STUDIES IN WORLD TOMATO (Lycopersicon esculentum Mill.) GERMPIASM COLLECTION: METHODOLOGY FOR ESTABLISHING A REPRESENTATIVE CORE SET USING CHARACTERIZATION DATA
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Abstract
The present paper discusses the formation of a core set of tomato (Lycopersicon esculentum Mill.)
germplasm comprising 2021 accessions and representing variability from 47 countries. Data on 41
morpho-agronomic and economic traits (qualitative as well as quantitative) scored/studied during
summer season of 1990, 1991 and 1992 were used in the analysis. Principal Component Analysis
(PCA) strategy was used to estimate the inertia and the corresponding Relative Contribution (Re)
of each accession. Fourteen principal components with eigen values over 1 and explaining a total
of 65 per cent of the variation were selected for computing the inertia and the relative contribution
of each accession and improved method based on the RC score requiring low number of accessions
to be sampled, was suggested for establishing the core set. The said method resulted into higher
values of Shannon Diversity Index (SDI)/Coefficient of variation (CV) for 36 out of 41 characters
scored. An optimum sample size of 140 was estimated on the basis of pooled diversity