|Ammar, Karim - VISITING SCIENTIST|
Submitted to: Plant Cell and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 15, 1998
Publication Date: N/A
Interpretive Summary: When high temperatures occur during wheat grain formation, grain yield is reduced. In order to develop genetic approaches to enhance heat tolerance of this cereal, a better understanding of how high temperature alters grain formation is needed. This study measured the effects of seven days of 35/25 deg C day/night temperatures on final kernel weight and on the accumulation of cytokinins, a group of hormones that regulate grain formation. Compared to developing grains from wheat plants maintained at 25/15 deg C temperatures, cytokinin accumulation was reduced 50-80% in grains collected from heat-treated plants. Kernel weight was reduced 18-27%. The number of kernels that were formed was not affected by this treatment. Addition of supplemental cytokinins to the plant during high temperature exposure partially mitigated these effects. These results will help to develop new approaches to increase heat tolerance in wheat and to reduce cropping risks.
Technical Abstract: The occurrence of high temperatures during reproductive development reduces grain yield in wheat (Triticum aestivum L.). A better understanding of high temperature-related alterations in grain formation is needed to develop genetic approaches to enhance heat tolerance in this cereal. This study quantified the effects of 7d of 35/25 deg C day/night temperatures on grain development and post- anthesis cytokinin accumulation in a soft white winter wheat (c.v. Stephens). Developing grains from control plants maintained at 25/15 deg C accumulated zeatin, dihydrozeatin and their corresponding 9- ribosides from 1-4 d post anthesis. Post-anthesis cytokinin accumulation was reduced 50-80% in grains collected from heat- treated plants. Cytokinin levels declined to baseline by 5d post- anthesis in control plants while heat-treated plants showed a secondary peak 6-8d after anthesis. Kernel weight was reduced by 18- 27%. This was correlated with a significant reduction in cytokinin accumulation. Kernel number was not affected by this treatment. These results suggest that altered cytokinin accumulation during endosperm cell proliferation is one mechanism by which high temperature reduces grain yield in wheat.