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10 September 2021, Volume 35 Issue 5 Previous Issue    Next Issue
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Research Progresses on Response Mechanisms and Control Measures of Cadmium Stress in Rice Xiaobo XU, Penghu AN, Tianjiao GUO, Dan HAN, Wei JIA, Wuxing HUANG 2021, 35(5): 415-426.  DOI: 10.16819/j.1001-7216.2021.201209 Abstract ( )   HTML ( )   PDF (3128KB) ( )   Soil cadmium pollution is one of the increasingly serious environmental problems. Rice is the bulk cereal crop with the highest cadmium uptake capacity. The accumulation of cadmium by rice and its transfer to the food chain pose a threat to human health. In recent years, a series of significant advances have been made in research on the uptake and accumulation processes of cadmium in rice and its influencing factors. In this review, three aspects were reviewed. First, the effects of cadmium on rice seed germination, growth and development, and yield. Second, the physiological and molecular mechanisms behind cadmium activation in soil, xylem loading and transport, and transfer of cadmium from phloem to grains. Third, the prevention and control measures such as variety selection, soil remediation, and agronomic measures. It is expected to provide theoretical references for research related to Cd stress in rice and to lay a basis for developing effective strategies to reduce Cd level in rice.

Research Papers

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Cloning and Functional Analysis of Leaf Senescence Gene LPS1 in Oryza sativa Xiaojie CHU, Tao LU, Hanfei YE, Sheng WANG, Han LIN, Xianmei WU, Rui HE, Gang YAN, Yuexing WANG, Sanfeng LI, Mei LU, Haitao HU, Yaolong YANG, Yuchun RAO 2021, 35(5): 427-438.  DOI: 10.16819/j.1001-7216.2021.210303 Abstract ( )   HTML ( )   PDF (3724KB) ( )   【Objective】 As a good carrier, the premature aging mutant plays an important role in exploring the genetic mechanism and mechanism of action on premature aging, as well as improving grain yield and quality of rice.【Method】 In this study, a premature senescence mutant lps1 was obtained by EMS mutagenesis, and phenotypic observation, cytological and histochemical analysis, physiological and biochemical analysis, genetic analysis, gene localization and hormone treatment were performed on wild-type and mutants.【Result】 The leaves of lps1 began to turn yellow during the three-leaf stage, and the plant height, effective tiller number, seed-setting rate, and thousand-grain weight were extremely significantly reduced in the maturing stage. Electron microscopy observation found that the surface of lps1 leaves was smooth, the numbers of silicified protrusions and chloroplasts decreased, and the lamella structure was disordered. Physiological and biochemical analysis showed that a large amount of reactive oxygen species accumulated in mutant lps1, accompanied by protein degradation, cell membrane damage and large-scale cell death. Genetic analysis showed that the progeria phenotype was controlled by a single recessive nuclear gene, which encodes an ubiquitin conjugating enzyme on chromosome 5. The subcellular localization results prove that LPS1 protein is expressed in both the cytoplasm and the nucleus. Exogenous hormone treatment demonstrated that the lps1 was more sensitive to exogenous hormone treatment, and the LPS1 mutation promoted the expression of genes related to ABA synthesis.【Conclusion】 LPS1 mutation makes the rice ABA synthesis signal pathway abnormal, which in turn triggers abnormal changes in a series of aging-related physiological indicators such as H2O2, leading to premature senescence of lps1, and ultimately resulting in a serious decrease in rice yield.

