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28 December 2006, Volume 13 Issue 4 Previous Issue    Next Issue
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Morphogenesis, Anatomical Observation and Primary Genetic Analysis of a Multi-glume Floral Organ Mutant in Rice PAN Cun-hong , LI Ai-hong , WU Ru , ZHANG Ya-fang , TANG Wen , WU Chang-yin , ZHANG Qi-fa , PAN Xue-biao 2006, 13(4): 227-233 .  Abstract ( )   PDF (974KB) ( )   A multi-glume (mg) mutant was obtained by screening the T-DNA inserted mutant pool. Anatomical observation revealed that the florets of the mutant showed elongated leafy paleas/lemmas and palea/lemma-like structures, just like multi-glumes. Among the 215 observed florets of the mutant, 14.27% were failed to produce pistil and stamens, 23.72% showed extra floret generated on the same rachilla, while 62.01% consisted of one to nine stamens and one to three pistils in a single floret. On the other hand, in some cases the transparent bulged vesile-like tissue could be observed at the basis of filament. The mutant showed glumaceous lodicules, which prevented the florets from opening in natural conditions, while the absolute male and female sterility was an obvious character of the current mutant. Observation on the process of floral organ morphogenesis by a scanning electron microscopy (SEM) indicated that no phenotype difference in floret primordia was found between the wild-type and the mutant. Meanwhile, for the mutant, the beginning of stamen and pistil primordial differentiation was later than the wild type and the palea/lemma-like structure continued to differentiate after the formation of normal palea and lemma. Furthermore, in the mutant the asymmetrical division of floral primordial caused variation in the number of stamens and pistils. Therefore, the genetic analyses indicated that the mutation phenotype was a recessive trait controlled by a single gene and co-segregated with the T-DNA. Based on the phenotypic characteristics, it could be deduced that the mutant was the result of homeotic conversion from the function of the class E genes in ABCD model.

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Transfer of Lysozyme Gene into indica Parents of Hybrid Rice by Backcrossing YI Zi-li, WANG Zi-xuan, QIN Jing-ping, JIANG Jian-xiong, TAN Yan-ning, ZHOU Qing-ming 2006, 13(4): 234-242 .  Abstract ( )   PDF (73KB) ( )   A lysozyme gene resistant to rice blast was transferred from the donor transgenic japonica rice Zhonghua 9 (D2-1-2) into a sterile line Pei’ai 64S(PA 64S) and restorer line 9311 of the two-line hybrid rice Liangyoupeijiu, and the restorer line Minghui 63 (MH 63) of three-line hybrid rice Shanyou 63 by successive backcrossing. The PCR analysis confirmed that foreign lysozyme gene was segregated at ratio of 1︰1 in backcross generations of B39311, B3MH63 and B2PA64S, and at ratio of 3︰1 in selfed generations of B2F2 9311, B2F2 MH63 and B1F2 PA64S, indicating that the foreign gene was stably inherited over successive generations as a dominant single copy gene. The resistance against rice blast in backcross or selfed generations and corresponding testcross combinations were investigated in 2003 and 2004. The results showed that the resistance of the transgenic rice to blast had a greater improvement than that of the corresponding recurrent parents or the corresponding check hybrid combinations. The resistance of the advanced backcross and selfed generations to rice blast is much stronger than that of the early generations. The study confirmed that transferring the lysozyme gene into hybrid parents by backcrossing was a simple and effective approach to develop new hybrid rice resistant to rice blast.

