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Orientation Improvement of Grain Length and Grain Number in Rice by Using CRISPR/Cas9 System Lan SHEN, Jian LI, Yaping FU, Junjie WANG, Yufeng HUA, Xiaozhen JIAO, Changjie YAN, Kejian WANG 2017, 31(3): 223-231.  DOI: 10.16819/j.1001-7216.2017.7029 223 Abstract ( )   HTML ( )   PDF (5642KB) ( )   【Objective】Gene orientation editing has become an important way for molecular breeding. We evaluated the improvement effects on the target traits following the construction of GS3 and Gn1a loss-of-function mutants so as to lay a solid foundation for high-yielding rice breeding. 【Method】GS3 and Gn1a were selected as targets for gene editing, which control the grain size and grain number in rice, respectively. The pC1300-2×35S:: Cas9-gGS3-gGn1a expression vector was constructed for knocking out both GS3 and Gn1a by using CRISPR/Cas9 system, and transformed into four good quality rice varieties by the Agrobacterium-mediated method. And the properties of mutations and the target traits were analyzed in the transgenic lines.【Result】The sequencing results showed the GS3 and Gn1a in four rice varieties were successfully edited. In T0 generation, we obtained mutants with frame shift mutations in GS3 and Gn1a in four rice varieties. In T1 generation, the marker-free plants were screened for analyzing the agronomic traits in four genetic backgrounds. For the agronomic characters, the gs3 and gs3gn1a mutants had the longer grain length and the increased 1000-grain weight compared to the wild type, and the gs3gn1a mutants had more grains per panicle compared to the gs3 mutants.【Conclusion】CRISPR/Cas9-mediated gene editing can improve rice target traits, which has great potential in orientation improvement of rice varieties.

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Expression of Pns10 Protein of Rice ragged stunt virus in Rice Protoplasts Jie ZHANG, Xiaomin CHEN, Jinhong WU, Chongqing ZHU, Xinlun DING, Zujian WU 2017, 31(3): 232-237.  DOI: 10.16819/j.1001-7216.2017.6148 232 Abstract ( )   HTML ( )   PDF (14268KB) ( )   【Objective】Pns10 of Rice ragged stunt virus (RRSV) forms viroplasm-like inclusion bodies which are essential for virus infection to vector insects. However, the expression pattern and function of Pns10 in rice remain unknown.【Method】Polyclonal antibody against Pns10 protein was prepared by immunizing rabbits with a bacterially expressed Pns10; the cellular distribution of Pns10 protein in rice protoplasts was observed with an immunofluorescence microscopy; the accumulation of Pns10 RNA in rice protoplasts infected by RRSV was quantified with real-time quantitative RT-PCR and that of the Pns10 protein was investigated using Western blot.【Result】Pns10 ORF was cloned into the Gateway prokaryotic expression vector pDEST17 and its expression was induced by IPTG. Polyclonal antiserum against the Pns10 was obtained and it can react with the Pns10 protein from the naturally RRSV-infected rice by Western blot detecting. Pns10 formed viroplasm-like inclusion bodies in protoplasts. The Pns10 RNA was first detected at 8 h post RRSV inoculation. The accumulation of Pns10 RNA peaked at 24 h post virus inoculation but began to decline thereafter. The Pns10 protein was first detected at 24 h post virus inoculation. A high level of Pns10 protein was maintained until 60 h post virus inoculation.【Conclusion】Antiserum against RRSV Pns10 protein was obtained. Pns10 was expressed and viroplasm-like inclusion bodies formed in rice protoplasts. In addition, the expression of Pns10 RNA was earlier than that of the Pns10 protein.

