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10 September 2011, Volume 25 Issue 5 Previous Issue    Next Issue
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Fine Mapping of a Rolled Leaf Gene rl(t)    in Rice PAN Cun-hong1, 2, #, LI Lei1, #, CHEN Zong-xiang1, XUE Xiang1, ZHANG Ya-fang1, ZUO Shi-min1, DAI Zheng-yuan2, PAN Xue-biao1,*, MA Yu-yin1, 3,* 2011, 25(5): 455-460.  DOI: 10.3969/j.issn.10017216.2011.05.001 Abstract ( )   PDF (469KB) ( )   Moderately  rolled  leaf   is  one of the  most important morphological characters in ideal plant architecture breeding in rice. The heterozygous   rl(t) gene   could produce moderately rolled leaf and   increase rice yield, presenting a high breeding potential.  By using  BC5F3  and BC5F4 populations derived from   a rolled  leaf Zhenshan 97B(carrying rl(t) gene) and  a flatleaf  variety Qimiaoxiang(recurrent parent),  and a total of 15 polymorphic markers, the rl(t) gene was ultimately mapped into a region of 11 kb flanked by the markers P95053 and P113.6  on chromosome 2. The genetic  distance of  this region is about 0.04 cM. Only one predicated ORF (open reading frame)/gene was  found in this region, which encodes  a transcription factor of  the homeobox family HDGL2 (also known as HDZIP Ⅳ). The results laid a   foundation for further cloning  of rl(t)and understanding of  its regulation mechanism.

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Genetic Analysis and Gene Mapping of a White  Striped Leaf   and  White Panicle  Mutant in Rice JIN Yi1,2 , LIU Heqin1 , WANG Dekai1，*,TAO Yuezhi1,* 2011, 25(5): 461-466.  DOI: 10.3969/j.issn.10017216.2011.05.002 Abstract ( )   PDF (955KB) ( )   A white striped leaf  and white  panicle mutant, designated as wslwp,  was obtained from a rice  (Oryza sativa L. ssp. japonica  cv. Zhonghua 11) transfer DNA insertion mutant pool. The mutant was characterized by  white leaves at the 1leaf stage,   chlorotic leaves with  longitudinal green stripes    at the 2leaf stage,  and green leaves before heading. Moreover, at   the heading stage, the glume showed  white color, but the panicle axis and rachis remained green.  The grain   changed into yellow  at the maturity stage. Chlorophyll and carotenoid contents  and seed setting rate of the mutant were significantly reduced. Genetic analysis showed that the phenotype of the mutnt was controlled by a single recessive nuclear gene. An F2  population generated by crossing the  mutant with Longtefu B was used as a gene mapping population.  WSLWP locus was preliminarily located between SSR molecular markers RM5711 and RM6574 on chromosome 7,  then it was mapped to a physical distance 87 kb region between  newlydeveloped polymorphic STS markers STS763 and STS765.

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Single Nucleotide Polymorphism of  MicroRNA in  Rice YU Hao, YAN Xu, GUO Weidong, XIN Dedong* 2011, 25(5): 467-474.  DOI: 10.3969/j.issn.10017216.2011.05.003 Abstract ( )   PDF (1824KB) ( )   MicroRNAs  （miRNAs） are a class of endogenous small (about 22 nucleotides), noncoding RNAs, which play important roles in plant growth, development and stress tolerance by binding to the target sites in mRNAs. Since a single nucleotide change in miRNAs can affect the maturity and regulation of miRNA, study  on the distribution of  single nucleotide polymorphisms (SNPs) in miRNA gene may be of great  importance  for functional and evolutionary research. In order to explore the potential functional significance of SNPs in the premiRNA in rice, we analyzed the distribution of SNPs in premiRNA region and flanking region, including 5′   and 3′ flanking regions in rice. The results showed that there was  no significant difference in  the frequency of SNPs between the premiRNA region and its flanking region in rice, which was different from the results  in other species. Further study on the frequency of SNPs   across premiRNA  secondary structures showed that there was no significant difference  between seed region and loop region, which was thought to undergo less negative selection pressure in other species. However, in consistent with  other species, the frequency of SNPs in  proteincoding  gene region of rice was significantly lower than that in gene flanking region,  indicating  that the flanking region of premiRNA may  be essential for the  function of miRNA. Another reseaon was the uneven distribution of SNPs in  different miRNAs. Some miRNAs were  less important to rice function,  thus was subjected to relaxation of selective pressure, accumulating more and more mutations to become a new gene or loss of functions. However, we could not rule out the bias in the results because of  the unreliable data in current SNP database.

