Rice Science

Thoughts and Practice on Some Problems about Research and Application of Two-Line Hybrid Rice

CHEN Li-yun, LEI Dong-yang, TANG Wen-bang, XIAO Ying-hui

2011, 18(2): 79-85.

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The main problems about research and application of two-line hybrid rice were reviewed, including the confusing nomenclature and male sterile lines classification, the unclear characteristics of photoperiod and temperature responses and the unsuitable site selection for male sterile line and hybrid rice seed production. In order to efficiently and accurately use dual-purpose genic male sterile lines, four types, including PTGMS (photo-thermo-sensitive genic male sterile rice), TGMS (thermo-sensitive genic male sterile rice), reverse PTGMS and reverse TGMS, were proposed. A new idea for explaining the mechanism of sterility in dual-purpose hybrid rice was proposed. The transition from sterile to fertile was involved in the cooperative regulation of major-effect sterile genes and photoperiod and/or temperature sensitive ones. The minor-effect genes with accumulative effect on sterility were important factors that affected the critical temperature of sterility transfer. In order to make better use of dual-purpose lines, the characterization of responses to photoperiod and temperature of PTGMS should be made and the identification method for the characterization of photoperiod and temperature responses of PTGMS should also be put forward. The optimal ecological site for seed production could be determined according to the historical climate data and the requirements for the meteorological conditions during the different periods of seed production.

Disulphide Linkages Occur in Many Polypeptides of Rice Protein Fractions: a Two-dimensional Gel Electrophoretic Study

Arvinder SINGH, Narender K. MATTA

2011, 18(2): 86-94.

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Most of the work on rice storage proteins focused on the major fraction – glutelin. In contrast to previous reports of the occurrence of single legumin-like polypeptide pair in glutelin, two-dimensional gel electrophoresis revealed many glutelin bands, with some having and some lacking disulphide-linkages. Five legumin-like polypeptide pairs exhibited wide heterogeneity over a range of molecular weight (Mr) 25 to 60 kDa, each having a large subunit (Mr ranged from 18 to 40.5 kDa) disulphide-bonded to a small subunit (Mr ranged from 16.5 to 18.0 kDa). A band of 49 kDa was homodimeric with two subunits of 29 kDa each; a polypeptide of 51 kDa which altered position to ones corresponding to 53 kDa and 57 kDa on 2-D gels contained intrapolypeptide linkages. Polypeptides of 65 kDa and 60 kDa occurred as aggregates of 110 kDa. The number of polypeptides in other seed protein fractions albumins, globulins and prolamins, varied from four to ten. One of the albumin bands had intrapolypeptide disulphide linkages (20 kDa) and the globulins contained two such bands (13.5 and 20 kDa). Thus, the present study provides a description of the polypeptide composition of different rice protein fractions that is finely resolved with respect to the occurrence of disulphide linkages.

Monoclonal Antibody Production and Immunolocalization of a Salinity Stress-Related Protein in Rice (Oryza sativa)

Jackson MARCONDES, Ana Beatriz GARCIA

2011, 18(2): 95-101.

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Among various physiological responses to salt stress, the synthesis of a lectin-related protein of 14.5 kDa was observed in rice plants (Oryza sativa L.) under the treatment of 170 mmol/L NaCl. In order to better understand the role of the SALT protein in the physiological processes involving salinity, it was immunolocalized in mesophilic cells of leaf sheath and blade of a rice variety IAC-4440 following monoclonal antibodies produced by hybridome culture technique. This variety turned out to be an excellent model for that purpose, since it accumulates SALT protein even in absence of salt treatment and it has been classified as moderately sensitive to salinity and a superior grain producer. This feature was relevant for this work since it allowed the use of plants without the deleterious effects caused by salinity. Immunocytochemistry assays revealed that the SALT protein is located in the stroma of chloroplasts under non-stressing condition. Since the chloroplast is the main target affected by salinity and considering that the SALT protein does not present any apparent signal peptide for organelle localization, its lectin-like activity seems to play an important role in the establishment of stable complexes, either to other proteins or to oligosaccharides that are translocated to the chloroplast.

Transferring Translucent Endosperm Mutant Gene Wx-mq and Rice Stripe Disease Resistance Gene Stv-bi by Marker-Assisted Selection in Rice (Oryza sativa)

YAO Shu1, 2, CHEN Tao1, ZHANG Ya-dong1, ZHU Zhen1, ZHAO Ling1, ZHAO Qing-yong1,

2011, 18(2): 102-109.

