contaminated soil is urgent to improve environmental quality and enhance the food safety. As one of the fast-developing technologies, chemical stabilization has been widely studied, and the study on inhibition of heavy metal contamination by adding phosphorus-containing material to soil is becoming an international hotspot. In this study, two species of oilseed rapes, B. junea and B. napus, grown in containers with the uranium-tailing contaminated soil, were used to investigate the effects of phosphorus fertilization on plant growth and accumulation of heavy metals (U, Cd, Zn, and Pb). Container soil was treated by adding a phosphorus fertilizer NaH₂PO₄ with a rate of 0, 30, 60, 120, 240, and 480 mg P kg^-1, respectively. For the control soil (without adding phosphorus fertilization), there were a lower concentration of total nitrogen, phosphorus, potassium, and organic matter, and a higher concentration of U, Cd, Zn and Pb. Plant growth of both species was inhibited. Compared with the control group, the concentration of phosphorus significantly increased in plants grown in the P-fertilizer added soil. The DTPA-exactable concentrations of U, Cd, Zn, and Pb in this soil were decreased by 17.1–70.5%, 24.0–57.6%, 8.9–32.4%, and 8.6–55.8%, respectively. Also, addition of phosphorus in the uranium-tailing contaminated soil significantly decreased the contents of U, Cd, Zn, and Pb in plant organs. A significant positive correlation (P<0.01) was observed between the contents of U, Cd, Zn, and Pb in plant organs of both species and DTPA-exactable concentrations of these metals in the contaminated soil. Additionally, addition of phosphorus fertilization of 60-480 mg P kg^-1 significantly increased dry weight, height, root length and chlorophyll content of plants. A significant decrease of SOD activity and MDA content occurred in both species grown in the P-fertilizer treated soil compared to the control. Therefore, application of phosphorus fertilizer to the uranium-tailing contaminated soil is a practical and effective approach to reduce accumulation of heavy metals in plant organs of oilseed rapes and the risk of these pollutants entering the food chain.

Canopy Architecture Characteristics of Spring Wheat under Controlled Traffic Tillage with Mulching in Ridge

YANG Rong，HUANG Gao-Bao

Acta Agron Sin. 2010, 36(1):  163-169.  doi:10.3724/SP.J.1006.2010.00163

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In a field test on the experimental farm of Gansu Agricultural University in Zhangye, Northwest China, the characteristics of colony canopy architecture was investigated in spring wheat under the treatments of controlled traffic tillage with straw mulching in ridge (CTS), controlled traffic tillage without mulching in ridge (CT), controlled traffic tillage with film mulching in ridge (CTP), and conventional cultivation (LT, control). The plant height, leaf distribution, leaf area index, light intercept and capture ratio, and photosynthetic rate were measured at a thesis stage. Compared with LT, the plant height was 2.09, 3.27, and 5.65 cm lower in CTP, CTS, and CT, respectively, and there was a significant difference between CT and LT treatments. Under the treatments of CTP and CTS, an approximate ratio of 3:2:1 was observed in the relationship among the distance between flag leaf and the second leaf from top, and the distance between the second and the third leaf from top. Such ratio was optimal for the uniform distribution of light in the wheat colony. The leaf area index was in the order of LT>CTP>CTS>CT, especially from June 25 to July 15. Controlled traffic tillage reduced leaf area apparently, however, mulching in ridge alleviated such influence. In terms of the distribution of incident light within layers of wheat canopy, although wheat colony intercepted the most lights in treatment LT (97.2%), the light distribution varied sharply in the flag leaf layer (77.34%), the second leaf layer (12.17%), and the third leaf layer (7.17%), indicating an incompact colony canopy configuration and low photosynthetic rate. However, the light distribution in the three leaf layers was relatively well-proportioned in CTP and CTS, with only 8.03% and 11.23% of light penetration, respectively. The photosynthetic rate of flag leaf was higher in treatment CT than in other treatments at anthesis stage, but treatment CT had the highest penetration ratio of light and the smallest leaf area index among the four treatments. The results showed that treatments CTP and CTS were in favor of better colony architecture and solar energy use efficiency, resulting in yield promotion in spring wheat. In contrast, the colony configuration was too compact in treatment LT and too incompact in treatment CT to obtain high yield.