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Response Characteristics of Rice Cysteine-rich Receptor-like Kinases Family Genes to Rhizoctonia solani and Plant Hormones Zhiming FENG, Guangda WANG, Jianhua ZHAO, Ran JU, Mengchen LI, Peng GAO, Keming HU, Zongxiang CHEN, Shimin ZUO 2021, 35(5): 439-448.  DOI: 10.16819/j.1001-7216.2021.210305 Abstract ( )   HTML ( )   PDF (26917KB) ( )   【Objective】 Clarifying the response characteristics of rice cysteine-rich receptor-like kinases (CRKs) family genes to Rhizoctonia solani and plant hormones is important preliminary work to analyze the functions of CRKs in rice resistance to R. solani. 【Method】 A phylogenetic tree of 45 CRKs in rice was constructed by bioinformatics. qPCR was used to analyze their response characteristics to R. solani, plant hormones ethylene (ET), jasmonic acid (JA), salicylic acid (SA) and cytokinin (CK), and their expression patterns in different tissues.【Result】 The rice CRKs family can be divided into four groups. Most of the CRKs clustered or closely distributed on chromosomes from the same group or branch. Forty-one CRKs responded to R. solani infection, and 17 of them responded strongly. Combined with their tissue expression patterns, it was found that 10 of the 17 CRKs, including CRK15, CRK23, CRK24, CRK26, CRK27, CRK28, CRK29, CRK30, CRK31 and CRK33, were expressed strongly in leaf sheathes and leaves, suggesting that these genes may be involved in regulating resistance to sheath blight. Most of CRKs from the same branch had similar response characteristics to R. solani, indicating that these CRKs may have functional redundancy in regulating resistance to R. solani. Forty CRKs responded to three or four kinds of plant hormones, and their responses to different hormones varied, indicating that CRKs might be widely involved in these plant hormones-mediated defense pathways. There were 17 CRKs with opposite responses to JA and SA, 21 with similar responses to JA and SA, 21 with similar responses to ET and JA, and 23 with similar responses to ET and SA, respectively. These genes may be involved in the interactions among ET, JA and SA. The results not only reflected the synergistic and antagonistic effects of ET, JA and SA signaling pathways, but also indicated that these genes may participate in the interactions among ET, JA and SA.【Conclusion】 Some rice CRKs involved in the regulation of rice sheath blight resistance have been identified, and they may play roles in the plant hormones-mediated defense pathways, which provides scientific clues for us to further explore the function of CRKs in regulating rice sheath blight resistance.

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QTL-Seq Mapping of Head Rice Rate QTLs in japonica Rice Xina CHEN, Zeke YUAN, Zhenzhen HU, Quanzhi ZHAO, Hongzheng SUN 2021, 35(5): 449-454.  DOI: 10.16819/j.1001-7216.2021.201105 Abstract ( )   HTML ( )   PDF (21798KB) ( )   【Objective】 Rice milling quality is largely measured by head rice rate. So QTL mapping for head rice rate will lay a theoretical basis for rice quality improvement.【Method】 Using an F2 segregated population from two japonica rice cultivars with similar grain shape but different head rice rates, QTL-Seq bulked segregated sequencing method was used to locate the QTLs controlling head rice rate in japonica rice. 【Result】 Three QTLs were found on chromosomes 8 and 12 by QTL-Seq analysis, and the target regions were further verified by traditional QTL mapping method using 200 F2 individuals. Of the three QTLs, qHRR8.1 was located at 21.8-23.2 Mb with 10.80% phenotype variation contribution. The QTL qHRR8.2, located on chromosome 8 at 24.2-25.2 Mb and qHRR12, located on chromosome 12 at 2.9-4.5 Mb had smaller contribution of 3.26% and 4.06%, respectively. 【Conclusion】 The head rice rate controlling QTL qHRR8.1 was mapped on chromosome 8, which lay a theoretical foundation for further clone of head rice rate genes, and grain quality improvement in japonica rice.

