Submitted to: American Society of Plant Physiologists Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 4/1/2001
Publication Date: N/A
Technical Abstract: At harvest and for an indeterminate period thereafter, potato tubers will not sprout and are in a state of dormancy. Although the internal processes regulating tuber dormancy are largely unknown, it is becoming evident that endogenous hormones are involved in tuber dormancy control. Early studies demonstrated that exogenous GA-3 could prematurely terminate tuber dormancy and these observations led to the hypothesis that endogenous GAs were involved in dormancy regulation. To date, this hypothesis has not been rigorously tested. In the studies to be reported, the endogenous levels of GAs 19, 20, 1, 3, 4, and 8 were determined during dormancy progression by GC-MS using deutero-GAs as internal stds. Immediately after harvest when the tubers were most dormant, internal levels of GA 19, 20, 1 and 3 ranged from 0.37-0.95 ng/g FW. The content of all GAs declined during the first 90 days of storage and, with the exception of GA-3, began to rise as dormancy ended and sprout growth commenced. Neither GA-4 or GA-8 were detected in tuber extracts at any time point. Immediately after harvest, injection of up to 5 ug of any of these GAs was without effect. Thereafter, tubers exhibited a time- dependent increase in apparent sensitivity to GAs with the order of biological activity being: 1>20>19. Exogenous kaurene, GA-12, or GA-8 had no effect on dormancy status or subsequent sprout growth. The role of GAs in tuber dormancy was assessed through the use of GA biosynthesis inhibitors. Continuous exposure of developing tubers to CCC, AMO-1618, ancymidol, or tetcyclasis did not extend the length of tuber dormancy but rather accelerated the onset of sprouting. The significance of these results with respect to dormancy control in potatoes will be discussed.