Discovery of and Preliminary studies on a Rapid-Leafing Rice Genotype at the Vegetative G rowth Stage

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 grovvth 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 tiltering 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.     

崇仁县：种粮大户不晒谷

7月14日下午,两辆满载着从相山镇枧上村种粮大户袁冬生田里收割来的稻谷拖拉机驶进了崇仁县郭溪乡丰粮农机专业合作社的大门,工人们赶忙把上午刚收割的湿稻谷搬进机房,接着把湿谷倒进粮口,机房里顿时忙了起来。驾着拖拉机来烘谷子的袁冬生笑着说从今以后,收割稻子再也不要看老天爷的脸色了,这几天下雨我照旧割稻子。以往稻子收割期出现连续阴雨,导致粮食发霉发芽已成为老皇历。     

Gene Tagging by Activating DNA Transposon nDart in lndica Rice

As International Rice Genome sequencing Project （2005） demonstrated, the rice genome contains various transposons and about 13% of the genome is occupied by DNA transposons. So far, only a few DNA transposons have been reported to be actively transposed. Since transposons are important for gene-functional analysis, it is necessary to explore active transposon source. We identified an active nonautonomous DNA transposon, nDart1-0, belonging to the hAT superfamily in a spontaneous mutable virescent, pyl-v plant. Blast searches in the available databases revealed that Nipponbare and 93-11 carries 13 and 7 nDart1 homologues, respectively, nDart1-0 was found to be transposed most frequently among these homologues. Furthermore, nDart1-0 carries a specific basesubstitution at position 173, and this sequence alteration generates nDart1-0-specific restriction enzyme cleavage site. So, we developed an nDart1-0-specific detection system using iPCR （nl-0SPiPCR）, which should be useful for our nDart1-0-specific tagging system. Since we could not find either any active nDarts or active autonomous element Darts in indica varieties, we tried to introduce japonica-derived nDart1-0 and aDart into indica variety Kasalath by backcrossing. In BC2F2, a mutable chlorophyll mutant was newly generated. Through genetic analysis,     

Marker Assisted Selection for Submergence Tolerance in Rice

Yields in the irrigated rice areas have improved remarkably over the last three decades. Farmers with access to assured water supply have adopted improved varieties, resulting in higher yields and improved income in rural areas. In contrast, yields remain low in the vast rainfed areas that are associated with higher levels of poverty. A few improved varieties have spread in these areas, but abiotic stresses such as drought and submergence prevent farmers from realizing their yield potential. Stress tolerant versions of these varieties are urgently needed to improve the standard of living and stabilize household food supplies. It has been found that tolerance to a number of abiotic stresses is controlled by a few QTLs of large effect, and that incorporation of these QTLs into the high yielding varieties could make a significant impact in stabilizing the yields of these varieties in stress-prone areas （Mackiil, 2006）. Submergence tolerance provides a good example of how marker assisted selection can be very effective to develop improved varieties for the rainfed lowlands.     

Discussion on Photoreceptor for Negative Phototropism in Rice Roots

To properly explore the photoreceptor for the negative phototropism in rice (Oryza sativa L.) root, lights with different wavelengths were applied to investigate the effect of light quality on phototropic bending. The phototropic bending could be induced prominently by blue/ultraviolet light, whereas not by red or far-red light. The absorption spectrum of the extracted solution from rice root cap had two peaks at 350 nm and 450 nm, respectively, and the molecular weight of the 120 kD protein in the root cap under unilateral light was larger than that under the dark. It suggested that the blue light receptor might be the photoreceptor for the negative phototropism in rice root.     

Effects of 1,2,4-Trichlorobenzene and Mercury Ion Stress on Ca^2＋ Fluxion and Protein Phosphorylation in Rice