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Rapid Breeding of New Semi-glutinous japonica Rice Varieties with Good Eating Quality by Crossing Between Sister Lines Cailin WANG, Yadong ZHANG, Tao CHEN, Zhen ZHU, Qingyong ZHAO, Shu YAO, Ling ZHAO, Chunfang ZHAO, Lihui ZHOU, Xiaodong Wei, Kai LU, Wenhua LIANG 2021, 35(5): 455-465.  DOI: 10.16819/j.1001-7216.2021.210405 Abstract ( )   HTML ( )   PDF (4465KB) ( )   【Objective】 In recent years, semi-glutinous japonica rice with good taste is favored by farmers and consumers in the Yangtze River Delta region due to its good taste quality, and has become the main varieties for high-quality rice brand building in this region. In order to speed up the breeding of new varieties, we tried to breed new varieties of semi- glutinous japonica rice with good taste by crossing between sister lines of semi-glutinous japonica rice with different growth durations. 【Method】 By the reciprocal crossing between the mid-maturing late japonica rice Nanjing 46 (whole growth duration 165-170 d) and the late-maturing medium japonica rice Nanjing 9108 (whole growth duration 150-155 d) derived from the progeny of Wuxiangjing 14 / Kanto 194, 38 new semi-glutinous lines with different growth periods (whole growth period 140-170 d) were obtained in F6 generation through individual plant selection of F2 and superior line selection of F3-F5. Taking parents Nanjing 46 and Nanjing 9108 as control, 38 new lines were compared for several years, and their resistance to rice blast, agronomic traits, yield and their components, starch physicochemical indexes, RVA spectrum characteristic values and eating quality were analyzed. 【Result】 Most of the new lines have better agronomic characters than their parents, and most of them showed good eating quality, stable agronomic traits, excellent comprehensive characters and high yield. Among them, Nanjing 9036, Nanjing 9308 and Nanjing 66 achieved the variety approval in Jiangsu Province, and five new lines are in the middle of the regional trails in Jiangsu Province. 【Conclusion】 New varieties of semi-glutinous japonica rice with good eating quality and comprehensive characters can be rapidly bred by crossing between sister lines of semi-glutinous japonica rice falling into different ecological types.

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Effects of Chinese Milk Vetch and Reduced Chemical Fertilizer Application on Quality and Nutrient Uptake of Early Rice in Red Soil Paddy Field Xiangan TANG, Jinshui XIE, Changxu XU, Jia LIU, Fusheng YUAN, Guangrong LIU, Zuzhang LI 2021, 35(5): 466-474.  DOI: 10.16819/j.1001-7216.2021.200802 Abstract ( )   HTML ( )   PDF (5291KB) ( )   【Objective】 It is important to clarify the mutual effects of reduced chemical fertilizer application on the quality and nutrient uptake of early rice and soil fertility after planting and utilizing Chinese milk vetch, and lay a scientific basis for fertilizer application of rice in red-soil paddy field. 【Methods】 With red-soil paddy field as the subject, the effects of planting and utilization of Chinese milk vetch on the growth, development as well as nutrient uptake and utilization of early rice in paddy field in Gaoan, Jiangxi Province were investigated from 2015 by setting six experimental treatments: 1)control treatment without fertilization (CK); 2)green manure application with 22 500 kg/hm2 Chinese milk vetch returning (G); 3)100% chemical fertilizer application (N100); 4)Chinese milk vetch (22 500 kg/hm2) returning + 100% chemical fertilizer application (GN100); 5)Chinese milk vetch (22 500 kg/hm2) returning + 80% chemical fertilizer application (GN80); 6)Chinese milk vetch (22 500 kg/hm2) returning + 60% chemical fertilizer application (GN60). 【Results】 Chinese milk vetch returning and reduced chemical fertilizer application by an appropriate amount (20%) could promote rice yield, guarantee the N and P nutrition of rice and increase the contents of soil organic matters and alkali-hydrolysed nitrogen. Chinese milk vetch combined with chemical fertilizer application could improve head rice rate, chalkiness and gel consistency of early rice but reduce protein content. The yield, brown rice rate, head rice rate, chalky grain rate and protein content of early rice were significantly positively correlated with grain N content while significantly negatively correlated with grain Si content. A significantly positive correlation was found between grain Mg content and head rice rate. The uptake of P, Ca and Mg in grains showed a positive effect on milling quality, protein content and chalky grain rate but negatively affected gel consistency. Soil alkali-hydrolysed nitrogen presented an indirectly positive effect on grain N content but indirectly negatively affected grain Si content. Alkali-hydrolysed nitrogen, available phosphorus and available potassium had an indirect positive effect on N, P and K uptake in grains. The pH’s effects on grain Ca and P contents and those of exchangeable Ca and Mg contents on grain P content were indirectly negative. 【Conclusion】 Chinese milk vetch returning to the field (22 500 kg/hm2) and chemical fertilizer application reduced by 20% can promote rice yield and improve rice quality.

