Evaluation of genetic diversity and development of core collection of onion

Onion (Allium cepa L.) is a bulbous crop, grown in three different seasons viz. kharif, late kharif and rabi in India. ICAR-Directorate of Onion and Garlic Research being the National Active Germplasm Site (NAGS), holds a vast collection of onion accessions collected from different parts of the country. Being a highly crosspollinated crop, onion collection depicts tremendous variation at phenotypic, biochemical and molecular level. Handling of more number of accessions becomes difficult for evaluation, hence formulation of core group become pre-requisite. Addressing this, Power Core software has been used to constitute a seasonwise core group using mean data of 24 important traits. Total 131, 150 and 237 onion accessions were used to formulate core group where 27, 35 and 38 accessions were constituted in the core for kharif, late kharif and rabi seasons, respectively. The formulated core was validated using mean difference percentage (MD%), variance difference percentage (VD%), coincidence rate percentage (CR%) where MD% for all the three sets ranged between 7 to 11%, VD% between 25 to 46% and CR% between 94 to 96%. Scattered diagram of Principal Component Analysis (PCA) for core and entire collection showed core group which represented the entire collection. Further correlation strength among traits for entire and core group was found to be similar. This characterization and formulated group accessions will be helpful for further critical analysis and identifying trait-specific accessions.