Integrated Physiological, Biochemical, and Molecular Analysis Identifies Important Traits and Mechanisms Associated with Differential Response of Rice Genotypes to Elevated Temperature

In changing climate, heat stress caused by high temperature poses a serious threat to rice cultivation. A multiple organizational analysis at physiological, biochemical and molecular level is required to fully understand the impact of elevated temperature in rice. This study was aimed at deciphering the elevated temperature response in eleven popular and mega rice cultivars widely grown in India. Physiological and biochemical traits specifically membrane thermostability (MTS), antioxidants, and photosynthesis were studied at vegetative and reproductive phases which were used to establish a correlation with grain yield under stress. Several useful traits in different genotypes were identified which will be important resource to develop high temperature tolerant rice cultivars. Interestingly, Nagina22 emerged as best performer in terms of yield as well as expression of physiological and biochemical traits at elevated temperature. It showed lesser relative injury, lesser reduction in chlorophyll content, increased super oxide dismutase, catalase and peroxidase activity, lesser reduction in net photosynthetic rate (PN), high transpiration rate (E) and other photosynthetic/ fluorescence parameters contributing to least reduction in spikelet fertility and grain yield at elevated temperature. Further, expression of 14 genes including heat shock transcription factors and heat shock proteins was analyzed in Nagina22 (tolerant) and Vandana (susceptible) at flowering phase, strengthening the fact that N22 performs better at molecular level also during elevated temperature. This study shows that elevated temperature response is complex and involves multiple biological processes which are needed to be characterized to address the challenges of future climate extreme conditions

Biochemical and physiological characterization for nitrogen use efficiency in aromatic rice genotypes

Not AvailableIn a set of 78 aromatic rice genotypes, cluster analysis was performed for yield and its related traits in field under two nitrogen (N) conditions viz., application of N fertilizer (N100) and without application of N fertilizer (N0) during wet season, 2011 and dry season, 2012. Basmati370 and Ranbir basmati were selected as high nitrogen use efficiency (NUE) genotypes and Kolajoha-3 and Ratnasundari as low NUE genotypes for characterization in terms of biochemical, physiological and agronomical aspects of NUE. A total of 32 biochemical, physiological and agronomical characters were measured in the selected four genotypes, growing in field under two N levels i.e., N0 and N100 during wet season 2012. Five efficiency parameters were also studied to determine their NUE. GS activity increased under low N and the increase was more in two high NUE genotypes (41.3%) than that of two low NUE genotypes (5.43%). NR activity increased with application of N fertilizer and low NUE genotypes expressed higher NR activity (8.8% and 2.02% more in N0 and N100 respectively). Chlorophyll content recorded maximum (3.6 mg g−1) in low NUE genotypes under N100 condition, where as the chlorophyll content was minimum (0.43 mg g−1) in high NUE genotypes under N0 condition. Electron transport rate (ETR), quantum yield (ΦPSII) and Fv/Fm were not affected by N levels but there were significant variations in non-photochemical quenching (qN) (15% more in N0) and photochemical quenching (qP) (25% more in N0). Grain yield, total dry matter and N uptake by grain and straw were higher in high NUE genotypes. Higher GS activity, maintenance of sufficient chlorophyll fluorescence and chlorophyll content in case of high NUE genotypes support their higher grain yield and total dry matter content under low N conditions by efficient N uptake, and utilization of nitrogen.Not Availabl