CHILL-RESPONSIVE DEHYDRINS IN BLUEBERRY: ARE THEY ASSOCIATED WITH COLD HARDINESS OR DORMANCY TRANSITIONS?

Authors: ARORA, RAJEEV - WEST VIRGINIA UNIVERSITY; Rowland, Lisa; PANTA, GANESH - UNIVERSITY OF GEORGIA

Submitted to: Physiologia Plantarum
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/2/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: To survive winters, woody perennials of the temperate zone become dormant and cold hardy. Resumption of growth in the spring requires sufficient exposure to low temperature (chilling requirement) in winter, which also plays a role in the development of cold hardiness. Physiological studies on chilling requirement or breaking dormancy have focused on identifying proteins whose levels change in response to varying hours of chilling accumulation. However, whether these changes are associated with dormancy status or with cold acclimation, is not clear. Three proteins have previously been identified in blueberry flower buds which increase with chilling accumulation. To determine if they are more closely associated with dormancy or with cold acclimation, plants were given various treatments to separate these two phenomenon (dormancy and cold acclimation) and examine changes in these proteins in response to each one separately. Basically, plants were given a cold treatment at 4C which results in cold acclimation and chilling accumulation. A fraction of the plants were then moved to 15C, a treatment which results in deacclimation (loss of cold hardiness) but does not negate chilling accumulation. Levels of the proteins were found to decrease with this treatment at 15C. These results suggest that the chilling-responsive proteins are more closely associated with cold hardiness than with dormancy status.

Technical Abstract: In an effort to establish whether dehydrin proteins of blueberry are more closely associated with dormancy status or with level of cold hardiness, we have carried out a series of physiological experiments to attempt to separate cold acclimation/deacclimation and dormancy transitions and evaluate changes in dehydrin levels in association with each phenomenon separately. Potted plants of three cultivars with different chilling requirements were held at 4C (a temperature which results in cold acclimation) until they had received 0, 50, 100 and >100% of the chill units necessary to satisfy their chilling requirements. A fraction of the plants for which 50% of their chilling requirements had been met were also shifted to 15/12C (light/dark) for two weeks, a treatment which resulted in significant deacclimation but not negation of chill units. Floral buds were examined after each treatment for level of cold hardiness, dormancy status, and levels of the three dehydrin proteins of 65, 60, and 14 kD. Results indicated that level of cold hardiness and levels of the dehydrins were closely associated and that both decreased during the two week 15/12C temperature treatment. Results also confirmed that the two week treatment had no negative effect on the accumulation of chill units. In addition, levels of the dehydrin proteins and cold hardiness remained about the same between 50% and >100% satisfaction of the chilling requirement. These results suggest that levels of the dehydrins are more closely associated with cold hardiness than with dormancy status.