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10 March 2021, Volume 35 Issue 2 Previous Issue    Next Issue
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Functional Analysis on Four Receptor-like Protein Kinases Under Salt Stress in Rice Kai LU, Tao CHEN, Shu YAO, Wenhua LIANG, Xiaodong WEI, Yadong ZHANG, Cailin WANG 2021, 35(2): 103-111.  DOI: 10.16819/j.1001-7216.2021.0905 Abstract ( )   HTML ( )   PDF (20367KB) ( )   【Objective】Salinity stress is one of the main harsh environmental factor that greatly hinders rice growth and production, and it is meaningful to study salt-responsive genes for understanding the mechanisms behind plant response to salt stress and breeding salt tolerance variety. The receptor-like protein kinases are involved in regulation of plant cell signaling and responding to stress. In this study, we analyzed the expression pattern and function of four RLKs under salt stress. 【Method】 Quantitative real-time PCR was employed to detect the expression level of the four RLKs under NaCl treatment and its tissue specificity. 【Results】The transcription of Os04g0275100 was induced by NaCl, which was expressed mainly in roots. The transcription of Os07g0541900 was inhibited by NaCl, which was expressed mainly in roots. The transcription of Os09g0353200 was inhibited by NaCl, which was expressed mainly in leaves. The transcription of Os01g0852100 was inhibited by NaCl, which was expressed in roots, shoots, leaves and sheath. Loss-of-function mutants of the four RLKs were obtained by sequencing, which exhibited the identical response to NaCl as compared with the wild-type. 【Conclusion】The expression of the four RLKs identified in this study were regulated by NaCl and were tissue-specified. Mutation of one of the four RLKs has no effects on rice salt tolerance. This study lays a basis for revealing the biological function and mechanisms of RLKs under salt stress.

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Identification of a Knockout Mutant of OsWOX3B Gene in Rice (Oryza sativa L.) Yali ZHENG, Linchuang YU, Xiaoxiao AN, Xinle CHENG, Lijun REN, Zilong SU, Xiaoya ZHENG, Tao LAN 2021, 35(2): 112-120.  DOI: 10.16819/j.1001-7216.2021.0602 Abstract ( )   HTML ( )   PDF (39039KB) ( )   【Objective】The OsWOX3B gene regulates leaf morphology and trichome development in rice. This study aims to further understand the role of OsWOX3B gene in regulating rice development. 【Method】In this study, OsWOX3B of indica rice variety R401 was knocked out by CRISPR/Cas9 gene editing technique. The mutation sites and phenotype of the obtained materials were analyzed as well as the expression levels of related genes. 【Result】The 341st base of the coding region of OsWOX3B of the obtained plant was changed from T to C, and the 395th-397th bases were absent, and the leaves and glumes of the mutant were glabrous, the same as the phenotype of dep/nuda/glr1. Therefore, the plant was Oswox3b mutant. In addition to the reported loss-of-function phenotype of OsWOX3B, new phenotypes of Oswox3b were found in this study. Compared with wild-type R401, mutant Oswox3b showed prolonged growth duration, decreased tiller number, wider and shorter leaves, longer panicle and more grains per panicle. At the same time, the mutant Oswox3b had increased number of vascular bundles in the blade, increased distance between the small vascular bundles. The changes in the expression levels of the two genes related to the development of lateral organs in the mutant Oswox3b were also consistent with the phenotypic changes. 【Conclusion】A new mutant of rice OsWOX3B gene was identified that affects lateral organ development in rice.

