Fungicidal activity of extracts obtained from Solanum species against the postharvest citrus pathogens Geotrichum citri-aurantii and Penicillium digitatum

ÁLVAREZ, N.H.; STEGMAYER, M.I.; PENSIERO, J.F.; ZABALA, J.M.; FAVARO, M.A.; DERITA, M.G.

Conferencia; Poland Conference: Plant productivity and food safety: Soil science, Microbiology, Agricultural Genetics and Food quality; 2021

Citrus spp. are the most widely produced fruits for human consumption and they are cultivated in over one hundred countries. Postharvest handling practices in citrus packing houses try to obtain fruits with maximum quality, increasing their postharvest life and reducing losses, particularly those from phypathological origin. Geotrichum citri-aurantii, the cause of sour rot; and Penicillium digitatum, the cause of green mold, are two of the most economically important postharvest diseases of citrus in all production areas. Considering the concerns of consumers about the inadequate use of fungicides as well as its impact on the environment and public health, this study aims to provide information on alternatives such as the use of extracts obtained from Solanum species for the control of postharvest diseases of citrus. The genus Solanum comprises around 1500 species and 158 of them, are present in Argentina. For this study, four of them (Solanum argentinum Bitter & Lillo, S. granulosum-leprosum Dunal, S. pilcomayense Morong and S. caavurana Vell., all native species reported as antibacterial or antifungal in traditional medicine systems) were evaluated in vitro as fungicides against G. citri-aurantii and P. digitatum. Fresh material from each species was collected and a specimen was herborized and deposited in ?Arturo E. Ragonese? (SF) Herbarium. The plant material was successively dried and extracted (24 h x 3 at RT and constant stirring) using dichloromethane (DCM) and methanol (MeOH). The extractive solutions were concentrated under reduced pressure, in order to obtain the corresponding extracts that were evaluated for their fungicidal capacity by PDA diffusion method, at a concentration of 500 ppm and using Petri dishes with four repetitions. After 7 days, the averages of the percentages of fungal growth inhibition were determined, using a commercial product based on imazalil as a negative control and DMSO as a positive one. The growth inhibition percentages for G. citri-aurantii were: 63,84±0,87% and 73,31±11,92%; 41,33±12,94% and 61,43±7,44%; 71,17±1,89% and 100±0% and 79,80±4,53% and 100±0% for DCM and MeOH extracts of S. argentinum, S. granulosum-leprosum, S. pilcomayense and S. caavurana, respectively. For P. digitatum, the percentages of growth inhibition were: 45,17±9,63% and 62,25±12,19%; 54,67±6,00% and 49,49±4,55%; 46,38±13,59% and 100±0,00% and 59,98±7,74% and 94,55±1,45% for DCM and MeOH extracts of S. argentinum, S. granulosum-leprosum, S. pilcomayense and S. caavurana, respectively. Most of the extracts exceeded 45% of fungal growth inhibition, but MeOH extracts of S. pilcomayense and S. caavurana showed the highest activity, displaying 100% of inhibition against both fungal strains. Results presented in this study show the potential of alternative methods for the control of post-harvest diseases of citrus.