Phenotypic Diversity and Genetic Variation within a Collection of Onion (Allium cepa L.) Germplasm from Peninsular India

Twenty three diverse germplasm lines collected from varying agro-ecological regions of Peninsular India during 2007-08 were characterized and evaluated along with three controls viz. Nasik Red, Light Red and White Marglobe, in an augmented block design during kharif 2009-10, at NBPGR Regional Station, Rajendranagar, Hyderabad. The accessions exhibited good variation for qualitative traits like early seedling vigour, leaf cross section, leaf arrangement, stem shape, bulb shape, bulb skin color, bulb size, bulb hearting and bulb flesh colour and quantitative traits like plant height, number of leaves per plant, leaf length, leaf girth, number of scales per bulb, total soluble solids (TSS) (°Brix), bulb weight and bulb yield per plant. Correlation study revealed that high significant positive correlation was recorded between number of scales per bulb and bulb weight (r=0.71) and significant negative correlation was observed between leaf length and leaf girth (r= -0.88), leaf length and bolting (-0.63) among others. Principal component analysis (PCA) revealed that the first four principal components explained 99.76% of the total variation among the 23 accessions and three controls. PCA I accounted for 97.04% of variation, had maximum influence on bulb weight followed by plant height. The PCA II traits were leaf length and plant height which accounted for 1.97 % of the variance. The PCA III and PCA IV have contributed for 0.39 and 0.39% of total variance. The cluster analysis revealed that dendrogram formed four distinct clusters and cluster III was found to be the largest including controls. The promising accessions for bulb weight were IC 571959, IC 564056, IC 571927, IC 571919 and IC 564059, which may be effectively tapped in sound breeding and conservation program.