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10 July 2022, Volume 36 Issue 4 Previous Issue    Next Issue
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Reviews and Special Topics

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Roles of Polyamines and Ethylene in Grain Filling, Grain Weight and Quality of Rice XU Yunji, TANG Shupeng, JIAN Chaoqun, CAI Wenlu, ZHANG Weiyang, WANG Zhiqin, YANG Jianchang 2022, 36(4): 327-335.  DOI: 10.16819/j.1001-7216.2022.211010 Abstract ( )   HTML ( )   PDF (15601KB) ( )   It is of great significance to study grain yield and quality characteristics for breeding and cultivation of rice with high quality and high yield. Polyamines (PAs) and ethylene (ETH) are two important endogenous plant growth regulators, which play crucial roles in regulating grain filling, grain weight and quality in rice. In this manuscript, we introduced the characteristics of PAs, ETH, grain filling, grain weight and rice quality, briefly described the relationships of grain filling with grain weight and quality, and then focused on reviewing the regulation and physiological mechanism of PAs and ETH on grain filling, grain weight, and quality (including milling, appearance and nutritional qualities, and grain starch quality) in rice. The existing problems and future research direction were also discussed.

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Research Progress of Rice with Low Glycemic Index LI Xia, JIANG Yanjie, TAO Yajun, LI Wenqi, WANG Fangquan, CHEN Zhihui, XU Yang, WANG Jun, FAN Fangjun, ZHU Jianping, Sreenivasulu NESE, YANG Jie 2022, 36(4): 336-347.  DOI: 10.16819/j.1001-7216.2022.210902 Abstract ( )   HTML ( )   PDF (103817KB) ( )   Milled white rice is typical starch-rich food, serves as the major daily caloric source for a majority of the world population especially for Asian. Most rice varieties are of high glycemic index, a food quality inferenced to contribute to the health problems surrounding high-calorie intake and dysregulated glucose metabolism. A lot of studies have been carried out attempting to lower glycemic index. The effects of various factors, large-scale screening methods, genetic mechanism and its related genes, starch structure and genetic improvement on low glycemic index of rice were summarized in this review. And proposal researches were put forward as well.

Research Papers

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OsLOX10 Positively Regulates Defense Responses of Rice to Rice Blast and Bacterial Blight ZHOU Yonglin, SHEN Xiaolei, ZHOU Lishuai, LIN Qiaoxia, WANG Zhaolu, CHEN Jing, FENG Huijie, ZHANG Zhenwen, CHEN Xiaoting, LU Guodong 2022, 36(4): 348-356.  DOI: 10.16819/j.1001-7216.2022.210604 Abstract ( )   HTML ( )   PDF (62674KB) ( )   【Objective】Rice blast caused by Magnaporthe oryzae and bacterial blight caused by Xanthomonas oryzae pv. oryzae (Xoo) seriously affect rice yield and quality. The transgenic materials of OsLOX10 were created to evaluate the resistance to M. oryzae and Xoo. The possible mechanism of OsLOX10 in regulating the defense responses to rice blast and bacterial blight were elucidated. 【Method】The knockout vector of OsLOX10 was constructed using CRISPR/Cas9 system, and the overexpression vector of OsLOX10 was constructed by linearizing pCXUN-HA with restriction enzyme XcmⅠ and linking with TA ligation. Transgenic rice was obtained by genetic transformation, and the homozygous transgenic lines were screened for fungal and bacterial resistance analysis. The expression dynamics of SA (salicylic acid) and JA (jasmonic acid) pathway marker genes were analyzed by qRT-PCR after infection with M. oryzae. The outbreak of reactive oxygen species (ROS) induced by chitin and flg22 in rice was also observed. 【Result】qRT-PCR analysis showed that the OsLOX10 expression was up-regulated 24 h after inoculation with M. oryzae and Xoo. The OsLOX10 knockout lines were more susceptible to the rice blast than that of the wild type (Nipponbare) when inoculated with the spore suspension of M. oryzae Guy11, while the overexpressed lines had no typical disease symptoms. At 6, 12, 24 and 36 hours post inoculation, the transcriptional levels of three pathogenesis-related genes, OsPBZ1, OsPR1a and OsPR1b, and two JA pathway genes, OsAOS2 and OsLOX5, and SA pathway gene OsPAL1, were significantly down-regulated in the knockout transgenic lines. However, they were significantly up-regulated in overexpressed transgenic lines. The OsLOX10 transgenic rice was inoculated with Xoo (PXO99A), and the OsLOX10 knockout lines were more susceptible to bacterial blight. qRT-PCR analysis showed that the relative expression levels of OsPR1b, OsPAL1 and the three genes (OsAOS2, OsAOC and OsJAZ) involved in the JA synthesis pathway were up-regulated in OsLOX10 overexpression lines, significantly down-regulated in OsLOX10 knockout lines seven days after Xoo inoculation. OsLOX10 knockout also significantly reduced the ROS level induced by chitin and flg22 in rice, delayed the peaking time of ROS induced by chitin, and reduced the sensitivity of rice to chitin and flg22.【Conclusion】OsLOX10 could be induced by infection with M. oryzae and Xoo. OsLOX10 may be involved in pathogen-associated molecular patterns triggered immunity, and play a positive regulatory role in rice resistance to rice blast and bacterial blight. Moreover, the OsLOX10 may regulate rice resistance to M. oryzae and Xoo through SA and JA mediated signaling pathways.