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Metabolism of γ-aminobutyrate and 2-acetyl-1-pyrroline Analyses at Various Grain Developmental Stages in Rice (Oryza sativa L.) Yangyang PAN, Yibo CHEN, Chongrong WANG, Hong LI, Daoqiang HUANG, Degui ZHOU, Zhidong WANG, Lei ZHAO, Rong GONG, Shaochuan ZHOU 2021, 35(2): 121-129.  DOI: 10.16819/j.1001-7216.2021.0805 Abstract ( )   HTML ( )   PDF (26535KB) ( )   【Objective】It is important to reveal the dynamic changes of metabolites and genes involved in γ-aminobutyric acid (GABA) and 2-acetyl-1-pyrroline (2AP) metabolic pathways at various grain developmental stages in scented and non-scented rice cultivars by metabolomes and transcriptomes. The purpose of this study is to lay a theoretical basis for high GABA and 2AP rice breeding. 【Method】The metabolomics and transcriptomics of grains including milky grains (8D, 8 days after flowering), dough grains (15D), mature grains (30D) and milled rice (40D) of scented rice cultivar Meixiangzhan 2(MXZ) along with non-scented rice cultivar Huanghuazhan (HHZ) were performed by LC-MS/MS and RNA-seq, respectively. Finally, the metabolites and transcript profiles of GABA and 2AP metabolic pathways were analyzed. 【Result】The LC-MS/MS-based metabolic PCA analysis illustrated that the 8D and 40D grains of both varieties were dispersedly distributed, while 15D and 30D grains were concentrated in a relatively narrow area. In a total of 623 metabolites were detected in all samples, among which 161 were different metabolites. The contents of nine metabolites, detected in the GABA and 2AP pathways, followed a similar changing trend in all samples. We found that putrescine was located in embryo and aleurone layer, while spermidine was specifically accumulated in the endosperm. About 33 000 genes were identified through the gene expression analysis, among which 14 genes involved in GABA pathway showed high transcriptional levels. These related genes had similar abundance patterns between two varieties, while the Badh2 was the only differentially expressed gene. GAD1, GABA-T1, DAO4 and PAO4 showed higher expression levels as compared with respective homologous genes. The L-arginine and putrescine profiles minimized in HHZ 5D grains, while the polyamine degradation had strong activity in whole MXZ grain development. There were all metabolites required for the 2AP synthesis in the grains, and both polyamine degradation pathway and the glutamate-proline pathway contributed to the accumulation of 2AP in grains. 【Conclusion】The GABA metabolite was mainly degraded, and GABA-T1 and GABA-T2 were responsible for GABA degradation. The metabolites involved in GABA pathway were mainly concentrated in the aleurone layer, and the metabolites and gene expression profiles had similar patterns in both rice varieties. A higher mitochondria activity was found in MXZ grains than HHZ.

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Analysis on Genetic Diversity, Population Structure, and Linkage Disequilibrium of 273 Rice Germplasms Junjie DONG, Yuxiang ZENG, Zhijuan JI, Yan LIANG, Changdeng YANG 2021, 35(2): 130-140.  DOI: 10.16819/j.1001-7216.2021.0513 Abstract ( )   HTML ( )   PDF (23681KB) ( )   【Objective】The assessment of genetic diversity and population structure of 273 rice germplasms would provide important references for breeding as well as association mapping. 【Method】In this study, genetic diversity, population structure, and linkage disequilibrium for 273 rice landraces and breeding materials from 14 countries were assayed based on genotyping with 214 markers. 【Result】The test population were classified into two subgroups (SG1 and SG2) and one mixed group(AD) through population structure analysis, and the results of UMPGA clustering analysis and principal component analysis were consistent with the results of population structure analysis. Genetic diversity analysis showed that a total of 524 alleles were detected with 214 markers, the number of alleles detected on each locus ranged from 2 to 5 with the average genetic diversity of 0.44 and the average polymorphism information content (PIC) of 0.355. The genetic diversity and PIC were higher in SG2 than those in SG1. Analysis of molecular variance showed that 34 percent of variation was attributed to the genetic variation among groups and 66 percent to the genetic variation within groups. There was significant genetic differentiation between SG1 and SG2 (Fst=0.725, P<0.01). Linkage disequilibrium analysis showed that there were linkage disequilibrium loci in each linkage group, and the minimum distances extended when linkage disequilibrium was attenuated to below 75% in SG1 and SG2 were 13.7 Mb and 90.5 kb, respectively. 【Conclusion】Given rich genetic variation, the population consisting of 273 rice germplasm resources is suitable for excellent alleles mining through association mapping.

