Abstract
A weedy rice with a red pericarp, called Toukon in Japanese, has recently become a problem in parts of Nagano Prefecture, Japan. To determine the survivability of shattered seeds of weedy rice, we collected typical weedy rice accessions in Nagano and studied the overwintering ability of seeds placed on the soil surface (surface-seeds) and the longevity of seeds buried at 10 to 15 cm in the soil (buried-seeds). All the surface-seeds had died by the second winter season. On the other hand, all the buried-seeds had died by the third winter season. The overwintering ability and longevity of weedy rice seeds varied greatly with the accession. In the first winter, seeds with deeper dormancy had a higher overwintering ability and tended to have longer longevity than those with shallow dormancy. These results suggest that death of shattered seeds of weedy rice could be accelerated by exposure to the cold of winter on the soil surface and that their seed banks could be eradicated by implementing thorough weed control for two years while preventing the transfer of seeds by farm machinery from other fields.
