水稲コシヒカリ同質遺伝子品種ヒカリ新世紀の耐倒伏性  [in Japanese] Lodging-related Characteristics of Hikari-Shinseiki, an Isogenic Variety of Koshihikari  [in Japanese]

十石に由来する半矮性遺伝子sd1を持つコシヒカリ同質遺伝子品種であるヒカリ新世紀の倒伏関連形質について,堆肥施用条件下において検討した.ヒカリ新世紀の最長稈長や平均稈長はコシヒカリに比べていずれも短く,短稈品種であった.出穂期後26〜30日に測定したヒカリ新世紀の第4節間(穂首節間を第1節間とする)の挫折荷重はコシヒカリと同等の強度を示した.このときのヒカリ新世紀の曲げモーメント(挫折荷重を測定した節間以上の長さと重さの積)はコシヒカリに比べて小さく,これは短稈化による地上部長の短縮による影響が大きかった.このため,ヒカリ新世紀の倒伏指数(曲げモーメント・挫折荷重^<-1>・100)は127〜100で,コシヒカリの173〜148に比べて小さかった.倒伏のみられた年次の収穫期におけるヒカリ新世紀の倒伏程度(0:倒伏無〜4:倒伏程度甚の5段階表示)は1.1で,コシヒカリの2.6に比べて小さく,倒伏指数の小さいことと対応した関係がみられた.以上のことから,ヒカリ新世紀の耐倒伏性が優れた要因は,倒伏関連形質からみると,曲げモーメントの低下による影響が大きく,第4節間の強度には影響されないと判断された.

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 19cm shorter, and average culm length 14cm 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.