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Evaluation of Dynamic Plant Type and Radiation Use Efficiency of indica Hybrid Rice Restorer Lines Feng WANG, Yilong LIAO, Wuge LIU, Diling LIU, Xueqing ZENG, Youqiang FU, Manshan ZHU, Jinhua LI, Chongyun FU, Xiaozhi MA, Xing HUO 2021, 35(2): 141-154.  DOI: 10.16819/j.1001-7216.2021.0207 Abstract ( )   HTML ( )   PDF (5728KB) ( )   【Objective】A restorer (R) line with ideal dynamic plant type (DPT) is the premise of hybrid rice breeding with high and stable yield. The purpose of this study is to evaluate the DPT and radiation use efficiency (RUE) of the R lines bred in different periods, and investigate the characteristics of ideal DPT for efficient utilization of light energy, and lay a theoretical basis for breeding of high-yielding hybrid rice with high RUE. 【Method】A field experiment was conducted under the ecological conditions of South China with eight widely and commercially used R lines of indica hybrid rice Minghui 63, Minghui 82, Shuhui 527, Guanghui 998, Guanghui 308, Guanghui 128, Guanghui 122 and Gui 99 as material. The dynamic changes of tiller number, leaf area index (LAI), light transmittance of the population, leaf size, leaf angle and leaf color (SPAD value), as well as the photosynthetic rate in the heading stage, heading date, yield related traits and RUE were measured. 【Result】There existed significant difference in dynamic changes of plant type, yield and RUE among the restorer lines. Ideal DPT was closely related to RUE. With the most ideal DPT under the ecological conditions of South China, Guanghui 998, Guanghui 308 and Minghui 82 had the highest RUE. According to the cluster analysis, Guanghui 998, Guanghui 308 and Minghui 82 were classified into ClusterⅠwith high RUE, and the other five restorers fallen into ClusterⅡ. Finally, based on the ecological conditions in South China, an ideal DPT model of rice for efficient utilization of light energy was proposed. And the key indicators of breeding and selection were as follows: a) The tiller number and leaf area increased rapidly after transplanting; it cost less than 27 d to make LAI≥1.0, and less than 38 d to peak tiller number with moderate tillering ability, and the highest tiller number less than 600/m2 ; b) Narrow, droopy and long leaves in the early stage. On 15 days after transplanting, the average length, width and opening angle of the top three complete leaves were about 37 cm, ≤0.9 cm and ≥80°, respectively; narrow and straight leaf in late stage; on the 20th day after heading, the average opening angle, length and width of the top three leaves were ≤65°, 43 cm and ≤1.3 cm, respectively, belonging to medium sized leaf type. c) In the late stage, the leaf color turned from green to orange or yellowish gradually without premature senescence. The SPAD values ranged from 35 to 40, the decrease of SPAD value between 20 days before heading and 20 days after heading was less than 13%; the average number of grains per panicle was about 180 with the number of effective panicles more than 300 / m2 and seed setting rate≥85%. 【Conclusion】Guanghui 998 and Guanghui 308 have better DPT and higher RUE. The hybrid rice Tianyou 998, Boyou 998 and Wuyou 308 derived from these restor lines, have become the leading rice varieties for many years in southern China. Breeding hybrid rice with high and stable yield through the developing of R lines with ideal DPT and high RUE is an effective and important way.

