Development of winter wheat with excellent resistance to pre-harvest sprouting and rain damage

Pre-harvest sprouting and high alpha-amylase activity are the most serious problems for the wheat production in Hokkaido, the northern most part of Japan. It has become more frequent for wheats to be exposed to continuous rain for several days in harvest time. In addition, low temperature below 15 degrees C, combined with rainfall, accelerates the damage of pre-harvest sprouting. Therefore, we started a breeding program in 1998 to develop wheat varieties with excellent resistant to sprouting damage in Hokkaido. Selection and evaluation of pre-harvest sprouting of resistant lines were conducted by two tests. One test was artificial rain treatment of intact spikes and the other was a germination test of hand-threshed grains at 10, 15 and 20 degrees C. The spikes of each line and variety were collected at physiological maturity and at one week after the first sampling date. Falling number was also measured. We have succeeded in breeding a deeply dormant breeding line, Kitakei 1802, from 1,923 doubled haploid lines raised by anther culture from the cross between Kitakei 1616 and Nishikazekomugi. Kitakei 1802 hardly sprouted through 10 days' continuous rainfall treatment at low temperature (15 degrees C) and maintained high falling number (> 300 s) in 2002 and 2003.