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10 January 2019, Volume 33 Issue 1 Previous Issue    Next Issue
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Identification and Gene Mapping of a white-stripe leaf after transplanting at low temperature Mutant in Rice Tianzi LIN, Liting SUN, Hongbin GONG, Yihua WANG, Linglong LIU, Zhigang ZHAO, Ling JIANG, Jianmin WAN 2019, 33(1): 1-11.  DOI: 10.16819/j.1001-7216.2018.8026 Abstract ( )   HTML ( )   PDF (1426KB) ( )   【Objective】 Isolation and characterization of leaf-color mutation related genes lays a firm theoretical foundation for dissecting the molecular mechanism underlying chloroplast development, chlorophyll biosynthesis, and photosynthesis in rice. 【Method】A spontaneous leaf-color mutant, termed as white stripe leaf after transplanting at low-temperature (wltt), was obtained from the progeny of japonica cultivar Zhennuo 19. The main agronomic traits of the wild type and wltt were determined at maturity. The pigment contents and ultrastructure of chloroplast of newly emerged leaves were analyzed at the seedling stage, fifteen days after transplanting, at the tillering stage under direct seeding. Genetic analysis was carried out by reciprocal cross of the wild type and wltt. An F2 population derived from the cross wltt×9311 was used for gene mapping. Quantitative RT-PCR was carried out to analyze the relative expression of genes associated with chloroplast development and chlorophyll biogenesis in the wild type and the wltt mutant. 【Result】The white-striped leaves in the wltt mutant only emerged at 15 days after transplanting at low temperature such as 20℃. No white-striped leaf was observed under direct seeding treatment. However, leaves of the mutant developed normally at the late tillering stage. Simulation experiments showed that the mutant phenotype was caused by root injury at low temperature. Compared with the wild type, the pigment contents in white-stripe leaves of the wltt mutant were significantly decreased, accompanying by reduced photosynthetic rate. Simultaneously, most of the mesophyll cells had no chloroplasts. The expression levels of genes associated with chloroplast development, chlorophyll biosynthesis, and photosynthetic system were all down-regulated in the mutant. At maturity, the mutant was featured with reduced plant height, panicle length, flag leaf length and number of spikelets per panicle relative to its wild type. Genetic analysis revealed that the mutant phenotype was controlled by a single recessive nuclear gene. Moreover, the WLTT gene was mapped within an 853 kb region near the centromere on chromosome 2, between InDel markers L22 and L26, in which no gene related to leaf color was reported. 【Conclusion】WLTT is a key gene regulating leaf color after transplanting at low temperature, which plays an important role in chloroplast development.

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Mapping of a New Rice Blast Resistance Gene in Ziyu 44, a Rice Landrace from Yunnan Province, China Xiaoxuan ZHUO, Linlin FAN, Xingyu AN, Jingwei GUO, Rui YANG, Qianchun ZENG, Qiong LUO 2019, 33(1): 12-19.  DOI: 10.16819/j.1001-7216.2019.8054 Abstract ( )   HTML ( )   PDF (865KB) ( )   【Objective】Ziyu 44 (Oryza sativa L. subsp. geng), a landrace of Yunnan Province, has broad-spectrum and durable blast resistance. In order to understand the molecular mechanism of resistance to rice blast, 【Method】we carried out the genetic analysis of resistance of Ziyu 44 to the Magnaporthe oryzea LP36 from Luoping County, Yunnan Province, and mapped the gene responsible for resistance to strain LP36 by using an F2 population from the cross between Jiangnanxiangnuo and Ziyu 44. 【Result】The resistance of Ziyu 44 to LP36 is controlled by a single dominant gene, termed as Pi-zy4(t), which was located on the long arm of chromosome 4 between simple sequence repeat markers RM5503 and RM3276 within about 318 kb.【Conclusion】Pi-zy4(t) is a new gene conferring resistance to rice blast. Our results provide essential information for further utilization of the blast resistance gene in rice breeding and its cloning.

