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28 March 2008, Volume 15 Issue 1 Previous Issue    Next Issue
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Research Paper

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Fine Mapping of C (Chromogen for Anthocyanin) Gene in Rice FAN Fang-jun, FAN Ye-yang, DU Jing-hong, ZHUANG Jie-yun 2008, 15(1): 1-6 .  Abstract ( )   PDF   Seven residual heterozygous lines (RHLs) displaying different genotypic compositions in the genomic region covering probable locations of C (Chromogen for anthocyanin) gene on the short arm of rice chromosome 6 were selected from the progenies of the indica cross Zhenshan 97B/Milyang 46. Seeds were harvested from each of the seven plants, and the resultant F2:3 populations were used for fine mapping of C gene. It was shown in the populations that the apiculus coloration matched to basal leaf sheath coloration in each plant. By relating the coloration performances of the populations with the genotypic compositions of the RHLs, the C locus was located between rice SSR markers RM314 and RM253. By using a total of 1279 F2:3 individuals from two populations showing coloration segregation, the C locus was then located between RM111 and RM253, with genetic distances of 0.7 cM to RM111 and 0.4 cM to RM253. Twenty-two recombinants found in the two populations were assayed with seven more markers located between RM111 and RM253, including six SSR markers and one marker for the C gene candidate, OsC1. The C locus was delimited to a 59.3-kb region in which OsC1 was located.

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Genetic Analysis and Molecular Mapping of a Novel Chlorophyll-Deficit Mutant Gene in Rice HUANG Xiao-qun, WANG Ping-rong, ZHAO Hai-xin, DENG Xiao-jian, 2008, 15(1): 7-12 .  Abstract ( )   PDF   A rice etiolation mutant 824ys featured with chlorophyll deficiency was identified from a normal green rice variety 824B. It showed whole green-yellow plant from the seedling stage, reduced number of tillers and longer growth duration. The contents of chlorophyll, chlorophyll a, chlorophyll b and net photosynthetic rate in leaves of the mutant obviously decreased, as well as the number of spikelets per panicle, seed setting rate and 1000-grain weight compared with its wild-type parent. Genetic analyses on F1 and F2 generations of 824ys crossed with three normal green varieties showed that the chlorophyll-deficit mutant character was controlled by a pair of recessive nuclear gene. Genetic mapping of the mutant gene was conducted by using microsatellite markers and F2 mapping population of 495R/824ys, and the mutant gene of 824ys was mapped on the short arm of rice chromosome 3. The genetic distances from the target gene to the markers RM218, RM282 and RM6959 were 25.6 cM, 5.2 cM and 21.8 cM, respectively. It was considered to be a new chlorophyll-deficit mutant gene and tentatively named as chl11(t).

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ISSR Analysis on Genetic Diversity of the 34 Populations of Oryza meyeriana Distributing in Yunnan Province, China WAN Ya-tao, A Xin-xiang, FAN Chuan-zhang, XU Fu-rong, YU Teng-qiong, TANG Cui-feng, DAI Lu-yuan, 2008, 15(1): 13-20 .  Abstract ( )   PDF   The genetic diversity of the 34 populations of wild rice Oryza meyeriana Baill. distributed in Yunnan Province, China was analyzed using 13 inter-simple sequence repeat (ISSR) markers. A total of 168 bands were amplified, of which 135 polymorphic bands were discovered and the percentage of polymorphic bands (PPB) was 80.36%. A genetic diversity was revealed as Nei's gene diversity (H) = 0.2666 and Shannon information index (I) = 0.4028 at population level. The 34 populations were divided into different groups based on administrative regions, latitude and longitudes, river areas, altitudes of their origins, and their indexes such as Na (number of alleles), Ne (effective number of alleles), H, I and PPB were calculated. Richer genetic diversity was found in the wild rice populations distributed in Simao Prefecture than that in Lingcang Prefecture or Xishuangbanna Prefecture whereas the least genetic diversity was in Baoshan Prefecture or Dehong Prefecture. Rich genetic diversity was also discovered in the wild rice populations originated from higher than 710 m altitude around the middle and lower reaches of the Lancang River belonging to the Pacific Ocean drainage system. The 34 populations could be classified into two groups, one group covered the wild rice distributing in Simao Prefecture only while the other group covered ones in Lingcang, Xishuangbanna and Dehong Prefectures. The issue on how to effectively conserve the wild rice germplasm was discussed.

