Coumarin and salicylic acid activate resistance to Macrophomina phaseolina in Helianthus annuus

The induction of resistance to charcoal rot disease caused byMacrophomina phaseolina(Tassi) Goidanich in sunflower (Helianthus annuusL.) was studied after seed treatments with coumarin (COU) and salicylic acid (SA) at three different levels (0.3, 1.0 and 3.0 mM). The priming of sunflower seeds with 0.3 mM COU or 1.0 mM SA resulted in decreased disease severity and offered about 50% protection and more than 80% reduction in the length of stem lesions under greenhouse conditions. Both COU and SA treatments induced the accumulation of soluble sugars and phytoalexins, as well as stimulating the activity of β-1,3-glucanase and chitinase.