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28 March 2006, Volume 13 Issue 1 Previous Issue    Next Issue
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Review or Special Topic

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Review and Prospects on Rice Breeding and Extension in China YANG Shi-hua, CHENG Ben-yi, WU Jian-li, SHEN Wei-feng, CHENG Shi-hua 2006, 13(1): 1-8 .  Abstract ( )   PDF (91KB) ( )   A large number of new varieties, especially hybrid rice, have been developed and released in China since 1998. The yield potential and grain quality of hybrid rice have also been improved significantly both for three-line and two-line hybrid rice including indica and japonica types as well. The trends on extension of rice varieties in China since 1986 has been marked by the increasing number of new varieties, decreasing annual planting area per variety, decreasing number of varieties with a large-scale extension area, while both the renewal rate and the proportion of core varieties with cross-provincial extension have remained unchanged. This current major problems and future goals of rice breeding and extension in China were also discussed.

Research Paper

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Identification of Multiple Alleles at the Wx Locus and Development of Single Segment Substitution Lines for the Alleles in Rice ZENG Rui-zhen, ZHANG Ze-min, HE Feng-hua, XI Zhang-ying, Akshay TALUKDAR, SHI Jun-qiong, QIN Li-jun, HUANG Chao-feng, ZHANG Gui-quan 2006, 13(1): 9-14 .  Abstract ( )   PDF (122KB) ( )   The microsatellite markers 484/485 and 484/W2R were used to identify the multiple alleles at the Wx locus in rice germplasm. Fifteen alleles were identified in 278 accessions by using microsatellite class and G-T polymorphism. Among these alleles, (CT)12-G, (CT)15-G, (CT)16-G, (CT)17-G, (CT)18-G and (CT)21-G have not been reported. Seventy-two single-segment substitution lines (SSSLs) carrying different alleles at the Wx locus were developed by using Huajingxian 74 with the (CT)11-G allele as a recipient and 20 accessions containing 12 different alleles at the Wx locus as donors. The estimated length of the substituted segments ranged from 2.2 to 77.3 cM with an average of 17.4 cM.

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Development of Chromosomal Segment Substitution Lines from a Backcross Recombinant Inbred Population of Interspecific Rice Cross CHEN Jie , Hafeez Ur Rahman Bughio , Chen Da-zhou , LIU Guang-jie , Zheng Kang-le , Zhuang Jie-yun 2006, 13(1): 15-21 .  Abstract ( )   PDF (100KB) ( )   A backcross recombinant inbred line population consisting of 202 lines was developed from Xieqingzao B // Xieqingzao B / Dongxiang wild rice. The population was assayed with DNA markers and phenotyped on planthopper resistance and yield traits. A linkage map consisting of 119 DNA markers and spanned for 1188 cM over the 12 rice chromosomes was constructed. Thirty-two chromosomal segment substitution lines were selected based on the percentage of Xieqingzao B allele at marker loci. These lines are of great potential for gene mapping and alien gene introgression.

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Breeding Rice Restorer Lines with High Resistance to Bacterial Blight by Using Molecular Marker-Assisted Selection DENG Qi-ming , WANG Shi-quan , ZHENG Ai-ping , ZHANG Hong-yu , LI Ping , 2006, 13(1): 22-28 .  Abstract ( )   PDF (104KB) ( )   Two bacterial blight (BB) resistance genes, Xa21 and Xa4, from IRBB24 were introduced into hybrid rice restorer line Mianhui 725, which is highly susceptible to BB, by using hybridization and molecular marker-assisted selection technology. Four homologous restorer lines were obtained through testing the R target genes with molecular markers and analyzing parental genetic background. Inoculation of the four lines and their hybrids with the specific strains of Xanthomonas oryzae pv. oryzae, P1, P6 and seven representative strains of Chinese pathotype, CⅠ-CⅦ, showed that all of the four lines and their hybrids were highly resistant and presented broad resistance-spectrum to BB. The hybrids of G46A / R207-2 displayed good agronomic characters and high yield potential, and R207-2 was named Shuhui 207.

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Isolation and Analysis of the Promoter of OsRacD from Photoperiod Sensitive Genic Male Sterile Rice LIANG Wei-hong , WU Nai-hu 2006, 13(1): 29-33 .  Abstract ( )   PDF (104KB) ( )   By using OsRacD cDNA as probe to screen the genomic library of photoperiod sensitive genic male sterile rice line Nongken 58S, a positive clone containing 2 kb promoter and 396 bp coding region of OsRacD was obtained. Compared with the promoter of OsRacD cloned by reverse PCR from normal rice variety Nongken 58 (Nongken 58N), the homology was 99.8%, and the different nucleotides were outside the predicted response elements in promoter, suggesting that the fertility between rice varieties Nongken 58S and Nongken 58N under the long-day conditions was not attributed to the difference in the structure of OsRacD upstream regulation sequences, but to the developmental regulation of gene differential expression.

