Genotypic Variation for High Temperature Tolerance in Relation to Carbon Partitioning and Grain Sink Activity in Wheat

Abstract

Effect of high temperature tolerance in relation to carbon partitioning and grain sink activity was studied in ten genotypes of wheat (viz C 306, PBW 343, PBW 502, PBW 509, PBW 521, PBW 522, PBW 550, Inqalab, WL 711 and Sonalika) under normal (November, 25.6°C during grain filling) and late planting conditions (December, 29.4°C). Contents of reducing sugars first increased till actively metabolizing stage i.e. 14 days after anthesis (DAA) in parallel with the activity of acid invertase and thereafter declined. Significant reduction in total free sugars and sucrose content was observed during grain development. Acid invertase activity got induced especially in PBW 343 and C 306 under late sown conditions, whereas sucrose synthase, total amylase activities got repressed. Sucrose synthase was significantly high at all stages and it predominated over invertases. Neutral invertase and total amylase showed peak activity of one week earlier in the late sown crop as compared to normal sown crop. A premature cessation of starch deposition occurred in cvs PBW 521, PBW 522 under late sown conditions due to shortening of grain filling period. Our results suggest that decline in sugar content in spite of high sucrolytic enzymes may be correlated to more utilization of assimilates over production/translocation for grain sink activity under high temperature influences. Knowledge of the mechanisms that underlie carbohydrate partitioning in diverse genotypes could be exploited for generating germplasm that can tolerate high temperature.