Submitted to: Journal of Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/22/2003
Publication Date: 3/1/2004
Citation: SUTTLE, J.C. INVOLVEMENT OF ENDOGENOUS GIBBERELLINS IN POTATO TUBER DORMANCY AND EARLY SPROUT GROWTH: A CRITICAL ASSESSMENT. JOURNAL OF PLANT PHYSIOLOGY. 2004. v. 161(2). P. 157-164. Interpretive Summary: For an indeterminate period of time following harvest, potatoes will not sprout and are physiologically dormant. Dormancy is gradually lost during postharvest storage and the resultant sprouting is detrimental to the nutritional and processing qualities of potatoes. Because of this, sprouting results in severe financial loss to producers. Currently sprouting is controlled through the use of synthetic sprout inhibitors. The research being conducted in this lab is directed towards 1) identifying key physiological processes that naturally regulate tuber dormancy and, ultimately 2) modifying these processes genetically or chemically with naturally occurring sprout inhibitors thereby eliminating the need for artificial sprout suppression. Much of our current research concerns the roles of plant hormones in tuber dormancy regulation. Based on limited experimental data, several classes of plant hormones have been implicated in tuber dormancy control. In this paper, the roles of gibberellins,a class of plant hormones implicated in dormancy control, has been re-evaluated. Injection of gibberellins native to potatoes into dormant tubers rapidly terminates dormancy. However, internal levels of these gibberellins do not change appreciably prior to the loss of tuber dormancy and treatment of tubers with specific inhibitors of gibberellin synthesis does not extend dormancy. These results do not support a role for gibberellins in dormancy termination. Identification of the actual hormones controlling tuber dormancy is essential in developing new methods to control this costly postharvest process in stored potatoes.
Technical Abstract: The effects of postharvest storage duration on the endogenous content and bioactivities of selected gibberellins (GAs) were determined in relation to potato (Solanum tuberosum L. cv. Russet Burbank) tuber dormancy status. The tubers used in these studies were completely dormant after 98 days of storage. Between 98 and 134 days of storage, dormancy began to end. Tuber dormancy weakened with further storage and tubers stored for 212 days or longer were completely non-dormant and exhibited vigorous sprout growth. Immediately after harvest, the endogenous contents of GA19, GA20, and GA1 were relatively high (0.48-0.62 ng g fresh weight-1). The content of these GAs declined between 33 and 93 days of storage. Internal levels of GA19, GA20, and GA1 rose slightly between 93 and 135 days of storage reaching levels comparable to those found in highly dormant tubers immediately after harvest. Levels of GA19, GA20, and GA1 continued to increase as sprout growth became more vigorous. Dormant tubers exhibited a time-dependent increase in apparent GA sensitivity. Freshly harvested tubers were completely insensitive to exogenous Gas. As postharvest storage continued, exogenous GAs promoted premature dormancy release with GA1 and GA20 eliciting the greatest response. Sprout growth from non-dormant tubers was also promoted by exogenous GA in the following sequence of activity: GA1 = GA20 > GA19. Continuous exposure of developing tubers to inhibitors of GA biosynthesis did not extend tuber dormancy but rather hastened dormancy release. These results do not support a role for endogenous GA in potato tuber dormancy release but are consistent with a role for GAs in the regulation of subsequent sprout growth.