Chelating agents proven to have fungicidal activity in citrus fruits against Penicillium spp.

Penicillium digitatum is the primary pathogenic fungus affecting citrus fruits during the postharvest stage. A research group at CSIC-IATA (Spanish National Research Council (CSIC) at the Institute of Agrochemistry and Food Technology (IATA)), of which Dr. Luis González Candelas is a member, has conducted an in-depth study of the interaction between this fungus and citrus fruits to gain a better understanding of both the fruits’ defense response to the pathogen and the fungus’s pathogenicity mechanisms. A key finding from these studies: metal ion metabolism in Penicillium plays a significant role during the infection process.

To explore this further, the importance of metal ion metabolism—specifically iron—was investigated. It was observed that, during the infection of oranges, the fungus experiences iron deficiency and requires a metabolic machinery that allows it to efficiently obtain this metal in order to develop. Thus, the research group generated mutants lacking this mechanism, which are virtually incapable of infecting fruits, yet indistinguishable from the parental strain under normal growth conditions in culture medium.

Furthermore, it was demonstrated that the application of chelators (metal ion-sequestering agents) inhibits the development of this pathogen in citrus fruits under various application and storage conditions.

It is noteworthy that phenantrolin, an iron chelating agent, is as effective as imazalil, even against strains resistant to this fungicide. This chelating agent is also effective against other postharvest pathogenic fungi, such as Penicillium italicum and Penicillium expansum. A particularly interesting characteristic is the high curative activity exhibited by this chelating agent even at relatively low concentrations. Although the industrial application of phenantrolin may be difficult to achieve due to issues of ecotoxicity and fruit staining, these results open the door to the development of other metal ion chelating agents as an alternative treatment to conventional fungicides.

There is a vast array of molecules with chelating capacity, both synthetic and natural in origin. Within the group of synthetic chelating agents, the research team is investigating EDTA, a food additive widely used in both agriculture and the food industry. Although it has proven less effective than phenantrolin in the pilot trials conducted, it is believed to be a good starting point for the development of a new generation of fungicides against post-harvest pathogenic fungi.

Dr. Luis González Candela will participate as a speaker at the 5th Citrus Postharvest Conference, organized by Poscosecha.com, IVIA, and AgroBank, which will take place in Valencia on September 17 at the AgroBank headquarters.

Source: Dr. Luis González Candela