Abstract
Tuber size is an important trait in determining the market value of red potatoes. From 2019 to 2022, the average price for C Size (<74g) was twice that of the larger A Size (>114g ) red potatoes. Several methods are commonly used to manipulate tuber size profile, including adjusting in-row spacing, vine kill dates, and managing apical dominance through seed aging heat treatments or the use of growth regulators such as gibberellic acid (GA). Previous research has shown these treatments to be effective in managing size profile, but the responses to treatment are often cultivar specific. The timing and rate of plant and tuber growth are also unique features of each cultivar. In Chapter 2, the timing and rate of vine growth, tuber set, and tuber bulking for the red potato cultivar ‘Chieftain’ are established and find GA treatment resulted in moderate effects, including accelerated emergence, increased stem number, and tuber number, while having no significant effect on vine weight and tuber yield. Chapter 3 demonstrates the cultivar’s response to two GA treatments applied to seed pieces after cutting (0, 0.009g a.i. MT-1) and four vine kill date treatments (85, 90, 95, 100 days after planting). Delayed vine kill was found to increase yields while shifting tuber size profile towards the largest size class. Conversely, GA seed treatment resulted in a shift in size profile towards smaller size classes and a trend towards an increase in tuber number plant-1. Further, results showed GA treatment combined with delayed vine kill, can be used to increase yield while maintaining a small size profile, significantly increasing market value. Chapter 4 demonstrates the cultivar’s response to two GA treatments (0, 0.009g a.i. MT-1) and four in-row spacing treatments (15, 20, 25, 30cm). Both GA treatment and closer in-row spacing were found to shift tuber size profile towards smaller size classes. Changes in tuber size distribution resulting from GA treatment and closer in-row spacing were also found to increase net market value.