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28 November 2019, Volume 26 Issue 6 Previous Issue    Next Issue
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Increasing Fatty Acids in Rice Root Improves Silence of Rice Seedling to Salt Stress Ling Liu, Jin Chen, Yanning Tan, Tianshun Zhou, Ning Ouyang, Jia Zeng, Dingyang Yuan, Meijuan Duan 2019, 26(6): 339-342.  DOI: 10.1016/j.rsci.2019.01.005 Abstract ( )   HTML ( )   PDF (682KB) ( )

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Sensing and Uptake of Nitrogen in Rice Plant: A Molecular View Saiful Islam Md 2019, 26(6): 343-355.  DOI: 10.1016/j.rsci.2018.12.007 Abstract ( )   HTML ( )   PDF (703KB) ( )   As a main feature of plant autotrophy, assimilation of inorganic nitrogen (N) is not only of fundamental interest to the crop, but also a crucial factor in crop productivity. N is the main plant mineral nutrient needed for chlorophyll production and other plant cell components (proteins, nucleic acids and amino acids). I highlighted the novel aspects of N responsive sensors, transporters and signaling molecules recently identified in the monocot rice plant, and discussed their potential roles in N sensing and transporting. Furthermore, over the last couple of years, N sensing has been shown to be affected by different external factors, which act as local signals to trigger systemic signaling coordinated by long-distance transport or mobile signals in plant body. Understanding of this complex regulatory network provides a foundation mechanism for the development of novel strategies to increase the acquisition and transportation efficiency of nitrogen under varying N conditions for rice production.

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Application of Micronutrients in Rice-Wheat Cropping System of South Asia Nadeem Faisal, Farooq Muhammad 2019, 26(6): 356-371.  DOI: 10.1016/j.rsci.2019.02.002 Abstract ( )   HTML ( )   PDF (603KB) ( )   Rice-wheat cropping system (RWCS) is one of the most important cropping systems in South Asia. However, sustainability of this system is under threat owing to several factors, of which deficiency of micronutrients particularly zinc (Zn), boron (B) and manganese (Mn) is one of the major problems. Continuous rotation of rice and wheat, imbalanced fertilizer use and little/no use of micronutrient-enriched fertilizers induce deficiencies of Zn, B and Mn in the RWCS of South Asia. Here we review that (i) imbalanced fertilizer use and organic matter depletion deteriorate soil structure resulting in low efficiency of applied macro- and micro-nutrients in RWCS. (ii) The micronutrients (Zn, B and Mn) are essentially involved in metabolism of rice and wheat plants, including chlorophyll synthesis, photosynthesis, enzyme activation and membrane integrity. (iii) Availability and uptake of Zn, B and Mn from rhizosphere depend on the physico-chemical soil properties (which differ under aerobic and anaerobic conditions) including soil pH, soil organic matter, soil moisture and interaction of these micronutrients with other nutrients. (iv) Plant ability to uptake and utilize the nutrients is affected by several plant factors such as root architecture, root hairs, transport kinetics parameter and root exudates. (v) Crop management and application of these microelements can help correct the micronutrients deficiency and enhance their grain concentration.

Research Paper

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Characterization of a Novel Gain-of-Function Spotted-Leaf Mutant with Enhanced Disease Resistance in Rice Ting Chen, Zheng Chen, Prakash Sathe Atul, Zhihong Zhang, Liangjian Li, Huihui Shang, Shaoqing Tang, Xiaobo Zhang, Jianli Wu 2019, 26(6): 372-383.  DOI: 10.1016/j.rsci.2019.03.001 Abstract ( )   HTML ( )   PDF (1500KB) ( )   We here reported the identification and characterization of a novel gain-of-function spotted-leaf 26 (Spl26) mutant from an ethylmethylsulfone (EMS)-induced rice cultivar IR64. Spl26 displayed reddish- brown lesions that firstly appeared on the leaf tips at the early tillering stage and spread gradually downward to cover the whole leaf blades that wilted subsequently. The lesion development was light- dependent under natural conditions. Spl26 exhibited impaired photosynthetic capacity with decreased chlorophyll content and lowered photosynthetic parameters which ultimately led to the poor performance of agronomic traits. Severe cell death occurred in Spl26 in accompany with increased malonaldehyde level and membrane ion leakage rate, elevated reactive oxygen species (ROS) accumulation, altered ROS scavenging activities, increased DNA fragmentation and decreased soluble protein levels. Defense responses were activated in Spl26 with enhanced resistance to rice bacterial blight, up-regulation of defense response genes and altered endogenous hormone levels. The spotted-leaf phenotype is controlled by a single dominant nuclear gene localized to a 305 kb region between RM5490 and InDel42 on the short arm of chromosome 7. The data suggested that Spl26 is a novel gain-of-function spotted-leaf mutant with enhanced bacterial disease resistance and immunity-associated premature leaf senescence and would provide the basis for cloning of the target gene.