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Morphological and Molecular Genetic Analysis of a Dwarf and Small Grain Rice Variety Xiaoxiang’ai Yusong LÜ, Yunfeng XIE, Zhonghua SHENG, Yawen WU, Shaoqing TANG, Peisong HU, Xiangjin WEI 2017, 31(3): 238-246.  DOI: 10.16819/j.1001-7216.2017.6156 238 Abstract ( )   HTML ( )   PDF (9029KB) ( )   【Objective】To uncover the genetic mechanism of a dwarf and small grain variety Xiaoxiang’ai (XXA), and lay an important theoretical foundation in rice dwarfing breeding.【Method】Rice variety XXA characterized as a dwarf and small grain phenotype was derived from natural mutation under breeding process. The agronomic traits of XXA were investigated. Its sensibility to phytohormone was analyzed under GA3 and BR treatments at various concentrations. Genetic analysis of XXA with different varieties and fine mapping of xxa gene from the F2 population derived from the cross between near-isogenic lines NIL(NIP) and XXA were done. Furthermore, complementary assay was performed to confirm the candidate gene.【Result】The XXA shows short spikes and compact panicles, with significant decrease in 1000-grain weight under GA3 and BR treatments, we found that XXA is partially sensitive to GA3, whereas insensitive to BR. The segregation behavior in each of the derived F2 populations between XXA and either varieties was consistent with the Mendelian monogenic ratio of 3:1. The xxa gene was finally narrowed down to a 70 kb physical region between the InDel markers F81 and F82 on chromosome 5. Within this region, eight open reading frames (ORFs) were predicted, of which, ORF5 (LOC_Os05g26890) has been annotated as a Dwarf1 gene (D1). Furthermore, sequence analysis of all the region revealed that there are only two mutation sites including one 1-bp nonsense mutation in the 5th exon and a 3-bp deletion that resulted in a lysine deletion in the 12th exon of D1. The complementary assay showed that the abnormal phenotype of XXA can be recovered.【Conclusion】The dwarf and small grain phenotype is probably associated with GA3 metabolism. The abnormal phenotype is mainly controlled by a single recessive gene. The D1 indisputably corresponds to mutation phenotype of XXA.

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Characterization and Gene Mapping of a No-pollen Genic Sterile Mutant whf41 in Rice Dandan XUAN, Lianping SUN, Peipei ZHANG, Yingxin ZHANG, Weixun WU, Zhengfu YANG, Xiaodeng ZHAN, Xihong SHEN, Liyong CAO, Shihua CHENG 2017, 31(3): 247-256.  DOI: 10.16819/j.1001-7216.2017.6159 247 Abstract ( )   HTML ( )   PDF (15660KB) ( )   【Objective】The anther cuticle and wax layer act as structural support and protective barriers for the development of pollen sac in rice. Phenotypic analysis and genetic mapping of the related genes can provide genetic resources and lay theoretical basis for further cloning and molecular mechanism analysis. 【Method】We identified a no-pollen male sterile mutant whf41 from the mutant progeny of 60Co-γ-treated indica cultivar Zhonghui 8015. Anthers of the wild-type and whf41 mutant at different development stages were fixed for transverse section analysis and mature anthers of which were randomly selected for scanning electron microscopy analysis. BC1F1, F1 lines and BC1F2, F2 populations derived from whf41/ Zhonghui 8015 and whf41/ 02428 were used for genetic analysis and fine-mapping of the mutation site. 【Result】 Comparing with wild type,the whf41 mutant exhibited thin and transparent milky anther without mature pollen grains. Transverse section analysis showed that the whf41 mutant displayed aborted pollen grains,none detectable exine and swollen tapetal layer without expected PCD (programmed cell death), finally resulting in fragments of tapetal layer and pollen grains in the chamber. Scanning electron microscopy analysis further revealed the mutant had smoother anther wall, fewer lipids both on the inner and outer sides and fragments of degragated pollens. Genetic analysis revealed that whf41 was controlled by a single recessive genic gene, which was fine-mapped to a 45.6-kb region that harbored nine Open Reading Frames(ORFs) on the short arm of chromosome 3 between markers XD-5 and XD-11. Sequence analysis revealed that the whf41 mutant carried a nucleotide substitution and three nucleotide deletion, which led a substitution of one amino acid (D to M)and a deletion of one amino acid (V) in the fourth exon of one Cytochrome P450 family gene, LOC_Os03g0725, which is named as OsWHF41 and probably responsible for the no-pollen male sterility phenotype. Furthermore, qPCR analysis showed that the expression level of CYP704B2 and seven anther lipid synthesis and transportation related regulators changed significantly in whf41. 【Conclusion】Based on all these results, we deduced that the OsWHF41 gene was a new allelic to CYP704B2 gene and this further confirmed the important role of CYP704B2 in anther lipid synthesis and pollen exine formation .

