2008 Annual Report
1a.Objectives (from AD-416)
Determine the extent of variation in genetic control of freezing tolerance in wheat with the purpose of identifying wheat lines with different and new combinations of genes that confer freezing tolerance. Define the role of phospholipid-related genes in cold acclimation and freezing tolerance.
1b.Approach (from AD-416)
The overall approach is to use artificial freezing of cold-acclimated winter wheat plants, with temperature measurements taken every two minutes in the crown zone of the plants, to precisely describe the components of the freezing process that are injurious to the plants. Pharmacological agents that enhance or inhibit phospholipase enzyme activity will be used in whole-plant assays to assess their impact on cold acclimation and freezing tolerance; concomitant microarray analysis will be used to define the genes involved.
This project was initiated April 14, 2008 in continuation of project 5348-21430-003-00D. Progress during the reporting period prior to April 18, 2008 is reported under the previous project. After April 18, we assembled a collection of 24 wheat lines and accompanying preliminary cold tolerance information. We initiated studies to determine the impact of various chemicals on the ability of the plants to develop cold tolerance. The objective of this study is to elucidate the role of specific metabolic pathways in the development of cold tolerance. Very preliminary evidence suggests that gibberellic acid, a plant hormone, may impact the cold acclimation process differently in plants that develop a high level of cold tolerance, compared to those that do not.
A study of the dynamics of phospholipase A2 (PLA2) activity during the cold acclimation process was completed and submitted to a journal for publication. The activity of PLA2 was strongly correlated with the development of cold tolerance. In plants that developed high levels of cold tolerance, PLA2 activity rapidly increased significantly in response to cold temperature. In plants that were poorly cold tolerant, PLA2 activity was much more slow to increase. As the level of cold acclimation reached its maximum, the level of the PLA2 activity decreased significantly. These results suggested that PLA2 activity forms an integral part of the cold acclimation process, but is not responsible for the perception of the cold temperature signal. These results provide new information on the metabolic processes that are involved in the development of cold tolerance in wheat.
This research addresses National Program 301 Action Plan Component 3. Genetic Improvement of Crops; Problem Statement 3C: Germplasm Enhancement/Release of Improved Genetic Resources and Varieties.
Membrane altering enzyme related to cold tolerance. Cold temperature tolerance in wheat, essential to fall – seeded crops, is a complex phenomenon that is poorly understood. The dynamics of phospholipase A2 (PLA2), an enzyme that is active in membrane restructuring, were monitored, by the ARS scientists at the Wheat Genetics, Quality Physiology, and Disease Research Unit in Pullman, WA, during cold acclimation of wheat lines differing in their ability to develop cold tolerance. The levels of PLA2 activity increased more rapidly in cold tolerant lines than in less cold tolerant lines. As the plants reached maximum cold tolerance, the PLA2 activity declined. These results showed that PLA2 forms an integral part of the cold acclimation process, providing a new means to monito the cold acclimation status of plants during the process of breeding for improved cold tolerance. This research addresses National Program 301, Component 3, Problem Statement 3C.
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Skinner, D.Z., Garland Campbell, K.A. 2008. Evidence of a major genetic factor conditioning freezing sensitivity in winter wheat. Plant Breeding 127:228-234.