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10 November 2020, Volume 34 Issue 6 Previous Issue    Next Issue
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Research Progress and Breeding Prospects of Grain Size Associated Genes in Rice Yiwei KANG, Yuyu CHEN, Yingxin ZHANG 2020, 34(6): 479-490.  DOI: 10.16819/j.1001-7216.2020.9135 Abstract ( )   HTML ( )   PDF (3024KB) ( )   The breeding objectives of rice include high yield and good quality. Grain size is the three-dimensional structure ofseeds, which is one of the key traits determining grain yield and quality in rice. To date, more than 60 genes associated with grain size have been cloned, but the application of grain size genes in rice breeding has not been summarized. This review covers the current advances which can deepen our understanding, such as the key genes for grain size, genetic mechanism behindthis trait, breeding application of cloned genes, functional markers for molecular breeding and prospects for future study, which will provide information of molecular breeding for rice breeders.

Research Papers

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Function Analysis of Sucrose Transporter OsSUT4 in Sucrose Transport in Rice Mengzhu LI, Gaopeng WANG, Yue WU, Yi REN, Ganghua LI, Zhenghui LIU, Yanfeng DING, Lin CHEN 2020, 34(6): 491-498.  DOI: 10.16819/j.1001-7216.2020.0316 Abstract ( )   HTML ( )   PDF (3775KB) ( )   【Objective】The transmembrane transport of sucrose is mainly mediated by sucrose transporters, among which five SUT coding genes have been identified inrice. However, the role of OsSUT4 in the sucrose transport is unclear. 【Method】CRISPR/Cas9 techniques were used to construct ossut4-deletedmutants. The ossut4 mutant was featured by lower plant height and grain yield as well as higher tiller number as compared withwildtype plants.【Result】Sucrose and starchaccumulationin the leaf of the ossut4 mutants lead to slower net photosynthetic rate; insufficient sugar supply results in the postponeof grain filling. Base on the subcellular and histochemical localization,OsSUT4 was located on the cytoplasmic membrane. Tissue localization showed that OsSUT4 was expressed in the embryo of germinating seed, vascular bundles of coleoptile, glume shell, anthers at flowering stage and aleurone layer of caryopsis atfilling stage. 【Conclusion】OsSUT4 plays an important role in sucrose transport.

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QTL Analysis for Yield Traits Related to Low Nitrogen Tolerance Using Backcrossing Recombinant Inbred Lines Derived from Dongxiang Wild Rice (Oryza rufipogon Griff.) Ting WU, Xia LI, Derun HUANG, Fenglin HUANG, Yulong XIAO, Biaolin HU 2020, 34(6): 499-511.  DOI: 10.16819/j.1001-7216.2020.0408 Abstract ( )   HTML ( )   PDF (12486KB) ( )   【Objective】Dongxiang wildrice (Oryzarufipogon Griff.) has strong low nitrogen toleranceand is an important germplasm for low nitrogen tolerance improvement. Identification of genes responsible for low nitrogen tolerance in Dongxiang wild rice is of great importance to understand molecular mechanisms of low nitrogen tolerance and develop rice varieties with low nitrogen tolerance. 【Method】Quantitative trait loci (QTLs) for plant height and yield traits under low and normal nitrogen conditions wasidentified using backcrossing recombinant inbred lines (BC1F12) derived from an interspecific cross Xieqingzao B // Dongxiang wild rice/Xieqingzao B and its genetic linkage. 【Result】A total of 57 QTLs were detected in 33 regions on all chromosome, exceptchromosome 4 and 8. They explained individually 3.17%~63.40% phenotypic variation, and 32 QTLsof them had favorable alleles derived from Dongxiang wild rice.NineteenQTLs were simultaneously detected under both nitrogen treatments, and 38QTLs were only identified under single nitrogen treatment, suggesting variousgenetic mechanismsin rice growth and yield formation under low and normal nitrogen conditions. 【Conclusion】Fourteen QTLclusters, 43 QTLs included, scattered on sevenchromosomes, indicatingthe common genetic-physiological mechanisms behind different traits, and theQTL pyramiding for low nitrogen tolerance can be achieved by molecular marker-assisted selection.