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Identification and Genetic Analysis of Fertility Restoration Ability in Dongxiang Wild Rice (Oryza rufipogon) CHEN Xiao-rong, YANG Kong-song, FU Jun-ru, ZHU Chang-lan, PENG Xiao-song, HE Xiao-peng, HE Hao-hua 2008, 15(1): 21-28 .  Abstract ( )   PDF   Two populations of Dongxiang wild rice (Oryza rufipogon), Shuitaoshu and Dongtangshang, were crossed with five male sterile rice lines with different cytoplasmic backgrounds (B06S, Zhenshan 97A, Xieqingzao A, Zhong 9A, and Yuetai A), and the seed setting rate of the F1 was used to judge the fertility restoration ability in the Dongxiang wild rice. With P1, F1, P2, and F2 populations as materials, the Akaike’s Information Criterion (AIC) was used to identify the major genes affecting quantitative traits, and when the major genes existed, the genetic effects of the major gene and the polygene and their genetic variance were estimated through segregation analysis. The seed setting rates of the F1 generation varied from 45.98% to 76.57%, suggesting that the Dongxiang wild rice had the fertility restoration ability. One major gene plus polygene mixed inheritance model was the most fitted genetic model for this trait in all the F2 populations. The heritability values of the major genes varied from 56.63% to 88.29% and those of the polygenes from 2.74% to 30.97%, and the total heritability values were from 63.17% to 94.01%. The major gene inheritance of the combination Zhong 9A/Dongtangshang was controlled by the additive effect without dominant effect, and the other nine combinations were by the completely dominant inheritance.

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Discovery of and Preliminary studies on a Rapid-Leafing Rice Genotype at the Vegetative Growth Stage MAO Hai-yan, PAN Cun-hong, CHEN Zong-xiang, ZHANG Ya-fang, ZUO Shi-min, CHENG Jin-rong, PAN Xue-biao 2008, 15(1): 29-35 .  Abstract ( )   PDF   The leafing rates of fourteen rice varieties were measured in a sowing-time experiment, and a rapid leafing genotype at the vegetative growth stage was discovered in an indica variety Yanhui 559. The leaf number on the main culm of Yanhui 559 was always 4–5 leaves more than that of Lemont, and the leafing rate of Yanhui 559 was significantly higher than that of Lemont based on similar growth durations from sowing to heading. Furthermore, the difference of the leafing rate was significant at the vegetative growth stage, but not distinctive at the panicle initiation stage. Genetic analysis of the leafing rates in the two backcross populations of Yanhui 559 and Lemont showed that major and quantitative genes controlled the expression of rapid leafing character. Based on results of investigation for some plants with similar growth durations in the backcrossing populations, the rapid leafing genotypes exhibited earlier tillering and more tiller numbers per plant, and its yield components including the number of panicles per plant and number of grains per panicle were superior to those of the slow leafing genotypes. Further research and application feasibility of the rapid leafing genotype in breeding were discussed.

