Relationship between Dry Matter Production and Canopy Structure in Wheat Cultivar "Haruyutaka" Bred in Hokkaido when Grown in Warm Area of Western Japan

A wheat cultivar Haruyutaka bred in Hokkaido showed a very low crop growth rate (CGR) after anthesis when it grew in Yamaguchi. The plant figures, leaf area index, the surface area of ear and the penetration rate of photosynthetically active radiation (PAR) into the canopy of this cultivar were compared with those of Daichinominori, a wheat cultivar bred in Kyushu, in 1991-2001. The photosynthetic rate in the leaf blade at each nodal position of the two cultivars was also compared. Haruyutaka showed a low CGR and low net assimilation rate during the grain filling period (from anthesis until maturity). One of the reasons was thought to be the larger surface areas of the organs in the upper layer of canopy, such as ear, flag and second leaves, than those in Daichinominori reducing the penetration rate of PAR into the canopy. Moreover, Haruyutaka had a larger total surface area index than Daichinominori and showed over-luxuriant growth. Thus, the photosynthetic rate of the leaf blade, especially that during the later grain filling period, was very low in Haruyutaka.