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28 July 2019, Volume 26 Issue 4 Previous Issue    Next Issue
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Ustilaginoidea virens: A Fungus Infects Rice Flower and Threats World Rice Production Jiehua Qiu, Shuai Meng, Yizhen Deng, Shiwen Huang, Yanjun Kou 2019, 26(4): 199-206.  DOI: 10.1016/j.rsci.2018.10.007 Abstract ( )   HTML ( )   PDF (591KB) ( )   Rice false smut disease, which is caused by the fungus Ustilaginoidea virens, is currently one of the most devastating rice fungal diseases in the world. Rice false smut disease not only causes severe yield loss and grain quality reduction, but also threatens food safety due to its production of mycotoxins. In this review, the most recent progresses regarding the life cycle, infection processes, genome and genetic diversity, pathogenic gene and disease resistance in rice were summarized in order to provide theoretical basis for the control of U. virens. We also proposed some future directions and key questions that need to be addressed for a better understanding of the molecular mechanism that leads to rice false smut disease and the prospects for sustainable control of rice false smut.

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Physiological Responses of Contrasting Rice Genotypes to Salt Stress at Reproductive Stage Elisa B. Gerona Maria, P. Deocampo Marjorie, A. Egdane James, M. Ismail Abdelbagi, L. Dionisio-Sese Maribel 2019, 26(4): 207-219.  DOI: 10.1016/j.rsci.2019.05.001 Abstract ( )   HTML ( )   PDF (901KB) ( )   Salinity is a major abiotic stress affecting plant growth and productivity. Considerable genetic variation is present in rice in response to salt stress, with higher sensitivity during early seedling and reproductive stage. In this study, physiological changes in leaves and developing panicles of rice genotypes (IR686, Sadri, Rc222, CSR28, IR670 and Pokkali) contrasting in salt tolerance at the reproductive stage were evaluated in greenhouse experiment under salt stress. The results showed that IR670 and the tolerant-check Pokkali maintained lower Na+/K+ ratio, less reduction in chlorophyll concentration, lower malondialdehyde (MDA) production, higher concentrations of reduced ascorbate (reduced AsA), higher proline accumulation and lower percentage reduction in pollen viability than the salt-sensitive genotypes under salt stress. The higher concentration of reduced AsA suggests an efficient ROS-scavenging system. Physiological measurements and pollen viability analysis revealed that Sadri (moderately tolerant at the seedling stage) is sensitive to salt stress at the flowering stage. The findings will be useful in breeding salt tolerant varieties at both seedling and reproductive stages by selecting appropriate genotypes and phenotypes.

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Fine-Mapping of qTGW1.2a, a Quantitative Trait Locus for 1000-Grain Weight in Rice Wenhui Wang, Linlin Wang, Yujun Zhu, Yeyang Fan, Jieyun Zhuang 2019, 26(4): 220-228.  DOI: 10.1016/j.rsci.2019.04.004 Abstract ( )   HTML ( )   PDF (945KB) ( )   Thousand-grain weight (TGW) is a key component of grain yield in rice. This study was conducted to validate and fine-map qTGW1.2a, a quantitative trait locus for grain weight and grain size previously located in a 933.6-kb region on the long arm of rice chromosome 1. Firstly, three residual heterozygotes (RHs) were selected from a BC2F11 population of the indica rice cross Zhenshan 97 (ZS97)///ZS97//ZS97/Milyang 46. The heterozygous segments in these RHs were arranged successively in physical positions, forming one set of sequential residual heterozygotes (SeqRHs). In each of the populations derived, non-recombinant homozygotes were identified to produce near isogenic lines (NILs) comprising the two homozygous genotypes. The NILs were tested for grain weight, grain length and grain width. QTL analyses for the three traits were performed. Then, the updated QTL location was followed for a new run of SeqRHs identification-NIL development-QTL mapping. Altogether, 11 NIL populations derived from four sets of SeqRHs were developed and used. qTGW1.2a was finally delimitated into a 77.5-kb region containing 13 annotated genes. In the six populations segregating this QTL, which were in four generations and were tested across four years, the allelic direction of qTGW1.2a remained consistent and the genetic effects were stable. For TGW, the additive effects ranged from 0.23 to 0.38 g and the proportions of phenotypic variance explained ranged from 26.15% to 41.65%. These results provide a good foundation for the cloning and functional analysis of qTGW1.2a.

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Screening for Spikelet Fertility and Validation of Heat Tolerance in a Large Rice Mutant Population Cheabu Sulaiman, Panichawong Nat, Rattanametta Prisana, Wasuri Boonthong, Kasemsap Poonpipope, Arikit Siwaret, Vanavichit Apichart, Malumpong Chanate 2019, 26(4): 229-238.  DOI: 10.1016/j.rsci.2018.08.008 Abstract ( )   HTML ( )   PDF (1100KB) ( )   A total of 10 000 M4 individuals in Jao Hom Nil (JHN) mutant population was treated with high temperature (40 ºC to 45 ºC) during the day time (6 h) from the booting to the harvesting stages, and ambient temperature (33 ºC to 35 ºC) was used as the control. The results of screening and yield trials found that the mutant line M9962 had a high spikelet fertility of 78% under heat stress. In addition, the other mutant lines, including M3181 and M7988, had a spikelet fertility of approximately 70%. However, the JHN wild type, Sin Lek, RD15 and RD33 had very low spikelet fertility of 34%, 14%, 9% and 4%, respectively. The lower spikelet fertility at an elevated temperature resulted in a dramatic decrease of filled grain and contributed to a loss in 100-grain weight. M9962 is a potential genetic stock for use in a heat tolerance breeding programme. In addition, spikelet fertility at high temperature was representative of heat tolerance and can be used as a screening trait for heat tolerance during the reproductive phase on a large scale.

