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

Abstract

AbstractThe present study was conducted to clarify the effect of temperature and daylength on heading in tetraploid cultivars of rhodesgrass (Chloris gayana Kunth). Five cultivars, Tochiraku‐kei (2χ), Fords Katambora (2χ), Callide (4χ), Masaba (4χ) and Pokot (4χ), were planted on three dates at 1‐month intervals (4 May, 4 June and 4 July) in three of the Ministry of Agriculture, Forestry and Fisheries research institutions in Ishigaki (Tropical Agriculture Research Center), Nishigoshi (Kyushu National Agricultural Experiment Station) and Nishinasuno (National Grassland Research Institute) in 1978. Three tetraploid cultivars were planted on three dates at 1‐month intervals (4 May, 4 June and 4 July) under four daylength‐treatments of natural daylength (ND), 12 h daylength [12 h], ND/12 h and 12 h/ND, and changed daylength at the eighth leaf stage, in Nishinasuno in 1978. Under natural daylength, although heading was not observed for Masaba and Pokot, heading was observed in all plots for Tochiraku‐kei, Fords Katambora and Callide, and their days to heading (DH) linearly decreased with increases in daily mean temperature (DMT). The result indicated that, under natural daylength in summer, temperature was a major factor in determining DH in tetraploid Callide, which was the same as in diploid rhodesgrass cultivars. Callide reached heading under all four daylength treatments. However, Masaba and Pokot reached heading only under 12 h and ND/12 h treatments, suggesting that Masaba and Pokot have qualitative sensitivity to photoperiods that operate after the ninth leaf stage. These findings would be useful in tetraploid rhodesgrass for estimating foliage harvesting time in the field and for conducting cross‐pollination in a greenhouse during winter.