BIOCONTROL OF GREEN MOULD IN ORANGES BY EPIPHYTIC BACTERIA AND BIOACTIVE COMPOUNDS

BELLO, FERNANDO; VÁZQUEZ, DANIEL; FERREIRA, FLAVIA VANINA; MUSUMECI, MATÍAS ALEJANDRO

Congreso Virtual

Congreso; XVI Annual Meeting of the Argentinean Society for General Microbiology (SAMIGE); 2021

Sociedad Argentina de Microbiología General (SAMIGE)

Penicillium digitatum is a filamentous fungus that infects citrus fruits through injuries and wounds produced on the peel during harvest and post-harvest handling, causing rots known as green mould. The fruits are more susceptible to this infection in packing facilities and storage rooms, especially in those lacking of appropriate hygiene, where high concentrations of spores prevail. The decays caused by P. digitatum result in significant production losses; therefore, strategies aimed to control this fungus are highly relevant. The application of synthetic fungicides is the mainly applied approach to control P. digitatum. However, the intensive usage of fungicides has led to the proliferation of P. digitatum strains with resistance to one or more fungicides. Besides, this practice poses a risk for the human health, decreases the population of fungal crop symbionts, produces soil and water pollution and is incompatible with the organic market. These concerns demand alternative approaches, which must be harmless to human and environmental health and fulfil the restrictions of different countries regarding to limit values of chemical residues on fruits. Biological control and natural bioactive compounds are promising alternatives to the control of post-harvest decays and may contribute to sustainable production of citrus. The objective of this work is to evaluate the potential of bacterial strains native from the surface of oranges and the application of a natural bioactive compound to control P. digitatum growth.Eleven bacterial strains were isolated from oranges peel and identified by sequencing of 16S rRNA gene. The strains corresponded to Microccus luteus, Staphylococcus xylosus, Bacillus mojavensis, Bacillus velezensis, Bacillus subtilis and Pseudomonas psychrotolerans. Three of them showed effective antagonist performance in vitro against P. digitaum A21, a strain resistant to the fungicide pyrimethanil previously isolated by our group. Reductions of green mould growth by 80%-90% were obtained when culture filtrates were used by the poison agar method. Reproducible results were also obtained upon in vivo conditions and preventive treatments. The capability of 6 pentyl-alpha-pyrone (6PP) to inhibit the growth of P. digitatum was also assayed. This harmless compound has shown fungicide activity against different crop pathogens and is produced by the saprophytic fungus Trichoderma atroviride, which was isolated by our group. Significant differences were observed with respect to the control in curative treatments. These results suggested that epiphytic bacteria and 6PP are optimal tools for the control of green mould spreading in post-harvest citrus fruits. The combination of these tools with supplementary strategies such temperature regulation, UV irradiation and GRAS substances could lead to sustainable management of green mould decays, preserving post-harvest quality of oranges and dispensing with synthetic fungicides.