Phenyl tetramethyl cyclopropane carboxamide class: New broad-spectrum postharvest fungicides

Abstract

Fresh postharvest fruit and vegetable loss due to the development of postharvest diseases is enormous. Synthetic fungicides are the primary and most effective tool to control postharvest disease caused by fungal pathogens. However, broad-spectrum synthetic fungicides possess a high risk to the environment and human health. Therefore, in recent years many authorized fungicides have been banned or their permitted maximal residue levels were reduced. Hence, there is a need to develop new compounds with low toxicity and antifungal properties. In the current study, 13 compounds from the Aromatic-tetramethyl-cyclopropane-carboxamide (PTCC) class that have no neurotoxicity were screened for possible antifungal activity. Three of the tested compound (JS-2, JS-9, and JS-10) significantly reduced the growth of Botrytis cinerea, Penicillium expansum, and Colletorichum gloeosporioides, three major postharvest pathogens, and reduced B. cinerea germ tube elongation. The initial mode of action studies revealed that the PTCC increased fungal membrane polarity, indicating the induction of changes in the membrane composition. Additionally, JS-2 increased the mitochondrial membrane potential and ATP production, which hinders the fungal respiratory activity by a possible interference with the proton pump in the mitochondria. JS-9 reduced ROS, and ATP production, which suggests interference with metabolic activity. The third compound JS-10, reduced fungal viability, however, more study is needed to identify the specific metabolic pathway that is affected. Furthermore, the PTCC compounds reduced decay development in mango, apple fruit, and grape berries. The greatest effect was observed in the pathosystem of B. cinerea-grape. Overall, the results of the current study emphasize the potential of the new PTCC class compounds as new fungicides.