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Origin, Distribution and Sequence Diversity of Rice Blast Resistance Locus LABR_64 in Rice Yufei DENG, Minghao LIU, Dan WANG, Shimin ZUO, Houxiang KANG, Guoliang WANG 2019, 33(1): 20-27.  DOI: 10.16819/j.1001-7216.2019.8017 Abstract ( )   HTML ( )   PDF (1828KB) ( )   【Objective】 A better understanding of the origin and distribution of disease resistance genes in rice germplasm is useful for breeding highly resistant varieties.【Method】We analyzed sequence diversity of the rice blast resistance locus LABR_64, which contains two homologous genes, LABR_64-1 and LABR_64-2, is located in the allelic region of Pi3/Pi5/Pii/Pi15 on rice chromosome 9. In addition, we analyzed the microsynteny of the LABR_64 orthologous region in different monocotyledons.【Result】The presence frequency (PF) of LABR_64 is 16%. All of the japonica rice cultivars carrying LABR_64 are highly resistant to rice blast and all of those without the locus are susceptible. In addition, the PF of LABR_64 in the indica subpopulation is lower than 5%. Although LABR_64 is correlated with the resistance to rice blast, many indica rice cultivars without LABR_64 are also resistant to rice blast. We also found that the LABR_64-2 sequence is much conserved. Moreover, the microsynteny analysis of the LABR_64 orthologous region in different monocotyledons indicated that LABR_64 originates after the separation of the monocotyledonous and dicotyledonous species, and at the early differentiation stage of monocotyledons.【Conclusion】The rice blast resistance phenotypes are closely correlated with the presence of the LABR_64 locus in japonica subpopulation, but not in indica, indicating that there are many other resistance loci in the indica subpopulation. The LABR_64-2 sequence can be used for developing molecular markers in marker-assisted rice blast resistance breeding. It also indicated that LABR_64 may play a role in disease resistance in different monocotyledons.

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Rice Seed-specific Glutenin GluB1 Promoter Drives Exogenous Gene Expression in Rice Callus Yan ZHAO, Yongzhou TANG, Yuqian SHI 2019, 33(1): 28-34.  DOI: 10.16819/j.1001-7216.2018.8036 Abstract ( )   HTML ( )   PDF (796KB) ( )   【Objective】The promoter of rice glutelin B1(pGluB1) has been intensively used to study high seed-special expression of exotic genes, and as a model to understand regulation mechanism of seed-storage protein genes. Former researchers reported that pGluB1expressed only in rice seed endosperm with no expression activity in other tissues such as root, stem, leaf, sheath and glume etc. The present study is aiming to overcome the shortcoming of time consuming for screening of seed-special expression promoters.【Methods】The expression vector pCAMBIA1302-pGluB1sig- CTBIN-NOS, in which a fusion gene of the cholera toxin B subunit and human proinsulin (CTBIN) was driven by the 2.3 kb promoter sequence of rice glutelin GluB1 with its signal peptide (pGluB1sig), was transformed into the rice calli from mature embryo via Agrobacterium-mediated method. The expression of fusion gene CTBIN at both transcription and translation level was tested by RT-PCR and Western-blotting assay.【Results】Among the seven transgenic calli clones, six clones of the fusion gene CTBIN were expressed at transcription level. The selected four clones subjected to Western-blotting assay were all fatherly verified in their expression at translation level. Additionally, according to the molecular weight, we speculated that the signal peptide (24 aa) of GluB1 at N-terminus of the fusion protein CTBIN has been excised successfully from callus cells of all the test clones.【Conclusion】The rice seed-specific expression promoter pGluB1 can drive an exotic gene expression in callus, and the seed protein body subcellular-targeted signal peptide could be excised from callus cells. The results lay a foundation of the quick detection of expression activity of plant seed-specific expression promoters in callus and exploiting the mechanism of protein subcellular sorting selection in callus cells.