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Mapping and Genetic Analysis of Quantitative Trait Loci for Related Traits of Cooked Rice SHEN Nianwei1,#, LAI Kaikai1,2,#, NIAN Jinqiang1,3, ZENG Dali1, HU Jiang1, GAO Zhenyu1, GUO Longbiao1, ZHU Li1, LIU Jian1, DONG Guojun1, YAN Meixian1, QIAN Qian1,*, ZHANG Guangheng1,* 2011, 25(5): 475-482.  DOI: 10.3969/j.issn.10017216.2011.05.004 Abstract ( )   PDF (26KB) ( )   The milled rice length, cooked rice length and    elongation traits are very important in the quality of cooked rice. Mapping of quantitative trait locus (QTL)   for cooked rice   related traits   was conducted using a doubled haploid population from a cross between a typical indica rice  cultivar ‘TN1’ and a typical japonica   rice  cultivar ‘Chunjiang 06’. Using a linkage map based on 177 SSR molecular marker loci covering  the distance of  1670.92 cM, a total of 14 QTLs were identified for the cooked rice related traits. One putative QTL for milled rice length and one for soaked rice length were mapped on chromosome 2, with the explained variance of 15.20% and 18.50%, respectively. One putative QTL for soaked rice expansion was mapped on chromosome 6, with the explained variance of 13.39%. One putative QTL for boiled rice length was mapped on chromosome 9, with the explained variance of 1360%. Three QTLs for steamed rice length were detected on chromosomes 1, 3  and 12,  totally explaining  variance of 45.00%. Four QTLs for boiled rice elongation were detected on chromosomes 3, 6, 9 and 10,   totally explaining  variance of 61.30%. Three QTLs for steamed rice elongation were detected on chromosomes 1, 3, and 6,  totally explaining variance of 49.10%. Two QTLs for elongation related traits of  cooked rice were detected on the Wx gene cluster and ALK gene cluster, respectively. Comparing to the Wx gene cluster, the  QTL in the ALK gene cluster  played a  much more important role in  regulation of  related traits of cooked rice with  the LOD score of 6.35. These results  provide  a foundation for further cloning of genes that regulate  cooked rice  related traits  and a theoretical basis for the improvement  of rice cooking quality and  markerassisted breeding of highyielding and  highquality rice varieties.

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Mapping of QTLs for  Flag Leaf Shape Using WholeGenome Resequenced Chromosome Segment Substitution Lines in Rice XU Jianjun1,2, ZHAO Qiang3, ZHAO Yuanfeng1, ZHU Lei1, XU Chenwu1, GU Minghong1, HAN Bin3, LIANG Guohua1,* 2011, 25(5): 483-487.  DOI: 10.3969/j.issn.10017216.2011.05.005 Abstract ( )   PDF (18KB) ( )   Flag leaf shape is one of the most important target traits in rice ideal plant type breeding. Identification and localization of new rice flag leaf shape QTLs would be of great significance to facilitate the genetic analysis of complex traits, and provide QTLs/genes to develop new plant type rice varieties via markerassisted selection. One hundred and twenty eight  chromosome segment substitution lines with 9311 as recipient and Nipponbare as donor  were genotyped by wholegenome resequencing. The pairwise correlation analysis on three flag leaf shape traits was conducted. The correlations between flag leaf length and flag leaf area, and between flag leaf width and flag leaf area were significantly positive. Correlation analysis revealed that  the flag leaf length and flag leaf area have a direct positive impact on spikelet number per panicle. By combining  the sequencingbased Binmap with  multiple linear regression analysis,  four, four and six QTLs for flag leaf length, flag leaf width and flag leaf area were mapped, respectively, with contributions from 4.08% to 60.40%. The results provided a foundation for fine mapping  and subsequent   cloning of the QTLs.

