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28 June 2010, Volume 17 Issue 2 Previous Issue    Next Issue
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Breeding Methodology and Practice of Super Rice in China CAO Li-yong, ZHAN Xiao-deng, CHEN Shen-guang, FENG Yue, WU Wei-ming, SHEN Xi-hong, CHENG Shi-hua 2010, 17(2): 87-93 .  DOI: 10.1016/S1672-6308(08)60109-2 Abstract ( )   PDF   To meet the growing demand for rice production, the Ministry of Agriculture, P. R. China initiated a nationwide project on the development of super rice in 1996. Through efforts in research, super rice breeding in China has gained significant advances in the aspects of breeding theories, creation of breeding materials and selection and promotion of elite rice varieties. A creative super rice breeding path of the construction of harmonious plant type combined with the utilization of heterosis was proposed. Super rice plays more and more important roles in rice production. Totally, 71 super rice varieties in China have been successfully developed and released to production. These varieties have 12 t/hm2 yield potential in on-farm demonstration fields, 8% to 15% higher than the check varieties with high resistance to pest and medium to high level of grain quality, the total growing area of which has reached 23.7 million hectares, and rice grain production increased by 17.7 million tons from 1996 to 2009. This paper reviewed the development and achievements of super rice breeding in aspects of the breeding methodology and breeding practices, summarized the successful experience of super rice breeding in China and proposed the developmental strategies of super rice for the future.

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On Significance of Heterotic Group Theory in Hybrid Rice Breeding Lu Zuo-mei: Xu Bao-qin, 2010, 17(2): 94-98 .  DOI: 10.1016/S1672-6308(08)60110-9 Abstract ( )   PDF   Heterotic group theory (HGT) has played a major role in supporting hybrid maize breeding for about 100 years. The basic content and studies of HGT, and its application in rice and maize were summarized in this paper. Additionally, difficulties and challenges for hybrid rice breeding in China were analyzed, and necessity and urgency in hybrid rice breeding by using HGT were proposed.

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Dissection of QTLs for Hull Silicon Content on the Short Arm of Rice Chromosome 6 WU Ji-rong, FAN Fang-jun, DU Jing-hong, FAN Ye-yang, ZHUANG Jie-yun 2010, 17(2): 99-104 .  DOI: 10.1016/S1672-6308(08)60111-0 Abstract ( )   PDF   The QTL qHUS6 for hull silicon content in rice was previously located on the short arm of rice chromosome 6. By using an F2:3 population segregating in the RM587–RM19784 region harboring qHUS6 in an isogenic background, two QTLs for hull silicon content were detected, of which qHUS6-1 was located in the distal region and qHUS6-2 in the region proximal to the centromere. Three rice plants carrying small heterozygous segments in the target region were selected, of which two covered the qHUS6-1 region and the other covered the qHUS6-2 region. Three F2:3 populations were derived from the selfed seeds of the three plants, respectively. QTL mapping was performed using the two populations segregating in the qHUS6-1 region, and qHUS6-1 was delimited to a 147.0-kb region flanked by the markers RM510 and RM19417. Five groups of F3 lines with different genotypic compositions in the qHUS6-2 region were selected from the other F2:3 population. Two QTLs were separated with two-way ANOVA, of which qHUS6-2a was located in the interval defined by RM19706–RM19795 and qHUS6-2b in the interval RM314–RM19665.

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Inheritance of Rice Seed Germination Ability under Salt Stress WANG Zhou-fei, WANG Jian-fei, BAO Yong-mei, WU Yun-yu, SU Xuan, ZHANG Hong-sheng 2010, 17(2): 105-110 .  DOI: 10.1016/S1672-6308(08)60112-2 Abstract ( )   PDF   A population of recombinant inbred lines (RILs, F2:9), derived from a cross between IR26 (Oryza sativa subsp. indica) and Jiucaiqing (Oryza sativa subsp. japonica), was used to identify seed germination ability of rice under 100 mmol/L NaCl for 10 days. Six germination traits including imbibition rate, germination rate, germination index, root length, shoot length and vigor index were investigated. A mixed major gene and polygene inheritance model was applied to conduct genetic analysis for germination ability. Significant differences were detected in all the germination traits under salt stress among RILs in rice, and the early germination stage (0–5 days) might be the salt sensitive stage. The frequency distributions of the germination traits under salt stress in the RIL population showed continuous segregation, suggesting that they were quantitative traits controlled by several genes. The germination traits under salt stress were regulated by two or three major genes plus polygene, and mainly dominated by major genes with high heritability values, accounting for 12.5%–99.0% of the total phenotypic variation. Each trait was controlled by the specific genetic model: imbibition rate was controlled by two major genes, germination index and vigor index by two major genes plus polygene, germination rate and shoot length by three major genes plus polygene, and root length by two major genes or two major genes plus polygene.