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Effects of Interaction Between Irrigation Mode and Nitrogen Application Rate on the Yield Formation of Main Stem and Tillers of Rice Cheng YANG, Yang WANG, Wanyang ZHANG, Tinghong YE, Jianwei LU, Geng ZHANG, Xiaokun LI 2021, 35(2): 155-165.  DOI: 10.16819/j.1001-7216.2021.0519 Abstract ( )   HTML ( )   PDF (8546KB) ( )   【Objective】 The effects of the interaction between irrigation mode and nitrogen application rate on root morphology, yield formation of main stem and tillers were studied in order to lay a theoretical basis for green rice production and efficient use of water and fertilizer. 【Method】 Using the cultivar Liangyou 287 as the material, nine treatments were designed using the combinations of three irrigation modes (immersion irrigation, conventional irrigation, and submerged irrigation, abbreviated as W1, W2, and W3) and three nitrogen fertilizer rates (0, 165.0, and 247.5 kg/hm2, abbreviated as N0, N1, and N2). Sampling was conducted at key growth stages of rice to determine root morphology and vitality, tiller dynamics, biomass and nutrient content, and to study the effects of irrigation mode and nitrogen application rate and their interaction on rice growth and development, grain yield, nitrogen fertilizer use efficiency and rice quality. 【Result】Compared with W2 treatment, although the productive tiller percentage of rice under W1 treatment was reduced by 9.2% on average, the yield of main stem, primary tillers and secondary tillers increased by 32.7%, 18.1% and 33.4%, respectively. The total yield increased by 18.5% on average. The productive tiller percentage of rice under W3 decreased by 5.0% on average, and the yield of main stem, primary tiller and secondary tiller increased by 9.3%, 2.0% and 46.4%, respectively as compared with W2 treatment. However, there was no significant difference in total yield between W2 and W3. Compared with the N0 treatment, the productive tiller percentage at two nitrogen application levels increased by 6.1% on average, the main stem and primary tiller yields increased by 8.1% and 92.6% on average, and the secondary tiller yield increased by 0.57 t/hm2 on average (N0 secondary tiller emerged in the N0 treatment), the total yield increased by 88.0% on average. The results of analysis of variance showed that there was a significant interaction between irrigation mode and nitrogen application rate on the yield of main stem and tillers, total yield and number of spikelets per panicle. In addition, irrigation mode and nitrogen application rate have significant effects on root morphology, root vitality, nitrogen uptake and nitrogen dry matter production efficiency. The results of analysis of variance showed that there were significant interactions between irrigation mode and nitrogen application rate on total root length, root volume, number of root tips, root bleeding rate, root biomass, crop growth rate, and so on. 【Conclusion】 Irrigation mode and nitrogen application rate significantly affect rice root morphology, tiller formation and yield, and there is a clear interaction. Under the experimental conditions, the appropriate application level of nitrogen fertilizer (165.0 kg/hm2) in the immersion irrigation mode can increase the water and nitrogen fertilizer use efficiency and improve rice quality while obtaining higher yield.

