PHYSIOLOGICAL AND BIOCHEMICAL RESPONSE OF WHEAT GENOTYPES UNDER TEMPERATURE STRESS

This paper focuses on the evaluation and performance of newly developed wheat genotypes (DH-7, DH-8, DH-11, DH12, DH-18, DH-20)along with two local check varieties (Lu-26s and Kiran-95) under three different sowings at various dates viz. November 07 (optimum condition), November 27 (heat stress condition) and December 17 (high heat stress condition) under wire gauze house during 2014-15. All the genotypes showing sensitive, tolerant, medium sensitive, medium tolerant responses to heat stress conditions were selected for various physiological and biochemical plant characters (osmotic pressure, proline, Glycine betain, Sugar, Sodium, Potassium, K/Na ratio, Leaf area, Chlorophyll-a, Chlorophyll-b, total chlorophyll, cell membrane stability and grain yield) with the objective to determine their impact on the grain yield. All the physio-chemical plant characters revealed significant variation among genotypes and temperature conditions in their interactions and means. Heat stress conditions showed significant increase in osmotic pressure, proline, glycine betain, sugar, sodium and cell membrane stability and significant decrease in potassium, K/Na ratio, leaf area, chlorophyll a, chlorophyll b, total chlorophyll and grain yield over optimum condition. Osmotic pressure, proline and glycine betain showed negative and non-significant correlation with the grain yield whereas sodium and cell membrane stability had negative and significant effect on the grain yield. The overall investigations showed that potassium, K/Na ratio, leaf area, chlorophyll-a, chlorophyll-b and total chlorophyll displayed positive and significant correlation with the grain yield. Multiple linear regression analyses of variance revealed that potassium contents in the leaves have highest impact i.e. 25.5 percent in grain yield change followed by proline, sodium and glycine betain contents showing 16.0, 13.7 and 13.2 percent impact on yield fluctuation. It is concluded that four genotypes (DH-7, DH8, DH-11 and DH-18) and one local check Lu-26s were identified to have the potential to perform economically under high heat stress condition.