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Cluster Analysis on Japonica Rice (Oryza sativa L.) with Good Eating Quality Based on SSR Markers and Phenotypic Traits ZHANG Chun-hong, LI Jin-zhou, ZHU Zhen, ZHANG Ya-dong, ZHAO Ling, WANG Cai-lin 2010, 17(2): 111-121 .  DOI: 10.1016/S1672-6308(08)60113-4 Abstract ( )   PDF   Diversity of 60 conventional japonica rice accessions with good eating quality at home and abroad was analyzed using SSR molecular markers, agronomic traits and taste characteristics. A total of 290 alleles were detected in the 60 accessions at 72 SSR loci with the high similarity coefficients varying between 0.600 and 0.924. The loci on chromosome 5 showed the greatest value in average allele number. Additionally, most of the SSR loci could detect 3 to 4 alleles. An UPGMA dendrogram based on the cluster analysis of the genetic similarity coefficients showed that the grouping trend of part of the rice accessions was geographic-related and most of the rice accessions in Jiangsu Province, China were clustered together. Furthermore, many domestic accessions from south and north origins in China were close to the foreign japonica rice varieties, as proved by their pedigree origin from the foreign high-quality sources. For taste characteristics, part of the accessions with excellent taste were clearly clustered into one category though they came from different geographical regions, which indicates that taste characteristics of some varieties were mainly genetically determined. In addition, the agronomic traits of japonica rice with good taste might be closely related with their geographical origins, but the relationship between superior taste characteristics and agronomic traits should be further clarified.

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Characterization of Agro-diversity by Seed Storage Protein Electrophoresis: Focus on Rice Germplasm from Uttarakhand Himalaya, India Arun JUGRAN, Indra D. BHATT, Ranbeer S. RAWAL 2010, 17(2): 122-128 .  DOI: 10.1016/S1672-6308(08)60114-6 Abstract ( )   PDF   The characteristics of 48 rice varieties from Uttarakhand Himalaya, India were detected by morphological and biochemical markers. The grains of the selected rice varieties varied in their morphological (grain length, grain width and grain weight) and biochemical characters (sodium dodecyl sulfate polyacrylamide gel electrophoresis, SDS-PAGE). Based on the presence of 70, 65, 60, 57, 37–39, 22–23, 13 and 10 kDa protein bands in the 48 rice varieties, seven types of profiles were identified. An unweighted pair group average method with arithmetic mean (UPGMA) dendrogram based on cluster analysis of genetic similarity of the protein bands showed two distinct groups with 1%–78% similarity coefficients. The presence of characteristic bands in selected varieties is a useful parameter for identification of rice germplasm.

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Isolation of Gene Mutation from a Pathogenicity-Enhanced Mutant of Magnaporthe oryzae WU Xiao-yan, WANG Jiao-yu, ZHANG Zhen, JING Jin-xue, DU Xin-fa, CHAI Rong-yao, MAO Xue-qin, QIU Hai-ping, JIANG Hua, WANG Yan-li, SUN Guo-chang 2010, 17(2): 129-134 .  DOI: 10.1016/S1672-6308(08)60115-8 Abstract ( )   PDF   To find new genes involved in fungal pathogenicity, a mutant (B11) exhibiting enhanced pathogenicity was isolated from an Agrobacterium-mediated transformed Magnaporthe oryzae mutant library. Southern blotting analysis showed that T-DNA insertion in the B11 genome was a single copy. TAIL-PCR and sequence alignment analyses revealed that a putative gene locus MG01679 was interrupted by the T-DNA fragment. By using the PCR-based method, the DNA and cDNA of the mutant gene MG01679 was cloned and sequenced. The open reading frame of MG01679 includes one intron and two exons, and the coding sequence is 696 bp in length and encodes a 231 amino acid peptide. Protein similarity analysis indicated that the gene belongs to the ThiJ/Pfp I protein family, and the gene was thus designated MgThiJ1. MgThiJ1 showed 57% similarity to FOXG_09029 from Fusarium oxysporum and 54% similarity to FGSG_08979 from F. graminearum in protein sequence. MgThiJ1 gene might act as a negative regulator in vegetative growth and pathogenesis in filamentous fungi, and its specific mechanism needs to be studied further.

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Induced Effects of Exogenous Phenolic Acids on Allelopathy of a Wild Rice Accession (Oryza longistaminata, S37) XU Gao-feng, ZHANG Fu-dou, LI Tian-lin, WU Di, ZHANG Yu-hua 2010, 17(2): 134-140 .  DOI: 10.1016/S1672-6308(08)60116-X Abstract ( )   PDF   Four exogenous phenolic acids, including salicylic acid, fumalic acid, p-coumaric acid and p-hydroxybenzonic acid, were used to investigate the regulatory effects on allelopathy of a wild rice accession of S37 (Oryza longistaminata), which is a known allelopathic rice. The four exogenous phenolic acids induced the enhancement of the allelopathic potential of wild rice S37 in target weeds though the weed-suppressive activities were low, and the inducible effects were dependent on the specific phenolic acid, concentration and treatment time. After foliar application of exogenous phenolic acids, the inhibition rates for plant height, root length and fresh weight of barnyard grass (Echinochloa crus-galli) were significantly higher than those of the control. Especially at the concentration of 100 mg/L, the inhibition rates for plant height and fresh weight of barnyard grass by fumalic acid were 38.12% and 26.31% higher than those of the control, showing that fumalic acid was more effective compared with other phenolic acids in inhibiting monocotyledon weed growth. Furthermore, the weed- suppressive activity of aqueous extract from the leaves of wild rice S37 treated with exogenous phenolic acids was increased, and it peaked at 48 h after the treatment with the aqueous extract, and then gradually declined.