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Study on Physiological Characteristics Behind Mitigative Effects of Flooding on Low Temperature-caused Chilling Damage to Direct Seeded Early indica Rice at the Seedling Stage Wenxia WANG, Liming CHEN, Haixia WANG, Youqing LIU, Ziming WU, Yongjun ZENG, Xueming TAN, Xiaohua PAN, Qinghua SHI, Yanhua ZENG 2021, 35(2): 166-176.  DOI: 10.16819/j.1001-7216.2021.0914 Abstract ( )   HTML ( )   PDF (29683KB) ( )   【Objective】It is important to explore the effects of flooding on the growth of direct seeded early indica rice seedlings under low-temperature stress, and lay a physiological basis for direct seeded rice production and stress-resistant cultivation in South China. 【Method】The cold-tolerant cultivar Xiangzaoxian 6 and cold-sensitive cultivar Zhongjiazao 17 were used as materials in this experiment, and three treatments each lasting three days including low temperature treatment (8ºC), low temperature & flooding treatment (8ºC plus flooding) and ambient temperature as control treatment (25ºC) were designed to analyze the physiological characteristics including agronomic characters, antioxidant enzyme activities, osmotic regulation substances contents, photosynthesis enzyme activities and endogenous hormone contents of rice seedlings. 【Result】 Compared with low temperature (LT), the seedling height, fresh weight, dry weight and T3 (the 3rd leaf from top) leaf length of different cultivars significantly increased after three days at low temperature under flooding (LTF), and the root number, root length, T1 (the first leaf from top) leaf length and T2 (the 2nd leaf from top) leaf length also increased. Flooding could reduce the damage induced by low temperature to the agronomic characters of rice seedlings with the cold-tolerant cultivar Xiangzaoxian 6 less affected as compared with cold-sensitive cultivar Zhongjiazao 17. In addition, compared with LT, LTF significantly decreased the antioxidant enzymes activities (SOD, POD, CAT), soluble protein contents, osmotic regulatory substances contents (MDA, proline) and endogenous growth inhibitory hormone contents, ABA content, whereas increased the content of endogenous growth promoting hormone GA3 under low temperature; Flooding could alleviate the accumulation of reactive oxygen species (ROS) and the aggravation of membrane lipid peroxidation in plants, and improve the regulation of endogenous hormones in plants. Meanwhile, LT and LTF significantly decreased the contents of chlorophyll and ATP in leaves, resulting in the decrease of photosynthetic enzyme activities (Rubisco, PEPCK); but LTF had lower damage than that of LT, and LTF could play a mitigating role. After the recovery treatment, the physiological activity indexes of rice subjected to LTF were close to the level of CK, whereas the self-response mechanism of cold-tolerant cultivar could reduce the damage caused by low temperature stress. 【Conclusion】 Low temperature treatment affected the growth characteristics and photosynthetic enzyme activity of direct seeded early indica rice seedlings, and increased the antioxidant protective enzyme activity and osmotic regulation potential of leaves, but flooding treatment help to alleviate the physiological damage of leaves caused by low-temperature stress.

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Differential Responses of Grain Yields to High Temperature in Different Stages of Reproductive Growth in Rice Youjin SONG, Chao WU, Ziyu LI, She TANG, Ganghua LI, Shaohua WANG, Yanfeng DING 2021, 35(2): 177-186.  DOI: 10.16819/j.1001-7216.2021.0203 Abstract ( )   HTML ( )   PDF (11332KB) ( )   【Objective】Our aim is to study the response of rice yield to different types of high temperature in different growth periods, and lays a basis for selection and breeding of heat-resistant rice varieties. 【Method】Heat-tolerant rice varieties Nagina 22, Shanyou 63 and heat-sensitive varieties Liangyoupeijiu were pot-cultured at high daytime temperature, high nighttime temperature, high day- plus night-time temperature, and normal temperature during panicle initiation, flowering, and grain filling in artificial climate rooms, so as to elucidate the response of rice yield and yield components to high temperature in different growth periods. 【Result】Shanyou 63 had comprehensive tolerance in the three growth stages; Nagina 22 had strong tolerance to high temperature during flowering and filling, but was susceptible to high temperature during panicle initiation; Liangyoupeijiu was sensitive to high temperature during all reproductive growth stages. Shanyou 63 showed stable root bleeding intensity at different reproductive growth stages, while the root bleeding intensity of Liangyoupeijiu decreased significantly at high temperature. 【Conclusion】There is no significant correlation between high temperature tolerance of rice in different periods. Comprehensive tolerance to high temperature in different periods should be taken into consideration in selection or breeding of heat-resistant rice varieties.