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Identifying QTLs for Thermo-tolerance of Grain Chalkiness Trait in Rice Guilian ZHANG, Bin LIAO, Wenbang TANG, Liyun CHEN, Yinghui XIAO 2017, 31(3): 257-264.  DOI: 10.16819/j.1001-7216.2017.6172 257 Abstract ( )   HTML ( )   PDF (17515KB) ( )   【Objective】The molecular markers linked to high temperature tolerance of rice appearance quality were screened for the purpose of providing an important foundation of improvement for rice grain quality. 【Method】The quantitative trait loci (QTLs) for heat tolerance of grain chalkiness trait were identified using the recombinant inbred lines(RILs) derived from a cross between the heat tolerant rice line 996 and the heat sensitive line 4628. The heat tolerance indexes of chalky grain rate, chalkiness size and chalkiness degree were used as the heat-tolerance indicators. 【Result】24 QTLs for heat tolerance of grain chalky traits were detected in two years by using composite interval mapping analysis including eight for heat tolerance of chalky grain rate(HTCGR), twelve for heat tolerance of chalkiness size and fourteen for heat tolerance of chalkiness degree(HTCD). Two HTCGR QTLs on chromosome 6 and two HTCD QTLs on chromosome 7 could be detected repeatedly in two years. The two HTCD sites coincided with two HTCGR sites on chromosome 7 detected in 2015. Moreover, anyone of the four pleiotropic QTLs had impacts on the chalky grain rate, chalkiness size and chalkiness degree. 【Conclusion】The QTL controlling the heat tolerance index of chalkiness degree qHTCGR6.1 and the QTL controlling the heat tolerance of chalkiness degree qHTCD7.1 might be new findings.．

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Effects of Mechanically-transplanted Modes and Density on Photosynthetic Production and Yield in Hybrid Rice at Different Seedling-ages Yinghong LI, Haiyue WANG, Tengfei LÜ, Shaowen ZHANG, Mingjin JIANG, Qiaolin HE, Yongjian SUN, Jun MA 2017, 31(3): 265-277.  DOI: 10.16819/j.1001-7216.2017.6091 265 Abstract ( )   HTML ( )   PDF (610KB) ( )   【Objective】 In order to elucidate the effects of mechanical transplanting modes and density on photosynthetic production characteristics and yield of super hybrid rice (F you 498) and to lay a theoretical basis for the application of mechanical transplanting, 【Method】 a split-plot design was used as follows: bowl mechanical-transplanting with high density (M1D1), bowl mechanical-transplanting with middle density (M1D2), bowl mechanical-transplanting with low density (M1D3), carpet mechanical-transplanting with high density (M2D4), carpet mechanical-transplanting with middle density (M2D5), and carpet mechanical-transplanting with low density (M2D6) using 25-day-old and 40-day-old seedlings. 【Result】The seedling-age and mechanically-transplanted modes coupled with density and grain yield played a significant role in the regulation of main growth stages in rice. The seedling quality, number of tillers, leaf area index (LAI), exportation and export rate of leaf,culm and sheath per shoot, dry matter weight per stem and population, dry matter accumulation during each stage, population growth rate, photosynthetic potential, net assimilation rate after heading stage and yield for 25-day-old seedling were significantly better than those of 40-day-old ones under the same mechanical-transplanting modes and density. The number of stems and tillers, leaf area index of each period and leaf area decay rate, dry matter weight of population, photosynthetic potential, and the dry matter accumulation before heading population growth rate, net assimilation rate before heading stage increased with the increasing density at the same seedling-age and mechanical-transplanting modes. The dry matter accumulation after heading, population growth rate, and net assimilation rate after heading under bowl mechanical-transplanting increased firstly and then decreased with the increase of density. In this experiment, M1D2 is the best. 【Conclusion】 For 25-day-old seedlings, the row of 33 cm and planting space of 15.5 cm had the advantages of total spikelet number and seed setting rate, and its yield was the highest. So the treatment could give full play to advantages of indica hybrid rice plant type of the local research area and improve photosynthetic production and yield. The yield will decrease when increase of seedling-age and planting density reduced of carpet mechanical-transplanting, which is because of the poor of population quality index and reduction of the number of effective panicles.

