GANGAPKASAD, S.VINUTHA, B.2019-10-152019-10-152001-08-07Th-5972http://krishikosh.egranth.ac.in/handle/1/5810131113Onion, Allium cepa var. cepa L. is one of the important bulb crops cultivated extensively in India and it is considered as second most important vegetable after tomatoes in the world. Extent of heterosis was examined in relation to genetic divergence in onion (Allium cepa L.) The material consisted of fifteen F1 hybrids derived by corssing Ten parents. Mahalanobis' was used to estimate genetic distance. The progenies were grouped into six clusters. Cluster I, possessed six parents and nine hybrids followed by cluster II with one parent and two hybrids and cluster IV with three hybrids. The cluster VI included one parent and one hybrid. Cluster III and V were solitary clusters with single parent in each. Fresh bulb weight contributed maximum towards divergence followed by split bulbs, marketable bulbs, storage loss in weight, loss due to sprouting, plant height and loss due to rotting. Selection of parents for hybridization based on fresh bulb weight, marketable bulbs and split bulbs would lead to the selection of genetically divergent material. Heterosis was calculated over mid parent, better parent and standard check.Heterosis was observed for most of the characters except for number of leaves and neck thickness. Heterosis for yield to the extent of upto 28.36 per cent as measured over standard check, was observed. The parents were grouped into 3 clusters. The range, mean and standard deviation of intraand inter- cluster divergence were used to define four divergence classes. The frequency of heterotic crosses for most of the charaters were found to be higher in crosses between the parents with intermediate divergence followed by highly divergent genotypes. The parents Agri found rose, Nasik red and Arka bindu are suggested to use as one of the parent to generate high yielding, better storage life and good quality hybrids.ennullThesis