Alternaria leaf spot on Paeonia peregrina and Paeonia tenuifolia in Serbia

Abstract

<p><em>Paeonia peregrina</em> Mill. and <em>Paeonia tenuifolia</em> L. are endangered species of herbaceous plants with high ornamental and medicinal values. There are a few natural habitats in Serbia where these plants spontaneously grow: Krivi Vir, Skrobnica, Golina, Pirot, Deliblato Sands, and Sokobanja, in the municipality of Knjaževac. In July 2021, the symptom of leaf spots was observed on <em>P. peregrina</em>, while spots on leaves, stems, and lower branches on <em>P. tenuifolia</em> in the localities of Pirot and Deliblato Sands. Disease incidence was estimated to 32% in Pirot and 25-35% in Deliblato Sands. Therefore, the aim of the study was to identify the causal agent of leaf spot on <em>P. peregrina</em> and <em>P. tenuifolia</em> in Serbia by molecular identification and characterization, and morphological characterization. For molecular identification and characterization, nuclear ribosomal internal transcribed spacer (ITS) region, partial translation elongation factor 1-alpha (<em>EF-1α</em>), beta-tubulin (<em>TUB2</em>) and histone 3 (<em>H3</em>) genes were amplified using primer pairs ITS1/ITS4, EF1-728F/EF1-986R, T1/Bt2b, and H3-1a/H3-1b, respectively. Morphological characterization of the representative isolates was done on potato dextrose agar (PDA) and potato carrot agar (PCA) media at 22 <sup>◦</sup>C under an 8 h light:16 h dark regime. Based on the molecular and morphological characteristics of the obtained isolates, <em>Alternaria alternata </em>was identified as the causal agent of leaf spot on <em>P. peregrina</em> and <em>P. tenuifolia</em>. In Serbia, to the best of our knowledge, this is the first report of <em>A. alternata </em>causing a leaf spot of <em>P. tenuifolia</em>.</p>