Studies on genetics of resistance to purple blotch disease, yield, yield components and quality traits in onion (Allium cepa L.)

Abstract

The studies on genetics of resistance to purple blotch, yield, yield components and quality traits in onion was taken up during 2002-2004 at the Division of Vegetable Crops, Indian Institute of Horticultural Research, Hessaraghatta, Bangalore. The material for the heterosis study comprised of five lines (resistant to purple blotch) and six testers (susceptible to purple blotch) which were crossed to get 30 hybrids. The crosses PBR 139 x AN 184 and PBR 140 x AN 187 were found promising over standard check for higher total bulb yield along with purple blotch resistance. Inheritance of resistance to purple blotch disease in four crosses PBR 138 X AN 187, PBR 139 X AN 184, PBR 139 X AP 195 and PBR 140 X AN 184 indicated the presence of both additive and non-additive gene effects. However, dominance and dominance x dominance gene actions were more predominant than other gene actions with duplicate type of epitasis. So it is suggested to go for heterosis breeding to exploit dominant gene action. Joint scaling test suggested the presence epitasis in all the yield and quality traits except days to maturity (dominance), neck thickness (additive), unmarketable bulb yield (additive), and per cent loss due to sprouting (additive). Hence, it is suggested to follow simple selection for the characters neck thickness, unmarketable bulb yield, and per cent loss due to sprouting and heterosis breeding for the character days to maturity. The other characters which were governed by all the gene effects and their interactions, it is suggested to follow reciprocal recurrent selection to improve those traits. The heritability and genetic advance as per cent over mean ranged from -10.0 (total soluble solids) to 130.55 (per cent dry matter and bulb) and 0.49 (ten bulb weight) to 432.64 (neck thickness of bulb), respectively. Most of the traits under study showed high heritability and genetic advance. So, improvement of these traits would be easy in reciprocal recurrent selection method.