Manipulating apical dominance, tuber set, size, and shape to optimize yield and quality of potato (Solanum tuberosum L.)

Cody James Dean

Controlling tuber set, size distribution, and shape (length-to-width ratio, L/W) in relation to market requirements (seed, fresh, processing) is key to maximizing profits in potato production. While both gibberellin (GA) and naphthaleneacetic acid (NAA) are registered individually for managing tuber size, the efficacy of combination treatments has never been explored. In chapter 1, we demonstrate the utility of GA/NAA combination dip and spray seed treatments for modifying tuber set, size, and shape phenotype to increase raw product recovery (≥7.6-cm-long French fries) from Payette Russet and Alturas; two late-season frozen-processing cultivars that often produce tubers with undesirably low tuber L/W ratios. When combined with GA as a seed treatment, NAA maintained apical dominance and attenuated the shift in tuber size distribution caused by GA, but had no effect on the GA-induced increase in tuber L/W ratio, and only partly moderated the GA-induced stimulation of plant emergence. Raw product yield increased from 12-39% in seed spray application trials by using NAA to confine the effects of GA to tuber shape and limit the loss of U.S. No. 1 tubers to undersize. GA/NAA combination treatments offer a novel management solution to hasten plant emergence and modulate reduction in tuber size, with minimal to no effect on U.S. No. 1 yield, and in the case of frozen processing cultivars with round tuber phenotype, GA increased raw product recovery. The cultivar Shepody is the early-season standard for direct-from-field frozen processing in the Pacific Northwest. ‘Shepody’ produces high yields of tubers with excellent processing qualities but sets relatively few tubers that often become excessively large, which is undesirable for processing and especially for seed production. In chapter 2, we evaluated the efficacy of seed aging and GA seed treatments for modifying tuber set and size of ‘Shepody’. Relative to cultivars studied previously, ‘Shepody’ proved to be resistant to seed aging treatments. However, GA applied as a seed dip (1-2 mg L-1) or spray (2 mg L-1) effectively altered tuber set and size to increase returns on a seed contract by 25 to 38%, and to better satisfy the needs of processors for more moderate size tubers.

Manipulating apical dominance, tuber set, size, and shape to optimize yield and quality of potato (Solanum tuberosum L.)

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