Control of citrus pathogens by protein extracts from Solanum tuberosum tubers

Abstract

A national program for citrus certification was started in Argentina in 2005 in order to provide healthy fruits free of toxic residues. In line with this goal, the aim of this study was to evaluate the efficacy of natural products, protein extracts obtained from potato tubers for the control of fungi responsible for disease in post-harvest citrus fruits. Different protein fractions were obtained from Solanum tuberosum tubers (IF25, IF50, SF25 and SF50) and their effect were evaluated on Penicillium digitatum and Geotrichum candidum, two citrus-pathogenic fungi. All fractions showed antifungal activity against both fungi species, the intensity of this activity being dependent on the type of fungus and extract. The fraction IF25 was the most active as an antifungal agent: it inhibited the mycelia growth of both pathogens, the elongation of the germ tube ofP. digitatum and the conidial isotropic growth of G. candidum as well as its polygalacturonase activity. None of the IF25 concentrations were mutagenic in Salmonella typhimurium TA98 or TA100 strains. The efficacy of protein extracts to control P. digitatum and G. candidum growth was tested in artificially inoculated citrus fruits. Extracts were tested built-in to the wax used in citrus industry to coat and protect the fruit. The IF25 extract was effective in inhibiting the growth and development of P.digitatum and G. candidum. Consequently, the IF25 extract plus the wax could be used preventively in controlling fungal infection on post-harvest citrus.