Varietal variations of heading time among rice [Oryza sativa] landraces in Myanmar
2003
Irie, K. (Tokyo Univ. of Agriculture (Japan)) | Aye, K. | Nagamine, T. | Fujimaki, H. | Kikuchi, F.
Abstract The Union of Myanmar is located in the westernmost part of Southeast Asia between latitudes 9 deg 32' N and 28 deg 31' N, and longitudes 92 deg 10' E and 101 deg 10' E. Due to diversity, various ecotypes of rice landraces have evolved, such as floating rice, deep water rice, irrigated rice, rainfed lowland rice, and upland rice which are cultivated in various regions of Myanmar. A total of 1,240 rice landraces collected throughout Myanmar were grown to examine the genetic diversity in heading time in 2000 at the Central Agriculture Research Institute (19 deg 16' N) in Yezin, Myanmar. In the following year, 1,391 rice landraces were sown twice a year on 12 March and 25 August. to observe heading responses under different day-length conditions. Rice landraces were sown under longer day conditions in the former season starting in March, while grown under shorter day conditions in the latter season from August. The basic vegetative growth (BVG) was estinrated based on the number of days to heading of the landraces sown on 25 August The photoperiodic sensitivity (PS) was evaluated based on the differences in the number of days to heading between the March 12 and the August 25 sowings. A great diversity was observed in BVG as well as in PS. The PS of the Myanmar landraces was categorized into three groups in order to analyze regional variations in photosensitivity. The PS of group 1 was less than 59 days, that of group 2 which ranged from 60 to 100 days and that of group 3 which exceeded 110 days. The regional variations in PS showed distinctive clines. This differentiation in the PS of the landraces cultivated in different regions of Myanmar was considered to be significantly related with diversified cropping systems and environmental conditions.
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