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Mechanism Analysis of Rice Resistance Protein OsRRK1 Againstthe Brown Planthopper Yinhua MA, Pingfang LI, Wenjing DONG, Songwang YI, Fang YANG, Bo DU, Chenzhong JIN 2020, 34(6): 512-519.  DOI: 10.16819/j.1001-7216.2020.0406 Abstract ( )   HTML ( )   PDF (7016KB) ( )   【Objective】OsRRK1 (Rop-interacting receptor-like kinase 1) protein in rice is the first RLCK VI family protein in rice that has been studied.It plays an important role inregulating the curling of rice leaves and the defense against brown planthoppers. However, the mechanism of its regulation of resistance to the brown planthopperremains unclear. Weattempt to further explore the mechanism of OsRRK1gene resistance to the brown planthoppers.【Method】The interaction between OsRRK1 protein and OsLecRK (lectin-like receptor kinase), OsLecRK1, OsLecRK2 and OsLecRK3 was analyzed by yeast two-hybrid method.OsLecRK is a candidate gene forBPH15 range of anti-brown planthopper, and is an important member of rice innate immune system. OsLecRK is involved innot only rice innate immune response, including resistance to brown planthoppers, white leaf blight and rice blast, but alsothe development of rice. The gene clusters of OsLecRK1, OsLecRK2 and OsLecRK3 constitute the anti-brown planthopper gene BPH3. Rice containing the BPH3 gene has a broad spectrum and lasting insect resistance. Meanwhile, DNAMAN software was used to analyze the homology of OsLecRK with OsLecRK1, OsLecRK2 and OsLecRK3.【Result】The analysis results of DNAMAN showed that OsLecRK has high homology with OsLecRK1, OsLecRK2 and OsLecRK3, and the proteinsshared more than 50% identity.The results of yeast two-hybrid analysis showed that OsRRK1 interacted with OsLecRK, OsLecRK2 and OsLecRK3.【Conclusion】OsRRK1 participates in the process of resistance to the brownplanthoppersthroughinteracting with BPH15 and BPH3 candidate genes.

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Identification and Genetic Analysis of Cross-incompatibility ina RiceDW-type Sterile Line Tao XIONG, Yuanyuan NIE, Fangming MAO, Jianguo LEI, Linghua MAO, Shan ZHU, Renliang HUANG, Xianhua SHEN, Song YAN 2020, 34(6): 520-524.  DOI: 10.16819/j.1001-7216.2020.0610 Abstract ( )   HTML ( )   PDF (1526KB) ( )   【Objective】In the process of breeding DW-type three-line hybrid rice, cross incompatibility (CI) was found when the cytoplasmic male sterile (CMS) lines were crossed/backcrossed with some varieties. We focused on the traittolayatheoretical basis for improving CI of DW-type CMS lines, so as to promote the application ofDW-type three-line. 【Method】With isocytoplasmallonuclear materials of DW-type and isonuclear alloplasmic male sterile lines of WA-type as female parents, maintainer lines as male parents, cross experimentswere carried out to investigate the cause of CI. Genetic analysis and gene rough mapping were conducted using a set of chromosome single segment substitution lines, which were crossed to a DW-type CMS line DY1A, respectively.【Result】The CI was caused by nuclear-cytoplasmic interactions. Two types of CI were observed that the first type occurred in F0 crosses and another after backcrossing. For the first type, primarily genetic analysis showed that the CI was controlled by a recessive gene in the nucleus, temporarily named CI1(t), which was then mapped between the two markers RM6838 and RM5767, linked toRM3395,on chromosome 8.【Conclusion】The CI of DW-type CMS linescould beimprovedby molecular methods.

