Effect of Day Length on the Development of Bulbils in Water Yam (Dioscorea alata L.) and Chinese Yam (D. opposite T_HUNB.)

Abstract

The effect of the day length on the development of bulbils in Chinese yam (D. opposita) and Water yam (D. alata) was investigated from March 2007 to January 2009. The initiation of bulbils in either species was not affected by the day length. However the time of bulbil initiation was different in Chinese yam and Water yam. Bulbil initiation in Chinese yam occurred earlier than in Water yam. Comparison of the time of tuber and bulbil development, showed that bulbil development occurred later than tuber enlargement in both species. When Long-day treatment (24 hrs) was applied after the solstice, the enlargement of the bulbils was inhibited in Water yam, but not effected in Chinese yam. The photoperiodic sensitivity of bulbil development in Chinese yam was lower than that in Water yam. Tuber development in both species was related to the photoperiodic sensitivity. The bigger bulbils as yam seed tubers developed in Water yam on Miyako island in Okinawa prefecture. Early planting (longer cultivation period) without stake cultivation may result in larger bulbils for seed tubers in Water yam on Miyako island in Okinawa prefecture.