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28 September 2005, Volume 12 Issue 3 Previous Issue    Next Issue
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Research Paper

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Identification of QTLs for Plant Height and Its Components by Using Single Segment Substitution Lines in Rice (Oryza sativa) HE Feng-hua, XI Zhang-ying, ZENG Rui-zhen, Akshay TALUKDAR, ZHANG Gui-quan 2005, 12(3): 151-156 .  Abstract ( )   PDF (94KB) ( )   QTLs for plant height and its components on the substituted segments of fifty-two single segment substitution lines (SSSLs) in rice were identified through t-test (P≤0.001) for comparison between each SSSL and recipient parent Huajingxian 74. On the 14 substituted segments, 24 QTLs were detected, 10 for plant height, 2 for panicle length, 4 for length of the first internode from the top, 5 for length of the second internode from the top and 3 for length of the third internode from the top, respectively. All these QTLs were distributed on nine rice chromosomes except chromosomes 5, 9 and 11. The additive effect ranged from –4.08 to 3.98 cm, and the additive effect percentages varied from –19.35% to 10.43%.

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Lowering Grain Amylose Content in Backcross Offsprings of indica Rice Variety 057 by Molecular Marker-Assisted Selection ZHANG Shi-lu, NI Da-hu, YI Cheng-xin, LI Li, WANG Xiu-feng, WANG Zong-yang, YANG Jian-bo 2005, 12(3): 157-162 .  Abstract ( )   PDF (75KB) ( )   To lower the amylose content (AC) of the indica rice restorer line 057 with high AC, backcrosses were made respectively by using four indica varieties (R367, 91499, Yanhui 559, Hui 527) as low AC donor parents and 057 as the recurrent parent. A molecular marker (PCR-Acc I) was used to identify the genotypes (GG, TT and GT) of the waxy (Wx) gene. Plants with GT genotype were selected and used as female parent and crossed with 057 to advance generation. The ACs of rice grains harvested from plants with different Wx genotypes were measured and compared to analyze the efficiency of marker-assisted selection. The ACs of the rice grain, harvested from the plants of Wx genotypes GG, GT and TT, were higher than 20%, in the range of 17.7–28.5%, and less than 18%, respectively. The PCR-Acc I marker could be used for efficiently lowering the AC of 057 through backcrossing, and there were some influence of parental genetic background on the AC of rice grains with the same Wx genotype.

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Mapping a Novel Gene of Cold Tolerance at Booting Stage by Using Near-Isogenic Lines in japonica Rice SHEN Shi-quan, ZENG Ya-wen, LI Shen-chong, WEN Guo-song, PU Xiao-ying 2005, 12(3): 163-167 .  Abstract ( )   PDF (55KB) ( )   Genetic analysis showed that cold tolerance at booting stage of near-isogenic lines (NILs) of Kunmingxiaobaigu was controlled by a gene with large phenotypic variance. One hundred and sixty-four simple sequence repeats (SSR) distributed over 12 chromosomes were used to screen polymorphism between Towata (recurrent parent, RP) and near-isogenic line pool (NILP), and two SSR markers at the long arm of chromosome 5 showed polymorphism in comparison with RP genome. Of the two markers, RM31 was found possibly linked with the cold tolerance gene at booting stage through one-way ANOVA. Twelve SSR markers around RM31 were then used to detect polymorphism between RP and NIL, and only RM7452 had polymorphism. The gene of cold tolerance at booting stage was further mapped on chromosome 5 between RM7452 and RM31 with genetic distances of 4.8 cM and 8.0 cM, respectively. This gene explained 10.50% of phenotypic variance and 5.10% of phenotypic variance of fully filled grains, and was tentatively designated as Ctb(t).

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Effect of Rolled Leaf Gene Rl(t) on Grain Quality in Hybrid Rice SHAO Yuan-jian, CHEN Zong-xiang, CHEN Hong-qi, ZHANG Ya-fang, PAN Xue-biao 2005, 12(3): 168-172 .  Abstract ( )   PDF (37KB) ( )   Effects of rolled leaf gene Rl(t) on grain quality characters of hybrid rice were analyzed by using three pairs of rolled leaf near-isogenic lines under two fertilizer treatments. Under normal fertilizer level (e.g. 450 kg urea per ha), head rice rates and milled rice recovery of rolled leaf hybrids were significantly higher than those of corresponding non-rolled crosses, while the chalky rice rate and chalkiness were all lower. Of the RVA profiles, the peak viscosity, the hot paste viscosity and the breakdown viscosity of the rolled were all higher than those of the corresponding non-rolled ones to various degrees. Increasing fertilizer application for promoting panicle development increased the brown, milled and head rice rates except for Shanyou 63, furthermore, significant difference of head rice rates existed between the rolled leaf Shanyou 559 and Shanyou 559; while the peak viscosity, the hot paste viscosity and the breakdown viscosity all decreased to different levels; changes of values of other characters had no apparent regularity. It suggested that Rl(t) could improve rice quality under certain conditions.