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Effects of RowSpacing on Canopy Structure and Yield in Different Type Rice ZHAO Haixin1,2 , YANG Limin2, CHEN Shuqiang1, JIANG Shukun3, HUANG Xiaoqun1, SHAN Lili1, PAN Guojun1,* 2011, 25(5): 488-494.  DOI: 10.3969/j.issn.10017216.2011.05.006 Abstract ( )   PDF (654KB) ( )   Two cold region japonica  rice varieties Longjing 20 (more tillers and curved panicle type, MCP) and Longjing 21 (few tillers and halferect panicle type, FEP) were used as materials to study the effect of rowspacing on canopy structure, morphological  traits and yield. The  productive tiller percentage reduced first and then increased as rowspacing widened   and followed  a quadratic regression. Leaf area index (LAI) at later tillering stage and the  highest stem number per unit area  followed a quadratic regression,  increasing first and then reducing. The effect of rowspacing on primary rachis  branch was larger than on  secondary  rachis branch    in Longjing 20 and the trend of Longjing 21 was reverse. The rowspacing showed a negative correlation with seed setting rates  of secondary  rachis branch and  panicle.  The correlation between rowspacing and yields of Longjing 20 and Longjing 21 was positive  and significantly negative, respectively. The morphological  traits of MCP were more easily affected by rowspacing and the rowspacing showed positive   correlation with flag leaf length, flag leaf width,  the 1st internode length from the top, the 2nd internode length from the top  and panicle length. Otherwise，the  morphological  traits of FEP were not significantly affected by rowspacing. The wide rowspacing was propitious to accumulate dry matter of panicle, stem and leaf and to form yield in MCP (the best rowspacing of Longjing 20 was 30 cm), the narrow rowspacing was suit to Longjing 21 which has few tillers and half erect panicle (the best rowspacing of Longjing 21 was 21 cm). It was suggested that wide rowspacing was benefitial  to improving population environment of MCP and narrow rowspacing   was favorable to increase space  utilization of FEP.

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Thermal Resistance of Common Rice Maintainer and Restorer Lines to  High Temperature Stress During Flowering and Early Grain Filling Stages FU Guanfu#, SONG Jian#, LIAO Xiyuan, ZHANG Xiufu, XIONG Jie, WANG Xi, LE Mingkai, TAO Longxing* 2011, 25(5): 495-500.  DOI: 10.3969/j.issn.10017216.2011.05.007 Abstract ( )   PDF (813KB) ( )   Fifteen common rice maintainer lines and 26 highyielding   restorer lines were used to evaluate their thermal resistance and fertility during flowering and early grain filling stages. The  rice plants were subjected to high temperature stress at  39-43 ℃ for 1-15 d  from main stem flowering. Based on the high temperature stress index, they were divided into thermal resistant lines, semithermal resistant lines, semithermal sensitive lines and thermal sensitive lines. Therefore, the maintainer lines K22B，  Bobai B and V20B  belonged to  thermal resistant lines, whereas Ⅱ32B，  Zhongzhe B and Zhong 9B to thermal sensitive lines. The rice restorer line  Minghui 63 had the highest  thermal  resistance,  followed by  R207, P929,  and the lowest thermalresistant  P6222，  R8006 and P51. The correlation analysis indicated that  the high temperature stress index was not  significantly  correlated with  seedsetting rate, abortive grain rate, unfilled grain rate  under natural conditions, but significantly correlated with   seedsetting rate and unfilled grain rate under high temperature stress. This indicated that high temperature stress occurred during floweringearly grain filling stage mainly decreased the  seed setting rate and significantly increased the unfilled grain rate in both rice maintainer and restorer lines.