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A high-yielding japonica rice variety, Wuyunjing 7, bred in Jiangsu Province, China as a female parent was crossed with a Japanese rice variety Kantou 194, which carries a rice stripe disease resistance gene Stv-bi and a translucent endosperm mutant gene Wx-mq. From F2 generations, a sequence characterized amplified region (SCAR) marker tightly linked with Stv-bi and a cleaved amplified polymorphic sequence (CAPS) marker for Wx-mq were used for marker-assisted selection. Finally, a new japonica rice line, Ning 9108, with excellent agronomic traits was obtained by multi-generational selection on stripe disease resistance and endosperm appearance. The utilization of the markers from genes related to rice quality and disease resistance was helpful not only for establishing a marker-assisted selection system of high-quality and disease resistance for rice but also for providing important intermediate materials and rapid selection method for good quality, disease resistance and high yield in rice breeding.

Molecular Mapping of Sterility QTLs qSS-3, qSS-6a and qSS-7 as Single Mendelian Factors via NIL strategy

LI Jing1, XU Peng1, ZHOU Jia-wu1, HU Feng-yi1, DENG Xian-neng1, CHEN Zhi-wei2, TAO Da-yun1

2011, 18(2): 110-115.

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Hybrid sterility between Oryza glaberrima and O. sativa seriously hampers the introgression of favorable genes from each other. In order to further understand this issue, identification and isolation of hybrid sterility QTLs as single Mendelian factors are an effective strategy. A genetic map was constructed using a BC1F1 population derived from a cross between an O. sativa japonica cultivar and an O. glaberrima accession. Four main-effect QTLs for pollen sterility were detected in the BC1F1. Five BC8F1 advanced backcross populations were developed via successive backcrosses based on phenotype and molecular selections. The BC8F1 populations showed bimodal distribution for pollen fertility and could be classified into semi-sterile and fertile types, fitting single Mendilian factor inheritance ratios. Three QTLs detected in the BC1F1 corresponding to qSS-3, qSS-6a and qSS-7 were mapped on chromosomes 6, 3 and 7, respectively, as single Mendilian factors.

Impeded Carbohydrate Metabolism in Rice Plants under Submergence Stress

Malay Kumar ADAK1, Nirmalya GHOSH1, Dilip Kumar DASGUPTA2, Sudha GUPTA1

2011, 18(2): 116-126.

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The detrimental effects of submergence on physiological performances of some rice varieties with special references to carbohydrate metabolisms and their allied enzymes during post-flowering stages have been documented and clarified in the present investigation. It was found that photosynthetic rate and concomitant translocation of sugars into the panicles were both related to the yield. The detrimental effects of the complete submergence were recorded in generation of sucrose, starch, sucrose phosphate synthase and phosphorylase activity in the developing panicles of the plants as compared to those under normal or control (i.e. non-submerged) condition. The accumulation of starch was significantly lower in plants under submergence and that was correlated with ADP-glucose pyrophosphorylase activity. Photosynthetic rate was most affected under submergence in varying days of post-flowering and was also related to the down regulation of Ribulose bisphosphate carboxylase activity. However, under normal or control condition, there recorded a steady maintenance of photosynthetic rate at the post-flowering stages and significantly higher values of Ribulose bisphosphate carboxylase activity. Still, photosynthetic rate of the plants under both control and submerged conditions had hardly any significant correlation with sugar accumulation and other enzymes of carbohydrate metabolism like invertase with grain yield. Finally, plants under submergence suffered significant loss of yield by poor grain filling which was related to impeded carbohydrate metabolism in the tissues. It is evident that loss of yield under submergence is attributed both by lower sink size or sink capacity (number of panicles, in this case) as well as subdued carbohydrate metabolism in plants and its subsequent partitioning into the grains.

Methods on Identification and Screening of Rice Genotypes with High Nitrogen Efficiency

CHENG Jian-feng1, JIANG Han-yan1, LIU Yi-bai1, DAI Ting-bo2, CAO Wei-xing2

2011, 18(2): 127-135.

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In order to establish methods for indentification and screening of rice genotypes with high nitrogen (N) efficiency, N absorption efficiency (NAE), N utilization efficiency (NUE) and N harvest index (NHI) in ten rice genotypes were investgated at the elongation, booting, heading and maturity stages under six N levels in a pot experiment with soil-sand mixtures at various ratios. NAE in various rice genotypes firstly increased, peaked under a medium nitrogen rate of 0.177 g/kg and then decreased, but NUE and NHI always decreased with increasing nitrogen levels. NAE in various rice genotypes ever increased with growing process and NUE indicated a descending tendency of elongation stage>heading stage>maturity stage>booting stage. N level influenced rice NAE, NUE and NHI most, followed by genotype, and the both effects were significant at 0.01 level. In addition, the interaction effects of genotype and nitrogen level on rice NAE and NUE were significant at 0.01 level, but not significant on rice NHI. Because the maximum differences of NAE and NUE were found at the elongation stage, it was thought to be the most suitable stage for identification and screening these two paremeters. Therefore, the optimum conditions for identification and screening of rice NAE, NUE and NHI in a pot experiment were the nitrogen rate of 0.157 g/kg at the elongation stage, low nitrogen at the elongation stage, and the nitrogen rate of 0.277 g/kg at the maturity stage, respectively.