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Ecological Differences in Yield, Growth Period and the Utilization of Temperature and Light Resources of Double-cropping Late japonica Rice in the Middle and Lower Reaches of the Yangtze River Mengjia WANG, Min YIN, Guang CHU, Yuanhui LIU, Chunmei XU, Xiufu ZHANG, Danying WANG, Song CHENG 2021, 35(5): 475-486.  DOI: 10.16819/j.1001-7216.2021.201109 Abstract ( )   HTML ( )   PDF (28197KB) ( )   【Objective】 The aim of this study is to clarify the differences in yield, growth period and the allocation of temperature and light resources of different types of double-cropping late japonica rice in different ecological regions in the middle and lower reaches of the Yangtze River, so as to lay a theoretical basis for application of early indica and late japonica model in the rice growing area of the middle and lower reaches of the Yangtze River.【Method】 The experiment was conducted at Fuyang (30.13°N, 41.7 m above sea level) and Wenzhou (28.52°N, 83 m above sea level ), Zhejiang Province from 2018 to 2019. Rice cultivars were selected based on the large area of application, including inbred japonica (IJR) and indica/japonica hybrid rice (IJHR) with the high-yield indica rice (IR) as a control. The differences in yield, growth period and the allocation of temperature and light resources of IR, IJR and IJHR in the late growing season in different ecological regions were compared.【Result】 1) The dry matter, effective panicle number and sink of japonica rice declined at low latitude as compared to high latitude. As a result, the yield declined by 2.4%–19.1%, while the grain setting and 1000-grain weight remained stable or went up slightly. Meanwhile, the yield of IJHR was 8.8–10.3 t/hm2 in Fuyang and 8.0–10.2 t/hm2 in Wenzhou, being the highest in both sites. 2) The growth period of the tested cultivars at two latitudes differed. Compared with the high latitude, there was no significant difference in the vegetative stage at the low latitude, and the reproductive stage was slightly reduced (4.2%–27.3%), while the grain filling stage was significantly shortened, among which IR, IJR and IJHR shortened by 7.3%–11.9%, 20.8%–41.9%, 23.1%–35%, respectively. 3) The differences in the temperature and light allocation in different growth period mainly reflected in the grain filling stage. The average temperature during the grain filling stage at the low latitude was higher than that at the high latitude (IR, IJR and IJHR increased by 0.4–2.4 ℃, 2.3–3.5 ℃ and 2.5–2.8 ℃, respectively). The effective accumulated temperature at the two latitudes varied with cultivars, and IR had no significance, while IJR and IJHR declined by 24.7–126.4 ℃ and 25.7–107 ℃, respectively. 4) The analysis of PCA showed that latitude was the primary cause for the accumulation differences of temperature and light resources and the yield (PC1 and PC2, contribution of 49%), followed by the cultivars' temperature and light sensitivity (PC5, contribution of 18%) and the panicle and grain structure (PC3, contribution of 14%).【Conclusion】 Compared to the high latitude, the decrease of yield of japonica rice is mainly due to the shortened growth period especially the grain filling stage, decreased effective accumulative temperature and sink. IJHR is characterized by higher yield advantages, which may be due to its grain superiority. Therefore, japonicas with heavy or large panicles may have higher application potential in the middle and lower reaches of the Yangtze River.

