Morphological variability pattern of Sri Lankan weedy rice - an ecological appraisal

Abstract

Weedy rice (Oryza sativa L. f. spontanea) is one of the most widespread and problematic weeds in rice ecosystems with divers characteristics. The study was carried out to determine the morphological variation pattern of the weedy rice populations in relation to agro-ecology of Sri Lanka. Twelve weedy rice populations collected from infested locations in Ampara, Matara and Kurunegala districts representing dry, wet and intermediate zones were evaluated in a common garden for ten quantitative traits to estimate the phenotypic diversity. The diversity level of weedy rice populations was high as revealed by ShannonWeaver Index. Dry zone of Sri Lanka has more diversity hotspots of weedy rice. Analysis of variance revealed significant differences (p< 0.05) among populations than within populations implying the presence of substantial amount of genetic variability. Seed shattering percentage exhibited the highest variation while thousand seed weight showed the lowest variation explained by coefficient variation (CV). Principal component analysis indicated that the first two components accounted for 72.3% of the total variation and number of tillers, plant height (cm) at both seedling and heading stages, panicle length (cm), seed shattering % and the thousand seed weight (g) were the major determinants of genetic diversity in the weedy rice collection. Clustering identified two clusters and they were not associated with the geographical distribution of the populations. All the analysis based on plant morphology suggested that weedy rice in Sri Lanka has great variability but no association with ecology of the country