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Fertility Expression of TGMS-Genes in the Backgrounds of indica CMS-lines, B-lines and R-lines of Hybrid Rice WANG Ji-feng, LU Zuo-mei 2006, 13(4): 243-249 .  Abstract ( )   PDF (48KB) ( )   The generation fertility of 51 F1, 19 F2 and 6 BC1 between 3 thermo-sensitive genic male sterile lines (TGMS-lines) Pei’ai 64S, 6311S and 360S, and the three lines of hybrid rice including 7 indica cytoplasmic male sterile lines (CMS-lines) and their corresponding maintainer lines (B-lines) and 3 indica restorer lines (R-lines) were investigated to study the expression of TGMS-genes in the backgrounds of the three lines of hybrid rice. Pei’ai 64S has stronger fertility restoring (Rf) genes for CMS-lines and its TGMS trait is governed by 2 pairs of independent recessive genes; The TGMS trait of 6311S is governed by a single recessive gene with weaker Rf-gene in 6311S and the TGMS trait of 360S is governed by a single recessive gene with no Rf-gene in 360S. The investigation on the fertility of F1 plants between 5 CMS-lines and 4 TGMS generations selected from F2 plants of 4 CMS-lines × 6311S confirmed that the expression of TGMS-gene was controlled by Rf-gene in the genetic background of cytoplasm of CMS-lines, but not affected by Rf-gene in the genetic background of normal fertile cytoplasm. The potential breeding strategies of TGMS-lines with cytoplasm of CMS-lines and CMS-lines with the nucleus of TGMS-genes were discussed.

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Source-Sink Relationship in Intersubspecific Hybrid Rice LI Ji-hang, XIANG Xun-chao, HE Li-bin, LI Ping, 2006, 13(4): 250-256 .  Abstract ( )   PDF (54KB) ( )   Three indica restorer lines (Mianhui 725, Shuhui 527, Shuhui 881), an American rice variety Lemont and a javanica rice variety Xiangdali were crossed with japonica Kitaake, and five F1 hybrids were obtained to study the photosynthetic and agronomic traits. The data on photosynthetic characteristics indicated that the net photosynthetic rate (Pn) of the five F1 hybrids was significantly higher than that of their parents (or one of them) under high photosynthetic flux density (PFD); while the overall performance of hybrids was better than their respective parents in apparent quantum yield (AQY), carboxylation efficiency (CE) and CO2 compensation point (CCP). Moreover, the photosynthetic performance of the five F1 were different due to the variation in heredity and the typical indica-japonica hybrids, Mianhui 725/Kitaake and Shuhui 527/Kitaake, were better than the others on this aspect. The agronomic traits revealed that the five F1 exhibited different heterosis, with Shuhui 881/Kitaake the largest sink followed by Mianhui 725/Kitaake, Shuhui 527/Kitaake, Lemont/Kitaake and Xiangdali/Kitaake. The production potential of indica-japonica hybrids was higher than that of the other two hybrids, which was consistent with the performance of Pn. However, the superior trait of indica-japonica hybrids on sink size has not been fully turned into high yield because of abnormal seed setting. Therefore, attention should be paid to the proper genome coordination and appropriate genetic distance so as to achieve super high yielding.

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Abnormal Structure of Embryo Sac in Autotetraploid Rice GUO Hai-bin, FENG Jiu-huan, LU Yong-gen, LIU Xiang-dong 2006, 13(4): 257-264 .  Abstract ( )   PDF (306KB) ( )   The structures of mature embryo sacs in 13 genetic stock lines of autotetraploid rice (Oryza sativa L.), including indica, japonica and javanica, were studied by using the whole-mount stain-clearing laser scanning confocal microscopy (WCLSM). Among the 13 autotetraploid rice, the majority of ovaries possess normal polygonum-type embryo sacs, while a few ovaries were characterized by abnormal embryo sacs. The abnormalities of embryo sacs could be classified into six categories, i. e. no female germ unit, abnormal polar nuclei, embryo sac degeneration, no egg apparatus, small embryo sac and ‘double set’ of embryo sacs. The frequency of abnormal embryo sac in japonica (26.6%) was higher than that in indica (19.34%). In addition, the major abnormalities in each autotetraploid line varied, suggesting that the abnormalities may be related to the genotypes of the varieties.

