Adaptability of onion (Allium cepa) genotypes to alkali and salinity stresses

The performance of seven onion (Allium cepa L.) genotypes, viz 'Pusa White Flat','Agri Darle Red', 'PBR 5', 'Amrawati', 'Pusa White Round', 'Phule Saf ed', and 'Agri Light Red' was evaluated during rabi 1995 and 1996 both unde r alkali (pH 9.20, 9.45 and 9.70) and salinity (ECe 3.5 and 5.2 dS/m) stres ses besides a non-stress control. Under increasing alkali stress, mean seed ling fresh weight declined, ranging from 32% (pH 9.2), 54% (pH 9.45) and 85 % at pH 9.7 compared to control. In general, onion bulb yield declined by 4 1 and 49% at pH 9.2 and 9.45 respectively, compared with the control and dr opped to negligible level at pH 9.7. On an average, over different alkali l evels, CV 'Amrawati' gave maximum bulb yield followed by 'Agri Light red'. 'Agri Light Red' recorded minimum reduction both in seedling fresh weight a nd final bulb yield up to pH 9.45. Further, under salinity stress, seedling fresh weight declined by 13 and 26% while mean bulb yield (at harvest) dec lined by 54 and 65% at ECe 3.5 and 5.2 dS/m respectively. Highest mean bulb yield obtained under salinity was by 'Pusa White Flat' followed by 'Amrawa ti' amongst different genotypes tested. Simultaneously, minimum reduction o f 38 and 46% in bulb yield was observed in 'Pusa While Flat' at ECe 3.5 and 5.2 dS/m. Final bulb yield was positively correlated with seedling fresh w eight both under alkali (r = + 0.86) and salinity (r = + 0.56) stresses. Si milarly, bulb yield was negatively correlated with Na/K ratio under alkali (r = - 0.83) and salinity (r = - 0.79) stresses. Fifty percent reduction in bulb yield (C-50) was observed at pH 9.14 and ECe 3.93 dS/m under two type s of stresses.