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Effects of Nitrogen Fertilizer Level on  Chlorophyll Fluorescence Characteristic in Flag Leaf of Super Hybrid Rice at Late Growth   Stage LONG Jirui1, MA Guohui1,*, WAN Yizhen1, SONG Chunfang1, SUN Jian2 2011, 25(5): 501-507.  DOI: 10.3969/j.issn.10017216.2011.05.008 Abstract ( )   PDF (1352KB) ( )   To compare the effects   of nitrogen fertilizer level on     chlorophyll fluorescence characteristics   in super hybrid rice flag leaves, a field fertilizer (slow release nitrogen) experiment was conducted  with a super hybrid rice Y Liang you 1 as material.  The photosynthetic electron transport rate (ETR),   effective quantum yield (EQY), photochemical quenching coefficient(qP), and nonphotochemical quenching coefficient(NPQ) of flag leaves  were measured at the heading,  full heading,  10 d after full heading,  20 d after full heading.  The results indicated that the  ETR and EQY were increased   from heading   to  20 d after full heading, whereas, the NPQ  decreased. During the same period, ETR, EQY, qP increased firstly and then decreased with  increasing nitrogen  level.  The ETR and EQY  at 135   kg/hm2  nitrogen level were the highest. In conclusion, the adaptive  nitrogen amount for photosynthesis were 135-180 kg/hm2.

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Effects of Different SeedlingAges and Planting Densities on Physiological  Characteristics  and Grain Yield of Hybrid Rice ⅡYou 498 under TrianglePlanted System of Rice Intensification During Filling Stage HE Yangdong1,2, TONG Ping1， MA Jun1,*, SUN Yuanyuan3, SUN Yongjian1, LIU Shujin1, XU Yuanming4 2011, 25(5): 508-514.  DOI: 10.3969/j.issn.10017216.2011.05.009 Abstract ( )   PDF (440KB) ( )   The grain yield formation and some physiological  characteristics  were investigated during filling stage under triangleplanted system of rice intensification (TSRI) at different transplanting seedlingages and planting densities with Ⅱyou 498 as material. The results showed that  obvious compensation effect of planting density to transplanting seedlingage of rice under TSRI   improved some morphological  and physiological characteristics during grain filling stage and promoted yield. Transplanting  2leafage seedlings at a suitable planting density (40 cm × 40 cm) was the best, which increased effective tiller number of plant population, gained reasonable structure of populations, had high leaf area index (LAI) and much higher percentage of efficient LAI, delayed the descending rate of LAI, and enhanced root activity, consequently, promoted dry matter accumulation and transportation during grain filling, and was helpful to coordinate the conflict among filled grain number per panicle, seed setting rate and 1000grain weight.  Effective panicle number and grain yield  significantly decreased as seedlings were transplanted at 8leaf age stage and lower planting density (50 cm×50 cm). For  5leafage seedlings, the suitable planting  density  ranged from 30 cm × 30 cm to 40 cm × 40 cm, alleviating  the contradiction of crop  rotation. In addition, transplanting high leaf age  seedlings was easy to accelerate the  senescence process of rice during grain filling stage and decreased yield. It was noteworthy that   high leaf age seedlings should be transplanted at relatively high planting densities, and the optimum planting density was 30 cm × 30 cm for the  8leafage seedlings.

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Effects of Lower Limit of Soil Water Potential on  Grain Quality of Rice in Cold Region LU Yandong1,2, ZHENG Guiping2, GUO Xiaohong2, YIN Dawei1, MA Dianrong1, XU Zhengjin1, CHEN Wenfu1,* 2011, 25(5): 515-522.  DOI: 10.3969/j.issn.10017216.2011.05.010 Abstract ( )   PDF (812KB) ( )   With Kenjiandao 5 and Kendao 12 as materials, the effects of intermittent watercontrolling treatments at -8 to  -10 kPa of soil water potential on rice  grain quality in cold region   from reviving  to maturity were studied in a pot experiment  in  a chamber rainproof by examining soil water potential with a negative pressure soil moisture  meter.The results of  showed that head rice rate, amylose content, setback value of grains at different positions  decreased,  whereas protein content, prolamin  content, glutelin content, globulin  content, peak viscosity value and  breakdown value of grains at different positions   increased.  Therefore, the rice  taste value decreased.

