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28 July 2015, Volume 22 Issue 4 Previous Issue    Next Issue
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Acclimation and Tolerance Strategies of Rice under Drought Stress Pandey Veena, Shukla Alok 2015, 22(4): 147-161.  DOI: 10.1016/S1672-6308(14)60289-4 Abstract ( )   HTML ( )   PDF (6494KB) ( )   Rice (Oryza sativa L.) is an important food crop and requires larger amount of water throughout its life cycle as compared to other crops. Hence, water related stress cause severe threat to rice production. Drought is a major challenge limiting rice production. It affects rice at morphological (reduced germination, plant height, plant biomass, number of tillers, various root and leaf traits), physiological (reduced photosynthesis, transpiration, stomatal conductance, water use efficiency, relative water content, chlorophyll content, photosystem II activity, membrane stability, carbon isotope discrimination and abscisic acid content), biochemical (accumulation of osmoprotectant like proline, sugars, polyamines and antioxidants) and molecular (altered expression of genes which encode transcription factors and defence related proteins) levels and thereby affects its yield. To facilitate the selection or development of drought tolerant rice varieties, a thorough understanding of the various mechanisms that govern the yield of rice under water stress condition is a prerequisite. Thus, this review is focused mainly on recent information about the effects of drought on rice, rice responses as well as adaptation mechanisms to drought stress.

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Phenotype of Rice Floury Endosperm Mutant flo7 and Fine Mapping of Mutated Gene Zhong-hua Sheng, Peng-fei Fang, San-feng Li, Gui-ai Jiao, Li-hong Xie, Pei-song Hu, Shao-qing Tang, Xiang-jin Wei 2015, 22(4): 162-170.  DOI: 10.1016/S1672-6308(14)60299-7 Abstract ( )   HTML ( )   PDF (31744KB) ( )   The major storage substance in rice endosperm is starch, which accounts for 80% of dry matter weight. In this study, rice mutant flo7, selected from the progeny of Nipponbare’s tissue culture, displayed floury and opaque endosperm. Compared with its corresponding wild type (WT) Nipponbare, the mutant flo7 produced longer, narrower, thinner and lighter grains. The levels of glucose, fructose and sucrose in the mutant flo7 endosperm were higher than those in the WT endosperm, whereas the protein content was not affected. With respect to both amylose content and gel consistency, the mutant flo7 was lower than WT, but its alkali value was higher. Scanning electron microscopic examinations showed that the endosperm of the mutant flo7 contained irregular, loosely packed and compound starch granules. Genetic analysis indicated that the mutant phenotype was determined by a single recessive nuclear gene. The flo7 locus was mapped to a region on the long arm of chromosome 12, within a 95.1 kb interval defined by the markers C2-11 and C5-15. There are 13 open reading frames in the mapping interval. Transcription profiling of the developing grains showed that a number of genes involved in starch synthesis were affected differently in the mutant flo7.

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Identification and Characterization of Reduced Epicuticular Wax Mutants in Rice H. Tai Thomas 2015, 22(4): 171-179.  DOI: 10.1016/S1672-6308(14)60295-X Abstract ( )   HTML ( )   PDF (3195KB) ( )   Epicuticular wax forms the outermost protective barrier of the aerial surfaces of land plants, working in concert with other components of the plant cuticle to prevent uncontrolled loss of water and to provide protection against an array of external environmental stress. In this study, chemically- mutagenized populations of rice (Oryza sativa L.) derived from approximately 4 750 M2 families were screened for adhesion of water droplets resulting in a wet leaf/glossy (wlg) phenotype. Mutants were identified in 11 independently-derived M2 families. Scanning electron microscopy analysis confirmed the association of the wlg phenotype with changes in the epicuticular wax crystals of these plants. The phenotypes of five mutants (7-17A, 26.1, 524.2, 680.2, and 843.1) were confirmed to be the result of single recessive gene mutation. Evaluation of mutants from 3 (6-1A, 7-17A, and 11-39A) of 11 M2 families revealed significant reductions (> 50%) in surface wax content and increases in cuticle membrane permeability.

