Abstract:
Weedy rice (WR) was first reported in 1990 and it is reported in varying
population densities from all agro-ecological zones in Sri Lanka. The main
problem faced by the famers and the agronomist is the identification of WR
bio-types using agro-morphological characters varying with time. The WR
population possibly possesses a number of derived characters and primitive
characters. This study focuses on identification of primitive and derived
characters observed in WR. The identification of salient trends of characters
specialization in WR populations facilitates the understanding of the rate
diversification of WR populations. Seeds of presumed WR bio-types were
collected from five different locations in Kurunegala and Matara districts.
Five replicates of each bio-type were planted in plastic pots with
representative paddy soils from each location. Replicates were arranged in
Complete Randomized Design (CRD). Agro-morphological characterization
(using thirty six characters) of WR bio-types, Wild rice and cultivated rice
varieties was made using a Standard Characterization Catalogue. The
collected data were separated into nominal and scalar variables and the
nominal data were used to construct Classification and Regression Trees
using CART algorithm. The long-fully awned and absence of awn are
apomorphic and short-fully awned and long-partly awned characters are
pleisomorphic in WR biotype populations in Sri Lanka. These characters are
hypothesized as derived from mixing of germplasm either of cultivated or
wild rice varieties indicating possibilities of cross-pollination among wild,
cultivated and weedy rice bio-types.
