Seed dormancy in rice seed is a natural mechanism for survival. Pathum Thani 1 rice has a natural dormancy period of 3-4 weeks. This affect post-harvest processes during seed production, such as seed conditioning and storage because the germination test is needed to be used in the decision-making before doing the right process. The objective of this experiment was to study the after-ripening period of Pathum Thani 1 rice seed after storage in the particular temperatures and relative humidity. Seed breaking-dormancy methods were also tested. Paddy rice and brown rice were stored in a cool-moist condition (100%RH and 15ºC) and cool-dry condition (20%RH and 15ºC). Another part was incubated at 50ºC for 5 days. After treating, all sample of rice seeds was tested for germination and seed vigour, using a radicle emergence (RE) test, according to ISTA rules at 0, 1 and 3 months. The results showed that breaking dormancy of rice seeds Pathum Thani 1 at 50ºC for 5 days was the best method when compared with other methods. Germination after treating, at 1 month and 3 months after storage were 91.75%, 98 %, 97.75%, respectively. After incubating at 50ºC for 5 days, seed vigour was 91.75%. However, seed vigour reached 99% when was stored till 1 month.
