Breeding for High Quality Glutinous Rice in Hokkaido in Northern Japan

Glutinous rice produced in the coldest rice cultivation region of Hokkaido Japan has low hardening speed and is suitable for Japanese sweet and steamed glutinous rice called okowa. However, compared to the main branded glutinous varieties in the area south of Tohoku district, rice produced in Hokkaido has a high protein content, low whiteness of milled rice, and low eating quality of pounded rice cake. Moreover, recently in order to expand demands for Hokkaido rice, it’s required to develop a new variety suitable for sliced rice-cake, molded rice-cake and rice cracker while haｓ high hardening speed of pounded rice-cake. In order to develop a new variety quickly, we used accelerated generation advancement and drug cultivation techniques. In addition, for efficient selection, we analyzed the whiteness of brown and milled rice, the protein content and gelatinization property which is related to hardening speed from early generations of breeding materials mechanically. We also measured hardening speed using a small amount of rice sample. We tested the eating quality of steamed glutinous rice and of pounded rice-cake from the intermediate generations. In this way, agronomic characters and quality were improved at the same time. We obtained newly bred varieties with larger grain size and higher cold tolerance at both the flowering and the booting stages, leading to higher stability for production. Compared to earlier generation, later generation varieties had a lower protein content, higher whiteness of milled rice, and higher eating qualities of steamed glutinous rice and pounded rice-cake. Moreover, a negative correlation was found between the protein content and the whiteness of milled rice. On the other hand, in addition to new rice varieties with low hardening speed, two new varieties with high hardening speed were developed. However, concerning eating quality and hardening speed of pounded rice cake, these new varieties were inferior to the top branded glutinous varieties in the area of south of Tohoku district, and need to be improved further.