Bulbil formation and yield responses of Chinese yam to application of gibberellic acid, mepiquat chloride and trinexapac-ethyl

A field experiment was conducted in three successive years at the Institute of Bioresources, Kyongbuk Provincial Agricultural Technology Administration, Andong, South Korea, to determine the effects of gibberellic acid (GA₃) and the two plant growth retardants mepiquat chloride (MC) and trinexapac-ethyl (TNE) on bulbil formation and yield, including tuber yield responses, in the Chinese yam. The most effective plant growth retardant in inducing early bulbil formation was MC in the three successive seasons. MC treatment greatly increased bulbil yield compared with the control in the three successive years. It also markedly increased the ratio of bulbil size (> 4 mm) compared with the control. Furthermore, the ratio of bulbil size (> 4 mm) was greatly increased at highest MC concentration (600 p.p.m.) to 65.4%. Tuber yield per hectare was significantly increased by GA application compared with the control. GA application at the highest concentration (600 p.p.m.) was most effective in increasing tuber size in Chinese yam.