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Analysis of Chloroplast Ultrastructure, Photosystem Ⅱ Light Harvesting Complexes and Chlorophyll Synthesis in a Chlorophyll-Less Rice Mutant W2555 XU Pei-zhou , LI Yun , YUAN Shu , ZHANG Hong-yu , WANG Xu-dong , LIN Hong-hui , WU Xian-jun 2006, 13(4): 265-270 .  Abstract ( )   PDF (107KB) ( )   A comparative study on chloroplast ultrastructure and light harvesting complex of photosystem Ⅱ (LHC Ⅱ) was conducted between a new rice mutant (W2555) and its wild type (WT). The chloroplasts of W2555 had less thylakoids and grana stacks compared with the wild type. There was no significant change in the composition of LHC Ⅱ polypeptide in W2555, while a decline had been noted in LHC Ⅱ content. Northern blot analysis with a specific cab gene probe showed no appreciable difference in the LHC Ⅱ mRNA level between the W2555 and its wild type. The precursors of chlorophyll synthesis, δ-aminolevulinic acid (ALA) and porphobilinogen (PBG) were over accumulated in W2555, but the other precursors were all decreased. These results indicated that the decreased level of LHC Ⅱ in the mutant W2555 was attributed to the change of cab gene transcription, but a blockage in chlorophyll biosynthesis due to the formation of uroporphyrinogen Ⅲ (Urogen Ⅲ).

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Formula for Determining Number of Basic Seedlings at Scattered-Planting with Seedling Dry-Raised on Plastic Trays in Double-Season Rice PAN Xiao-hua, CHEN Xiao-rong, YANG Fu-sun* 2006, 13(4): 271-277 .  Abstract ( )   PDF (47KB) ( )   The tiller emergence in seedling nursery beds and field, and panicle formation in the field were investigated under scattered-planting with seedling dry-raised on plastic trays in double-season rice. A significant difference was noted in the non-synchronously-emerged tillers (the tillers that formed from latent buds and did not emerge following the normal tillering law on seedling nursery beds and recovered to grow after scattered-planting or transplanting) as well as the percentage of the available synchronously-emerged tillers between seedlings raised on plastic trays under dry-land conditions (DPT) and seedlings raised on nursery beds under wetland conditions (WB). The seedlings under DPT had some non-synchronously-emerged tillers, but those under WB had not. Therefore, the traditional formula for determining the number of rice seedlings was improved, and the formula for determining the number of basic seedlings under scattered planting with DPT in double-season rice was introduced. For early rice, it was X=Y/{(1+t1r1)[1+(N－n－SN)Rr2]+(SN－3－t1)R2r5}, and for late rice, it was X=Y/{(1+t1r1)[1+(N－n－SN)Rr2]+(N－n－SN－3)Rr2R1r3+(SN－3－t1)R2r5}. Where, X represents reasonable number of basic seedlings per unit area at scattered-planting; Y, number of fitting panicles per unit area; t1, total number of tillers per plant; r1, percentage of the total available tillers; N, total number of leaves of the main culm; n, total number of elongated internodes in the main culm; SN, seedling leaf ages at scattered-planting; R, percentage of the primary tillers emerged in available node-position; r2, percentage of the available primary tillers; R1, percentage of the secondary tillers in the field (except the secondary tillers of the seedlings); r3, percentage of the available secondary tillers; R2, percentage of the asynchronously-emerged tillers after scattered-planting; r5, percentage of the available non-synchronously- emerged tillers after scattered-planting.

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Variation among Rice Cultivars in Root Acidification and Its Relation to Cadmium Uptake LIU Jian-guo , XU Hai , CAI Guo-liang , QIAN Min , WANG De-ke , ZHU Qing-sen 2006, 13(4): 278-282 .  Abstract ( )   PDF (52KB) ( )   To understand the mechanisms of Cd uptake and accumulation in rice, soil acidification by root activities was investigated in six rice cultivars differing in Cd accumulation. The results showed a significant difference among the cultivars in pH of pot water and root exudate. Soil acidification abilities varied with rice cultivars. Both pH of pot water and root exudate were lower in indica cultivars than in japonica ones. The difference in root acidification was larger in Cd treated cultivars than the control. Under Cd stress, the pH of pot water and root exudate correlated negatively and significantly with Cd concentrations in rice plants. It was suggested that the soil acidification by root exudates, especially in Cd contaminated soils, may be one of the mechanisms responsible for Cd uptake in rice cultivars.