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Phenotypic Identification and Gene Mapping of a Lesion Mimic Mutant lmm7 in Rice SUN Zhiguang, DAI Huimin, CHEN Tingmu, LI Jingfang, CHI Ming, ZHOU Zhenling, LIU Yan, LIU Jinbo, XU Bo, XING Yungao, YANG Bo, LI Jian, LU Baiguan, FANG Zhaowei, WANG Baoxiang, XU Dayong 2022, 36(4): 357-366.  DOI: 10.16819/j.1001-7216.2022.210711 Abstract ( )   HTML ( )   PDF (54710KB) ( )   【Objective】The study of lesion mimic mutants (LMMs) is helpful to understand the interaction between growth and defense response in plants.【Method】We herein reported a novel lesion mimic mutant 7 (lmm7) derived from a japonica rice variety FI135 by embryo culture. For deciphering the effect of lmm7 on plant growth, phenotype and agronomic traits were compared between the wild type (WT) and lmm7 plants. The ultrastructure of mesophyll cells and histochemical characterization was done in WT and lmm7 plants. Evaluation of WT and lmm7 was observed for resistance to pathogens was employed to explore the underlying effect of lmm7 on plant defense response. An F2 population derived from the cross between lmm7 mutant and 9311B was used for genetic analysis and gene mapping.【Result】The seedlings of lmm7 were normal at the seedling stage, but the basal leaves began to exhibit brown spots at the initial tillering stage, which then spread to the whole plant, and the number of mosaic spots increased along with the development of lmm7 plants. Compared with the wild type, agronomic traits including plant height, panicle length, effective panicle number, grain number per panicle, and seed setting rate were significantly decreased in the mutant. However, no significant difference in seed traits and heading date was observed between WT and lmm7 plants. The shading assay indicated that lesion formation in lmm7 was induced by light. The mesophyll cells of lmm7 mutant were seriously chlorotic, and the photosynthetic pigment contents of the mutant were significantly decreased at the heading stage. Histochemical analysis showed that a large amount of hydrogen peroxide (H2O2) accumulated at the lesion sites. The observation with a transmission electronic microscope (TEM) demonstrated that the number of chloroplasts in mesophyll cells of lmm7 plants was decreased, the lamellar structure of chloroplasts was seriously damaged, and osmiophilic granules were obviously increased in the mutant. Moreover, the levels of reactive oxygen species (ROS) were increased in the internal and surrounding regions of the lesions. The lmm7 plants displayed higher resistance to rice blast compared to the wild type. Genetic analysis revealed that in lmm7 the mutation was controlled by a single recessive gene. Using a map-based cloning strategy, lmm7 was narrowed down to a 260 kb region between InDel markers 7B35 and 7B43 on the short arm of chromosome 7 in rice. Sequencing analysis revealed that a deletion of T base at 2891 nucleotide position occurred in the DNA sequence of LOC_Os07g0203700, resulting in a frame-shift mutation and a premature stop codon.【Conclusion】The results reveal the target gene is allelic to spl5, and the mutation of lmm7 enhances resistance to rice blast, while it curbs the growth and development of lmm7 plants.

