Cellular damage induced by a sequential oxidative treatment on Penicillium digitatum

To investigate the cellular damage on Penicillium digitatum produced by a sequential oxidative treatment (SOT), previously standardized in our laboratory, to prevent the conidia growth. Lethal SOT consists of 2-min preincubation with 10 ppm NaClO followed by 2-min incubation with 6 mmol l(-1) CuSO(4) and 100 mmol l(-1) H(2)O(2) at 25°C.

After the application of lethal SOT or sublethal SOT (decreasing only the H(2)O(2) concentration), we analysed several conidia features such as germination, oxygen consumption, ultrastructure and integrity of the cellular wall and membrane. Also, we measured the production of reactive oxygen species (ROS) and the content of thiobarbituric acid-reactive species (TBARS). With the increase of H(2)O(2) concentration in the SOT, germination and oxygen consumption of conidia became inhibited, while the membrane permeability, ROS production and TBARS content of conidia increased. Several studies revealed ultrastructural disorganization in P. digitatum conidia after lethal SOT, showing severe cellular damage without apparent damage to the cell wall. In addition, mycelium of P. digitatum was more sensitive than conidia to the oxidative treatment, because growth ceased and permeability of the membranes increased after exposure of the mycelium to a SOT with only 50 mmol l(-1) H(2)O(2) compared to a SOT of 100 mmol l(-1) for these effects to occur on conidia.

Our insights into cellular changes produced by the lethal SOT are consistent with the mode of action of the oxidant compounds, by producing both alteration of membrane integrity and intracellular damage.

Our results allow the understanding of SOT effects on P. digitatum, which will be useful to develop a reliable treatment to control postharvest diseases in view of its future application in packing houses.