Agriculture & Horticulture

The origin of weedy rice has long been a controversial issue and opinions on the origin of WR are greatly varied across

the scientific community. As far as Sri Lankan WR ecotypes are concerned, a geographical pattern of distribution which

associated with the wild rice and cultivated rice varieties in each climatic zone. Genetic diversity of 85 weedy rice eco-types,

60 cultivated rice varieties and 2 wild relatives distributed in wet, intermediate, dry zone were studied using 10 microsatellite

(SSR) markers distributed across the rice genome. Total genomic DNA was extracted from 7-day old seedlings of respective

WR eco-types, wild rice and cultivated types. A total of 10 SSR primer pairs were used for molecular study. Fragment analysis

using capillary electrophoresis was performed and identified different peaks among WR eco-types and wild rice varieties.

Obtained data were subjected to cluster (CA), principle component (PCA) and self-organizing map. Results of the PCA and

CA indicated that SSR distribution across the weedy rice eco-types, cultivated rice varieties and wild relatives provide strong

evidences supporting the hypothesis that the wild relative O. rufipogon and O. nivara ecologically diversified into wet and dry

habitats, respectively. Thus, origins of the weedy rice eco-types are results of the spontaneous hybridization and out-crossing

between wild relatives and cultivated rice varieties. Further, SOM imply that four out of 10 SSR primers (RM 211, RM 280,