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Effects of Moisture Content on Root Vigor and the Expression of Aquaporin-related Genes in Rice Seedlings Under Low Temperature Stress HUANG Qina, JIANG Su, WANG Limin, ZHANG Yan, YU Linfei, LI Chunfu, DING Liqun, SHAO Guosheng 2022, 36(4): 367-376.  DOI: 10.16819/j.1001-7216.2022.210805 Abstract ( )   HTML ( )   PDF (12286KB) ( )   Abstract：【Objective】The purpose of this study is to explore the effects of moisture content or humidity on root vigor and water transport of rice seedlings under low temperature stress. 【Method】Two rice cultivars (Jiaxian 7 and Fu 8329) with different chilling tolerance were used as materials. Experiment I (humidity 30%, 60% and 90%) and experiment Ⅱ (quick rewarming experiment) were carried out. 【Result】Compared with lower humidity (30%), higher humidity (60% and 90%) could effectively increase the root vigor, ensure the survival rate of rice seedlings and alleviate the chilling injury. The expression level of OsPIP2;5 and OsPIP2;6 were closely related to root vigor, which had a significant regulatory effect on cold tolerance of rice. Compared with normal rewarming treatment (CK), the water content and root vigor of rice seedlings were decreased after quick rewarming treatment. The survival rate in CK was significantly higher than in the quick rewarming experiment. 【Conclusion】 Low temperature stress affects the growth and development of rice seedlings. After chilling injury, high humidity can alleviate the damage and ensure the rice survival rate. Humidity environment after low temperature stress significantly influenced the water content, root vigor and the expression levels of genes related to aquaporin. The expression levels of OsPIP2;5 and OsPIP2;6 were positively correlated with root vigor, and played an important role in resistance to cold injury of rice seedlings. Therefore, compared with large-scale irrigation in the field after low temperature stress, the slow soil temperature rise had less effect on root vigor and can help rice seedlings to restore their life activities.

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Effects of High Temperature in Various Phases of Grain Filling on Rice Starch Physicochemical Properties SHEN Hong, YAO Dongping, WU Jun, LUO Qiuhong, WU Zhipeng, LEI Dongyang, DENG Qiyun, BAI Bin 2022, 36(4): 377-387.  DOI: 10.16819/j.1001-7216.2022.210413 Abstract ( )   HTML ( )   PDF (67520KB) ( )   【Objective】The effects of high temperature on the composition, structure and physicochemical properties of rice starch at different parts of grain filling were studied to reveal the effect of high temperature and the relationship among high temperature, structure and function.【Method】Heat-tolerant Huanghuazhan and heat-sensitive near-isogenic lines of 9311 were used as experimental materials. The experiment was conducted in artificial climate boxes at high temperature (38℃/30℃) and control temperature (28℃/22℃) to clarify the effects of high temperature during early (1－15 d after full heading) and late (from 16 d after full heading to maturity) grain-filling on rice processing quality, appearance quality, starch composition, amylopectin chain length distribution, particle size distribution, gel consistency, viscosity, gelatinization, crystalline properties and starch granule morphology. 【Result】High temperature at grain-filling stage significantly reduced brown rice rate, polished rice rate and head milled rice rate, but significantly increased chalky grain rate and chalkiness, resulting in poor processing and appearance quality. High temperature during grain filling obviously decreased total starch contents, amylose content, short chain amylopectin content, percentage of large granule, amylose/amylopectin ratio, while increased medium chain amylopectin content, percentage of small & medium granule and gelatinization temperature, gelatinization enthalpy and significantly affected viscosity properties, relative crystallinity with same crystalline type, as well as pitting and unevenness on the surface of the starch granules, making starch granules more fragmented and cooking and eating quality worse. The effects of high temperature at different times of grain filling stage on rice quality were different. The damage degree of high temperature at early grain filling stage was greater than that at late grain filling, and the effect on the heat-tolerant variety was less than that of the heat-sensitive variety. The high temperature at early grain filling stage led to the highest setback and the lowest breakdown, which degraded the viscosity properties. The high temperature at late grain filling had the lowest setback and the highest breakdown, which made the viscosity properties better. 【Conclusion】The starch structure and physicochemical properties were more affected by the high temperature during early grain filling as compared with late grain filling stage. The processing, appearance, cooking and eating quality of rice were worse due to the high temperature at early grain filling stage. The high temperature at late grain filling stage was helpful to improve the viscosity property of rice.