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Response ofRice Starch Synthesis to Night Temperature Changes Yuping ZHANG, Junke WANG, Yaliang WANG, Yanhua CHEN, Dengfeng ZHU, Huizhe CHEN, Jing XIANG, Yikai ZHANG, Xiaojun LIU, Yan ZHU, Weixing CAO 2020, 34(6): 525-538.  DOI: 10.16819/j.1001-7216.2020.0701 Abstract ( )   HTML ( )   PDF (90827KB) ( )   【Objective】To clarify the effect of night temperature changes on rice starch accumulation, and to explore circadian changes ofphysiological characteristics of rice amylose/amylopectin formation atvarious night temperatures.【Method】High-quality japonica rice ‘Zhehexiang 2’ was subjected to three night temperature gradients of 31℃/20℃ (LT), 31℃/24℃ (NT), and 31℃/28℃ (HT) at the beginning of grain ripening stage, and the amylose and amylopectin contents, the key enzyme activities involvedin amylose and amylopectin formation and the expression of related genes were measured at noon and midnight. 【Result】The results showed that1) compared with NT, LT and HT treatments significantly reduced grain weight and starch accumulation, LT and HT both reduced amylopectin content and increased amylose content, meanwhile the effect of HT was greater than LT. LT and HT treatments decreased grain pasting temperature and gel consistency, and hada significantinfluence on branched chain length. 2) The net photosynthetic rate of leaves under LT and HT presented no significant difference compared to NT, but LT and HT significantly reduced the accumulation of non-structural carbohydrates, meanwhile down-regulated the expression level of sucrose transporter genes OsSUT1, OsSUT2, and OsSUT4 both at noon and midnight.3) LT and HT treatment reduced sucrose hydrolysis-related enzyme activities, meanwhile promoted starch hydrolase activities, resulting in increased soluble sugar contents,sugar utilization in grain was blocked.4) Compared with NT, the adenosine diphosphate glucose content showed a downward tendency during the day and a rising trend at night under the treatment of LT and HT,which presented that the accumulation and utilization of adenosine diphosphate glucose were inhibited. And the granules bound starch synthetaseactivity weresignificantly reduced under LT and HT compared to NT with the prolongation of the treatment, and the enzyme activity at daytimewas significantly influenced by temperature changing at night.5) Compared with NT, LT and HT reduced the activitiesof night-time amylopectin synthesis-related enzymes and inhibited the expression of night-time related genes, which retarded formation of amylopectin, but the enzyme activitiesrelated to amylopectin synthesis was not significantly influenced by night temperature changing. 【Conclusion】High night temperature hada lesseffect on starch accumulation than low night temperature. High or low night temperatureinhibitedsucrose transport and metabolism,resulting in declined starch accumulation. The retarding of amylopectin formation was the main reason for the increase of relative content of amylose at high or low night temperature.Night temperature changes directly affected the metabolic process of starch formation at night, but the daytime activities of amylose-related enzymes wereaffected by night temperature changes, while the daytime activities of amylopectin-related enzymes werenot significantly affected by night temperature changes.