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Genome-Wide Association Analysis and Allelic Mining of Grain Shape-Related Traits in Rice Yang Lv, Yueying Wang, Jahan Noushin, Haitao Hu, Ping Chen, Lianguang Shang, Haiyan Lin, Guojun Dong, Jiang Hu, Zhenyu Gao, Qian Qian, Yu Zhang, Longbiao Guo 2019, 26(6): 384-392.  DOI: 10.1016/j.rsci.2018.09.002 Abstract ( )   HTML ( )   PDF (1063KB) ( )   Excavating single nucleotide polymorphisms (SNPs) significantly associated with rice grain shape and predicting candidate genes through genome-wide association study (GWAS) can provide a theoretical basis for discovery and utilization of excellent genetic resources in rice. Based on 16 352 SNPs, 161 natural indica rice varieties with various grain sizes in southern China were used for GWAS of grain shape-related traits, referring to grain length (GL), grain width (GW), 1000-grain weight (TGW), and grain length/width (GLW). Phenotypic statistics showed that coefficient of variation values for these four traits GL, GW, TGW and GLW were 9.92%, 9.09%, 20.20% and 16.38%, respectively. Each trait showed a normal distribution, and there was a certain correlation between these traits. Through general linear model correlation analysis, a total of 38 significant loci were identified, and a range of 100 kb upstream and downstream of the significant loci was identified as the candidate interval. On chromosome 3, GS3 and qGL3 were found to regulate GL. On chromosome 6, TGW6 and GW6a were found to regulate TGW. Also, some QTLs related to grain shape were found on chromosomes 5 and 9. Besides that, using sequenced 3K-germplasm resources, we found that there are 22 overlapped varieties between these two natural populations. Twenty-six SNPs and fourteen haplotypes were identified in five regions of GS3 genes. The detection of multiple candidate genes/QTLs within the candidate interval is beneficial for further excavation of superior rice genetic resources.

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Genetic Diversity and Allelic Frequency of Selected Thai and Exotic Rice Germplasm Using SSR Markers Pathaichindachote Wanwarang, Panyawut Natjaree, Sikaewtung Kannika, Patarapuwadol Sujin, Muangprom Amorntip 2019, 26(6): 393-403.  DOI: 10.1016/j.rsci.2018.11.002 Abstract ( )   HTML ( )   PDF (974KB) ( )   A collection of 167 Thai and exotic rice accessions was subjected for evaluation of genetic diversity and assessment of relationship by simple sequence repeat (SSR) markers. Among a total of 49 SSR markers, 13 markers distributing over 12 rice chromosomes showed clear polymorphic band patterns, and they were selected for genetic assessment. A total of 110 alleles were detected with an average of 8.46 alleles per locus. The averages of gene diversity, heterozygosity and polymorphic information content were 0.59, 0.02 and 0.56, respectively. The unweighted-pair group method with arithmetic averages (UPGMA) clustering analysis was performed for genetic distance, and phylogenetic tree was constructed. The result showed that this rice collection was divided into two major groups, classified as japonica and indica subspecies. Within the japonica group, temperate japonica and tropical japonica subgroups can be clearly separated. Three-dimensional principal component analysis projection and model-based population structure analysis showed consistent clustering results with two major groups of UPGMA analysis, supporting the classification of japonica and indica subspecies. The indica allelic frequency was also investigated to provide an indicative guide for breeders to overcome the practical problems on sterility of inter-subspecies hybrid offspring. This rice collection and information obtained in this study will be useful for rice breeding programs.

