Effect of plant growth regulators on seed tuber yield in potatoes
Seed potato growers seek to maximize the number of desirable sized tubers. This study examined how foliar application of plant growth regulators (PGRs) influence total tuber number (TTN) and drop (25 -50 mm) seed tuber number (STN) in Norland (NOR), Russet Burbank (RB) and Shepody (SH) potatoes under field conditions in 1993 and 1994. In 1993, PGRs, paclobutrazol (PTZ; 300, 450, 600 mg/L), kinetin (KIN; 10 and 20 mg/L), all possible combinations of the above rates of PTZ and KIN and Methyl jasmonate (MJ; 10-7, 10-6, 10-5 and 10-4 M) were applied to NOR and RB potatoes. In 1994, PTZ (300 mg/L), both KIN rates, and the two lowest rates of MJ were eliminated and KIN 20 mg/L or GA3 250 mg/L were applied to some of the PTZ treatments. The potato cultivar, SH was also included. Plants were treated with the PGRs at two growth stages; NOR (1993), RB (1993 and 1994) SH (1994) were treated when tubers were <10 mm or <20 mm in diameter). NOR potatoes (1994) were treated at stolon initiation (no tubers) or early tuber initiation (<8 mm in diameter). PTZ increased STN in RB by 29 to 40% and in SH by 57 to 70 % over the controls. However, PTZ had no effect on TTN and STN in NOR in either year. MJ had no effect on STN in NOR (1993), in RB in either year or in SH in 1994. In 1994, the highest rate of MJ increased STN in NOR by 40% over the control. Application of KIN alone, in combination with PTZ or following PTZ treatment and GA3 to PTZ treated plants had no beneficial effect on either TTN or STN of all three cultivars, compare to the PTZ treatments applied alone. This study suggests that under field conditions PTZ can be used to increase seed tuber production in RB and SH while MJ appears to be effective in NOR potatoes.
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