Cultivar Differences in the Grain Cracking of Rice under the High Air Temperature Conditions during Grain Filling

Twenty cultivars were grown in paddy fields seven times from 2008 to 2010. The percentage of cracked grains was positively correlated with the temperature during the early stage of grain filling. Among the cultivars used, Futaba, Yamahikari and Fujisaka 5 showed high percentages of cracked grains. Cultivars Hananomai, Hanaechizen, Nikomaru and Himenomai showed high percentages of grain cracking when the temperature during grain filling was high although cracks were scarcely formed when it was low. On the other hand, Chinese cultivar Yan Xuang 203 showed stably lower percentages of cracked grains under higher temperature conditions. In the pot experiments conducted in 2009, the temperature conditions after the heading stage were identical for all cultivars and high temperature treatment was given during the early stage of grain filling. In this experiment, the percentage of cracked grains was significantly lower in Yan Xuang 203 than in the other cultivars. We concluded that Yan Xuang 203 is highly resistant to grain crack formation even when the air temperature during the grain filling stage is high.