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Recovery Effect of Root Soaking in Brassinosteroid (BR) on Transplanting Shock of Hydroponically GrownLong-Mat Rice Seedlings Under Mechanical Transplanting Yuxiang LI, Zhizhou He, Yanfeng DING, Shaohua WANG, anghua LIG 2020, 34(6): 539-549.  DOI: 10.16819/j.1001-7216.2020.0308 Abstract ( )   HTML ( )   PDF (24282KB) ( )   【Objective】Mechanical transplanting results in serious transplanting shock of rice seedlings and a longer recovery stage, which negatively impacts the growth of rice seedlings in the paddy field and the yield formation of machine-transplanted rice. The objective of the research is to investigate the effects of brassinosteroid (BR) soaking on transplanting shock and grain yield of hydroponically grown long-mat seedlings (HLMS) under mechanical transplanting. 【Method】We analyzed the effects of different concentrations of BR (CK, T1, T10, T20,BR concentrations of 0 mg/L, 1 mg/L, 10 mg/L, 20 mg/L in the nutrient solutions, respectively) soaking on morphological traits, dry matteraccumulation, antioxidant system, endogenous hormone concentrations and grain yield of HLMS under mechanical transplanting. 【Result】Root soaking in BR could promote above-ground part growth of rice, the plant height under T1, T10, T20 was 11.68%, 8.12% and 7.61% higher than CK,respectively;and the effect on the root was more obvious, BR soaking significantly increased the root length, root surface area, root tip number, root volume, root diameter, root weight and root/shoot ratio. At low BR concentration, root tip overnumbered thatathighBRconcentrationwhile other root system indicators were better under high concentration BR treatment. Compared with CK, BR (T1, T10, T20) soaking decreased the H2O2 content inleaves by 12.50%, 23.25% and 22.25% 12 days aftertransplanting, respectively, and increased the activities of antioxidantenzymes. Compared with the day of transplanting, thezeatin (ZT) concentration in the leaves under BR soaking treatmentsincreased rapidly (197.27%, 153.11% and 243.78%, respectively), while under CK treatment it increased slowly (2.94%), the rootperformance was consistent with leaves, and the auxin (IAA) concentration in the roots was significantly higher than that of CKon the second day after transplanting. The gibberellin (GA3) content of roots in BR soakingtreatments was significantly higher than that of CK within one week after transplanting. Compared with CK, T10 significantly increased the number of spikelet per panicle by 15.04%, and the seed-setting rate by 6.62%. T20 obviously increased the seed-setting rate by 6.17%. However, T1, T10, and T20 notably decreased 1000-grain weight. The grain yield underT10 and T20 treatments (the corresponding values were 10.58 t/hm2 and 10.84 t/hm2) were 5.11% and 7.99% higher than CK (10.04 t/hm2), while grain yield under T1 (9.68 t/hm2) was 3.58%lower than that of CK,and there was no significant difference among these treatments. 【Conclusion】Briefly, BR （T10, T20）soaking at proper concentrationscould mitigate the transplanting shock, increase antioxidant enzymes activities, decrease H2O2 content of leaves, improve the contents of ZT, GA3, and IAA to different extent, efficientlypromote roots growth, increase the number of spikelet number per panicle and seed-setting rate of HLMS under mechanical transplanting. This study willlay a theoretical basis and provide technical reference for reducing machine-transplanting shock and promoting high and stable yield of mechanical transplanted rice.

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Effects of Plant Spacing on Grain Yield and Population Quality in Mechanically-transplantedRice with Good Tasting Quality Yun CHEN, Yajun ZHANG, Honglu ZHANG, An ZHU, Jian HUANG, Hao ZHANG, Junfei GU, Lijun LIU, Jianchang YANG 2020, 34(6): 550-560.  DOI: 10.16819/j.1001-7216.2020.0205 Abstract ( )   HTML ( )   PDF (37125KB) ( )   【Objective】The mechanical transplanting density plays an important role in grain yield and quality in rice. However, the effects of plant spacing on grain yield and population quality ofmechanically transplanted rice with good tasting have not been clearly understood. Clarifying the optimal plant spacing for good tasting rice could lay a theoretical and practical basis for high yielding and good quality in mechanical cultivation.【Method】In this experiment, three rice cultivars with good tasting quality (Nanjing 9108, Nanjing 5055 and Nanjing 46) in Jiangsu Province were used as materials, and the effects of plant spacing (10 cm, 12 cm, 14 cm, 16 cm and 18 cm) on their grain yield and population quality were investigated under mechanical transplanting when the row spacing was fixed at 30 cm.【Result】Productive tillers rate, high efficientleaf area index, grain leaf ratio (grain weight/leaf area), canopy net photosynthetic rate after heading and dry matter accumulation from heading to maturity were the highest under the plant spacing of 12 cm in above three rice cultivars. Grain yields tended to increase at first and then decrease with the increase ofthe plant spacing, and the relationship of quadric curve was found between grain yield and plant spacing. The optimal plant spacing for grain yield in Nanjing 9108, Nanjing 5055 and Nanjing 46 ranged from 11.6 cm, 11.6–12.3cm and 10.8–11.4 cmin two years according to the curve equation, respectively.【Conclusion】When the row spacing was fixed at 30 cm, the plant spacing of 11–12 cm was helpful to improve the population quality and increase grain yield, and it could be used as the optimal plant spacingfor the typical rice cultivars with good tasting in Jiangsu Provinceunder mechanical transplanting.