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Small-Scale Duplications Play a Significant Role in Rice Genome Evolution GUO Xin-yi, XU Guo-hua, ZHANG Yang, HU Wei-min, FAN Long-jiang 2005, 12(3): 173-178 .  Abstract ( )   PDF (54KB) ( )   Genes are continually being created by the processes of genome duplication (ohnolog) and gene duplication (paralog). Whole-genome duplications have been found to be widespread in plant species and play an important role in plant evolution. Clearly un-overlapping duplicated blocks of whole-genome duplications can be detected in the genome of sequenced rice (Oryza sativa). Syntenic ohnolog pairs (ohnologues) of the whole-genome duplications in rice were identified based on their syntenic duplicate lines. The paralogs of ohnologues were further scanned using multi-round reciprocal BLAST best-hit searching (E<e-14). The results indicated that an average of 0.55 sister paralogs could be found for every ohnologue in rice. These results suggest that small-scale duplications, as well as whole-genome duplications, play a significant role in the two duplicated rice genomes.

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Response to High Temperature in Flag Leaves of Super High-Yielding Rice Pei’ai 64S/E32 and Liangyoupeijiu PENG Chang-lian , OU Zhi-ying , LIU Nan , LIN Gui-zhu 2005, 12(3): 179-186 .  Abstract ( )   PDF (57KB) ( )   Two newly bred hybrid rice combinations, super high-yielding Liangyoupeijiu (Pei’ai 64S×9311) and Pei’ai 64S/E32 (Pei’ai 64S×E32) were used to investigate the photosynthetic characteristics under high temperature in comparison with hybrid rice Shangyou 63. High temperature caused a decreased photosynthetic efficiency and aggravated photoinhibition. The optimum temperature for photosynthetic electron transportation and photosynthetic CO2 fixation were about 28℃ and 35–40℃ respectively. Linear electron transportation is more sensitive to high temperature than the photochemical process. The mechanism of high temperature adaptation was possibly as follows: super high-yielding rice has quickly increasing carotenoid, which acted as a more favorable antioxidant system to reduce the active oxygen production and avoid damage to the photosynthesis system; super high-yielding rice has a higher efficiency of xanthophylls cycle to dissipate excess heat energy; super high-yielding rice has a more stable photosynthetic function, higher photosynthetic efficiency and more heat stable protein content.

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Effects of Chilling Stress on Photosynthetic Rate and Chlorophyll Fluorescence Parameter in Seedlings of Two Rice Cultivars Differing in Cold Tolerance WANG Guo-li, GUO Zhen-fei 2005, 12(3): 187-191 .  Abstract ( )   PDF (57KB) ( )   A cold-tolerant cultivar, Xiangnuo 1, and a cold-sensitive cultivar, IR50, were used to study the influence of chilling on photosynthetic rate and chlorophyll fluorescence parameters in rice seedlings. The photosynthetic rates declined dramatically during chilling, and decreased by 48.7% and 67.5% in Xiangnuo 1 and IR50 seedlings, respectively, after being subjected to chilling treatment for two days. Chlorophyll fluorescence measurements showed that relatively higher qP and qNP in Xiangnuo 1 were maintained to dissipate the redundant excitation energy and protect the reaction centers from chill injury; accordingly, redundant excitation energy accumulated less in the reaction centers, and antenna systems were less injured by chilling in Xiangnuo 1. On the contrary, in IR50, qP and qNP declined rapidly while Ex increased, as the chilling persisted. This result indicated that the reaction centers and antenna systems in IR50 were damaged severely by chilling, which led to the lower photosynthetic rate.