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Growth Characteristics and Yield of Late-Season Rice under No-tillage and Non-flooded Cultivation with Straw Mulching WANG Dong, LI Hui-xin, QIN Jiang-tao, LI Da-ming, HU Feng 2010, 17(2): 141-148 .  DOI: 10.1016/S1672-6308(08)60117-1 Abstract ( )   PDF   A long-term field experiment (started at 2003) was conducted to determine the effects of different rice cultivation methods on growth characteristics and grain yield of late-season rice under double-rice cropping system in seasonal drought region of southeast China (Yujiang County, Jiangxi Province). The rice cultivation methods included no-tillage and flooded rice cultivation (N-F), no-tillage and non-flooded rice cultivation with straw mulching (N-SM), and no-tillage and non-flooded rice cultivation without straw mulching (N-ZM). There was no significant difference in rice grain yield between the N-SM and N-F treatments. However, the rice grain yields in the N-SM and N-F treatments were significantly higher than that in the N-ZM treatment. The late-season rice plants in the N-SM treatment had significantly higher numbers of effective panicles and total grains per hill compared with those in the N-ZM treatment. The above-ground dry matter of late-season rice was similar between the N-SM and N-F treatments. Compared with the N-F treatment, the N-ZM and N-SM treatments significantly decreased the leaf area at the heading stage. Moreover, the N-SM treatment could significantly increase total root length and root tip number at the grain-filling stage compared with the N-ZM treatment.

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Relationships of Panicle Type Index with Subspecies Characteristics and Yield Traits in Filial Generation of Crosses between Indica and Japonica Rice XU Hai, ZHU Chun-jie, GUO Yan-hua, XU Quan, MAO Ting, CHEN Kai, WANG Jia-yu, YANG Li, ZHENG Jia-kui, XU Zheng-jin 2010, 17(2): 149-155 .  DOI: 10.1016/S1672-6308(08)60118-3 Abstract ( )   PDF   Two recombinant inbred line (RIL) populations, one derived from a cross between Zhongyouzao 8 (indica) and Toyonishiki (japonica) and the other from a cross between Qishanzhan (indica) and Akihikari (japonica), were grown in Liaoning and Sichuan Provinces, China, to study the panicle type index (PTI, the ratio of a number of node position on panicle axis where the secondary branch with the most numerous secondary branch grains is located to the number of primary branches) and its relationships with subspecies characteristics and yield traits. With continuous distribution of PTI and numerous of lines with different PTIs in the progenies, indica-japonica hybridization could be a method for breeding cultivars with ideal panicle type. PTI was significantly influenced by environments, with a significant decrease from Liaoning to Sichuan. A significantly negative correlation was found between PTI and most of subspecies characteristics. PTI varied remarkably with different subspecies types. As a whole, it showed a trend of indica (H)>indicalinous (H’)>japonicalinous (K’)>japonica (K). However, it is not appropriate to regard PTI as a parameter for subspecies classification in rice because it was recombined in the filial generations of cross between indica and japonica rice. The negative correlations were found between PTI and most of panicle characteristics, as well as yield-related traits. Based on PTI, most of lines from the two populations were middle dominant panicle type (the number of grains on the secondary branch is numerous in middle position of the panicle) and lower dominant panicle type (the number of grains on the secondary branch is numerous in lower position of the panicle and becomes less towards the top of panicle) with significant yield advantages.

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Effects of Grain Protein Content Selection on Protein Content and Key Enzyme Activity Involved in Nitrogen Metabolism in Progenies Derived from a Rice Cross HUANG Xing, JIN Zheng-xun, LI Xiao-guang, LIU Hong-liang, XU Mei-lan, ZHANG Feng-zhuan, ZHANG Zhong-chen 2010, 17(2): 156-160 .  DOI: 10.1016/S1672-6308(08)60119-5 Abstract ( )   PDF   Two japonica rice parents (Tong 769 and Xixuan 1) and their progenies, significantly different in protein content of grains, were investigated to reveal the activities of proteinase in leaves and glutamine synthetase in grains, as well as the dynamic changes of soluble protein content in grains during rice grain filling. The results showed that the parents were very similar in protein content, however, advanced lines with different protein contents in grains and varied activities of proteinase and glutamine synthetase were acquired by consecutively directional selection of the grain protein content in their progenies. Moreover, the enzyme activity and the protein content in grains exceeded their parents during grain filling. The protein content in grains was positively related with the proteinase activity, and the soluble protein content was negatively related with the glutamine synthetase activity in grains to some extent.