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Genetic Diversity and Pathotype Variability of Xanthomans oryzae  pv. oryzicola Strains ZHANG Rongsheng1,2, CHEN Zhiyi1，*, LIU Yongfeng1 2011, 25(5): 523-528.  DOI: 10.3969/j.issn.10017216.2011.05.011 Abstract ( )   PDF (992KB) ( )   Genetic diversity and pathotype variability of Xanthomans oryzae  pv. oryzicola strains collected from Jiangsu, Yunnan, Jiangxi, Hunan and Anhui  Provinces were analyzed by using repPCR fingerprinting techniques. Genomic DNAs from 69  strains were amplified with two specific primers BOX and ERIC. Dendrograms were generated from the data by using UPGMA analysis. The tested strains were  classified into 10 and 8  groups at a similarity of 80% based on the amplification results with BOX and ERIC, respectively. The predominant groups were  group   3 and Group 5 for the  primers  BOX and ERIC, involving 27(39.1%) and 24(348%) strains, respectively. The genetic diversities of the population of  the tested strains were 0.9784 (with BOX) and 0.9833 (with ERIC), respectively, indicating the high  genetic diversity of Xanthomans oryzae  pv. oryzicola. According to  inoculation results  on  five differential cultivars including nearisogenic rice lines carrying single resistance gene, IRBB4, IRBB5, IRBB14, IRBB21 and IRBB24, and a highly susceptible cultivar Jingang 30, the 69 strains  were classified into 13 pathotypes. The predominant pathotype was C6 (26.1%). No relationships were observed between UPGMA groups (BOX and ERIC) of the 69 strains and pathotypes, but each group was partially associated with the regional origin of strains.

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Comparison of Sublethal Effects of Chlorpyrifos on Resistant and Susceptible   Populations of  Laodelphax striatellus  WANG Lihua, ZHANG Yueliang, GUO Huifang, FANG Jichao* 2011, 25(5): 529-534.  DOI: 10.3969/j.issn.1001-7216.2011.05.012 Abstract ( )   PDF (372KB) ( )   In order to study the sublethal effect of chlorpyrifos on   resistant and susceptible Laodelphax striatellus populations,   life parameters  of L. striatellus  were analyzed by construction of   life tables. The results showed that the population development of the resistant or susceptible strain  was significantly inhibited by the sublethal doses of chlorpyrifos (LC14). Compared with that of  the untreated populations, nymph mortality was significantly increased, developmental duration extended, adult longevity shortened, fecundity declined, and  the intrinsic growth rate and relative fitness decreased in chlorpyrifos treated populations. Moreover, fecundity decline of the resistant strains(1989%) was significantly lower than that of the susceptible strain (39.29%) and relative fitness decrease of the resistant strain(24%) was significantly lower than that of the susseptible strain(48%) after treated with  LC14 of chlorpyrifos,  implying  the less  inhibition of chlorpyrifos on the resistant strain than  on the susceptible strain.

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Effect   and Simulation of Plant Type on Canopy Structure and Radiation Transmission in Rice HU Ning1, YAO Kemin1, ZHANG Xiaocui2, LU Chuangen3,* 2011, 25(5): 535-543.  DOI: 10.3969/j.issn.10017216.2011.05.013 Abstract ( )   PDF (1553KB) ( )   By using three rice hybrids with  typical plant types as  materials, and changing their morphology of uppermost two leaves through  N fertilizer application   during the elongation of   the two leaves, relationships among plant type factor, layered leaf area and radiation transmission were determined at the full heading stage, 10 and 25 days after full heading, respectively. A model for calculating  the layered leaf area by plant type factors was established and validated, and were subjected to analyze  the effects of plant type factors on layered leaf area of  the three hybrids. Furthermore,    the relationship between layered leaf area and radiation transmission was validated using a light distribution model for plant canopy radiation transmission, and the effects of plant type factors on radiation transmission for the three hybrids were conducted  by  this  model. Thus,  a method for calculating canopy structure (layered leaf area index) and radiation transmission  was established by plant type factors in rice.

