Abstract: A field trial was conducted to investigate the changes of endogenous hormone concentration during formation and thickening of tuberous roots in sweetpotato (Ipomoea batatas L.) of different genotypes (Xushu 18, Minamiyutaka and I .trifida-K123). The present results suggested that the concentrations of zeatin riboside (ZR), dihydro-zeatin riboside (DHZR), abscisic acid (ABA), indole-3-acetic acid (IAA) and isopentenyl-adenine (IPA) of Xushu 18 and Minamiyutaka were significantly higher than those of I.trifida-K123. Dry tuberous root yields were positively correlated with the concentrations of ABA, ZR and DHZR at 1% or 5% significant level, but not correlated with the concentrations of IAA, IPA and GA4. The concentrations of ABA, ZR and DHZR played very important roles for the tuberous roots formation and thickening in sweetpotato. The concentrations of ZR, DHZR, ABA and IAA in the top or inner parts of tuberous roots were significantly higher than those of in the end or outer parts. Meanwhile, endogenous hormone concentrations of big tuberous roots were significantly higher than that of middle or small ones at early thickening period. In fast thickening period of tuberous roots, endogenous hormone concentrations of middle tubers were the highest. However, at late thickening period, endogenous hormone concentrations of small tubers ranked the highest.

Key words: Sweet potato, Tuber, Endogenous Hormone concentration, Formation, Thickening