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Effects of Ozone Stress on Feeding Quality of Straw of Different Rice Varieties During the Whole Growth Period Yanliu ZHANG, Zaisheng SHAO, Yang YANG, Kaicheng TONG, Yunxia WANG, Liquan JING, Yulong WANG, Lianxin YANG 2021, 35(2): 187-199.  DOI: 10.16819/j.1001-7216.2021.0710 Abstract ( )   HTML ( )   PDF (1196KB) ( )   【Objective】The purpose of this study is to investigate the effects of ozone stress on feeding quality of rice straw. 【Method】By using a new-type natural-light gas fumigation platform, eight rice varieties were treated with high ozone (80 nL/L) or clean air from transplanting to maturity. The physicochemical indexes related to feed quality of rice straw at heading, 20 days after heading (DAH20) and maturity were analyzed. 【Result】The ozone stress increased the concentrations of crude protein, lignin, cellulose, hemicellulose and total phenol in rice straw by 7.07% (P< 0.1), 10.88% (P< 0.1), 1.98%, 0.92% and 5.01% (P<0.01), respectively; while the concentrations of soluble sugar and starch decreased by 15.07% (P< 0.1) and 18.55% (P<0.01). In most cases, the changes of feed quality index in leaves under ozone stress were greater than those in stems, respectively. Significant genotypic differences were detected for each measured feed value indexes. The concentrations of lignin, cellulose, hemicellulose and total phenol in straw followed the tendency of DAH20 > maturity > heading, the concentrations of soluble sugar and starch showed the opposite trend of heading > maturity > DAH20, while the crude protein concentration decreased successively with the growth process. Analysis of variance revealed significant interactions between ozone stress and varieties for all measured feed value indexes. Significant interactions between ozone and plant organs were detected for all feed value indexes except total phenol concentration. Significant interactions between ozone and growth period were found for the concentrations of crude protein, cellulose, soluble sugar and total phenol. 【Conclusion】Physicochemical indexes related to feed value of rice straw varied with the growth stages, varieties and organs of plants, ozone concentration of 80 nL/L leads to deterioration of feed value of rice straw.

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Changes in Endogenous Hormones in Rice Seedlings Infested by White-backed Planthoppers Xuelu WEI, Baiyi LU, Fugang HUANG, Fahuo LI, Fang LIU, Yongfu QIU 2021, 35(2): 200-206.  DOI: 10.16819/j.1001-7216.2021.0815 Abstract ( )   HTML ( )   PDF (16137KB) ( )   【Objective】It is of great importance to study the changes of endogenous hormone concentration and relative expression level of associated genes in rice seedling after infestation by white-backed planthoppers (WBPH), which would provide reference for insight into WBPH resistance mechanism regulated by endogenous hormones. 【Method】Salicylic acid (SA), abscisic acid (ABA), jasmonic acid (JA), and auxin (IAA) in susceptible line 9311 and near isogenic line (NIL) of resistance were quantified using UPLC-MS at 0, 24, and 48 h after infestation by WBPH; and the relative expression levels of five associated genes between resistant and susceptible lines were detected by qRT-PCR. 【Result】SA concentration in NIL increased at 24 h after WBPH infestation and decreased at 48 h after WBPH infestation as compared to the untreated line; while it was on the contrary in 9311. ABA concentration was relatively stable in NIL after WBPH infestation, but increased at 24 h and then decreased at 48 h after WBPH infestation in 9311. Both IAA and JA concentration continuously increased in resistant and susceptible lines after infestation treatment. The result of qRT-PCR indicated that the relative expression levels of hormone pathway-related genes OsPAL06, OsZEP, OsLOX, and OsYUCCA1 were significantly different at 24 h after WBPH infestation between resistant and susceptible lines, but no significant difference was observed at 0 and 48 h after WBPH infestation. However, the relative expression level of OsICS1 showed significant difference at 48 h after WBPH infestation between the resistant and susceptible lines; whereas no significant difference was detected at 0 or 24 h after WBPH infestation. 【Conclusion】JA and ABA concentration in the resistant plants were higher than those in the susceptible ones, which was possibly associated with the resistant genes. SA concentration and the relative expression level of its associated genes OsPAL06 and OsICS1 indicated that the resistant line responded more quickly to WBPH infestation, which suggested that it might play an important role during insect infestation.