Abstract
Lodging is a serious problem, because it causes yield loss and deterioration in quality. Until now, lodging resistance has been improved mainly by shortening the plant height. However, even such rice varieties have been lodging due to super strong typhoons in recent years. In this study, we compared strong culm traits related to the lodging resistance of recently bred varieties and examined the superior haplotypes for a thick culm. Furthermore, we focused on the morphology of cortical fiber tissue and cell wall components to clarify the factors that cause varietal differences in culm stiffness. There was a large varietal difference in the bending moment at breaking (M). We examined the factors separately in terms of section modulus (SM) and bending stress (BS), and found that a large SM for rice cultivars for forage use and high BS for ‘Hinohikari’, a rice variety with high eating quality, were responsible for the high lodging resistance. The relationship between haplotypes of genes related to culm thickness and SM revealed that the varieties with the largest SM had several superior haplotypes derived from indica and tropical japonica rice varieties. In addition, the comparison of ‘Hinohikari’, ‘Koshihikari’, and ‘Akidawara’ to clarify factors related to culm stiffness of ‘Hinohikari’ suggested that hemicellulose and starch density, rather than the thickness of cortical fiber tissue, contributed to the differences in BS among three varieties.
