1Dept. of Botany, School of Life Sciences, Dr. B. R. Ambedkar University (formerly Agra University), Khandelwal Kothi, Civil Lines, Agra 282 002 (Uttar Pradesh).
2IARI, New Delhi 110 012.
National Bureau of Plant Genetic Resources, Pusa Campus, New Delhi 110 012.
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 (RC) 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. A sample of 140 accessions (nearly 7% of the base collection) was finally selected for the final core set.
Tomato, Lycopersicon esculentum, germplasm, variability, diversity, principal component analysis, core set, Shannon Diversity Index, relative contribution
