Influence of Foliar-Applied Growth Retardants on Russet Burbank Potato Tuber Production

The potato cv Russet Burbank grows poorly in the semi-arid climate of the High Plains, primarily due to its tendency to produce misshaped tubers. Since gibberellic acid (GA3) is associated with stem elongation and may be involved in tuber shape, the objective of this study was to determine whether GA3 biosynthesis inhibitors could improve tuber shape. Prohexadione-Ca and chlormequat-Cl are two well-known such inhibitors. They were applied to ‘Russet Burbank’ at 0, 70, 280, 1,120, 4,480 g/ha when the largest tubers were 20, 60 and 100 g/tuber from 2001 to 2003. Neither compound affected tuber shape. Yields increased 17–20 % by prohexadione-Ca at 280 g/ha and 9–33 % by chlormequat-Cl at 4,480 g/ha. In 2004, prohexadione-Ca at 280 g/ha was applied when the largest tubers were 3, 25, 100, 180, and 370 g to determine a tuber stage response. Yield increased 14 % when applied at 25 and 100 g/tuber growth stages, but the number of misshaped tubers increased from 48 % to 75 %. These two inhibitors did not overcome tuber misshaping and should not be used for that purpose.