Abstract
Hikari-Shinseiki, a variety registered in 2004, is an isogenic variety of Koshihikari which has the semidwarfing gene sd1 derived from variety Jikkoku. In this study, we examined lodging-related characteristics of Hikari-Shinseiki, which is presumed to be hard to lodge because of its short culm, under conditions of compost application. Hikari-Shinseiki is a short-culm variety with longest culm length 19 cm shorter, and average culm length 14 cm shorter than Koshihikari. The breaking load of the fourth internode of Hikari-Shinseiki at 26-30 days after heading was comparable to that of Koshihikari. At the same time, the bending moment (length·weight above the internode where the breaking load is measured) of Hikari-Shinseiki was smaller than that of Koshihikari, showing the impact of the reduction in the top length attributable to the shorter culm. Consequently, the lodging index(bending moment·breaking load-1·100) of Hikari-Shinseiki was 127-100, which was smaller than that of Koshihikari 173-148. The degree of lodging on a scale of 0 (none) to 4 (severe) of Hikari-Shinseiki in the field at the time of harvest was 1.1, which was smaller than that of Koshihikari 2.6 and well consistent with the breaking load values. These results revealed that the lodging resistance of Hikari-Shinseiki is primarily attributable to the reduced bending moment, and to the strength of the fourth internode counted from the first panicle neck internode.
