The mononuclear nickel(II) complex bis(azido-κN)bis[2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole-κ2N2,N3]nickel(II) protects tomato from Verticillium dahliae by inhibiting fungal growth and activating plant defences

BACKGROUNDThe antifungal properties of the nickel(II) complex bis(azido-N)bis[2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole-N-2(2),N-3]nickel(II) [NiL2(N-3)(2)] and its parental ligand 2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole were examined to evaluate their ability to protect tomato plants against Verticillium dahliae. Our main objectives were to determine their effects on the in vitro growth of the pathogen, and their aptitude for controlling verticillium wilt and activating plant defence responses in the greenhouse. RESULTSNiL2(N-3)(2) exhibited in vitro an elevated inhibition of radial growth of three strains of the pathogen. According to the strain, the EC50 values ranged from 10 to 29 mu g mL(-1) for NiL2(N-3)(2). In the greenhouse, it induced an elevated protection against V. dahliae when it was applied twice as foliar sprays at 50 mu g mL(-1). It reduced the leaf alteration index by 85% and vessel browning by 96%. In addition, its protective ability was associated with the accumulation of H2O2 and the activation of total phenolic content, as well as potentiation of the activity of peroxidase and polyphenol oxidase. CONCLUSIONThese results demonstrated that the coordination of the ligand with Ni associated with the azide as a coligand resulted in an improvement in its biological activity by both inhibiting the growth of V. dahliae and activating plant defence responses. (c) 2016 Society of Chemical Industry