Abstract
We examined how lodging resistance and physical characteristics of the basal culm change after heading in rice direct-seeded in a flooded paddy field using 14 rice varieties. At 5 weeks after heading, the pushing resistance was lower, and lodging index was larger than at 2 weeks after heading in the majority of varieties, and lodging was observed in some varieties. This is probably because panicle weight/top weight ratio was increased, and the section modules and breaking strength of the culm with leaf sheaths were decreased with decreasing number of living leaf sheaths at the basal culm. In Saikai 203 that had high yielding ability, the senescence of leaf sheaths was late, and the section modules and breaking strength of the culm with leaf sheaths were maintained high even at 5 weeks after heading. As a result, pushing resistance was high, and lodging index was small even at 5 weeks after heading, showing excellent lodging resistance.