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Effects of Water-nitrogen Coupling on Nitrogen Uptake, Utilization and Yield of Rice Under Wheat Straw Returning ZHANG Yujie, WANG Zhiqiang, MA Peng, YANG Zhiyuan, SUN Yongjian, MA Jun 2022, 36(4): 388-398.  DOI: 10.16819/j.1001-7216.2022.210803 Abstract ( )   HTML ( )   PDF (55820KB) ( )   【Objective】It is of significance to study the effects of different water and nitrogen coupling on nitrogen absorption, utilization and yield of indica hybrid rice with wheat straw returning.【Method】The nitrogen decomposition rate, nitrogen absorption and utilization were analyzed under two water treatments, three N treatments and two straw returning treatments with F You 498 as material with wheat straw returning at main growth stages. The two water treatments were alternative dry-wet irrigation and submerged irrigation and the straw returning treatments were full-burying returning and no straw returning and the N treatments were 150 kg/hm2 of N application rates with three N regimes—the ratio of the basal fertilizer, tillering fertilizer and panicle fertilizer were 3∶3∶4 (N1), 7∶3∶0 (N2) and 0 (N0), respectively.【Result】The results showed that the alternative dry-wet irrigation promoted the release of straw nitrogen, increased the aboveground nitrogen accumulation of rice after jointing by 4.85%－33.92%, improved the nitrogen transport capacity of stem and sheath at maturity, increased the nitrogen absorption of panicle by 10.73%－16.42%, finally leading to an increase in the number of effective panicles and grain yield by 2.51%－3.77%. Straw returning (S1) released nitrogen nutrition, increased the aboveground nitrogen accumulation of rice by 5.15%－53.21% and the nitrogen transport capacity of leaves at maturity, increased the nitrogen absorption of panicle by 4.93%－43.91%, and finally increased the yield by 9.62%－18.33%. Nitrogen application promoted the release of straw nutrients and improved the nitrogen absorption and transport capacity of rice plants, increased the number of effective panicles and significantly increased the yield by 16.21%－28.31%. Compared with the alternative dry-wet irrigation coupled with optimized nitrogen application (N1) mode, the flooding irrigation coupled with traditional nitrogen application (N2) mode promoted the release of straw nutrients, increased the aboveground nitrogen accumulation of rice by 1.17%－11.89%. It improved the aboveground nitrogen accumulation capacity and nitrogen transport capacity of stems, sheaths and leaves, and significantly improved the nitrogen recovery and utilization rate by 7.27%－26.06%.【Conclusion】Under the conditions of full burying of wheat straw and returning to the field, the alternative dry-wet irrigation coupled with optimized nitrogen application can promote the release of straw nitrogen, effectively improve the nitrogen accumulation and utilization capacity of rice, and improve the nitrogen recovery and utilization rate and water use efficiency. It is the most suitable water-fertilizer coupling model in this experiment.

