The Possible Mechanisms of Copper Resistance in the Pathogenpseudomonas Syringaepathovars in Stone Fruit Trees

Abstract

One of the most common diseases affecting Stone-fruits is Bacterial Canker, caused byPseudomonas syringaepv.syringae(Pss) andmorsprunorum(Psm). In this study,PssandPsmwere isolated from stone-fruit trees from the Western Aegean region (WA) and Lake Van Basin (LVB) of Turkey, where pesticide usage is high and low, respectively. We aimed to determine copper resistance levels, the involved resistance mechanisms and the reactions to copper pesticides of these isolates. The minimum inhibitory concentration (MIC) and lethal dose 50 (LD50) of the isolates were detected using CuSO(4)and other Cu-pesticides. To determine the mechanisms of copper resistance, the presence ofcopAandcusAgenes was investigated. The modified Fe/Cu Blue-CAS Agar media were used to investigate the relationship between the isolates' copper resistance and each isolate's ability to produce siderophores. The highest MIC value was 2 mM in CuSO4. The tolerance levels of the isolates from the WA and LVB regions were 29% and 47% susceptible, 29% and 47% low resistance and 42% and 6% resistant, respectively. The most successful pesticide was (CuSO4 + Ca (OH)2) + mancozeb. While none of the isolates had thecusAgene, four isolates had thecopAgene, which was proven to be plasmid-borne. Differences betweencopAgene sequences were detected and were determined to be not related to the pathovars. The amount of siderophore produced against copper inPspathovars affected seems to be related with the resistance level. Also,Pspathovars were able to tolerate copper at doses as high as 1.1 mM by producing siderophores, and at doses of 1.7 mM and above through thecopAgene.