Exogenous application of spermidine enhanced tolerance of pepper against Phytophthora capsici stress

Abstract

The effect of exogenous spermidine - Spd (0.1 and 1 mM) on the relation between polyaminoxidase (PAO), diaminoxidase (DAO), H2O2, and malondialdehyde (MDA) in three cultivars of pepper (Capsicum annum L.) exhibiting different tolerance to P. capsici stress: KM-Hot (P. capsici-tolerant), PM-217 (P. capsici-resistant), and CM-334 (P. capsici-highly resistant) was investigated. The 0.1 mM Spd pre-treatment led to an increase in DAO activity on the third day in three pepper cultivars under the stress of P. capsici, 1 mM Spd + P. capsici led to an increase in DAO and PAO activities on the fifth day if compared to P. capsici treatment alone. P. capsici alone caused an increase in the amounts of H2O2 at all times in all cultivars and in the amounts of MDA on the third and fifth days in all cultivars. Conversely; under the stress of P. capsici, pre-application of 0.1 mM Spd at all times in KM-Hot and CM-334 cultivars decreased the amount of MDA and H2O2 and on the first and third days in PM-217 cultivar decreased the amount of MDA and H2O2. This data indicates that exogenous Spd application before inoculation decreases the plasma membrane injury by decreasing the level of H2O2 and regulating the activities of amine oxidasein both P. capsici-sensitiveand P. capsici-resistant cultivars of peppers, so it may increase the tolerance of pepper cultivars against P. capsici.