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Evaluation of Rice Germplasm for Resistance to the Small Brown Planthopper (Laodelphax striatellus) and Analysis of Resistance Mechanism DUAN Can-xing, ZHANG Shi-xian, LEI Cai-lin, CHENG Zhi-jun, CHEN Qing, ZHAI Hu-qu, WAN Jian-min 2008, 15(1): 36-42 .  Abstract ( )   PDF   One hundred and thirty-eight rice accessions were screened for resistance to the small brown planthopper (SBPH) (Laodelphax striatellus Fallén) by the modified seedbox screening test. Twenty-five rice accessions with different levels of resistance to SBPH were detected, accounting for 18.1% of the total accessions, which included 2 highly resistant, 9 resistant and 14 moderately resistant varieties. Compared with indica rice, japonica rice was more susceptible to SBPH. Antixenosis test, antibiosis test and correlation analysis were performed to elucidate the resistance mechanism. The resistant check Rathu Heenati (RHT), highly resistant varieties Mudgo and Kasalath, and resistant variety IR36 expressed strong antixenosis and antibiosis against SBPH, indicating the close relationship between resistance level and these two resistance mechanisms in the four rice varieties. Antibiosis was the dominant resistance pattern in the resistant varieties Daorenqiao and Yangmaogu due to their high antibiosis but low antixenosis. Dular, ASD7 and Milyang 23 had relatively strong antixenosis and antibiosis, indicating the two resistance mechanisms were significant in these three varieties. The resistant DV85 expressed relatively high level of antixenosis but low antibiosis, whereas Zhaiyeqing 8 and Guiyigu conferred only moderate antibiosis and antixenosis to SBPH, suggesting tolerance in these three varieties. Antibiosis and antixenosis governed the resistance to SBPH in the moderately resistant accession 9311. Antixenosis was the main resistance type in V20A. Tolerance was considered to be an important resistance mechanism in Minghui 63 and Yangjing 9538 due to their poor antibiosis and antixenosis resistance. The above accessions with strong antibiosis or antixenosis were the ideal materials for the resistance breeding.

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Optimization of Electroporation Parameters for Immature Embryos of indica Rice (Oryza sativa) REN Yu-jun, ZHAO Jie 2008, 15(1): 43-50 .  Abstract ( )   PDF   To obtain a suitable condition for electroporation transformation in indica rice, the 10-day-old immature embryos were selected for optimization experiments. The results showed that one pulse at 850 V/cm, 950 µF capacitance, 200 µL electroporation buffer with 70 mmol/L sodium glutamate, 100 µg/mL plasmid, 50 µg/mL carrier DNA, 20 embryos per cuvette, 0°C treatment and CC medium were the best parameters, which not only improved the transformation efficiency to 30.89%, but also ameliorated the embryo survival ratio to 95.92%. To further verify the practicability of this condition, the embryos from another indica rice variety and a rice type II metallothionein-like gene (OsMT2bL) promoter::mgfp5::gusA construct were tested, and specific GUS expression on the embryos was visualized by histochemical staining. The results showed that the GUS expression on the embryos activated by the OsMT2bL promoter was mainly concentrated on the apical point of the plumule whereas the expression driven by CaMV35S promoter was distributed on nearly all areas of the electroporated tissues. These results indicated that the optimized embryo electroporation conditions could be used not only in genetic transformation of indica rice but also in assay of gene regulation on embryos.

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Evaluation and Application of Two High-Iron Transgenic Rice Lines Expressing a Pea Ferritin Gene YE Hong-xia, LI Mei, GUO Ze-jian, SHU Qing-yao, XU Xiao-hui, BAO Jin-song, SHEN Sheng-quan 2008, 15(1): 51-56 .  Abstract ( )   PDF   A total of 105 transgenic rice lines independently transformed with a pea ferritin gene (Fer) were previously obtained. After seven generations of selfing and β-glucuronidase (GUS) assisted selection, 82 transgenic lines with stable agronomic traits were got. Among the 82 transgenic lines, two high-iron transgenic rice lines Fer34 and Fer65, with the iron contents in the milled rice being 4.82 and 3.46 times of that of the wild type Xiushui 11, respectively were identified. In the two transgenic lines, the exogenous Fer gene was highly expressed, and inherited as a single locus. The transgene had no negative effect on the agronomic traits of rice plant, other mineral nutritional components, appearance quality and eating quality of the milled rice, indicating that these two lines were elite high-iron breeding lines. Furthermore, the practical application and further studies facilitating utilization of the two elite breeding lines were discussed.