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Effect of Phosphorus Deficiency on Leaf Photosynthesis and Carbohydrates Partitioning in Two Rice Genotypes with Contrasting Low Phosphorus Susceptibility LI Yong-fu, LUO An-cheng, Muhammad Jaffar HASSAN, WEI Xing-hua 2006, 13(4): 283-290 .  Abstract ( )   PDF (54KB) ( )   To study the effect of phosphorus (P) deficiency on leaf photosynthesis and carbohydrates partitioning and to determine whether the characteristics of leaf photosynthesis and carbohydrates partitioning are related to low P tolerance in rice plants, a hydroponic culture experiment supplied with either sufficient P (10 mg /L) or deficient P (0.5 mg /L) was conducted by using two rice genotypes different in their responses to low P stress. Results showed that the plant growth of Zhenongda 454 (low P tolerant genotype) was less affected by P deficiency compared with Sanyang’ai (low P sensitive genotype). Under P-deficient conditions, photosynthetic rates of Zhenongda 454 and Sanyang’ai were decreased by 16% and 35%, respectively, and Zhenongda 454 showed higher photosynthetic rate than Sanyang’ai. Phosphorus deficiency decreased the stomatal conductance for both genotypes, but had no significant influence on leaf internal CO2 concentration (Ci), suggesting that the decrease in leaf photosynthetic rate of rice plants induced by P deficiency was not due to stomatal limitation. Phosphorus deficiency increased the concentration of soluble carbohydrates and sucrose in shoots and roots for both genotypes, and also markedly increased the allocation of soluble carbohydrates and sucrose to roots. Under deficient P supply, Zhenongda 454 had higher root/shoot soluble carbohydrates content ratio and root/shoot sucrose content ratio than Sanyang’ai. In addition, phosphorus deficiency increased the concentration of starch in roots for both genotypes, whereas had no effect on the content of starch in shoots or roots. Compared to genotype Sanyang’ai, the better tolerance to low-P stress of Zhenongda 454 can be explained by the fact that Zhenongda 454 maintains a higher photosynthetic rate and a greater ability to allocate carbohydrates to the roots under P deficiency.

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Relation of Root Growth of Rice Seedling with Nutrition and Water Use Efficiency Under Different Water Supply Conditions ZHENG Bing-song , JIANG De-an , WU Ping , WENG Xiao-yan , LU Qing , WANG Ni-yan 2006, 13(4): 291-298 .  Abstract ( )   PDF (48KB) ( )   Water deficiency is one of the primary yield-limiting factors in rice. In plants, the nutrition and water use efficiency depend on root growth efficiency under different water supply conditions (WSC). Three rice genotypes, Azucena (an upland japonica), IR1552 (a lowland indica) and Jia 9522 (a lowland japonica), were grown under different WSC with 0 cm (submerged), 40 cm and 80 cm groundwater levels below the soil surface to investigate the root parameters, water use efficiency, nitrogen, phosphorous and potassium contents, net photosynthetic rate and transpiration rate of the rice plant. The relative parameters were defined as the ratio of the parameters under submerged conditions (0 cm groundwater level below soil surface) to these under upland conditions (40 cm and 80 cm groundwater levels below soil surface). The results indicated that different genotypes showed different relative root parameters and relative nutrition content and water use efficiency under different WSC. The length and number of adventitious root are more important than seminal root length in water and nutrition uptake, and maintaining the grain yield and increasing dry matter, but the adventitious root number could not be served as an index for screening drought-resistant genotypes. Furthermore, different drought-resistant genotypes have been also found, and Azucena was resistant to drought, IR1552 sensitive to drought and Jia 9522 neither sensitive nor resistant to drought.

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A Rapid DNA Mini-prep Method for Large-Scale Rice Mutant Screening QIU Fu-lin, WANG He-he , CHEN Jie , ZHUANG Jie-yun , Hei LEUNG , CHENG Shi-hua , WU Jian-li 2006, 13(4): 299-302 .  Abstract ( )   PDF (113KB) ( )   A high throughput rice DNA mini-preparation method was developed. The method is suitable for large-scale mutant bank screening as well as large mapping populations with characteristics of maintaining relatively high level of DNA purity and concentration. The extracted DNA was tested and suitable for regular PCR amplification (SSR) and for Targeting Induced Local Lesion in Genome (TILLING) analysis.