EFFECTS OF SUBSTITUTED NITROGUANIDINE SEED TREATMENTS ON THE POTATO VARIETY SUPERIOR

In earlier reports, foliar applications of AC 243,654, a substituted benzyl nitroguanidine with cytokinin-like activity, increased yields of larger tubers and altered plant morphology of potatoes (Solanum tuberosum L.) in greenhouse tests. AC 243,654 was applied as seed tuber treatments to the potato variety Superior. Applications were 0.2 to 10% active ingredient (ail dusts and 0.04 to 5% al dips. All seed treatments increased the number of sprouts per tuber. The higher concentrations of seed treatments decreased stem height, and increased stem/branch number, plant dry weight and the number of tubers. Dust and dip treatments of 0.2 and 1% increased the yield (11 to 33%) of tubers > 38 mm in greenhouse tests. Higher rates decreased yields. In field trials, dust applications of AC 243,654 and its analog AC 89,470, the unsubstituted benzyl nitroguanidine, at 0.1 and 0.4% ai increased total and US #1 (> 47 mm diameter) yields between 10 and 18%; and 8 to 18%, respectively. The high rate of 10% ai of either compound decreased yield. AC 239,604, a substituted phenyl nitroguanidine, as a 0.1% ai dust increased yields 21% while higher rates decreased them. Based on combined greenhouse and field data, AC 243,654 dust applications < 2% ai increased yields while greater application rates decreased yields.