LAUSR

The vigorous growth phenotype of ‘Bondi’ is characteristic of high endogenous gibberellins, making it ideal for evaluating the efficacy of gibberellin biosynthesis inhibitors to improve allometric partitioning and production efficiency in potato. Foliar applications of prohexadione-calcium decreased foliar growth with no effects on tuber number, size, or yield. In contrast, when applied pre-tuberization, paclobutrazol decreased maximum foliar growth from 91 to 63 MT ha−1, increased tubers plant−1 from 6.4 to 8.9, and decreased average tuber fresh weight from 296 to 188 g tuber−1 with no reduction in tuber yield, which effectively increased the harvest index. However, when applied post-tuberization, PBZ reduced maximum foliar growth from 91 to 72 MT ha−1 with no effects on tuber number, size, or yield. Paclobutrazol can alter source/sink relationships in potato to increase production efficiency and this may translate to reduced agronomic inputs. Application timing and concentration are important for modulating tuber set and size.