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Effects of Aeration Methods on Photosynthetic Characteristics and Yield of Rice Jijie HU, Lianfeng ZHU, Chu ZHONG, Yujiong LIN, Junhua ZHANG, Xiaochuang CAO, Shengmiao YU, Bohr JAMES Allen, Qianyu JIN 2017, 31(3): 278-287.  DOI: 10.16819/j.1001-7216.2017.6135 278 Abstract ( )   HTML ( )   PDF (1303KB) ( )   【Objective】The objective is to reveal the effects of different aeration methods on photosynthetic characteristics and dry matter production of rice, and to determine the suitable aeration method for the growth and improvement of grain yield of rice. The results will contribute to the understanding of the role of root aeration on rice growth, and provide a reference and a theoretical basis for aerobic cultivation of rice.【Method】Three rice varieties falling into different ecotypes, Zhongzheyou 1 (lowland rice), IR45765-3B (deep-water rice) and Zhonghan 221 (upland rice), were used to study the effects of aeration methods on rice photosynthetic characteristics and yield. Under such four oxygen enrichment treatments as calcium peroxide application (T1), micro-bubble aerated water irrigation (T2), water-controlled irrigation (T3) and water-logging (control).【Result】T1 and T2 increased the leaf SPAD value, leaf area index, net photosynthetic rate, transpiration rate, stomatal conductance and dry matter accumulation of the three rice varieties during the main growth stages, and significantly improved the effective panicle numbers and seed setting rate. Compared with the control, the SPAD value, leaf area index, photosynthetic parameters and dry matter weight were decreased in T3, and the seed setting rate also significantly dedined, but the water use efficiency of leaves was increased. At full ripe stage, compared with the control the grain yield of Zhongzheyou 1, IR45765-3B and Zhonghan 221 increased by 22.38%, 18.27% and 18.17%, respectively, in T1 and by 13.89%, 10.67% and 8.85%, respectively, in T2. However, it was 5.86%, 8.19% and 6.16%, respectively, lower than that of control in T3, with considerable differences between treatments.【Conclusion】T1 and T2 retarded leaf senescence, and improved leaf area index and photosynthetic capacity, and significantly increased the dry matter accumulation and yield of rice. The main reason for the decline of photosynthesis and yield of rice under T3 was the shortage of water supply.