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Dry Matter Production and Yield Characteristics of Machine-transplanted Rice Varieties Falling into Different Types in Sichuan Basin Qi LIU, Jianfeng HU, Wei ZHOU, Zhiping YANG, Yong CHEN, Wanjun REN 2019, 33(1): 35-46.  DOI: 10.16819/j.1001-7216.2019.8049 Abstract ( )   HTML ( )   PDF (1215KB) ( )   【Objective】The objective is to elucidate the dry matter production and yield characteristics of machine-transplanted rice varieties. 【Method】The dry matter production and yield formation of 10 varieties of three different types, medium-maturing indica hybrid rice, late-maturing indica hybrid rice and japonica rice included, were analyzed under mechanical transplanting in Sichuan Basin in 2012. 【Result】The main results were as follows: 1) The processes of dry matter accumulation of the three different types of rice varieties after transplanting are in accordance with the Logistic curve. The dry matter accumulation of medium-maturing indica hybrid rice and late-maturing indica hybrid rice were faster than that of japonica rice, with shorter slow growth period and longer fast growth period. However, the dry matter accumulation of japonica rice was slower with longer incremental growth period and slow growth period and shorter fast growth period. Therefore the dry matter accumulation of medium-maturing indica hybrid rice and late-maturing indica hybrid rice was superior to that of japonica rice. 2) The medium-maturing hybrid rice had the lowest proportion of vegetative organs and the highest proportion of reproductive organs, the late-maturing hybrid rice had the highest proportion of leaves at maturity, whereas the japonica rice had high proportion for stem but low proportion for panicles. 3) The percentage of output and transformation of stem and leaf in medium-maturing hybrid rice and late-maturing hybrid rice were all positive. However, the percentage of output and transformation of stem and the percentage of transformation of leaf in japonica rice were all negative, and the percentage of output of leaf was only 1.26%. 4) Medium-maturing indica hybrid rice has largest yield, grain number per panicle, grain filling rate, and filling degree, late-maturing indica hybrid rice has largest seed setting rate and 1000-grain weight, and japonica rice has largest effective panicle number and productive tiller percentage, which indicates that the indica hybrid rice yield is mainly associated with panicle traits, and japonica rice is mainly related to the number of panicles in the field.【Conclusion】Hybrid indica rice needs to increase its effective panicle number and the productive tiller percentage under the machine-transplanted conditions. For japonica rice, it’s necessary to breed large panicle varieties and increase the grain number per panicle and grain filling degree.

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Optimizing the Nitrogen Management for Yongyou 4949 and Chaoyou 1000 in Ratoon Rice System in Central China Aibin HE, Pengchao YU, Qian CHEN, Guanglei JIANG, Weiqin WANG, Lixiao NIE 2019, 33(1): 47-56.  DOI: 10.16819/j.1001-7216.2019.8078 Abstract ( )   HTML ( )   PDF (1011KB) ( )   【Objective】The grain yield, nitrogen partial factor productivity (PFPN) and regeneration rate of Chaoyou 1000 (CY1000) and Yongyou 4949 (YY4949) were investigated in ratoon rice system under various nitrogen rates. And the possibilities of introducing these varieties into ratoon rice system in central China were also evaluated.【Method】The experiment was laid out in a split-plot design with four replications. The nitrogen rates were designed as main plots with six levels: N1(120main150ratoon), N2(120main225ratoon), N3(185main150ratoon), N4(185main225ratoon), N5(250main150ratoon), N6(250main225ratoon). The varieties [YY4949, CY1000, Liangyou 6326 (LY6326, as control)] were set as sub-plots. The plant height, tiller numbers, leaf area index, aboveground biomass, grain yield, yield components and grain nitrogen concentration of each variety were measured under various nitrogen rates.【Result】The highest grain yields in the main season were 9.16t/hm2, 9.08t/hm2 and 11.15t/hm2 at the N levels of 185 kg/hm2, 120 kg/hm2 and 185 kg/hm2 in LY6326, CY1000 and YY4949, respectively.The average yields of LY6326, YY4949 and CY1000 in ratoon season were 5.41t/hm2, 4.98t/hm2, 6.02t/hm2 and 5.78t/hm2, 5.41t/hm2, 6.49t/hm2 at the nitrogen levels of 225kg/hm2 and 150kg/hm2, respectively. Moreover, the increases in nitrogen input(from 150 to 225kg/hm2) significantly decreased the PFPN. In summary, it suggested that the optimum nitrogen management for LY6326 and YY4949 should be N3(185kg/hm2 during main season and 150kg/hm2 during ratoon season).【Conclusion】The N management practice of YY4949 should be consistent with that of LY6326 when YY4949 was introduced into ratoon rice system, while the whole growth duration of CY1000 was too long to ensure maturity of ratoon season, so it is not suitable for ratoon rice production in Central China.