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Assessment of Genetic Diversity of Drought Tolerant and Susceptible Rice Genotypes Using Microsatellite Markers Donde Ravindra, Kumar Jitendra, Gouda Gayatri, Kumar Gupta Manoj, Mukherjee Mitadru, Yasin Baksh Sk, Mahadani Pradosh, Kumar Sahoo Khirod, Behera Lambodar, Kumar Dash Sushanta 2019, 26(4): 239-247.  DOI: 10.1016/j.rsci.2019.01.004 Abstract ( )   HTML ( )   PDF (566KB) ( )   The introgression of wild chromosomal segments into popular rice varieties is one of the potential approaches for developing varieties for drought stress condition. Sixteen genotypes, including nine indica, two tropical japonica and five chromosome segments substitution lines (CSSLs) with different levels of tolerance/susceptibility to drought stress, were selected for diversity study. Sixty-three microsatellite markers were utilized for assessing genetic diversity. A total of 95 alleles were amplified, and out of them, 60 were polymorphic. Six unique alleles, amplified by the microsatellite loci RM276, RM472, RM488, RM537, RM541 and RM28089, were identified in six genotypes, namely FR13A, Brahamanakhi, RUF44, Swarna-sub1, Brahamanakhi and Satyabhama. The highest genetic similarity was found among CSSLs. Polymorphism information content (PIC) value varied from 0 to 1.00 with an average of 0.66 per locus. Twenty-eight microsatellites were found to be polymorphic, which could be used in marker-assisted selection programme. All the sixteen genotypes were grouped into two major clusters at genetic similarity of 0.64. In the cluster I, five CSSLs identified as diverse genotypes had wild ancestor segments responsible for drought tolerance, and hence they could be utilized as potential donors. The popular Indian varieties, Swarna-sub1 and IR64-sub1, could be used as recurrent parents in the future breeding program for developing varieties for abiotic stresses such as submergence and drought.

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Comparison of Five Endogenous Reference Genes for Specific PCR Detection and Quantification of Rice Xiujie Zhang, Wujun Jin, Wentao Xu, Xiaying Li, Ying Shang, Sha Li, Hongsheng Ouyang 2019, 26(4): 248-256.  DOI: 10.1016/j.rsci.2019.04.005 Abstract ( )   HTML ( )   PDF (896KB) ( )   Endogenous reference genes (ERGs) provide vital information regarding genetically modified organisms (GMOs). The successful detection of ERGs can identity GMOs and the source of genes, verify stability and reliability of the detection system, and calculate the level of genetically modified (GM) ingredients in mixtures. The reported ERGs in rice include sucrose-phosphate synthase (SPS), phospholipase D (PLD), RBE4 and rice root-specific GOS9 genes. Based on the characteristics of ERGs, a new ERG gene, phosphoenolpyruvate carboxylase (PEPC), was selected, and further compared with the four existing genes. A total of 18 rice varieties and 29 non-rice crops were used to verify the interspecies specificity, intraspecies consistency, sensitivity, stability and reliability of these five ERGs using qualitative and quantitative PCR. Qualitative detection indicated that SPS and PEPC displayed sufficient specificity, and the detection sensitivity was 0.05% and 0.005%, respectively. Although the specificity of both RBE4 and GOS9 were adequate, the amplicons were small and easily confused with primer dimers. Non-specific amplification of the PLD gene was present in maize and potato. Real-time quantitative PCR detection indicated that PLD, SPS and PEPC displayed good specificity, with R2 of the standard curve greater than 0.98, while the amplification efficiency ranged between 90% and 110%. Both the detection sensitivities of PLD and PEPC were five copies and that of SPS was ten copies. RBE4 showed typical amplification in maize, beet and Arabidopsis, while GOS9 was found in maize, tobacco and oats. PEPC exhibited excellent detection sensitivity and species specificity, which made it a potentially useful application in GM-rice supervision and administration. Additionally, SPS and PLD are also suitable for GM-rice detection. This study effectively established a foundation for GMO detection, which not only provides vital technical support for GMO identification, but also is of great significance for enhancing the comparability of detection results, and the standardization of ERG testing in GM-rice.

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Photocatalytic Treatment of Waste Water from Rice Husk Alkaline Hydrolysate D. Arefieva Olga, S. Vasilyeva Marina, V. Ermolenko Ekaterina, V. Bychkova Anastasiia 2019, 26(4): 257-260.  DOI: 10.1016/j.rsci.2018.10.008 Abstract ( )   HTML ( )   PDF (469KB) ( )   We carried out photocatalytic treatment of a lignin-free solution of rice husk alkaline hydrolysate [pH of 2, chemical oxygen demand (COD) of 12.8 g/L] using photo-Fenton process in the ultraviolet (UV, wavelength of 365 nm) and visible spectrum. Oxidation of lignin was performed at a constant mass ratio of COD:H2O2 as 1:2 and Fe2+ concentration of 80 mg/L. It was established that for the destruction of alkaline lignin, exposure to visible or UV radiation was necessary. Decolorization efficiency of a lignin-free solution depends on the dilution rate of the solution. The advanced oxidative photo-Fenton process (UV/Н2О2/Fe2+) made it possible to reduce the color of lignin-free solution at a dilution ratio of 1:5 by 94% of decolorization efficiency, 87% of phenolic compound and 79% of COD. With the help of gas chromatography, the products of lignin destruction were low-toxic and usable.