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Differences in Response of Grain Yield, Nitrogen Absorption and Utilization to Elevated CO2Concentration in Different Rice Varieties Juan ZHOU, Xiaowei SHU, Shangkun LAI, Gaoping XU, Jianye HUANG, Youli YAO, Lianxin Yang, Guichun DONG, Yulong WANG 2020, 34(6): 561-573.  DOI: 10.16819/j.1001-7216.2020.0404 Abstract ( )   HTML ( )   PDF (3379KB) ( )   【Objective】Our aim is to investigate the differences in response of grain yield, nitrogen absorption and utilization toFACE (atmospheric CO2 concentration increase) of different rice varieties. 【Method】Six rice varieties, including conventional japonica rice, hybrid indica rice, and conventional indica rice, were used to study the effects of free-air CO2enrichment (FACE) (atmospheric CO2 concentration increase) on the nitrogen absorption, utilization, and yield of different types of rice.【Result】1) FACE treatment dramatically increased rice yield by 24.17% on average and the maximum increment was observed in conventional indica rice. Compared with other types of rice varieties, hybrid indica showed the highest grain yield under both FACE and control (CK) treatments. 2) Panicle number was significantly improved in FACE treatment with conventional japonica rice varieties having the maximum increment.Spikelet number per panicle was significantly improved in hybrid and conventional indica rice varieties in FACE treatment. 3) The nitrogen absorption(NA) and nitrogen use efficiency for grain yield (NUEg) were significantly higher in FACE treatment than those in CK treatment. The average increase of NA was 21.23% with the maximum increment in hybrid indica rice varieties. Compared with other rice varieties, conventional indica rice varieties had the highest NA both in FACE and CK treatments. The average increase of NUEg was 7.33% with hybridindica rice varieties enjoying the maximum increment. The hybrid indica rice varietieshad the highest NUEg in FACE treatment and in CK treatment, respectively.4) Nitrogen content was decreased in FACE treatment with the average decrease of 0.105%, amongwhichthe maximum decrease was observed in conventional japonica rice. Dry matter weight was extremely and significantly increased in FACE treatment. The average increase of dry weight was 23.95% with the maximum increment in conventional indica rice varieties. NA of single panicle was significantly improved in FACE treatment with the average increase of 10.79% in conventional indica rice varieties and 13.93% in hybrid indica rice varieties, but NA of single panicle was decrease by 9.60% in conventional japonica rice. FACE treatment significantly increased rice NA intensity with an average increase of22.29% and the maximum increment was observed inhybrid indica rice varieties. The growth duration was not influenced by FACE treatment in all rice varieties. NAs of stem, leaf and panicle were significantly higher in FACE treatment than in CK treatment with the highest increase of 51.86% in leaf. The largest increase of NA was observed in hybrid indica rice. NA in different rice growth stageswassignificantly improved with the maximum increment of 108.90% during heading-maturity. The maximum increment of NA from heading to maturity was observed in hybrid indica rice varieties. 5) Effects of dry matter weight, NA per panicle, NA intensity, NA of panicle and NA from heading to maturity on NA at maturity were greater thanthose of nitrogen content, panicle number, growth duration, NAA of leaf, stem andsheath, NAA during transplanting-tillering and tillering-heading. 6) Partial productivity of nitrogen fertilizer (PFPN) was significantly improved in FACE treatment with an average increase of 24.16% and the maximum increment in conventional indica rice. NAA per 100 kg grains was significantly reduced in FACE treatment with an average decrease of 4.7%.The maximum decrease of NAA per 100 kg grains was observed in conventional indica rice varieties.【Conclusion】The results indicated that FACE could markedly increased both grain yield and nitrogen use efficiency in all rice varieties, but theincreases variedwith the variety types.