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Effect of Rhizosphere Oxygen Environment on the Root Micromorphological Structure of Rice Seedlings and Its Physiological Mechanism XIAO Deshun, XU Chunmei, WANG Danying, ZHANG Xiufu, CHEN Song, CHU Guang, LIU Yuanhui 2022, 36(4): 399-409.  DOI: 10.16819/j.1001-7216.2022.211103 Abstract ( )   HTML ( )   PDF (31609KB) ( )   【Objective】This study was conducted to research the effect of rhizosphere oxygen environment on the root micromorphological structure of rice seedlings and its physiological mechanism, so as to lay a theoretical basis for the construction of ideal root type of rice.【Method】Two varieties, Chunyou 84 and Xiushui 09, were cultured in nutrient solution with different oxygen content (OC) levels (low oxygen, OC 0－1.0 mg/L; medium oxygen, OC 2.5－3.5 mg/L; high oxygen, OC >6.0 mg/L, continuous bubbling with atmospheric air, and normal conditions as CK, conventional hydroponics without oxygen regulation, the oxygen content in water approximately 0.3－2.5 mg/L) controlled by on-line dissolved oxygen meters. After different oxygen treatments, the biomass, root micromorphological structure, and some root physiological indexes (organic acid content, respiratory intensity, and so on) of rice seedlings were measured and analyzed.【Result】1) The proportions of fine roots (d1, 0－0.50 mm; d2, 0.51－1.00 mm; d3, 1.01－1.50 mm) were more than 90%, which were particularly important for the construction of root morphology for rice seedlings. At medium oxygen level, the root length and root surface area of Chunyou 84 with diameter d1 and d2, and Xiushui 09 with diameter d1 and d3 were significantly higher than those of the control. 2) Low oxygen treatment reduced the biomass of shoot and root, inhibited the growth of fine roots (d1), promoted the growth of coarse roots (d5, 2.01－2.50 mm), reduced the root respiration rate and increased the secretion of organic acids. Medium and high oxygen treatments both increased the biomass of rice plants, but had different effects on root physiology. Medium oxygen treatment increased root respiration rate, while high oxygen treatment decreased. Different oxygen treatments reduced the content of root auxin (IAA). Especially, there was obvious difference between medium and high oxygen treatments with the control. The content of nitric oxide (NO) increased significantly under the high oxygen treatment, but there was no significant difference among other treatments. 3) The results of correlation analysis showed that the morphological indexes (root length, surface area, and volume) of the total and fine roots (d2) of the two varieties were positively correlated with root organic acid secretion, respiratory intensity, and nitric oxide content, on the contrary, they were negatively correlated with auxin content.【Conclusion】Moderate increase of dissolved oxygen concentration (medium oxygen treatment) could improve the root respiration rate and organic acid secretion of rice seedlings, enhancing the root function and increasing the proportion of the length and absorption area of fine root (d1－d3), optimizing the root morphological structure. Therefore, appropriate cultivation measures could change the rhizosphere oxygen environment, regulate the micro morphological structure of rice roots at tillering stage and enhance the function of roots in field.

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Effect of Aeration Treatment on Soil Microbial Biomass Carbon, Nitrogen and Enzyme Activities in Paddy Field ZHANG Lu, WU Longlong, HUANG Jing, TIAN Cang, QI Jun, ZHANG Junhua, CAO Xiaochuang, ZHU Chunquan, KONG Yali, JIN Qianyu, ZHU Lianfeng 2022, 36(4): 410-418.  DOI: 10.16819/j.1001-7216.2022.211107 Abstract ( )   HTML ( )   PDF (5447KB) ( )   【Objective】 It is of great importance to elucidate the effects of different aeration methods on soil microbial biomass carbon, nitrogen and soil enzyme activities in paddy fields, 【Method】 Using Zhonghan 221 (upland rice), Zhongzheyou 8 (rice) and IR45765-3B (deepwater rice) as materials, the effects of the micro-nano bubble water aeration irrigation (MBWI), dry-wet alternate irrigation (AWD) and flooding irrigation (WL) on soil microbial biomass carbon, nitrogen in paddy soil, nitrogen metabplic intensity and activities of enzymes related to nitrogen transfomation were studied. 【Result】 Soil microbial biomass C and N could be significantly increased by micro-bubble aeration irrigation and dry-wet alternate irrigation. The soil microbial biomass C and N increased by 30.0%~46.1% and 7.1%~92.1% in Zhonghan 221, Zhongzheyou 8 and IR45765-3B, respectively. The activities of urease, sucrase, catalase, protease and hydroxylamine reductase in paddy soil were increased by micro-nano bubble water aeration irrigation and dry-wet alternate irrigation compared with flooding irrigation, the nitrate reductase activity and nitrite reductase activity were reduced. 【Conclusion】 Micro-nano bubble water aerobic irrigation and dry-wet alternate irrigation can improve the oxidation characteristics of paddy soil, increase soil enzyme activities, microbial biomass carbon, nitrogen and nitrification intensity, and contribute to the improvement of soil environment and fertility, strike a balance between C and N metabolism.