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Effects of Nitrogen Application Time on Caryopsis Development and Grain Quality of Rice Variety Yangdao 6 XIONG Fei, WANG Zhong, GU Yun-jie, CHEN Gang, ZHOU Peng 2008, 15(1): 57-62 .  Abstract ( )   PDF   A pot experiment was conducted to study the effects of different nitrogen application time (during the tillering or the booting stages) with the same nitrogen rates on the caryopsis development and grain quality of rice variety Yangdao 6. The increased nitrogen fertilizer (urea), especially applied during the booting stage, could evidently increase the milled rice rate, head rice rate and protein content in rice grains compared with the control (no nitrogen application), and decrease chalky grain rate and amylose content. Moreover, the increased nitrogen fertilizer significantly affected the caryopsis development and enhanced the grain weight when nitrogen applied during the tillering and the booting stages, especially during the booting stage. During caryopsis development the increased nitrogen fertilizer applied during the tillering and booting stages could obviously decrease the total starch and amylose contents, but not obviously for the amylopectin content in rice grain. Increased topdressing of nitrogen fertilizer, especially applied during the booting stage, had significant effect on the development and structures of amyloplasts and proteinoplasts. That is, it could change the distribution, number and shape of amyloplasts and proteinoplasts in the endosperm cells especially in grain abdomen. Compared with the control the arrangements of amyloplasts and proteinoplasts were closer, with more numbers, higher density and less interspaces each ohter. Furthermore, most amyloplasts showed polyhedron under the increased nitrogen fertilizer level.

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Protective Roles of Brassinolide on Rice Seedlings under High Temperature Stress CAO Yun-ying, ZHAO Hua 2008, 15(1): 63-68 .  Abstract ( )   PDF   Two indica rice (Oryza sativa L.) materials, Xieqingzao B (sensitive to heat stress) and 082 (tolerant to heat stress), were used to study the role of brassinolide (BR) in protection of rice seedlings from heat stress. Young seedlings were subjected to high temperature (38˚C/30˚C) and sprayed with 0.005 mg/L of BR. Analysis was conducted on the contents of chlorophyll, protein and malondialdehyde (MDA), the leakage of electrolyte, the activities of peroxidase (POD) and superoxide dismutase (SOD) and their isozymes expression levels in leaves. Under the high temperature treatment, application of BR significantly increased the contents of chlorophyll and protein, and the activities of POD and SOD, and reduced the content of MDA and the leakage of electrolyte in the leaves of the heat-sensitive material Xieqingzao B, whereas BR had less effect on those of the heat-tolerant material 082 relatively. The BR treatment enhanced the expression of POD isozymes in the leaves of both materials. Under the high temperature stress and BR treatment, the expression of four SOD isozymes reduced in 082, but the expression of two SOD isozymes increased in Xieqingzao B. This suggests that BR plays an important role in protection of rice seedlings from heat stress by enhancing the activities or expression level of protective enzymes in the leaves. The materials with various heat-tolerance might differ in the mechanism of response to heat stress with BR application.

Short Communication

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Accurate Measurement of Pasting Temperature by the Rapid Visco-Analyser: a Case Study Using Rice Flour BAO Jin-song 2008, 15(1): 69-72 .  Abstract ( )   PDF   Pasting properties are among the most important characteristics of starch, determining its applications in food processing and other industries. Pasting temperature derived from the Rapid Visco-analyser (RVA) (Newport Scientific), in most cases, is overestimated by the Thermocline for Windows software program. Here, two methods facilitating accurate measurement of pasting temperature by RVA were described. One is to change parameter setting to ‘screen’ the true point where the pasting viscosity begins to increase, the other is to manually record the time (T1) when the pasting viscosity begins to increase and calculate the pasting temperature with the formula of (45/3.8)×(T1–1)+50 for rice flour. The latter method gave a manually determined pasting temperature which was significantly correlated with the gelatinization temperature measured by differential scanning calorimetry.

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Response of Glutathione and Glutathione S-transferase in Rice Seedlings Exposed to Cadmium Stress ZHANG Chun-hua , GE Ying 2008, 15(1): 73-76 .  Abstract ( )   PDF   A hydroponic culture experiment was done to investigate the effect of Cd stress on glutathione content (GSH) and glutathione S-transferase (GST, EC 2.5.1.18) activity in rice seedlings. The rice growth was severely inhibited when Cd level in the solution was higher than 10 mg/L. In rice shoots, GSH content and GST activity increased with the increasing Cd level, while in roots, GST was obviously inhibited by Cd treatments. Compared with shoots, the rice roots had higher GSH content and GST activity, indicating the ability of Cd detoxification was much higher in roots than in shoots. There was a significant correlation between Cd level and GSH content or GST activity, suggesting that both parameters may be used as biomarkers of Cd stress in rice.