PHYSIOLOGICAL EFFECT OF HIGH TEMPERATURE STRESS ON SOME SALI RICE GENOTYPES
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Date
2019-07
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AAU, Jorhat
Abstract
Plants are sensitive to high temperature during critical stages such as flowering and seed development. With the increase in daily maximum temperature averaged over flowering period above about 360C, rice yield generally declined because of spikelet sterility induced by high temperatures. Rice crop exposure to the spells of high temperature results in grain yield diminish due to spikelet sterility, reduction in source and sink activities, assimilate partitioning. Identifying genotypic variation through field screening for high temperature tolerance is required for initiating successful breeding programme to develop rice cultivars capable of higher yields under projected climatic change conditions. In view of the importance of high temperature tolerance in rice, an experiment was carried out to study “Physiological effect of high temperature stress on some sali rice genotypes” during kharif, 2017 at Regional Agricultural Research Station, AAU, Titabar in split-plot design with conditions (control and high temperature) as main-plot treatment and 33 rice genotypes as sub-plot treatment including N22 as heat tolerant check variety. Heat stress was imposed in the field immediately after PI stage by enclosing the field grown crop with a make shift locally fabricated polythene tent (<92% transmittance), duly supported by bomboo sticks. The polythene cover was removed at the time of harvest. Enclosing the field crop during reproductive phase with polythene sheet had resulted in significant increase in maximum temperature. Another set of same varieties was grown in ambient condition. The increase in maximum temperature was 1-3.50C over the ambient temperature and minimum temperature had increased by 0.5-1.50C.
Elevated temperature had no significant effect on mean days to flowering and days to maturity for all the genotypes. However, significant differences were observed between varieties. Among the genotypes IET 26774, IET 26776, IET 26778, 175-2K, S-458, N22 were less affected in morphological traits under high temperature stress. The number of filled grains per panicle is an important yield determining character which was significantly affected by high temperature stress. The sterility percentage were minimum (2-7%) for 175-2K, S-458, IET 26778 due to heat stress. Yield attributes such as panicle weight, harvest index, test weight, panicle number m-2, grain number panicle-1, spikelet number panicle-1 and grain yield were significantly reduced under high temperature stress. Dry matter heat susceptibility index (DMHSI) varied between a minimum of 6.76 (N22) to a maximum of 41.52 (IET 26777). IET 26757, IET 26759, IET 26760, IET 26778, IET 26776, 175-2K, S-458 and N22 are the entries with DMHSI value <15 indicating relative tolerance to heat stress. The grain yield heat susceptibility index (GYHSI) was lowest 11.24 in 175-2K. Amongst the remaining varieties IET 26757, IET 26778, S-458 and N22 performed relatively better with < 15 GYHSI. Exposure to high temperature caused marked reduction in 1000 grain weight. The interaction between genotypes and treatment was found to be highly significant. Minimum reduction in test wt. were observed in IET 26776, 175-2K and S-458 (between 7-9% ) which were less than the check var. N22 (11%). The values for the traits namely leaf chlorophyll, starch content, nitrate reductase activity were found to decline under high temperature stress condition. Whereas, nitrogen content in leaf showed higher values under high temperature stress condition.The desirable traits of maintenance of low profile of the pace of reduction of chlorophyll content, starch content, NR acivity, leaf N content of the varieties viz. IET 26766, IET 26771, IET 26774, IET 26775, 175-2K, S-458 and N22 during high temperature stress condition. The varieties 175-2K, S-458, IET 26778 reflected the inherent capabilities to tolerate high temperature stress with less reduction in grain yield and yield components, grain sterility percentage and other biochemical parameters, could be used as a donor in various breeding programmes also could be adopted in farmer’s field to increase the economic yield.