Occurrence and Population Dynamics of Chironomids in Early-Season Rice Fields

LI Zhi-yu1, 2, YANG Hong1, LAI Feng-xiang2, FU Qiang2, HU Yang2

2011, 18(2): 136-141.

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The chironomid is one of the world wide distributed insects and normally occurs in a great abundance among many kinds of water bodies. Currently, our knowledge about the chironomid in rice fields is limited to the species survey, and it is considered as a group insect at the family level, termed as a kind of the neutral insects. By using the specially designed emergence traps, the species richness and the occurrence of the chironomid in rice fields were studied throughout the early season in Fuyang City, Zhejiang Province, China. There were four species, namely, Tanytarsus formosanus, Chironomus sinicus, Polypedilum nubifer and Tanypus punctipennis of chironomids collected from rice fields. All of them are widely distributed species. T. formosanus and C. sinicus were the most dominant species in rice fields. The succession of chironomids in the early season could be divided into two phases, the early and the late phases. The abundance of the chironomid was higher in the early phase than that in the late phase. It was estimated that there were around 3 million individuals of chironomids emerged from 667 m2 rice field throughout the early season. It was also found that the sex ratio of T. formosanus was female-biased during the early phase, whereas male-biased during the late phase. In contrast, the sex ratio of C. sinicus was male-biased throughout the early season.

Estimating Rice Yield by HJ-1A Satellite Images

2011, 18(2): 142-147.

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As illustrated by the case of Xuyi County, Jinhu County and Hongze County in Jiangsu Province, China, monitoring and forecasting of rice production were carried out by using HJ-1A satellite remote sensing images. The handhold GPS machines were used to measure the geographical position and some other information of these samples such as area shape. The GPS data and the interpretation marks were used to correct HJ-1 image, assist human-computer interactive interpretation, and other operations. The test data had been participated in the whole classification process. The accuracy of interpreted information on rice planting area was more than 90%. By using the leaf area index from the normalized difference vegetation index inversion, the biomass from the ratio vegetation index inversion, and combined with the rice yield estimation model, the rice yield was estimated. Further, the thematic map of rice production classification was made based on the rice yield data. According to the comparison results between measured and fitted values of yields and areas of sampling sites, the accuracy of the yield estimation was more than 85%. The results suggest that HJ-A/B images could basically meet the demand of rice growth monitoring and yield forecasting, and could be widely applied to rice production monitoring.

Retesting Early Generation Stability of a Japonica Rice Variety 84-15 by Using Allelic Differences of Two Qualitative Traits

LU Zuo-mei1, XU Bao-qin1, 2, 3, SUN Da-yun1

2011, 18(2): 148-151.

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Early generation stability of a japonica rice variety, 84-15, was retested by using the allelic differences of two qualitative traits, i.e., glume tip color and waxy endosperm. Results showed that both glume tip color and waxy endosperm segregated in progenies of single F1 plants derived from two crosses of 84-15/Zi 18 (purple color) and 84-15/Dahuaxiangnuo (waxy). The results denied the conclusion obtained in previous studies that 84-15 had a characteristic of early generation stability. Moreover, it was found that using the coefficient of variation as an indicator of early generation stability was unreasonable by analyzing plant height as an example. Importance of avoiding systematic error in research works was also discussed.

Transmission of Rice Black-Streaked Dwarf Virus from Frozen Infected Leaves to Healthy Rice Plants by Small Brown Planthopper (Laodelphax striatellus)

ZHOU Tong#, WU Li-juan#, WANG Ying, CHENG Zhao-bang, JI Ying-hua, FAN Yong-jian, ZHOU Yi-jun

2011, 18(2): 152-156.

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In order to preserve virus for identifying the resistance of rice varieties against rice black-streaked dwarf disease, a simple and reliable method was developed, through which virus-free small brown planthopper (SBPH) acquired rice black-streaked dwarf virus (RBSDV) from frozen infected leaves and the virus was transmitted to healthy rice plants. The experimental results showed that SBPH could obtain RBSDV from frozen infected rice leaves and the virus could be transmitted to a susceptible rice variety. For the ability to acquire RBSDV and transmit the virus to healthy plants by SBPH, there was no significant difference between frozen infected leaves and in vitro infected leaves. The novel method could be applied to identification of rice variety resistance to rice black-streaked dwarf disease, facilitating the breeding process for rice black-streaked dwarf disease resistance.

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