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Effect of Nitrogen Application on Yield, Rice Quality and ProcessingCharacteristics inRice Noodle-specific Varieties Chunyan WEN, XIONGYunhua, Xiaoyun YAO, Chunlian CHEN, Biaolin HU, Yongping HUANG, Yanshou WU 2020, 34(6): 574-585.  DOI: 10.16819/j.1001-7216.2020.0504 Abstract ( )   HTML ( )   PDF (9287KB) ( )   【Objective】We aimed to investigate the influence of nitrogen application on yield, rice quality and processing characteristics in noodle-specific rice.【Method】The experiments were conducted with threerice varieties suitable for making rice noodles(R0734, R2149, Jiazao 66), one variety commonly used for making rice noodles(Zhenguiai)and one variety unable to be processed into rice noodles(R0711)atthree nitrogen levels with 90, 140, 190 kg/hm2in 2018 and 2019.【Result】1) With the increasing nitrogen application levels, the yield of each varieties increased, but for R0734 and R2149 the grain yield maximized under the medium nitrogen level of 140 kg/hm2 in 2019; noodle-specific rice varieties, R2149 and Jiazao 66, had extremely high yield advantages, achievingthe highest yield at thenitrogen levels of140 kg/hm2 and 190 kg/hm2.Nitrogen application increased the effective panicle number, while the 1000-grain weight decreased.2) As more nitrogen was gradually applied, gel consistency and protein contentincreased whileamylose content decreased, fluctuating between 21.4% and 26.5%, which also brought about a downward trend in peak viscosity, trough viscosity and final viscosity. Breakdown reduced significantly and setback increased significantly.3)With the increase of nitrogen application, the broken rate and cooked loss rate of rice noodle increased significantly, but both were below 10%. R2149 and Jiazao 66 were more sensitive to nitrogen levels than R0734, but had better processing properties.【Conclusion】The amylose contents ranging from 21% to 27%(about 24% is the best) are favorable, so that the amylose content will notseriously exceeded the suitable range for processing at different nitrogen application levels in field cultivation. Moreover, due to the increase in the amount of nitrogen application, the processing characteristics of noodle-specific rice are deteriorated. Thusit is necessary to apply relatively low nitrogen in condition of its high yield level. In the breeding, the major parentswith moderate amylose contents and better processing characteristics should be selected for high-yieldingnoodle-specific rice variety.

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Diversity of Midgut Microbial Community of ChilosuppressalisExposed to Chlorobenzamide Juefeng ZHANG, Qin ZHANG, Fang LI, Haiying ZHONG, Jianming CHEN 2020, 34(6): 586-594.  DOI: 10.16819/j.1001-7216.2020.0101 Abstract ( )   HTML ( )   PDF (28650KB) ( )   【Objective】We aim toilluminatethestructural changes in the midgut microbial community of Chilosuppressalis exposed to chlorobenzamide.【Method】Macrogenomic sequencing and in vitro culturewere used to analyze the diversity of midgut microbiotaof Chilosuppressalistreatedwith different concentrations (100, 200, 400µg/mL) of chlorobenzamide.【Result】The results showed that chlorobenzamide treatmentdecreased the abundance anddiversityof the midgut bacteria of Chilosuppressalis,and the OTU number and specific OTU number of the intestinal bacteria of treated population were lower than those of the control;the proportion of Morganella, Provincia and Proteus in the chlorobenzamide treated population increased significantly. Meanwhile, the result of in vitro culture indicated besides enterobacter,Lelliottinimipressuralis, Leclerciadecarboxylata, Pantoeaagglomeranswere isolated from chlorobenzamide treated Chilosuppressalis population. COG classification and KEGG analysis didn’t show significant difference in number and relative abundance of functional genes among control and three chlorobenzamide treated populations.【Conclusion】The study had clarified the diversity of intestinal bacteria and the relationshipbetween gutbacteria of Chilosuppressalis andthe formation of chlorobenzamide resistance, and will lay a scientific basis for the role of intestinal bacteria in resistance of Chilosuppressalistochlorobenzamide.