M. I. Zarudniak, L. A. Dankevych*, I. P. Tokovenko, V. P. Patyka

D. K. Zabolotny Institute of Microbiology and Virology,
*e-mail: ldankevich@ukr.net

Received: 23 April 2025; Revised: 25 September 2025;
Accepted: 28 November 2025; Available on-line: 2025

Walnut (Juglans regia) is the most economically important and widespread nut crop in Ukraine. As bacterial diseases of walnut can reduce the yield of this culture by up to 40%, the monitoring of pathogens in a given crop and their identification are extremely important. The fatty acid composition of cell lipids is used in the taxonomy of plant pathogenic bacteria. The objective of this study was to determine the fatty acid composition of cell lipids of Agrobacterium, Xanthomonas, and Pseudomonas collection strains that can actually infect walnut, and those isolated from affected walnut trees in different regions of Ukraine. Fatty acid methyl esters were obtained by two different methods of extraction, with the use of 5% acetyl chloride in methanol at 100°C for 4 h, or 1.5% sulfuric acid in methanol at 80°C for 1 hour. Fatty acid methyl esters were analyzed using gas chromatography–mass spectrometry system. According to the found similarity of the fatty acid composition, the strains isolated from the affected walnut were related to representative collection strains of A. tumefaciens, X. arboricola and P. syringae. It should be noted that during the isolation of fatty acids with the use of 1.5% solution of H₂SO₄ in methanol, the amount of individual saturated and unsaturated fatty acids in the studied strains decreased and almost all hydroxyl acids, identified as a key taxonomic markers, disappeared in comparison with the using of 5% solution of acetyl chloride in methanol at the hydrolysis stage.