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Evaluation of Population Structure, Genetic Diversity and Origin of Northeast Asia Weedy Rice Based on Simple Sequence Repeat Markers Mao-bai Li, Hui Wang, Li-ming Cao 2015, 22(4): 180-188.  DOI: 10.1016/S1672-6308(14)60293-6 Abstract ( )   HTML ( )   PDF (40678KB) ( )   Weedy rice exerts a severe impact on rice production by competing for sunlight, water and nutrients. This study assayed the population structure, genetic diversity and origin of Northeast Asia weedy rice by using 48 simple sequence repeat markers. The results showed that weedy rice in Northeast Asia had a high genetic diversity, with Shannon’s diversity index (I) of 0.748 and the heterozygosity (He) of 0.434. In each regional population, I value varied widely. The widest range of I (0.228-0.489) was observed in the weedy rice of Eastern China, which was larger than that of Northeast China and Korea (0.168-0.270). The F-statistics of regional populations (Fis, Fit and Fst) also showed higher values in the weedy rice of Eastern China than those of Northeast China and Korea. All weedy rice accessions were grouped into two clusters in the unweighted pair group method with arithmetic mean cluster analysis dendrogram, namely Eastern China branch and Northeastern China plus Korea branch. There was significant differentiation in genetic characteristics in weedy rice of northeastern and eastern Asia, especially in Eastern China.

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Influence of Seed Priming on Performance and Water Productivity of Direct Seeded Rice in Alternating Wetting and Drying Ur Rehman Hafeez, Kamran Muhammad, Maqsood Ahmed Basra Shahzad, Afzal Irfan, Farooq Muhammad 2015, 22(4): 189-196.  DOI: 10.1016/S1672-6308(14)60297-3 Abstract ( )   HTML ( )   PDF (24047KB) ( )   Direct seeded rice is promising alternative to traditional transplanting, but requires appropriate crop and water management to maintain yield performance and achieve high water productivity. Present study evaluated the effect of seed priming and irrigation on crop establishment, tillering, agronomic traits, paddy yield, grain quality and water productivity of direct seeded rice in alternate wetting and drying (DSR-AWD) in comparison with direct seeded rice at field capacity (DSR-FC). Seed priming treatments were osmo-priming with KCl (2.2%), CaCl2 (2.2%) and moringa leaf extracts (MLE, 3.3%) including hydro-priming as control. Among the treatments, seed osmo-primed with MLE emerged earlier and had higher final emergence, followed by osmo-priming with CaCl2. Tillering emergence rate and number of tillers per plant were the highest for seed priming with CaCl2 in DSR-AWD. Total productive and non-productive tillers, panicle length, biological and grain yields, harvest index were highest for seed priming with MLE or CaCl2 in DSR-AWD. Similarly, grain quality, estimated in terms of normal grains, abortive and chalky grains, was also the highest in DSR-AWD with MLE osmo-priming. Benefit cost ratio and water productivity was also the highest in DSR-AWD for seed priming with MLE. In conclusion, seed priming with MLE or CaCl2 can be successfully employed to improve the direct seeded rice performance when practiced with alternate wetting and drying irrigation.

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Low Light During Grain Filling Stage Deteriorates Rice Cooking Quality, but not Nutritional Value Cheng-gang Liang, Jia Liu, Yan Wang, Dan Xiong, Chun-bang Ding, Tian Li 2015, 22(4): 197-206.  DOI: 10.1016/S1672-6308(14)60298-5 Abstract ( )   HTML ( )   PDF (1864KB) ( )   To investigate the effect of low light (LL, 50% natural light) during grain filling (GF) stage on rice transamination, amino acid (AA) accumulation, nutritional value, and cooking quality in three different rice genotypes, transaminase activities and AA levels in grains during GF stage and the traits that significantly affected rice quality (physical appearance, cooking quality, and nutritional value) were analyzed. LL did not disturb transamination in rice grains during GF stage, as minimal impact was found on alanine and aspartate transaminase activities. Nevertheless, most AAs in caryopses, including lysine and threonine, increased in response to LL, except for sulfur-containing AAs. These results suggest that AA metabolism and accumulation in rice grains were rarely suppressed by LL during GF stage. Rice nutritional ingredients at harvest, such as major protein components including glutelin and most important essential amino acids (EAAs) including lysine and threonine, increased significantly in response to LL, whereas most protein and EAA ratios were rarely affected. However, LL markedly affected physical appearance of rice grains by reducing brown rice rate, milled rice rate, and 1000-grain weight and increasing the chalkiness rate. In addition, cooking qualities decreased in response to LL, while breakdown values and amylose levels decreased and setback values increased. We concluded that LL during GF stage decreased the cooking quality of rice, but could potentially improve the nutritional value of rice.