The effects of 5 mg/L 1,2,4-trichlorobenzene (TCB) and 0.1 mmol/L mercury ion (Hg2 ) stresses on Ca2 fluxion and protein phosphorylation in rice seedlings were investigated by isotope exchange kinetics and in vitro phosphorylation assay. The Ca2 absorption in rice leaves and Ca2 transportation from roots to leaves were promoted significantly in response to Hg2 and TCB treatments for 4-48 h. The Ca2 absorption peaks presented in the leaves when the rice seedlings were exposed to Hg2 for 8-12 h or to TCB for 12-24 h. Several Ca2 absorption peaks presented in the roots during rice seedlings being exposed to Hg2 and TCB, and the first Ca2 absorption peak was at 8 h after being exposed to Hg2 and TCB. The result of isotope exchange kinetic analysis confirmed that short-term (8 h) Hg2 and TCB stresses caused Ca2 channels or pumps located on plasmalemma to open transiently. The phosphorylation assay showed that short-term TCB stress enhanced protein phosphorylation in rice roots (TCB treatment for 4-8 h) and leaves (TCB treatment for 4-24 h), and short-term (4-8 h) Hg2 stress also enhanced protein phosphorylation in rice leaves. The enhancement of protein phosphorylation in both roots and leaves corresponded with the first Ca2 absorption peak, which confirmed that the enhancement of protein phosphorylation caused by TCB or Hg2 stress might be partly triggered by the increases of cytosolic calcium. TCB treatment over 12 h inhibited protein phosphorylation in rice roots, which might be partly due to that TCB stress suppressed the protein kinase activity. Whereas, Hg2 treatment inhibited protein phosphorylation in rice roots, and Hg2 treatment over 12 h inhibited protein phosphorylation in rice leaves. This might be attributed to that not only the protein kinase activity, but also the expressions of phosphorylation proteins were restrained by Hg2 stress.     

Effects of Different Nitrogen Fertilizer Levels on Fe, Mn, Cu and Zn Concentrations in Shoot and Grain Quality in Rice （Oryza sativa）

In a pot experiment, effects of N fertilizer application on the concentrations of Fe, Mn, Cu and Zn in shoot of rice and the quality of brown rice were studied. In the treatments with N fertilizer application, the concentrations of Fe, Mn, Cu and Zn in most parts of rice shoot increased compared with control (no N fertilizer application). This indicated that the transportation ability of microelements from root to shoot in rice was improved with N fertilizer application. Effect of N fertilizer on IR68144 was similar to that of on IR64, but the concentrations of the microelements in plant differed, suggesting that the characteristic expression of the two rice genotypes was not controlled by the amount of N fertilizer supplied. The concentrations of those microelements in brown rice increased at first and then decreased with increasing N fertilizer application, reaching the highest at 160 kg/ha, at which the Fe, Mn, Cu and Zn concentrations in brown rice increased by 28.96%, 41.34%, 58.31% and 16.0% for IR64, and by 22.16%, 13.75%, 8.75% and 20.21% for IR68144 compared with control, respectively. Moreover, N fertilizer promoted the accumulation of protein, decreased the accumulation of amylose in grain, and enhanced gel consistency of brown rice. These results indicate that appropriate N fertilizer management could increase micronutrient contents in grain and improve nutrition quality of rice.     

The OryzaSNP Project-SNP Discovery in Diverse Rice

The OryzaSNP project （http：//www.oryzasnp.org） is undertaking SNP discovery across the entire rice genome for 20 diverse varieties （McNally et al., 2006）. These varieties include representatives from the indica, tropical and temperate japonicas, aus, deepwater, and aromatic types of rice. SNPs are identified by array-based re-sequencing technology using very high-density oligomer arrays at Perlegen （Patil et al., 2001; Hinds et al., 2005）. SNPs arc called as those bases where hybridization of the target line differs from that of the Nipponbare reference genome. Release 4 of the Nipponbare sequence （The International Rice Genome Sequencing Project, 2005） was first masked for repetitive DNA, the segments remaining after masking were each blasted to the unmasked genome, and those that gave a single or a few hits were selected. After this filtering, 100 Mb of the rice genome is tiled onto arrays for SNP detection. Since long-range PCR is being used to prepare target DNA for hybridization, amplicons were chosen that span both unique sequence and TIGR gene models （Yuan et al., 2005） to define the final sequence for tiling. There is usually at least one LR-PCR amplicon in every 100 kb window. From this analysis,     

Difference of Phytic Acid Content and its Relation to Four Protein Composition Contents in Grains of Twenty-nine japonica Rice Varieties from Jiangsu and Zhejiang Provinces, China

Twenty-nine japonica rice varieties collected from Jiangsu and Zhejiang Provinces, China were planted in Hangzhou, China, to investigate the phytic acid content in brown rice and its frequency distribution as well as the correlation among the contents of phytic acid, total protein and four protein compositions in brown rice. The phytic acid content in brown rice ranged from 0.699% to 1.034%, with a mean of 0.868% for the 29 tested rice varieties. Xiushui series rice varieties generally exhibited lower phytic acid level than Wuyujing and Huai series rice varieties. A rough normal distribution, with a mean of 8.722%, was observed for the total protein contents in the tested varieties. Of the four protein compositions, the glutelin, globulin and albumin contents had larger coefficient of variation than the prolamin content, although the difference in prolamin content was genotype-dependent. No significant correlation was found between the phytic acid and four protein composition contents, whereas the total protein content was significantly and positively related to the glutelin content in brown rice.