ESEARCH ARTICLE R ScienceAsia 46 (2020): 157–168 doi: 10.2306/scienceasia1513-1874.2020.029 Evaluation of japonica rice (Oryza sativa L.) varieties and their improvement in terms of stability, yield and cooking quality by pure-line selection in Thailand Pawat Nakwilaia, Sulaiman Cheabuc, Possawat Narumona, Chatree Saensukb, Siwaret Arikita,b, a,b, Chanate Malumpong ∗ a Department of Agronomy, Faculty of Agriculture at Kamphaeng Saen, Kasetsart University, Nakhon Pathom 73140 Thailand b Rice Science Center & Rice Gene Discovery Unit, Kasetsart University, Nakhon Pathom 73140 Thailand c Faculty of Agriculture, Princess of Naradhiwas University, Narathiwat 96000 Thailand ∗Corresponding author, e-mail:
[email protected] Received 3 Aug 2019 Accepted 3 Apr 2020 ABSTRACT: Many companies in Thailand have encouraged farmers, especially those in the northern regions, to cultivate DOA1 and DOA2 japonica rice varieties. Recently, the agronomic traits of DOA1 and DOA2 were altered, affecting yield and cooking quality. Thus, the objectives of this study were to evaluate the agronomic traits and cooking quality of DOA1 and DOA2 and those of exotic japonica varieties in different locations, including the Kamphaeng Saen and Phan districts (WS16). DOA2 was improved by pure-line selection. The results showed that the Phan district was better suited to grow japonica varieties than the Kamphaeng Saen district and that DOA2 produced high grain yields in both locations. Furthermore, DOA2 was selected by the pure-line method in four generations, after which five candidate lines, Tana1 to Tana5, were selected for yield trials. The results of yield trials in three seasons (WS17, DS17/18, WS18) confirmed that Tana1 showed high performance in terms of its agronomic traits and grain yield.