RESEARCH ACTIVITIES

Effects of Waterlogging Time on Rapeseed (Brassica napus L.) Growth and Yield

SONG Feng-Ping,HU Li-Yong,ZHOU Guang-Sheng,WU Jiang-Sheng,FU Ting-Dong

Acta Agron Sin. 2010, 36(1):  170-176.  doi:10.3724/SP.J.1006.2010.00170

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A huge amount of precipitation and higher water table during rapeseed growing season in Yangtze River regions grown with rice and rapeseed rotation system and heavy soil result in frequent waterlogging occurrence. A pot experiment was performed at four growth stages with three waterlogging time treatments which were followed by normal water administration. Two rapeseed lines with different levels of waterlogging tolerance were used to investigate the effects of the sustainable waterlogging time on rapeseed growth and yield. The treatments were waterlogging of 10, 20 and 30 days at seedling and budding stages and 10, 15 and 20 days at flowering and maturity stages. The results showed that (1) the sustainable waterlogging time affected the development of roots, the growth of up-ground part of plant and yield, which was significantly different between two lines; (2) waterlogging at seedling stage led to the decrease of chlorophyll content in leaves, and the increase of malondialdehyde and proline contents; (3) sensitivity to waterlogging judged by yield in different developmental stages of rapeseed ranked in the order of budding stage, flowering stage, seedling stage, podding and maturity stages; (4) the research on effects of sustainable waterlogging time on yield can provide a basis for estimating the influence of continuous rainfall on rapeseed production.

Construction of Molecular Genetic Linkage Map of Sugarcane Based on SSR and AFLP Markers

LIU Xin-Long,MAO Jun,LU Xin,MA Li,Karen Sarah AITKEN,Phillip Andrew JACKSON

Acta Agron Sin. 2010, 36(1):  177-183.  doi:10.3724/SP.J.1006.2010.00177

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To take advantage of the MAS technique and develop the molecular genetic linkage map in sugarcane breeding program in China, we constructed two molecular genetic maps by single dose markers (SDM) and double dose markers (DDM) from 36 SSR and 12 AFLP primers for two mapping populations (F₁ and BC₁). F₁ population was from cross combination of sugarcane commercial variety (Co419) × S. spontaneum (Y75/1/2) consisting of 269 true individuals, BC₁ population from backcross combination of F₁02/356×sugarcane commercial variety (ROC25) with 266 true individuals. All plants from two populations were detected by PCR.

Two molecular genetic linkage maps were established. 298 SDMs and DDMs were acquired by c² test from 630 segregation markers of F₁ population, about 47% of total markers; 264 SDMs and DDMs were obtained from 571 segregation markers of BC₁ population which were 46% of total markers, Co419>02/356>Y75/1/2>ROC25 in efficiency of getting SDMs and DDMs. Based on LOD ≥ 5.0, genetic distance ≤ 40 cM between markers, 134 of 298 SDMs and DDMs from F₁ population formed 55 linkage groups (LGs), among which 39 LGs were included in eight homology groups(HGs), 16 LGs were excluded, the map length reached 1 458.3 cM with an average distance of 10.9 cM between markers; 133 of 298 SDMs and DDMs from BC₁ population made up 47 LGs , among which 34 LGs were composed in eight HGs except for 13 LGs, the map covered 1 059.6 cM with an average distance of 8.0 cM. At the same time, these SDMs and DDMs from Co419 and Y75/1/2 formed 34 LGs and 20 LGs, respectively, and these SDMs from two parents only made up 1 LGs; 19 LGs were obtained from these SDMs and DDMs of 02/356, and ROC25, 9 LGS were formed by SDMs from two parents; Co419>Y75/1/2>02/356=ROC2 according to forming number of LGs. These results indicated that F₁ mapping population was better than BC₁ mapping population in quality of constructing linkage map. The maps will provide the valuable information for locating gene, further research on genetic linkage map and MAS breeding.

Observation of Chloroplast Ultrastructure of Zebra Leaf in Rice Mutant b411

QIU Yi-Lan,LI Hong,PENG Ke-Qin,LIU Zhu-Li,CHEN Song,LIU Ru-Shi,LIANG Man-Zhong

Acta Agron Sin. 2010, 36(1):  184-190.  doi:10.3724/SP.J.1006.2010.00184

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A rice zebra leaf mutant B411 was examined using transmission electron microscopy technique to study the chloroplast ultrastructure during development of zebra leaf. The results showed that there was a distinct difference between green and yellow zones of the same leaf when the leaf was enwrapped in the sheath. Chloroplasts were spindle-shaped with thylakoid membranes neatly arranged along the longitudinal direction in the green zone, however, chloroplasts in the yellow zone were oval-shaped with thylakoid membranes ranked irregularly. Along with zebra leaves shooting out of the sheath, difference between yellow zone and green zone in the same leaf became more and more evident, in the green zone, thylakoid membranes became rich, and piled up to be the grana. Nevertheless, thylakoid membrane fragmented, internal structure of chloroplast disaggregated seriously and had vesicle structures with high electron density in the yellow zone. With regreening in the yellow zone of zebra leaf, the shape of chloroplast in the yellow zone became spindle, and thylakoid membrane system reconstructed and gradually became rich, orderly arranging along with the long axis of the chloroplast, and some starch granules formed in the chloroplast which indicated that chloroplasts resumed the capacity of photosynthesis.