Improvement of seedling growth and forage yield of rhodesgrass (Chloris gayana Kunth) under low temperature conditions

Five rhodesgrass (Chloris gayana Kunth) cultivars (Asatsuyu, Hatsunatsu, Katambora, Osumi-5, and Osumi-7) were evaluated for forage yield in a 3-year field experiment in the main island of Okinawa located in the subtropical region of Japan. The new cultivar Asatsuyu was significantly higher than the widely used commercial cultivar Katambora in dry matter yields at spring, fall and winter harvests during the second and third harvest years. Asatsuyu had significantly higher annual dry matter yields than Katambora and Hatsunatsu in the second and third harvest years. It was also significantly higher than Katambora and Hatsunatsu in total dry matter yield for 3 years. Annual dry matter yield showed significant positive correlation coefficients with dry matter yields harvested from winter to spring and from fall to early winter, suggesting that improvement of plant growth under low temperature conditions increases annual dry matter yield in rhodesgrass. In a growth room experiment at the National Institute of Livestock and Grassland Science in Tochigi, Asatsuyu was significantly higher in plant heights at 2, 3 and 4 weeks after seedling emergence and in dry matter weight at 4 weeks after seedling emergence than Katambora and Hatsunatsu at a low temperature (21/16 degrees C, day/night temperature). These results indicate that Asatsuya has better performance than the other 2 cultivars at low temperatures. The results obtained in the field and growth room experiments show that the new cultivar Asatsuyu is superior to the other 2 commonly used cultivars Katambora and Hatsunatsu in seedling growth and forage production under low temperature conditions. The cultivar Asatsuyu can increase forage productivity and would extend periods of grazing and hay production in subtropical regions.