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Effects of Controlled Release Blend Bulk Urea on the Yield and Nitrogen Use Efficiency of Wheat and Rice Jingsheng ZHANG, Bing LI, Changquan WANG, Jing LUO, Jun GU, Sifan LONG, Jie HE, Hao XIANG, Bin YIN 2017, 31(3): 288-298.  DOI: 10.16819/j.1001-7216.2017.6143 288 Abstract ( )   HTML ( )   PDF (21514KB) ( )   【Objective】A field experiment was conducted to investigate the effect of controlled-release fertilizer(CRF) combined with urea(UR) on the yield, nitrogen use efficiency and growth in wheat-rice rotation system. 【Method】Seven fertilization patterns including non- N fertilization(CK), farmers’ practice(T1), 10% CRF+90% UR(T2), 20% CRF+80% UR(T3), 40% CRF+60% UR(T4), 80% CRF+20% UR(T5), 100% CRF(T6) were applied to test the effect of different nitrogen treatments on dry matter accumulation and distribution, the growth rate of dry matter, nitrogen accumulation and distribution, yield and yield components, nitrogen use efficiency.【Result】 The dry matter and nitrogen accumulation in the mid-late stage of wheat and rice increased under the treatment with over 20% of controlled release fertilizer. Over 80% CRF addition decreased the dry matter and nitrogen accumulation in rice panicles, but increased accumulation in the stem and leaf, which resulted in late-maturing. Compared with T1, the yield was increased significantly with over 20% CRF addition, especially in the T4 treatment. The yield of wheat was increased by 14.23% and for rice, by 10.93%. Compared with T6, the yield of wheat increased by 7.37% and for rice, by 3.83% respectively. With the increasing CRF addition ratio, the nitrogen partial productivity(NPP), nitrogen agronomy efficiency(NAE), nitrogen uptake efficiency(NUPE), nitrogen apparent utilization efficiency(NAUE) increased both in wheat and rice at beginning and decreased afterwards, with the peak in T4. In all the nitrogen treatments, the lowest nitrogen harvest index(NHI) was abserved in T6, the NHI of wheat and rice decreased by 3.99% and 8.51%, respectively. With the increasing CRF ratio, the contribution rate of soil nitrogen(CRSN) in both wheat and rice decreased at beginning and then increased, with the valley in T4. Compared with T1, the CRSN of wheat decreased by 14.38% and for rice, by 15.84% under T4 treatment. 【Conclusion】These results indicated that controlled-release fertilizer enhanced nitrogen absorption and distribution, promoted crop growth and development, as well as crops yield and nitrogen use efficiency. The rational addition ratio of CRF for wheat and rice production ranged frow 20% to 40%.

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Distribution of Eight Rice Blast Resistance Genes in indica Hybrid Rice in China Wenjuan WANG, Jiyong ZHOU, Congying WANG, Jing SU, Jinqi FENG, Bing CHEN, Aiqing FENG, Jianyuan YANG, Shen CHEN, Xiaoyuan ZHU 2017, 31(3): 299-306.  DOI: 10.16819/j.1001-7216.2017.6114 299 Abstract ( )   HTML ( )   PDF (9369KB) ( )   【Objective】The cloned rice blast resistant genes, Pi1, Pik-p, Pik-h, Pi2, Pi9, Piz-t, Pita and Pii, which showed broad-spectrum blast resistance in different rice growing regions, have been widely used in rice breeding for blast resistance. To clarify the distribution of these genes in hybrid rice in South China, 【Method】the genotypes of resistance genes Pi1, Pik-p, Pik-h, Pi2, Pi9, Piz-t, Pita and Pii in 328 hybrid rice combinations were detected with functional markers. 【Result】The distribution frequency of Pita and Pii was the highest, reaching 84.76% and 67.68% in the tested rice combinations, respectively; followed by Pi2 and Pik-p with the proportion of 22.87% and 13.72%, respectively; Pi1, Piz-t and Pik-h had the lowest distribution frequency, accounting for 5.18%, 3.35% and 2.13% of total; all of these varieties didn’t carry resistance gene Pi9. The number of blast resistance genes detected in hybrid rice combinations were at most four. The resistance evaluation showed that the frequency of resistant varieties rose with increasing number of resistance genes in hybrid combinations. In a hybrid combinations with four resistance genes, the distribution frequency of resistant varieties was 91.67%. Blast resistance contribution assay of the eight resistance genes revealed that Pi2 and Pi1 displayed the greatest resistance contribution in the local rice in South China, followed by Pik-h, Pik-p, Pita, Pii and Piz-t. 【Conclusion】This study provided a scientific basis for the rational distribution of resistant varieties with different genotypes in South China.

