Abstract
The genetic background of the 229 ‘Kanto’ lines developed by National Institute of Crop Science was studied. Cluster analysis based on coefficients of parentage among the ‘Kanto’ lines revealed the presence of two groups. One consisted of the old breeding lines closely related with ‘Kotikaze’ and ‘Nipponbare’, and the other consisted of the new breeding lines highly related with ‘Koshihikari’, which has a superior eating quality and weak blast resistance, and has been used extensively as a cross parent. However, we found some lines that were not closely related with ‘Koshihikari’ in the new breeding lines. We examined how the coefficient of parentage with‘Koshihikari’ correlated with the eating quality and degree of the symptom of leaf blast in these 22 lines, and found that the coefficient was not closely correlated with the eating quality and resistance to leaf blast. It is possible to develop rice varieties that have a good eating quality, high resistance to diseases, and wide genetic background to avoid genetic vulnerability by breeding the lines not closely related with ‘Koshihikari’ but having a good eating quality and high resistance to leaf blast and introducing useful genes from foreign cultivars.
