Abstract
Abstract : Genetic improvement of rice for increased grain yield has changed plant height and canopy architecture of the rice ( Oryza sativa 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. Keywords : Improved and traditional varieties, morphological variation, multivariate methods, rice, vegetative and reproductive characteristics. Doi: 10.4038/jnsfsr.v39i2.3173 J.Natn.Sci.Foundation Sri Lanka 2011 39 (2): 129 - 137
Highlights
Knowledge on the genetic diversity and population structure of germplasm collections is important for crop improvement
All traditional varieties were taller than 114 cm at heading while that of new improved varieties (NIVs) was less than 100 cm
The traditional varieties needed more than 115 days for their maturity while all the NIVs needed less than 105 days, except for Bg450 where it needed 125 days
Summary
Knowledge on the genetic diversity and population structure of germplasm collections is important for crop improvement. The remaining area is cultivated with traditional rice varieties with low yield (less than 2.5 t ha-1). The average rice yield in Sri Lanka has increased from around 1.3 t ha-1 in the 1950s to 3.1 t ha-1 by the late 1980s (IRRI, 1991). At present the national average rice yield is 4.2 t ha-1, which is 50-60% of the genetic potential (6-7.5 t ha-1) of NIVs recommended for cultivation in Sri Lanka (Dhanapala, 2000; Central Bank of Sri Lanka, 2008). Farmer’s perceptions (Efisue et al, 2008), improvement of system sustainability (Abeyratne, 1956) and the higher adaptability to problem soils (Mandal et al, 1999) further increased interest towards traditional rice varieties
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