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Resistance Monitoring and Cross-resistance to the Diamides in the Rice Stem Borer, Chilo suppressalis (Lepidoptera: Pyralidae) Dandan ZHAO, Liqi ZHOU, Shuai ZHANG, Rong YAO, Yunxia QIU, Congfen GAO 2017, 31(3): 307-314.  DOI: 10.16819/j.1001-7216.2017.6124 307 Abstract ( )   HTML ( )   PDF (409KB) ( )   【Objective】 We aim to learn about the chlorantraniliprole and flubendiamide resistance development of Chilo suppressalis from the main rice-growing area in China, meanwhile, to define the difference between resistance levels to 97.3% chlorantraniliprole TC and 20% chlorantraniliprole SC and the cross-resistance between cyantraniliprole, tetrachlorantraniliprole, cyhalodiamide and chlorantraniliprole, flubendiamide in Yuyao and Xiangshan resistance populations.【Method】 The resistance levels of nineteen Chilo suppressalis populations collected from seven provinces to chlorantraniliprole and flubendiamide, the resistance levels to 97.3% chlorantraniliprole TC and 20% chlorantraniliprole SC and the cross-resistance between cyantraniliprole, tetrachlorantraniliprole, cyhalodiamide and chlorantraniliprole, flubendiamide in Yuyao and Xiangshan resistance populations, were monitored by rice seeding dipping method in 2015. 【Result】 Yuyao and Cangnan populations from Zhejiang Province have developed high level of resistance to chlorantraniliprole (141.1-fold and 135.0-fold), and Xiangshan population also showed moderate level of resistance (87.9-fold). Moreover, the three field populations showed moderate level of resistance to flubendiamide (15.0-fold to 58.7-fold). In addition, Yuyao and Xiangshan populations showed various resistance ratios to 97.3% chlorantraniliprole TC and 20% chlorantraniliprole SC in with higher resistance ratio to 20% chlorantraniliprole SC. The result showed the two populations both have reached moderate or high level of resistance to flubendiamide and chlorantraniliprole (27.6-fold to 133.6-fold), meanwhile they also have exhibited moderate or high level of resistance to cyantraniliprole, SPY-9080 and cyantraniliprole (30.3-fold to 120.7-fold).【Conclusion】 Significant variations among field populations to chlorantraniliprole and flubendiamide were observed, showing 117.6-fold and 146.8-fold differences, respectively, as well as the higher resistance ratio to 20% chlorantraniliprole SC in Yuyao and Xiangshan resistance populations and strong cross-resistance among cyantraniliprole, tetrachlorantraniliprole, cyhalodiamide and chlorantraniliprole, flubendiamide.

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Oviposition and Feeding Preference of Cnaphalocrocis medinalis (Guenée) for Four Different Plants Chuanming LI, Guangjie HAN, Yajun YANG, Jianhang QI, Qin LIU, Jian XU, Zhongxian LÜ 2017, 31(3): 315-319.  DOI: 10.16819/j.1001-7216.2017.6054 315 Abstract ( )   HTML ( )   PDF (20638KB) ( )   【Objective】The rice leaffolder(RLF) [Cnaphalocrocis medinalis (Guenée)] is a kind of pests that bring serious harm to rice. The RLF can complete life cycle on a variety of gramineous plants, but almost only exclusively in rice in the field even in the outbreak years. Our aim is to recover the mechanism of oviposition and feeding preference of the RLF for rice and other host plants.【Method】We compared the oviposition and feeding preference of the RLF for four different plants: Zea mays L., Oryza sativa L., Echinochloa crus-galli (L.) Beauv and Setaria glauca (L.) Beauv. We also analyzed the influence of feeding experience on oviposition preference. 【Result】The results showed that the female adults of the RLF have obvious oviposition preference, 49.08% of eggs were laid on rice in rearing cages, significantly higher than other plants. The development duration of larvae fed on rice was 17.29d, significantly shorter than that on Zea mays and Setaria glauca. The oviposition preference of the female fed on rice and maize had no significant difference. The old larvae showed significant feeding preference. The feeding preference of the 3rd- and 4th-instar larvae fedon Oryza sativa followed the trend of Setaria glauca> Oryza sativa, Echinochloa crus-galli > Zea mays, while for the young larvae fed on Zea mays, the preference followed the tendency of Setaria glauca> Zea mays > Oryza sativa, Echinochloa crus-galli. 【Conclusion】These results suggest that rice had the highest number of eggs, but the oviposition preference was not positively related to larval feeding selectivity. The larval growth and development was the best on rice, and the feeding experience may change the feeding preference of larvae partially.