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Interactive Effects of HCO3− and Irrigation Methods on Iron Uptake and Utilization in Rice ZHANG Xinjiang, WANG Xiangbin, LIU Linghui, WEI Changzhou 2022, 36(4): 419-427.  DOI: 10.16819/j.1001-7216.2022.210904 Abstract ( )   HTML ( )   PDF (10035KB) ( )   【Objective】Drip-irrigated rice with plastic film mulch (DI-PFM) is a rice cultivation technique with both high yield and water-saving potential. However, DI-PFM rice on calcareous soil often exhibits Fe-chlorosis symptoms. Previous studies found that the inhibitory intensity of HCO3− on Fe uptake of DI-PFM rice was weaker than that of flooding irrigation rice, but the underlying mechanism remains unclear. The effects of HCO3− on soil DTPA-Fe concentration, xylem sap pH, Fe absorption and distribution of two kinds of irrigated rice were studied. 【Methods】The experiment included two irrigation methods [flooding irrigation (FI) and DI-PFM] and four HCO3− concentrations (0, 2, 10 and 40 mmol/L HCO3−, were expressed as BC-0, BC-2, BC-10 and BC-40, respectively) of irrigation water. 【Results】The concentration of soil DTPA-Fe in DI-PFM was significantly lower than that in FI. With the increase of HCO3− concentration, soil pH increased, while soil DTPA-Fe concentration decreased. Xylem sap pH of rice increased with the increase of HCO3− concentration in irrigation water, and the xylem sap pH of FI rice was significantly higher than that of DI-PFM. With the increase of HCO3− concentration, the apoplast Fe concentration in rice leaves and roots decreased at low HCO3− level and increased at high HCO3− level, and peaked under BC-40 treatment. The leaf active Fe concentration, symplastic Fe concentration, rice biomass and total Fe accumulation of two kinds of irrigated rice decreased with the increase of HCO3− concentration, but the decrease of these parameters under DI-PFM treatment were less than that of FI. The concentration ratio of symplastic Fe to apoplast Fe in rice roots and leaves decreased with the increase of HCO3− concentration, and the concentration ratio of symplastic Fe to apoplast Fe in rice roots and leaves in FI was higher than that of DI-PFM. 【Conclusion】The increased pH in xylem sap of rice caused by HCO3− affected the absorption and utilization of Fe in rice, but HCO3− was not the main factor leading to Fe deficiency in DI-PFM rice. The main reason for Fe deficiency of DI-PFM rice on calcareous soil may still be due to the low availability of soil Fe.

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Effect of Feed Protein Contents on Gaseous Nitrogen Emissions, Growth Performance of Catfish and Nitrogen Utilization in Rice-yellow Catfish Co-culture Model WANG Mengjie, WU Junnan, LIU Yaobin, XU Chunchun, FENG Jinfei, LI Fengbo, FANG Fuping 2022, 36(4): 428-438.  DOI: 10.16819/j.1001-7216.2022.211008 Abstract ( )   HTML ( )   PDF (7331KB) ( )   【Objective】 Clarifying the effect of protein contents in the feeds on N2O and NH3 emissions and on the growth of yellow catfish (Pelteobagrus fulvidraco) is conducive to the efficient and green development of rice-catfish co-culture model. 【Methods】In this study, pot-experiments were conducted to systematically study the effects of different dietary protein contents on the dynamics of N2O and NH3 flux rates, the nitrogen accumulation in the water and bottom soil, and the growth performance of yellow catfish in the rice-catfish co-culture treatments compared to the catfish monoculture. 【Results】 Rice-catfish co-culture significantly reduced the N2O emission, NH3 emission, total and inorganic nitrogen in the water by 18.30%, 76.20%, 41.30% and 48.85%, and significantly increased the protein accumulation of catfish and nitrogen use efficiency by 20.00% and 171.50%, respectively, as compared with catfish monoculture under the same protein streatment. The N2O emission and residual nitrogen in the water of rice-catfish co-culture treatments increased with the rise of the contents of protein in the feeds, but the NH3 flux rates did not show positive correlation with the contents of protein in the feeds. The specific growth rate and protein gain of catfish showed a quadratic correlation with the contents of protein in the feeds. And the nitrogen use efficiency decreased linearly with the increase of protein contents in the feeds.【Conclusion】The recommended protein contents in the feeds for rice-catfish co-culture model is less than 43.04% based on the synthetical evaluation on the effect of protein contents on the growth performance of catfish, N2O emission, and residue of nitrogen in the aquaculture water.