Abstract
Amylograph viscosity, an important index of wheat quality, is sometimes lowered by high α-amylase activity in grain caused by pre-harvest sprouting. In a new winter wheat variety, Kitanokaori, the percentage of pre-harvest sprouting, α-amylase activity and falling-number were investigated in the grains sampled at the maturing stage at 52 sites in Hokkaido from 2001 to 2005. Seven samples of wheat in the 2003 samples showed high α-amylase activity and low falling-number without pre-harvest sprouting. These phenomena were not observed in the major winter wheat variety, Hokusin. In Kitanokaori, falling-number at the maturing stage was not significantly correlated with precipitation and sunshine hours before the maturing stage, but significantly correlated with the mean temperature before the maturing stage, r=0.635 (p<0.01, n=52). Some of the Kitanokaori exposed to 17°C four weeks before the maturing stage ripened, and exhibited low falling-number. In the experiment under artificial temperature treatment, Kitanokaori grains ripened under a mean temperature of 15°C before the maturing stage showed relatively high α-amylase activity compared with the grains exposed to a mean temperature of 20°C. In artificial rainfall treatment after the maturing stage, percentage of germination and α-amylase activity were higher in Kitanokaori than in Hokusin. In conclusion, Kitanokaori grains were prone to activate α-amylase under a low temperature in the ripening period and to exhibit pre-harvest sprouting more frequently than the Hokusin variety.