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Effects of Dopamine Priming on Seed Germination and Seedling Growth of Rice Under Salt Stress Yuxiang LI, Hairong LIN, Qian LIANG, Guodong WANG 2021, 35(5): 487-494.  DOI: 10.16819/j.1001-7216.2021.200808 Abstract ( )   HTML ( )   PDF (32304KB) ( )   【Objective】 It is of significance to clarify the effects of dopamine priming on rice seed germination and seedling growth under salt stress. 【Method】 The effects of seed priming on seed germination, seedling growth and physiological characteristics under salt stress were analyzed. Rice (Variety: Xindao 17) seeds were primed with 0（H2O）, 0.1, 0.5, 1 and 1.5 mg/L dopamine solution, respectively. Salt stress was simulated with 100 mmol/L NaCl solution. The no-priming and no-salt stress treatment was kept as control 1(CK), and the no-priming with salt stress was kept as control 2(S-CK). 【Result】 Compared with CK, salt stress (S-CK) obviously slowed down or stopped the germination of rice seeds, and the rice seedlings grew weakly. The priming treatment relieved the inhibitory effect of salt stress on rice seeds germination, speeded up the germination (13.3%–25.8%), promoted seedling growth, increased the contents of soluble sugar(16.4%–51.8%), proline(6.5%–31.2%), and enhanced the activities of SOD(28.9%–72.7%), POD(15.0%–60.1%) and CAT(35.1%–133.0%), decreased the content of MDA(7.1%–26.8%). The results indicated that seed priming could enhance salt tolerance of rice seeds and seedlings by improving the vigor of rice seeds, the activities of antioxidant enzymes and the contents of osmotic regulatory substances, and decreasing the content of MDA. The medium concentration of dopamine solution (S1) was better than water(S0). 【Conclusion】 The suitable priming solution for Xindao 17 was 1.0 mg/L dopamine, which could effectively enhance salt tolerance of rice seeds, and promote seed germination and seedling growth.

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Effects of Precise Drill Sowing-based Seedling Raising of indica-japonica Hybrid Rice for Mechanical Transplanting on Yield Increase Under Nitrogen Reduction Conditions Yaliang WANG, Defeng ZHU, Huizhe CHEN, Yuping ZHANG, Jing XIANG, Zhigang WANG, Yikai ZHANG 2021, 35(5): 495-502.  DOI: 10.16819/j.1001-7216.2021.210202 Abstract ( )   HTML ( )   PDF (20045KB) ( )   【Objective】 The purpose of the study is to ascertain the effect of precise drill sowing on yield formation of mechanically transplanted rice and its beneficial effect on yield increasing with nitrogen reduction.【Method】 The seeds of Yongyou 538 and Yongyou 1540 were precise drill-sowed (PS) with 16 rows(in horizontal) in standard seedling trays for mechanical transplanting, and the same seed sowing rate was set in traditional broadcast sowing (BS) as the control. And three nitrogen application rate treatments including zero-nitrogen application rate (0 kg/hm2, 0N), suitable nitrogen application rate (240 kg/hm2, SN), and reduced nitrogen application rate (204 kg/hm2, RN) were set to analyze yield formation, plant uniformity, dry matter accumulation and nitrogen use efficiency. 【Results】 1) Compared with BS, PS significantly increased the yield of indica-japonica hybrid rice by 4.3% on average with the increasing productive panicles. Under nitrogen reduction, precise drill sowing led to a lower grain yield drop as compared with BS. 2) PS significantly reduced the unplanted hill percent, improved the uniformity of mechanically transplanted seedlings and productive panicle number. Compared with BS, PS increased the tiller number at peak tillering stage under RN for both cultivars. 3) Compared to BS, PS increased the leaf area index at heading stage, meanwhile increased dry matter accumulation and nitrogen uptake at both heading and post-anthesis stages, particularly under RN treatment. 4) Except 0N, there was no significant difference in N dry matter production efficiency and N grain production efficiency among different cultivars and nitrogen treatments, but PS treatment significantly increased N recovery efficiency and N agronomic use efficiency in both cultivars.【Conclusion】 PS improves plant uniformity of indica-japonica hybrid rice population, increases the tiller number at peak tillering stage and leaf area index, promotes dry matter accumulation and nitrogen absorption, and then increases yield and reduces rice yield losses under nitrogen reduction.

