Isolation of resistance source for combined diseases viz., purple blotch, basal rot and white rot in onion (Allium cepa L.) by saprophytic and gametophytic screening

Abstract

Onion is an important vegetable crop grown in India and throughout the world. Purple blotch caused by Alternaria porri is one among serious fungal diseases that affect onion, causing heavy yield loss ranging from 2.5 to 87.8 per cent. So there is need to develop hybrids with male sterility background for resistant to purple blotch disease coupled with higher yield. Twenty eight crosses resulting from a L x T design comprising of four lines and seven testers were studied to know the combining ability and magnitude of heterosis. Combining ability analysis revealed that L3 showed good general combiner for most of the characters. The tester T4 and T5 were identified as good general combiner for yield and yield attributing characters. Among the 28 crosses, L2 x T4 was identified as best specific combiner as it showed high sca effect and per se performance, were as cross L3 x T5 exhibited high per se performance for total and marketable bulb yield. For heterosis out of 28 crosses, L2 x T4 and L3 x T5 were the most heterotic and could be exploited for commercial cultivation. The cross L2 x T4 (-42.62%) had exhibited highest magnitude of heterosis over commercial check for purple blotch disease resistance in desired direction. L2 x T1 (-7.78%) exhibited significant stranded heterosis for days to maturity. L3 x T1 (36.84%) showed significant mid parent heterosis for ten bulb weight. The cross L3 x T5 exhibited highest magnitude of heterosis over commercial check for total bulb yield tonnes per hectare (27.44%) and for marketable bulb yield per hectare (28.65%), L2 x T2 (-33.33%) exhibited significant heterosis over standard check for unmarketable bulb yield per hectare.