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.
Highlights
High temperature (>30 ̊C) at the time of grain filling is one of the major constraints in increasing productivity of wheat in tropical countries like India [1]
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
Reducing sugar (RS) and sucrose contents declined throughout grain development from 7 to 40 days after anthesis (DAA) in all genotypes (Tables 1 and 2)
Summary
High temperature (>30 ̊C) at the time of grain filling is one of the major constraints in increasing productivity of wheat in tropical countries like India [1]. Information on high temperature effects on various parameters associated with heat tolerance of wheat genotypes under field conditions are still inadequate [3]. Sucrose upon entering into the grain is metabolized by invertases, sucrose synthases and sucrose—phosphate synthase [9,10] Activity of these enzymes has been associated with the developmental processes of sinks [11,12,13] and they appear to be potential targets of regulation in improving grain filling processes and yield in wheat under heat stress [14]. Some genotypes are reported to have a thermotolerant response and could be used as genetic sources for heat tolerance [15]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
