Weedy rice (Oryza sativa L.) seed dormancy features and potential usage for management

Weedy rice infestation has been expanding with the increasing proportion of direct-seeded rice (DSR) systems in China. Limited herbicides are effective against weedy rice due to its high similarity with cultivated rice. Hence, it is important to figure out some non-chemical management strategies for weedy rice. One of the methods is to reduce the size of seed bank by inducing weedy rice germination. Petri dish germination experiment found that weedy rice with different seed morphologies showed an absence of primary dormancy. The field phenology study showed that weedy rice differed from cultivated rice in many features including plant height, number of tillers, fresh weight, and days required for earing when sown from 1 June to 1 October, and in the case of late sowings (between 1 August and 1 October), the plants produced no heads despite a high germination rate. Simulated field experiment to induce germination found that when soil moisture content was 22.2% and day/night temperatures were 20/15 degrees C, respectively, germination was more than 60% up to 10 days after sowing; at higher levels of soil moisture and temperature, germination was faster and germination percentage was higher. These results indi-cated that weedy rice seed bank size could be reduced by inducing the seed germination with post harvest irrigation as the seedlings would be killed overwinter in lower-middle reaches of the Yangtze River in China.