Morphological variation in selected rice (Oryza sativa L.) germplasm of Sri Lanka

Genetic improvement of rice for increased grain yield has changed plant height and canopy architecture of the rice (Oryza saliva L.). Under such circumstances, selection based on grain yield only can lead to the loss of other important characteristics of the low-yielding traditional rice varieties. In this context, morphological variation among traditional and improved Sri Lankan rice varieties using important vegetative and reproductive characteristics was studied. Principal component (PC) and cluster analyses were used to assess the patterns of morphological variation. The first five PCs explained over 90% of the total variation. PC1 and PC4 represented vegetative characteristics (i.e. plant height, leaf dry weight, leaf area, stem dry weight), and PC2, PC3 and PC5 represented reproductive characteristics (i.e. number of filled and total grains panicle(-1), number of panicles m(-2), number of tillers hill(-1) and hundred grain weight). PC1 was found to be not important to explain the variability of grain yield among rice varieties in the presence of PC2-PC5. Based on both vegetative and reproductive characteristics, two clusters in each of the improved and traditional variety groups were identified and the existence of those clusters were proved by Wilks' lambda under multivariate analysis of variance (MANOVA). Traditional varieties had a comparatively higher variation in their vegetative and reproductive characteristics. The implications of the results for rice improvement and germplasm conservation are also discussed.