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Effects of Different Temperature from Full Heading to Milking on Grain Filling Stage on Grain Hormones concentrations, Activities of Enzymes Involved in Starch Synthesis and Accumulation in Rice Nanjing 9108 Chen CHENG, Yongjun ZENG, Huihuang CHENG, Xueming TAN, Qingyin SHANG, Yanhua ZENG, Qinghua SHI 2019, 33(1): 57-67.  DOI: 10.16819/j.1001-7216.2019.8077 Abstract ( )   HTML ( )   PDF (1250KB) ( )   【Objective】Our aim is to reveal the mechanism of the influence of different temperatures on grain-filling, starch and its components contents of late japonica rice during early-middle grain filling stage. 【Methods】With a representative japonica rice cultivar with high quality of Nanjing 9108 as material, high temperature (HT, average daily temperature of 31℃), medium temperature (MT, average daily temperature of 26℃) and low temperature (LT, average daily temperature of 21℃) were set during grain filling in plant incubators at natural temperature as control check (CK). The effects of high and low temperature on grain-filling, hormone contents, and activities of enzymes involved in starch synthesis and accumulation of late japonica rice were studied during early-middle grain filling stage. 【Result】With rising temperature (21℃~31℃), the seed setting rate and 1000-grain weight of late japonica rice were on the downward slide. The accumulation of total starch in grain was accelerated with shortened duration and decreased total contents. The amylose content and its proportion followed a decreasing trend during the whole grain filling period. The abscisic acid (ABA) content in grain was significantly increased during the early and middle grain-filling stage. The gibberellin (GA3) content decreased, and the zeatin riboside (ZR) content firstly increased and then dropped. The content of grain indole-3-acetic acid (IAA) was increased in MT plots during the grain filling stage. The IAA content in grains was reduced in HT and LT plots. The IAA content in the LT plots was decreased firstly and then increased, while in the HT plots, the content was consistently at lower level. The activity of soluble starch synthase (SSS) in grains was equal to that of ZR, which also showed ‘a increasing-decreasing trajectory’, but the SSS and the ZR activities were not synchronized in filling stage. The activity of grain starch branching enzyme (SBE) increased and the activity of grain starch decarboxylase (DBE) decreased.【Conclusion】The changes of grain endogenous hormones and activities of enzymes involved in grain starch synthesis of late japonica rice were significantly influenced by different temperature, as well as the accumulation of starch and its components, grain filling in late japonica rice.

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Morphophysiological Responses of Different Scented Rice Varieties to High Temperature at Seedling Stage Huoyi FENG, Haolin JIANG, Meng WANG, Xiangru TANG, Meiyang DUAN, Shenggang PAN, Hua TIAN, Shuli WANG, Zhaowen MO 2019, 33(1): 68-74.  DOI: 10.16819/j.1001-7216.2019.8022 Abstract ( )   HTML ( )   PDF (684KB) ( )   【Objective】The purpose of this research is to study the morphophysiological responses of different scented rice varieties to high temperature at seedling stage and to screen out heat-resistant varieties.【Method】With the super inbred fragrant rice Yuxiangyouzhan as control, a pot experiment was conducted in a light incubator, to reveal morphophysiological responses of seven inbred fragrant rice varieties (Basmati, Guixiangzhan, Nongxiang 18, Xiangwanxian 13, Xiangyaxiangzhan, Zhongxiang 1, Meixiangzhan 2) to high temperature stress. The morphophysiological indexes of the eight scented rice varieties were determined before and after high temperature treatment.【Result】Compared with Yuxiangyouzhan, the plant height, fresh weight, dry weight increased with a langer rate, the survival rate and POD activity in Basmati were higher under high temperature treatment. The malondialdehyde content was decreased by 33.39% for Basmati under high temperature treatment. It indicated that Basmati had higher tolerance to high temperature stress. The dry weight growth rate per plant of Xiangwanxian 13 under high temperature stress was equal to that of Yuxiangyouzhan with lower survival rate than Yuxiangyouzhan, and the change rate of intercellular CO2 concentration was lower after high temperature treatment, the SOD activity and the change rate of malondialdehyde content was the lowest among the eight varieties, indicating that its ability to withstand high temperature stress was slightly lower than that of Yuxiangyouzhan. The survival rates of Nongxiang18, Xiangyaxiangzhan and Meixiangzhan 2 were 13.33%, 12.67% and 16.00%, respectively. The survival rates of Guixiangzhan (4.33%) and Zhongxiang 1 (1.33%) under high temperature stress were the lowest among the eight varieties, indicating their weak high temperature tolerance.【Conclusion】In general, the heat resistance of the eight varieties from strong to weak was Basmati>Yuxiangyouzhan>Xiangwanxian 13>Nongxiang 18>Xiangyaxiangzhan>Meixiangzhan>Guixiangzhan>Zhongxiang 1.