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Rice Grain Chalkiness Is Negatively Correlated with Root Activity During Grain Filling ZHONG Xu-hua, HUANG Nong-rong 2005, 12(3): 192-196 .  Abstract ( )   PDF (40KB) ( )   Field and pot experiments were conducted using indica rice varieties with differential chalkiness. There were significant differences in root activity among the varieties. The percentages of chalky grains and chalky area were both negatively correlated with root activity expressed as α-naphthylamine oxidation ability (RA) per gram of fresh root (RAfw) , RA per spikelet (RAgrn), or RA per sink capacity (RAsink). The RAsink was more closely related to chalkiness than RAfw and RAgrn when varieties differed greatly in panicle size and grain weight. Application of NO3--N fertilizer at heading resulted in higher root activity and reduced chalkiness. Application of 30 mg/L NaN3 (respiration inhibitor) resulted in reduced root activity and increased chalkiness for one variety ‘GD9501’, but for the other variety ‘Qinluai’ was in reverse. The percentages of chalky grains and chalky area were negatively correlated with root activity at 10 days after heading under different chemical treatments (r =－0.8567* and r =－0.9211**, respectively).

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Effects of Pb Pollution on Seed Vigor of Three Rice Cultivars ZHANG Sheng, HU Jin, CHEN Zhen-hua, CHEN Jian-feng, ZHENG Yun-ye, SONG Wen-jian 2005, 12(3): 197-202 .  Abstract ( )   PDF (46KB) ( )   An experiment was conducted to study the effects of different Pb concentrations on rice seed germination and seedling growth in three cultivars (Jiayu 293, Jiayu 948 and Xieyou 963). The method of qualitative traits combining with quantitative traits by orthogonal polynomials was applied to analyze rice seed vigor by regression model. The seeds from different rice cultivars had different sensitivity to Pb poison. In the Pb concentration of 100-700 mg/L, Pb significantly decreased root length and shoot height, and the degree of the restraint would aggravate with the increasing of Pb concentration. However, Pb did not reduce root dry weight and shoot dry weight, which indicated that different physiological characteristics had different sensitive reactions to Pb. The predicting equations of regression were developed, which could be used to predict the effects of different Pb concentrations on rice seed vigor.

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Effects of Transgenic Bt Rice on the Food Consumption, Growth and Survival of Cnaphalocrocis medinalis (Guenée) Larvae LI Fang-fang , YE Gong-yin , CHEN Xue-xin , PENG Yu-fa 2005, 12(3): 202-206 .  Abstract ( )   PDF (45KB) ( )   The transgenic rice KMD1, expressing a synthetic Cry1Ab gene from Bacillus thuringiensis, showed effective resistance to the older (third- to fifth-instar) larvae of the rice leaf-folder (RLF), Cnaphalocrocis medinalis (Guenée) in laboratory bioassay. Significant declines were revealed in food consumption and growth of the older RLF nymphs fed on the cut-leaves of transgenic KMD1 plants. The increase rate of food consumption by larvae fed on KMD1 was drastically lower than those on Xiushui 11. Food consumption was varied with different instars when the larvae fed on the Bt rice. Those of fourth- and fifth-instar larvae were different compared to the third-instar, lower than those on the non-transgenic rice but still increased a little when the feeding time prolonged. It is indicated that younger RLF larvae are more sensitive to Bt rice than older ones. Also, about 81%, 78% and 68% of the third-, fourth- and fifth-instar RLF larvae died within 72 hours bioassay period on KMD1 leaves, respectively. These results demonstrated that Bt-transgene in KMD1 rice confers substantial protection against infestations with older RLF larvae.

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Geostatistical Analysis on the Temporal Patterns of the Yellow Rice Borer, Tryporyza incertulas YUAN Zhe-ming, WANG Zhi, HU Xiang-yue 2005, 12(3): 207-212 .  Abstract ( )   PDF (72KB) ( )   In order to comprehend temporal pattern of the larvae population of the yellow rice borer, Tryporyza incertulas, and provide valuable information for its forecast model, the data series of the population for each generation and the over-wintered larvae from 1960 to 1990 in Dingcheng District, Changde City, Hunan Province, were analyzed with geostatistics. The data series of total number, the 1st generation, the 3rd generation and the over-wintered larvae year to year displayed rather better autocorrelation and prediction. The data series of generation to generation, the 2nd generation and the 4th generation year to year, however, demonstrated poor autocorrelation, especially for the 4th generation, whose autocorrelation degree was zero. The population dynamics of the yellow rice borer was obviously intermittent. A remarkable cycle of four generations, one year, was observed in the population of generation to generation. Omitting the certain generation or interposing the over-wintered larvae only resulted in a less or slight change of autocorrelation of the whole data series generation to generation. Crop system, food, climate and natural enemies, therefore, played more important roles in regulating the population dynamics than base number of the larvae. The basic techniques of geostatistics applied in analyzing temporal population dynamics were outlined.