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Source-Sink and Grain-Filling Characteristics of Two-Line Hybrid Rice Yangliangyou 6 ZHAO Bu-hong , WANG Peng , ZHANG Hong-xi , ZHU Qing-sen , YANG Jian-chang 2006, 13(1): 34-42 .  Abstract ( )   PDF (107KB) ( )   With two-line hybrid rice Yangliangyou 6 (YLY6) and Liangyoupeijiu (LYPJ) and three-line hybrid rice Shanyou 63 (SY63) as materials, the source, sink and flow characteristics in association with grain filling were investigated. The seed-setting rate, grain filling degree and grain yield of YLY6 and SY63 were significantly higher than those of LYPJ. The export and transformation percentages of the matter in culms and sheaths of YLY6 and SY63 were significantly higher than those of LYPJ. Activities of sucrose synthase, adenosine diphosphoglucose pyrophosphorylase, starch synthase and starch branching enzyme in grains were higher for YLY6 and SY63 than for LYPJ, and were very significantly correlated with maximum grain filling rate, mean grain filling rate, grain filling degree and grain weight. The spikelet number, grain yield and total sink load per area of vascular bundle and phloem of YLY6 and SY63 were significantly smaller than those of LYPJ, and the greater the load, the lower seed-setting rate and the poorer grain filling. The transportation rate per area phloem of YLY6 was greater than that of LYPJ or SY63. The results suggest that YLY6 possesses strong source, great sink activity and efficient flow, which lay a physiological base for its high seed-setting rate and good grain filling.

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Relationship Between Variation in Activities of Key Enzymes Related to Starch Synthesis During Grain Filling Period and Quality of Eating and Cooking in Rice SHEN Peng, QIAN Chun-rong, JIN Zheng-xun, LUO Qiu-xiang, JIN Xue-yong 2006, 13(1): 43-50 .  Abstract ( )   PDF (47KB) ( )   Four japonica rice varieties with significant differences in quality of eating and cooking were used in the experiment. The varieties showed differences in amylose and amylopectin contents at different grain filling stages, which were attributed to the accumulative speed of starch at different grain filling stages. During grain filling period, the varieties had no difference in the time when the activities of ADPglocose pyrophosphorylase (AGPP) and soluble starch synthesis (SSS) reached a maximum, but had difference in the time when the activity of starch branching enzyme (SBE) reached a maximum, in which the inferior quality varieties were earlier than the high quality ones, and high quality varieties still kept high enzyme activities at the late stage of grain filling. The correlation and correlative degree between AGPP, SSS, SBE and amylose content, amylopectin content, taste meter value, and RVA properties varied with the different stages of grain filling. The correlation between SSS activity and taste meter value was not significant during the whole period of grain filling, but the activities of AGPP and SBE had significant or highly significant correlation with taste meter value. It was helpful for improving quality of eating and cooking of japonica rice to use the materials with low enzyme activity at the early stage of grain filling or high enzyme activity at the late stage as parents.

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Effects of Weak Light on Starch Accumulation and Starch Synthesis Enzyme Activities in Rice at the Grain Filling Stage LI Tian , Ryu OHSUGI , Tohru YAMAGISHI , Haruto SASAKI 2006, 13(1): 51-58 .  Abstract ( )   PDF (87KB) ( )   Dynamic changes of starch, amylose, sucrose contents and the activities of starch synthesis enzymes under shading treatments after flowering were studied using two rice varieties IR72 (indica) and Nipponbare (japonica) as materials. Under shading treatments, the starch,amylose and sucrose contents decreased, while ADP-glucose pyrophosphorylase (ADPGPPase) activity only changed a little, soluble starch synthase activity and granule bound starch synthase activity decreased, soluble starch branching enzyme (SSBE, Q-enzyme) activity and granule bound starch branching enzyme (GBSBE, Q-enzyme) activity increased, and starch debranching enzyme (DBE, R-enzyme) activity varied with varieties. Correlation analyses showed that the changes of starch content were positively and significantly correlated with the changes of sucrose content in the weak light. Both ADPGPPase activity and SSBE activity were positively and significantly correlated with starch accumulation rate. It was implied that the decline of starch synthase activities was related to the decrease of starch content and the increase of the activity of starch branching enzyme played an important role in the decrease of the ratio of amylose to the total starch under the weak light.