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AFLP Analyses of Genetic Diversity and Population Genetic Structure of Magnaporthe oryzae from South China Crop Breeding Area Minghai ZHU, Lei PI, Canwei SHU, Erxun ZHOU 2017, 31(3): 320-326.  DOI: 10.16819/j.1001-7216.2017.6136 320 Abstract ( )   HTML ( )   PDF (2040KB) ( )   【Objective】 In order to clarify the genetic differentiation of Magnaporthe oryzae in South China Crop Breeding Area in Hainan Province, 【Method】the genetic diversity and population genetic structure of 60 Magnaporthe oryzae isolates collected from the core region (Sanya, Ledong and Baoting) and non-core region (Qiongzhong, Tunchang and Ding’an) of South China Crop Breeding Area were comparatively analyzed using amplified fragment length polymorphism(AFLP) technique. 【Result】The cluster analysis showed that almost all isolates were clustered in one group, and there was no obvious subgroup. The analysis of population genetic structure showed that the percentage of polymorphic loci(PPL), Shannon’s information index(I) and gene flow(Nm) in the core population were 87.89%, 0.2738 and 4.2897, respectively, higher than those of non-core population whose PPL, I and Nm were 81.37%, 0.2703 and 3.5892, respectively. However, Nei’s gene diversity index(H) and genetic differentiation coefficient(Gst) in the core population were 0.1657 and 0.1044, lower than those of non-core population whose H and Gst was 0.1662 and 0.1223. 【Conclusion】 These results showed that there were rich genetic diversity in both isolates of core and non-core regions and wide gene flow existed among these populations, but the genetic variation was mainly within the population. In contrast, the genetic diversity and the degree of genetic differentiation in the isolates of core region were relatively larger.

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Research Advances in the Effects of Water, Nitrogen and Their Interaction on the Yield, Water and Nitrogen Use Efficiencies of Rice Junfeng LI, Jianchang YANG 2017, 31(3): 327-334.  DOI: 10.16819/j.1001-7216.2017.6078 327 Abstract ( )   HTML ( )   PDF (315KB) ( )   Understanding the effects of water, nitrogen (N) and their interaction on the yield, water and N use efficiencies of rice would have great significance in synergistically realizing high yield, high water use efficiency (WUE) and high N use efficiency (NUE). This paper reviewed the advances achieved in water-saving irrigation techniques, NUE and N fertilizer application techniques, coupling effect of water and N on grain yield, WUE and NUE in rice, and crop-soil relationship and its mechanism regulated by water and N. The existing problems were discussed, i.e., very limited work on synergistic interaction between water and N on the crop growth and soil quality; little information on the molecular mechanism that water and nitrogen interact on the efficient absorption and utilization of water and nitrogen in high-yielding rice; and yet to be established the crop-soil integrative management system for simultaneous increases in grain yield, WUE and NUE. Aiming to solve these problems, several important issues meriting further investigation were suggested, that is, the synergistic interaction between water and N on the crop and soil for high yield, high WUE and high NUE and its biological process, the physiological and molecular mechanism in which high-yielding rice absorbs and utilizes water and N efficiently, and crop-soil integrative approaches and key techniques to simultaneously increase grain yield, WUE, and NUE in rice.