ABSTRACT
Rice being a staple cereal is extremely susceptible towards abiotic stresses. Drought and salinity are two vital factors limiting rice cultivation in Eastern Indo-Gangetic Plains (EIGP). Present study has intended to evaluate the consequences of salinity stress on selected drought tolerant rice genotypes at the most susceptible seedling stage with an aim to identify the potential multi-stress (drought and salt) tolerant rice genotype of this region. Genotypic variation was obvious in all traits related to drought and salt susceptibility. IR84895-B-127-CRA-5-1-1, one of the rice genotypes studied, exhibited exceptional drought and salinity tolerance. IR83373-B-B-25-3-B-B-25-3 also displayed enhanced drought and salt tolerance following IR84895-B-127-CRA-5-1-1. Variations were perceptible in different factors involving photosynthetic performance, proline content, lipid peroxidation, K+/Na+ ratio. Accumulation of reactive oxygen species (ROS) disintegrated cellular and sub-cellular membrane leading to decreased photosynthetic activities. Therefore, accumulation and detoxification of reactive oxygen species was also considered as a major determinant of salt tolerance. IR84895-B-127-CRA-5-1-1 showed improved ROS detoxification mediated by antioxidant enzymes. IR84895-B-127-CRA-5-1-1 seedlings also displayed significant recovery after removal of salt stress. The results established a direct association of ROS scavenging with improved physiological activities and salt tolerance. The study also recommended IR84895-B-127-CRA-5-1-1 for improved crop performance in both drought and saline environments of EIGP. These contrasting rice genotypes may assist in understanding the multiple stress associated factors in concurrent drought and salt tolerant rice genotypes.
ABSTRACT
Potassium (K) is one of the limiting factors that negatively influenced rice growth and yield in submergence-prone soils. We conducted an experiment during the wet season of 2014-15 to achieve optimal doses of K and understand the effect of K application on submerged rice in terms of survival, chlorophyll content, non-structural carbohydrates (NSC), anti-oxidant activities and yield. Results revealed that chlorophyll and NSC content were significantly (P≤0.05) lower whereas the activity of anti-oxidants (catalase, superoxide dismutase and total peroxidase) were significantly (P≤0.05) higher after submergence compared with pre-submergence. Further, application of K at a higher basal dose (40kgha-1) was more beneficial to improve survival after de-submergence by maintaining NSC, chlorophyll content and higher activity of anti-oxidants with lower level of lipid peroxidation. Furthermore, results showed superiority of the treatments having application of higher doses with one foliar spray (T9-40kg K2O ha-1 (basal)+one foliar spray at 0.5% K at panicle initiation (PI) stage) for grain yield. We conclude that application of a higher dose of K with one foliar application at PI stage is more beneficial to enhance plant survival, better recovery and yield gain of rice during complete submergence.
ABSTRACT
The objective of the present study was to examine the effect of aerobic situation on yield, physiological and biochemical traits of advanced breeding lines of rice. Experiment was conducted with two set of rice genotypes under two water regimes (aerobic and irrigated), during three consecutive wet seasons 2010-2012. Significant decrease in yield was observed in rice genotypes grown under aerobic situation as compared to the irrigated ones. Promising rice genotypes having the ability to maintain high plant biomass, harvest index, early vegetative vigour, improved physiological and biochemical traits in terms of relative water content (RWC), leaf area index (LAI), total soluble sugar, starch, protien and proline content help to sustain higher grain yield under aerobic situation. The yield gap between aerobic and irrigated rice ranged between 24% to 68%. Grain yield showed positive correlation with harvest index (0.434), test weight (0.647), plant biomass (0.411) and effective tiller numbers (0.473), whereas spikelet sterility was negative associated (-0.380). The current study suggested that promising genotypes viz., IR77298-14-1-2-130-2, IR84899-B-182-3-1-1-2, IR84887-B-157-38-1-1-3 and IR 84899-B-179-1-1-1-2 for aerobic situation, showing yield advantage due to better performance of physiological and biochemical traits, might be adopted in large area of rainfed ecosystem as well as in irrigated areas where water scarcity was a major problem.