Occurrence of botrytis blight on Paeonia lactiflora in Serbia

In three consecutive years 2022-2024, during a survey of the commercial greenhouses in Serbia, leaf blight symptoms of botrytis blight were observed on Paeonia lactiflora Pall. Disease severity on observed peony leaves was nearly 20% with symptoms characterized as brown spots with abundant conidia developed on interior side of spot. Objective of this study was to characterize diversity of Botrytis cinerea population isolated from different locations in Serbia. Leaf samples with typical symptoms of botrytis blight were collected from ten diverse localities. Diseased leaves were dipped in a 1% sodium hypochlorite for 30 s, and then washed three times with sterilized distilled water. After this treatment symptomatic leave spots were transferred on potato dextrose agar and incubated at 22°C for 7 days in the dark. After incubation growing mycelia were initially white and slowly became grey three weeks later. Molecular characterisation of obtained B. cinerea isolates was established on sequences of genes for the internal transcribed spacer (ITS) region of rDNA, glyceraldehyde-3-phosphate dehydrogenase, heat-shock protein 60, and RNA polymerase subunit II. Pathogenicity test was done with all investigated isolates. Leaves of healthy P. lactiflora cv. Sarah Bernard plants were infected with PDA plugs containing mycelia taken from 14-day-old cultures. Molecular identification was completed with the results of morphological analyses of the isolates obtained in this research. Differences in virulence were found in performed pathogenicity tests. The Maximum likelihood trees derived from the single gene sequence alignments and concatenated sequences of the ITS, G3PDH, HSP60, and RPB2 of isolates recovered in this study identified isolates that belong to the B. cinerea species. The present study is the first morphological and molecular characterization of B. cinerea in regards to understanding the biology of the botrytis blight disease of peony in Serbia.