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Gram-Positive Bacteria Associated with Rice in China and Their Antagonists Against the Pathogens of Sheath Blight and Bakanae Disease in Rice LUO Jin-yan, XIE Guan-lin, LI Bin, LUO Yuan-chan, ZHAO Li-han, WANG Xiao , LIU Bo, LI Wen 2005, 12(3): 213-218 .  Abstract ( )   PDF (38KB) ( )   It is necessary to understand the bacterial populations associated with rice so as to provide more information and natural resources for effective management of major diseases in rice. A survey on screening and identification of gram-positive bacteria was conducted during 1998–2004. Seven hundred and fifty-six rice samples were collected from Zhejiang, Jiangsu, Fujian and Yunnan Provinces, China. Over 1000bacterial isolates were isolated and tested for colony morphology, pathogenicity, and some characteristics of bacteriology including Gram staining, fluorescent pigment on Kings medium B and microscopic observation for endospore. Together with five standard reference strains, 74 representative gram-positive bacterial isolates were confirmed by Biolog and gas chromatographic analysis of fatty acid methyl esters. Five bacterial species of Bacillus and other three genera were identified and isolates from Bacillus sublitis and Bacillus megaterium, exhibited the most effective inhibition against the pathogens of sheath blight and bakanae disease of rice. A few isolates from Bacillus pumilus and Bacillus megaterium showed weak virulent on rice together with some virulent isolates, risk should be considered when isolates from these species were screened for biocontrol agents.

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Status and Prospects of Hybrid Rice Breeding in Jiangsu, China WANG Cai-lin 2005, 12(3): 219-225 .  Abstract ( )   PDF (49KB) ( )   Research on hybrid rice in Jiangsu Province, China began in 1970. Great progress has been made since then, which can be divided into three stages according to the development of hybrid rice breeding and production in Jiangsu Province. The first stage was beginning stage from 1970 to 1980, when progress was mainly made in cytoplasmic male sterile line breeding. The second stage could be described as developing stage, from 1980 to 1995, when indica hybrid rice was rapidly popularized, and japonica hybrid rice became popular later. From 1996, hybrid rice breeding in Jiangsu Province entered the third stage, when both indica and japonica hybrid rice breeding in the three-line system or intersubspecific hybrid rice breeding in the two-line system made a great breakthrough with the successful breeding of the hybrids Teyou 559, 9 You 138 and Liangyoupeijiu. The developing trend of hybrid rice breeding in Jiangsu Province is also discussed.

Short Communication

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Screening for Rice Germplasms with Specially-Elongated Mesocotyl WU Ming-guo, ZHANG Guang-heng, LIN Jian-rong, CHENG Shi-hua 2005, 12(3): 226-228 .  Abstract ( )   PDF (44KB) ( )   The lengths of mesocotyl in the seedlings of 84 lowland rice varieties and 12 upland rice varieties were measured following the treatments of daylight and darkness during germination. The elongation of mesocotyl in the varieties tested was inhibited under daylight condition, and the mesocotyl of all the varieties elongated variably under darkness condition. The elongated lengths of the mesocotyl in upland rice, ranging from 0.36 cm to 1.61 cm with an average of 0.81 cm, was obviously longer than those in lowland rice, ranging from 0.12 cm to 1.56 cm with an average of 0.42 cm. Among 14 rice varieties with over 1 cm of mesocotyl length, five belonged to upland rice, and nine to lowland rice. The possible utilization of the elongated-mesocotyl rice germplasm in varietal improvement, direct-seeded planting and seed purity testing were discussed.

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Tissue Culture Responses from Different Explants of Rice WANG Xiu-hong, SHI Xiang-yuan, WU Xian-jun 2005, 12(3): 229-232 .  Abstract ( )   PDF (29KB) ( )   Different culture explants, including anther, young panicle, young embryo, and mature embryo, from 19 rice varieties were used for callus induction and green plantlet differentiation. The culture efficiency differed significantly among the four types of explants, and varied from genotype to genotype. Callus induction frequency presented significantly positive correlation each between anther and young panicle, anther and mature embryo, and young panicle and young embryo. Green plantlet differentiation showed no relationship between different types of explants. In addition, no relationship was found between callus induction frequency and green plantlet differentiation frequency.