Sclerotinia sclerotiorum and Sclerotinia minor are two necrotrophic fungal species that cause white mould disease in many crops. Oxalic acid, secreted by Sclerotinia species, is recognized to be a major virulence factor involved in the induction of cell death in host plants during infection establishment. The aim of this study was to determine relationship between oxalic acid production in S. sclerotiorum and S. minor isolates and their aggressiveness toward lettuce as a model plant. Ten isolates of S. sclerotiorum and ten isolates of S. minor, derived from diseased lettuce plants, were tested simultaneously for their ability to produce oxalic acid and to cause necrosis in an inoculation experiment. Oxalic acid production was measured spectrophotometrically in a liquid medium, while the inoculation test was conducted on lettuce leaf discs. As a control, sterile liquid medium and PDA (Potato Dextrose Agar) plugs were used, respectively. Higher production of oxalic acid was recorded in S. minor isolates, ranging from 19 to 96.3 μg oxalic acid mg−1 dry mycelium weight, while S. sclerotiorum isolates produced significantly lower amount of oxalic acid (21.9 to 29.9 μg oxalic acid mg−1 dry wt). All Sclerotinia spp. isolates were able to establish infection in inoculated leaf disks. On average, the diameter of necrosis was slightly higher for S. minor isolates (11.7 mm), although the difference between species was not statistically significant. Correlation between aggressiveness and oxalic acid production among Sclerotinia spp. isolates was not recorded, suggesting the contribution of some other factors to the necrosis establishment and spreading. Oxalic acid production and aggressiveness of Sclerotinia spp. isolates info:eu-repo/semantics/conferenceProceedings application/pdf 1578424 bytes Oxalic acid production and aggressiveness of Sclerotinia spp. isolates 2024 eng https://phaidrabg.bg.ac.rs/o:34970 ISBN: 978-86-912591-7-4 http://creativecommons.org/licenses/by-nc-sa/4.0/legalcode Mihajlović, Milica Živanović, Maja Hrustić, Jovana Jovanović, Aleksandra Pešić, Brankica virulence factor, lettuce, white mould disease