Abstract
Improving soybean yield in Japan is one of the most important goals in soybean breeding. Although the Tohoku region in Japan is one of the largest soybean production areas, the average yield in the region is lower than the national average. The improvement of soybean productivity in the Tohoku region would therefore lead to an overall improvement of soybean productivity in Japan. A reduction in soybean yield has occurred recently in the Tohoku region partly due to pod shattering caused by late harvesting and the soybean cyst nematode (SCN) infecting SCN race 3 resistant varieties. Through marker-assisted selection and back-crossing, we developed two elite lines of soybean, ‘Tohoku 185’ and ‘Tohoku 189’, using the high-yielding variety ‘Fukuibuki’ as a recurrent parent. ‘Tohoku 185’ was developed using ‘Hayahikari’, a variety resistant to pod shattering, as a donor parent, and showed significantly lower pod shattering rates than ‘Fukuibuki’. ‘Tohoku 189’ was developed using ‘To-8E’, a variety resistant to SCN race 1, as a donor parent, and showed resistance to SCN race 1. The following traits were evaluated to confirm whether the agronomic traits of the two developed lines were equivalent to those of ‘Fukuibuki’: time to maturity, lodging, plant height, height of lowest pod-bearing node, yield, 100-seed weight, and seed protein content. Although the yield and 100-seed weight of ‘Tohoku189’ were lower than those of ‘Fukuibuki’ in all examined environments, there were no significant differences in any of these traits between ‘Fukuibuki’ and the two developed lines. The varieties resistant to both pod shattering and SCN race 1 have not yet been developed for the Tohoku region. Although we must consider the effects of the genes controlling SCN race 1 resistance on both the yield and 100-seed weight, it should be possible to develop high-yielding varieties with resistance to both pod shattering and the SCN race 1 by crossing ‘Tohoku 185’ and ‘Tohoku 189’.