Experimental Technique

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Screening Reference Genes and Evaluating of Their Expression Stability for qRT-PCR Normalization in Chilo suppressalis (Lepidoptera: Pyralididae) Hongxing XU, Guorong WANG, Yanhui LU, Yajun YANG, Xusong ZHENG, Junce TIAN, Zhongxian LÜ 2019, 33(1): 75-84.  DOI: 10.16819/j.1001-7216.2019.8035 Abstract ( )   HTML ( )   PDF (1819KB) ( )   【Objective】We aim to screen reference genes stably expressed in striped stem borers (SSB), Chilo suppressalis, under certain conditions, to lay a foundation for the study on the gene expression in SSB. 【Method】According to the results of SSB transcriptome data, 11 candidate genes from SSB were selected and their expression stability was detected under different treatment conditions (including development duration, tissues, feeding on different diets and rice varieties, dsRNA and mixed samples under temperature stress, insecticide treatment), by using real-time fluorescence quantitative PCR. The stability of the 11 candidate genes was evaluated by RefFinder, BestKeeper, GeNorm, NormFinder and ΔCt. 【Result】AK, RPL10 and EF1 were highly stable in different development durations; EF1, TUB and ACTB were highly stable in different tissues. TUB, RPL10 and EF1 were relatively stable under temperature stress. TF4 and ACTA were stable in insecticide treated samples. TUB, TF4, EF1 and RPL10 were stable in samples fed on different diets. TUB and EF1 were stable reference genes in samples fed on different rice varieties. TUB, AK, ACTB and EF1 were stable in the sample treated with dsRNA. EF1, TUB and ACTB were stable in mixed samples. 【Conclusion】 It provide a reference for selection of suitable reference gene under different test conditions, and also provide more reliable and accurate data for research in gene expression in rice SSB.

Short Communications

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Resistance to Heterodera elachista and Evaluation Methods of Major Rice Varieties from Hunan Province, China Tao YUAN, Shan YE, Jianyu ZHOU, Deliang PENG, Wenkun HUANG, Zhong DING 2019, 33(1): 85-89.  DOI: 10.16819/j.1001-7216.2019.8053 Abstract ( )   HTML ( )   PDF (519KB) ( )   【Objective】Heterodera elachista is a new pathogenic nematode of rice. In order to screen the resistant rice cultivars to H. elachista, 【Method】 51 rice varieties from Hunan Province were evaluated by the second-stage juvenile inoculation test in greenhouse and field with average number of cysts per plant, relative resistance index (RRI) and Pf/Pi ratio as indicators. 【Result】No rice cultivar was immune or highly resistant to H. elachista. Among the 24 middle-season rice cultivars, only Guangliangyou 2010 showed resistance to H. elachista based on average number of cysts per plant, and Guangliangyou 2010, Zhunliangyou 527 and Guangliangyou 1128 showed resistance to H. elachista based on RRI evaluation in greenhouse. Among the 27 late rice varieties, Shengtaiyou 9712, Zhunliangyou 608, Nongxiangyou 204, Yueyou 9264, Yueyou 3700, Zhongzheyou 1, Yueyou 27, Xiangwannuo 1, Heyou 50 and Y Liangyou 9918, were resistant to H. elachista based on average number of cyst per plant. However, Xiangwannuo 1, Heyou 50 and Y liangyou 9918 were moderately susceptible based on RRI evaluation. Using Pf/Pi ratio as the evaluation index, nine late resistant varieties screened from greenhouse based on RRI evaluation were basically consistent with field resistance. 【Conclusion】RRI is an efficient index for evaluating the resistance of rice cultivars to rice cyst nematode.

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Rhizocotonia Solani Recognition Algorithm Based on Convolutional Neural Network Tingting LIU, Ting WANG, Lin HU 2019, 33(1): 90-94.  DOI: 10.16819/j.1001-7216.2019.8051 Abstract ( )   HTML ( )   PDF (771KB) ( )   【Objective】Rice sheath blight is one of the three major diseases in rice production.The convolutional neural network which stands out for automatic identification of rice shealth blight can compensate for the lack of human identification. To solve this problem and prevent diseases deterioration, accurate identification of diseases types is of great significance.【Method】The convolutional neural network method was used to recognize rice sheath blight and compared with the recognition method based on support vector machine.【Result】The convolutional neural network method showed the recognition rate of 97%, better than that of support vector machine(95%).【Conclusion】The application of convolutional neural network to the identification of rice sheath blight is feasible and makes up for the lack of artificial recognition. The model trained by this algorithm has great recognition performance.