Effect of salicylic acid (SA) and drought stress on growth, bulb yield and allicin content of garlic (Allium sativum) in field

Salicylic acid (SA) is an important signal molecule modulating plant response to stress. A field trial was, therefore conducted to study the impact of salicylic acid (SA) at 0, 0.1 and 0.5 mM on growth and biochemical parameters, bulb yield and allicin contents in a local garlic cultivar under drought stress in Iran. Drought significantly reduced all parameters recorded but allicin percentage. Whole plant fresh weight and bulb yield as the two economically important traits were reduced by 37% and 28%, respectively under drought stress conditions. On the contrary, SA increased root fresh and dry weights, bulb length, clove (length, number, brix and allicin percentage), harvest index and allicin percentage and the effect of 0.5 mM SA was more pronounced. The interaction of SA and drought was significant for most parameters recorded and in most cases SA was more effective under drought stress than non-stress conditions. Relative to the corresponding control, 0.5 mM SA increased bulb yield by 49% under drought stress and 24% under non stress conditions. This effect was even more pronounced for allicin content and the relative increases under stress and non stress conditions were 67% and 40%, respectively.