Abstract:
Common wild rice species, annual O. nivara and perennial O. rufipogon are closely related to
Asian cultivated rice and progenitors of modern rice cultivars. Observations of phenology stages
and their divergence were important to understand their life history patterns to select candidate
parents for breeding purposes. An Ex-situ common garden experiment was conducted using
seeds collected from two natural populations of each species. O. nivara seeds were collected
from Kilinochchi and Vavuniya in the dry zone and O. rufipogon seeds were collected from
Thihagoda and Seeduwa in the intermediate zone. Seedlings were transplanted for 30
individuals per population at the Faculty of Agriculture, University of Ruhuna. Life cycle
observations were recorded for one year. The findings revealed that the highest survival rate
belongs to O. rufipogon (85%, Thihagoda and 90%, Seeduwa) whereas, O. nivara showed a
comparatively low survival rate (75%, Kilinochchi and 55%, Vavuniya). After 49 ± 13 days of
transplanting, panicle emergence was appeared in O. rufipogon (Thihagoda) indicating the
shortest vegetative stage while Seeduwa recorded 54 ± 17. However, O. nivara (Vavunia)
recorded the longest vegetative stage about 59 ± 2 days while Kilinochchi recorded 56 ± 3 days.
Duration from Panicle emergence to 50% heading was comparatively low in O. nivara (15 days)
than that of in O. rufipogon (25 days). The reproductive period of O. nivara (157 ± 13 days)
seemed shorter compared to O. rufipogon (243 ± 19 days). Further, perennial O. rufipogon being
a short vegetative period for 88 ± 11 days (Thihagoda) and also began next flowering period due
to its bi-model flowering nature. After reproductive stage, O. nivara no longer exists in the field
owing to its annual nature. There were no clear differences in phenology stages among
populations in respective species. Conclusively, both species showed nearly similar patterns of
phenology stages. These findings may help to design successful breeding practices, germplasm
collection and implementing conservation strategies of these valuable genetic resources.
