Abstract
Factors contributing to lodging resistance i.e. culm stiffness and the related characters were examined by field experiments of 26 rice cultivars. Cultivars Koshihikari and Sasanishiki, which are known to have a taste quality, showed early start of and heavy degree of lodging at low as well as heavy fertilizer levels (Table 1, Fig.1). Semi-dwarf rice cultivars IR 8, IR 127 and IR 269 showed no sign of loding even at the high fertilizer livels. Fujiminori and Inabawase were found to have an intermediate lodging resistance, but the response to fertilizer levels and the time of start of loging differed with each other (Tables 2 and 3). Fujiminori lodged even at the low fertilizer levels, but showed no conspicuous increase in the degree of lodging at the high levels. Inabawase, on the contrary, lodged heavily at the high levels inspite of no lodging at the low levels. Start of lodging was earlier in Fujiminori than in Inabawase. The degree of lodging did not increase until maturity in the former, while abrupt lodging just before maturity was recognized for the latter. Culm type index and culm moment was defined by d/l and (d2/l)2, respectively, where d is external diameter of basal culm and l culm length. Culm length, culm moment and, particularly, culm type index showed a high correlation with degree of lodging at both and high fertilizer levels (Tables 4 and 5).