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Effects of Substrates with Different Properties on Chilling Tolerance of Early Rice Seedlings Chunquan ZHU, Qingshan XU, Xiaochuang CAO, Lianfeng ZHU, Yali KONG, Qianyu JIN, Junhua ZHANG 2021, 35(5): 503-512.  DOI: 10.16819/j.1001-7216.2021.200909 Abstract ( )   HTML ( )   PDF (11268KB) ( )   【Objective】 Early rice is easy to suffer from chilling damage during seedling raising, resulting in yield reduction. Therefore, it is necessary to reveal the effects of different types of substrates on early rice chilling tolerance.【Method】 To clarify the regulatory effect of different substrates on the tolerance of early rice seedlings to chilling stress, two representative substrates (soilless substrate and fermentation substrate) and paddy soil (as control) were used in present study. Six-day-old rice seedlings were subjected to different low temperature treatments, and the basic physicochemical properties and gene expression levels of rice were determined after 3 days of treatment.【Result】 1) The bulk density of soilless and fermentation substrates was significantly lower than that of the control, however, the electrical conductivity, aeration porosity, and the contents of alkali hydrolyzable nitrogen (N), available phosphorus (P), available potassium (K) and organic matter were significantly higher than those of the control. The root length, shoot and root dry weight per 100 rice seedlings grown in the fermentation substrate exceeded those of the control group, and the nutrient contents (shoot and root N, P, K contents) of seedlings grown in the soilless substrate and fermentation substrate were significantly higher than those of the control group. 2) With the decreasing temperature, the growth and nutrient uptake of rice seedlings were both inhibited. The low temperature exerted a slight influence on the growth of seedlings on the fermentation substrate, followed by soilless substrate, and the control was strongly inhibited. 3) The MDA content in the seedlings grown in soilless substrate and fermentation substrate was significantly lower than that in the control under low temperature (day 8℃/ night 4℃) treatment, indicating the lower oxidative damage induced by low temperature. The activities of superoxide dismutase (SOD), catalase (CAT), proline content and soluble protein content were higher in the seedlings grown in soilless substrate and fermentation substrate than those in the control. The peroxidase (POD) activity in the seedlings grown in fermentation substrate was higher than that of the control, and the activity of glutathione transferase (GST) was higher in the seedlings grown in soilless substrate than that in control. At the same time, the expression levels of OsCold1, OsCOIN, OsP5CS and OsSODB were significantly higher in the seedlings grown in soilless and fermentation substrate than those of the control, which improved the tolerance to low temperature. 【Conclusion】 The above results showed that the physiological and biochemical reactions and related gene expression were regulated by fermentation substrate and soilless substrate, leading to improved tolerance of rice seedlings to low temperature stress.

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Comparison of Droplet Deposition Characteristics in Rice Canopy and Benefit Between Unmanned Aerial Vehicle Spray and Artificial Spray Yanda LI, Chun YE, Zhongsheng CAO, Binfeng SUN, Shifu SHU, Licai CHEN 2021, 35(5): 513-518.  DOI: 10.16819/j.1001-7216.2021.210107 Abstract ( )   HTML ( )   PDF (1436KB) ( )   【Objective】 The primary objective of this study is to elucidate the characteristics of droplet deposition and distribution by unmanned aerial vehicle (UAV) spray and artificial spray in rice canopy, and the control efficacy, grain yield and economic benefit were compared between UAV spray and artificial spray. 【Method】 The electricity-driven four-rotor UAV was selected and three flying heights and three pesticide dosages were set. The droplet deposition and distribution in rice canopy was measured at booting stage with UAV. Then the controlling efficacy of rice blast, grain yield and economic benefit were compared with those of artificial spray treatment. 【Results】 The results showed that the deposition amount of droplet was decreased with increasing flying height. The uniformity and penetrability of droplets were improved with increasing flying height. The deposition amount, uniformity and penetrability of droplets were improved with increasing pesticide dosage by UAV spray and artificial spray. The uniformity and penetrability of droplets were greater in upper canopy than in middle and basal canopy at the same flying height. The uniformity and penetrability of droplets by UAV spray were greater than those by artificial spray. The UAV spray obtained equivalent grain yield and control efficacy with the labor cost reduced by 165 Yuan/hm2, while net income and yield-cost ratio was improved by 164 Yuan/hm2 and 20.9, respectively. 【Conclusion】 Compared with the artificial spray, the UAV spray can raise working efficiency, reduce production cost and higher economic benefits are also achieved on the premise of grain yield, which has a potential to be widely applied for precise management and high yield and high efficiency cultivation in rice production.