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Effects of Non-flooded Cultivation with Straw Mulching on Rice Agronomic Traits and Water Use Efficiency QIN Jiang-tao , HU Feng , LI Hui-xin , WANG Yi-ping , HUANG Fa-quan , HUANG Hua-xiang 2006, 13(1): 59-66 .  Abstract ( )   PDF (80KB) ( )   A field experiment was conducted to study water use efficiency and agronomic traits in rice cultivated in flooded soil and non-flooded soils with and without straw mulching. The total amount of water used by rice under flooded cultivation (FC) was 2.42 and 3.31 times as much as that by rice under the non-flooded cultivation with and without straw mulching, respectively. The average water seepage was 13 560 m3/ha under the flooded cultivation, 4 750 m3/ha under the non-flooded cultivation without straw mulching (ZM) and 4 680 m3/ha under non-flooded cultivation with straw mulching (SM). The evapotranspiration in the SM treatment was only 38.2% and 63.6% of the FC treatment and ZM treatment, respectively. Compared with the ZM treatment, straw mulching significantly increased leaf area per plant, main root length, gross root length and root dry weight per plant of rice. The highest grain yield under the SM treatment (6 747 kg/ ha) was close to the rice cultivated in flooded soil (6 811.5 kg / ha). However, the yield under the ZM treatment (4 716 kg/ ha) was much lower than that under the FS treatment and SM treatment. The order of water use efficiency and irrigation water use efficiency were both as follows: SM> ZM> FC.

Experimental Technique

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A Simplified Rice DNA Extraction Protocol for PCR Analysis CHEN Wen-yue , CUI Hai-rui , BAO Jin-song , ZHOU Xiang-sheng , SHU Qing-yao 2006, 13(1): 67-70 .  Abstract ( )   PDF (140KB) ( )   A simple protocol was established for DNA extraction using etiolated rice seedlings, whereby rice DNA was directly extracted in 0.5 mol/L NaOH solution in a single eppendorf tube. Results of comparative PCR analyses and electrophoresis showed that the DNA extracted using this method was as good and useful as that using standard CTAB method.

Short Communication

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SSR Marker Analysis on indica-japonica Differentiation of Natural Population of Oryza rufipogon in Yuanjiang, Yunnan Province LI Ya-li , YANG Xiao-xi , ZHAO Feng-ping , XU Ming-hui 2006, 13(1): 71-74 .  Abstract ( )   PDF (59KB) ( )   By using 19 pairs of primers that could identify two subspecies (indica and japonica) of cultivated rice (Oryza sativa L.), the indica-japonica differentiation of 56 individuals from the natural population of common wild rice (Oryza rufipogon Griff.) in Yuanjiang was analyzed by SSR (microsatellite DNAs, or simple sequence repeat). Of the 19 pairs of primers, 17 pairs (89.47%) could amplify only one kind of band type among all of the individuals, but primers RM251 and RM18 could amplify polymorphic band types. The bands amplified by 16 pairs of primers (84.21%) were identical to the indica-japonica diagnostic bands of relevant locus in cultivated rice, including 11 japonica-like loci and 4 indica-like loci. The bands amplified by the other three pairs of primers (RM18, RM202, RM205) were different from indica or japonica diagnostic bands of cultivated rice. The results showed that according to 19 loci analyzed, 84.21% of SSR loci in genomic DNA of common wild rice in Yuanjiang displayed indica-japonica differentiation and 13.79% of the loci still kept primitive, and most of the detected loci were homogenetic in the natural population.

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Content Variations of the Secondary Compounds in Rice Plants and Their Influence on Rice Resistance to Brown Planthopper, Nilaparvata lugens ZHAO Ying , TONG Xiao-li , HUANG Feng-kuan 2006, 13(1): 75-78 .  Abstract ( )   PDF (54KB) ( )   Content variations of the four components in the plants of rice ASD7, IR36 (resistant to brown planthopper) and TN1 (susceptible to brown planthopper), and their influence on rice resistance to brown planthopper (BPH, Nilaparvata lugens) were investigated. The resistance diversity of rice to BPH biotype II at different plant ages was chiefly attributed to the content variability of the secondary compounds. The contents in the leaf sheath were the lowest as compared with other parts of rice plant. It might explain the reason that BPH has a preference for feeding on leaf sheath aggregately from chemical point of view.