The effect of temperature and daylength on heading in diploid rhodesgrass cultivars (Chloris gayana Kunth)

The present study was conducted to clarify the effect of temperature and daylength on heading in diploid rhodesgrass cultivars. Three diploid cultivars, Tochiraku-kei, Fords-Katambora and Pioneer, were planted 9 times at 10-day intervals between April 24 (1) and July 14 (IX) in 1975. In 1976 the 3 cultivars were planted 3 times at 1-month intervals on May 4 (II), June 4 (V) and July 4 (VIII) under 5 day-length treatments of natural daylength (ND), 12 h daylength (12 h), 24 h daylength (24 h), 24 h/ND, and 24 h/12 h. DH (days to heading) decreased linearly with the increase in DMT (daily mean temperature) commonly in the 3 cultivars in 1975, suggesting that temperature is a major factor determining DH in diploid rhodesgrass. This relationship is described by a linear regression equation between DH and DMT in the period from sowing to heading date. From the results in 1976, a short daylength is considered to have an effect for accelerating flower initiation of diploid rhodesgrass under temperatures more than 22 deg C. These research findings would be useful in diploid rhodesgrass for estimating the first cutting time and/or seed harvesting time, and for conducting effective reproduction in green-houses during winter.