Reviews and Special Topics

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Current Situation and Suggestions  for Development of TwoLine Hybrid Rice in China SI Huamin, LIU Wenzhen, FU Yaping, SUN Zongxiu, HU Guocheng* 2011, 25(5): 544-552.  DOI: 10.3969/j.issn.10017216.2011.05.014 Abstract ( )   PDF (891KB) ( )   Great progress  has made in  Twoline hybrid rice breeding in China. Up to 2010, a total of 427 twoline hybrid combinations were registered in China. Among them, 62 were nationally registered and   titled  as “super rice” by the Ministry of Agriculture, China. From 1993 to 2009, there were 121 combinations with the  planting area over 6 700 hm2, and the total planting area reached 20.974 million hm2. With the  planting area of   825×105 hm2 in 2002,  Liangyoupeijiu  ranked   first among all hybrid combinations  in planting area. In the following 7 years, twoline hybrid combination ranked first  for 6 years, and second for one year. In recent years, twoline hybrid rice  has become an important type in rice production in China, accounting for about 20% of the total planting area of hybrid rice. The current situation of the development of twoline hybrid rice was introduced, the main problems were discussed and the suggestions were proposed.

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Physiological and Ecological Characteristics and Cultivation Regulation for High and Stable  Yield of Super   Hybrid Rice AI Zhiyong1,2, MA Guohui1, QING Xianguo2，3,* 2011, 25(5): 553-560.  DOI: 10.3969/j.issn.10017216.2011.05.015 Abstract ( )   PDF (473KB) ( )   The research progress was summarized in high yielding physiology of super hybrid rice in recent years. Compared with conventional high yielding rice, bigger sink capacity, more dry matter production and accumulation, higher photosynthetic rate，stronger root system served as super high yielding base for super hybrid rice. However, super hybrid rice was characterized by more nutrition absorption, more nutritional need at middle and late growth stages, more obvious asynchronism in grain filling between superior and inferior spikelets and more restricted ecological adaptation, putting forward a lot of new requirements in cultivation and regulation techniques for high and stable yield. Therefore, these cultivation and regulation techniques should be adopted in production of super hybrids, including planting according to variety and local ecological conditions, sowing at the most fitting time, proper addition of fertilizer application, relative enhancement of fertilizer ratio at booting and grain filling stages, constructing a steady and healthy population, and combing planting density increase for more panicle with controlling tiller number for more productive panicle. At the same time, several problems consist in large area of production, such as weak yield stability, lodging in super highyielding field, difficulties in coordination between high yield and high efficiency, climate change and so on. In order to reply to and solve these problems mentioned above, the research emphases in future should be focused on following cultivation and regulation technique as ecological adaptability, lodgingresistance, high efficiency, and climate change adaptation.

Short Communications

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QTL Analysis on Apical Spikelet Abortion in Rice WANG Bin1, LIU Hemei2, MAO Bigang3, GAO Suwei3, XU Hongbin1, GE Jiangui1,* 2011, 25(5): 561-564.  DOI: 10.3969/j.issn.10017216.2011.05.016 Abstract ( )   PDF (782KB) ( )   Quantitative trait loci (QTL) analysis on  abortion of apical spikelet was conducted  by using recombinant inbred lines (RILs)  derived from a cross between  indica variety Guichao 2 and Koshihikari   under three environments. The abortion trait of apical spikelets in the recombinant inbred lines demonstrated a continuous distribution together with transgressive segregations. Six QTLs were  mapped on  the  chromosomes 1,2,3,5,6 and 7  in RIL populations,  explaining 4.49% -9.74% phenotypic variations. Among these QTLs, qASA2 was detected  at  the interval flanked by the markers RM3355 and RM263 on  chromosome 2 under  different environments.  qASA1  was mapped between the markers RM6451 and OSR13 on chromosome 1   with its  positive alleles     from Guichao 2.

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Construction of Database for Chinese Rice Varieties and Their Genealogy E Zhiguo1, WANG Lei1,2,* 2011, 25(5): 565-566.  DOI: 10.3969/j.issn.10017216.2011.05.017 Abstract ( )   PDF (372KB) ( )   The database for Chinese rice varieties and their genealogy(http://www.ricedata.cn/variety/) is an important subplatform of the Chinese National Rice Data Center (http://www.ricedata.cn/), which collects different kinds of Chinese rice varieties, including  approved in provinces or by national committee, utilized in  wider areas, introduced or local. Retrieval for rice variety and pedigree search were developed as two core components of the database. During the collection  of the varieties and their pedigrees, a typical problem is that some names of varieties were confused or mistaken easily.