|Budget Amount *help
¥13,300,000 (Direct Cost: ¥13,300,000)
Fiscal Year 2003: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 2002: ¥4,100,000 (Direct Cost: ¥4,100,000)
Fiscal Year 2001: ¥7,900,000 (Direct Cost: ¥7,900,000)
Field experiments were carried out in 2001〜2003 to compare the yield and yield components of 12 new cultivars or lines with those of Akitakomachi and Hitomebore, the two widely-cultivated cultivars in the Tohoku region of Japan. Dry matter production and partitioning related to yield, and factors causing the yearly variation in yield among cultivars were also elucidated. The obtained results are shown as follows
1)The grain yield ranged from 765 to 908 g m^<-2> in 2001, from 700 to 770 g m^<-2> in 2002 and from 230 to 660 g m^<-2> us 2003. Low temperature and solar radiation during the end of Jane to the end of July in 2003 caused spikelet sterilization, resulting in the low percentage of ripened grains(PRG), and subsequently reduced grain yield in all cultivars. Yearly variation in grain yield was often smaller in the high cool resistant cultivars(Hananomai, Hatajirushi and Hitomebore) than in the low cool resistant ones because of a lower percentage of sterilized spikelets and the higher yield in the former cultivars in 2003.
2)The average yield in 5 years, except in 2003, ranged from 735 g m^<-2> in Akitakomachi to 817 g m^<-2> in Okiniiri, and the yield difference was about 80 g m^<-2>(11%). The low yield in Akitakomachi and Hananomai was because of a small sink size despite a high PRG. On the other hand, the high yield in Fukuhibiki, Okiniiri, Menkoina and Iwanan 7 was mainly caused by a large sink size and a high PRG.
3)In the early ripening stage, the increase of panicle weight was much greater than that of total dry weight in all cultivars. Cultivars with a larger decrease in stem and leaf sheath weight often had a higher PRG than those with a smaller decrease in stem and leaf sheath weight.
4)Lodging index was larger in the long-culm cultivars than in the short-culm ones. The breaking moment of a culm was larger in some new cultivars than in the widely cultivated ones because of a larger cross section index and bending stress in the former.