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Soil Nitrogen Distribution and Plant Nitrogen Utilization in Direct-Seeded Rice in Response to Deep Placement of Basal Fertilizer-Nitrogen Danying Wang, Chang Ye, Chunmei Xu, Zaiman Wang, Song Chen, Guang Chu, Xiufu Zhang 2019, 26(6): 404-415.  DOI: 10.1016/j.rsci.2018.12.008 Abstract ( )   HTML ( )   PDF (1213KB) ( )   Deep placement of controlled-release fertilizer increases nitrogen (N) use efficiency in rice planting but is expensive. Few studies on direct-seeded rice have examined the effects of deep placement of conventional fertilizer. With prilled urea serving as N fertilizer, a two-year field experiment with two N rates (120 and 195 kg/hm2) and four basal N application treatments (B50, all fertilizer was broadcast with 50% as basal N; D50, D70 and D100 corresponded to 50%, 70% and 100% of N deeply placed as basal N, respectively) were conducted in direct-seeded rice in 2013 and 2014. Soil N distribution and plant N uptake were analyzed. The results showed that deep placement of basal N significantly increased total N concentrations in soil. Significantly greater soil N concentrations were observed in D100 compared with B50 at 0, 6 and 12 cm (lateral distance) from the fertilizer application point both at mid-tillering and heading stages. D100 presented the highest values of dry matter and N accumulation from seeding to mid-tillering stages, but it presented the lowest values from heading to maturity stages and the lowest grain yield for no sufficient N supply at the reproductive stage. The grain yield of D50 was the highest, however, no significant difference was observed in grain yield, N agronomic efficiency or N recovery efficiency between D70 and D50, or between D70 and B50, while D70 was more labor saving than D50 for only one topdressing was applied in D70 compared with twice in other treatments. The above results indicated that 70% of fertilizer-N deeply placed as a basal fertilizer and 30% of fertilizer-N topdressed as a panicle fertilizer constituted an ideal approach for direct-seeded rice. This recommendation was further verified through on-farm demonstration experiments in 2015, in which D70 produced in similar grain yields as B50 did.

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Impact of Rice-Catfish/Shrimp Co-culture on Nutrients Fluxes Across Sediment-Water Interface in Intensive Aquaculture Ponds Yaobin Liu, Lin Qin, Fengbo Li, Xiyue Zhou, Chunchun Xu, Long Ji, Zhongdu Chen, Jinfei Feng, Fuping Fang 2019, 26(6): 416-424.  DOI: 10.1016/j.rsci.2019.06.001 Abstract ( )   HTML ( )   PDF (1014KB) ( )   Exchange of nitrogen and phosphorus across sediment-water interface plays an important role in the management of nutrient recycling in the aquaculture pond. In this study, a plot experiment was conducted to study the effect of rice-catfish/shrimp co-culture on the micro-profile of oxygen (O2), pH and nutrient exchange across sediment-water interface in the intensive culture ponds. The results showed that rice-catfish co-culture increased the concentration and penetrating depth of O2, but decreased the pH value across the sediment-water interface, compared with catfish monoculture. Additional rice cultivation significantly reduced the flux rates of ammonium (NH4+) and nitrate (NO3-) across sediment-water interface in the catfish and shrimp ponds. The flux rates of NO2- and soluble phosphorus (PO43-) showed no significant difference between rice-catfish/shrimp co-culture ponds and catfish/shrimp monoculture ponds. Rice only affected the dissolved inorganic nitrogen and phosphorus fractions in the sediment. The concentrations of NH4+ were significantly lower in the sediment of co-culture ponds than in the monoculture ponds. Additional rice cultivation also significantly reduced the content and percentage of dissolved inorganic phosphorus in the sediment of catfish ponds.