First Report of <i>Epicoccum italicum</i> Causing Leaf Spots on <i>Eugenia uniflora</i> in Brazil

Eugenia uniflora is a fruit tree native to Brazil. In July 2024, in the experimental area of the Federal University of Technology, Paraná (UTFPR), Brazil, a disease was observed in 30 trees, with 50% to 60% of the leaves affected. Symptoms were small, irregular, circular or ovoid, dark brown spots with yellow halos. The lesions increased in both mature and young tissues over time, resulting in leaf drop. Thirty symptomatic leaves from 10 trees grown in different orchard locations were collected. Leaf surfaces were disinfested with 0.5% NaOCl solution for 1 min, rinsed in sterile distilled water, and dried on sterile filter paper. Three diseased leaf fragments were placed on each of ten plates with potato dextrose agar medium. Five plates showed fungal colonies with identical morphology: yellow on the upper surface and reddish on the undersurface, with circular to ovoid, multicellular conidia (23.00 µm x 24.45 µm, n = 30), agreeing with the description of Epicoccum (Valenzuela-Lopez et al. 2018). Conidia and conidiophores were fluorescent, a characteristic of Epicoccum spp. (Bell and Karuso 2003). Identification of two of the five isolates (EP1077 and EP1078) was confirmed by amplification and sequencing of three loci (ITS, β-tubulin, and RPB2) by primer pairs ITS1/ITS4, Bt2a/Bt2b, and 5F2/7cR, respectively (Glass and Donaldson 1995). The isolates were analyzed and results submitted to GenBank (PQ562358, PQ568243, PQ568242, PQ892022, PV060550 and PQ998300). Bayesian inference was used to reconstruct phylogenetic trees starting from random trees for 5,000,000 generations using MrBayes v. 3.2.1 (Ronquist et al. 2012). The isolates clustered with an isolate of Epicoccum italicum CGMCC 3.18361 (Chen et al. 2017) with high probability (1.0). To fulfill Koch's postulates, ten healthy seedlings four months old were inoculated by spraying with 1.5 mL of EP1077 conidial suspension (106 conidia. mL-1), covered with perforated transparent plastic bags and misted with distilled water (14ºC to 25ºC). A sterile distilled water (SDW) spray was used as control. There were three replicates (total of 60 seedlings). Five days after inoculation, irregular brown lesions with a yellow halo appeared. Symptomatic fragments were cultured in PDA medium and formed colonies identical to those of isolate EP1077. The SWD sprayed seedlings remained symptom free. The inoculation test was repeated once, with the same symptoms observed. This pathogen reduces tree vigor and fruit quality by reducing photosynthetic capacity, in part by defoliation. It is important to identify this causal agent because the literature lists rust Austropuccinia psidii as the sole pathogen for this native fruit tree, and this results in confusion of symptoms and incorrect management for this leaf spot disease. This is the first report of leaf spots caused by E. italicum in E. uniflora in Brazil.