The coconut (Cocos nucifera L., Arecaceae) is one of the most important tropical species used by humans. In Brazil, its cultivation has been expanding in the recent years (Souza et al. 2020) and many diseases have emerged. The pestalotia spot, caused by Pestalotiopsis guepinii (Desm.), is a leaf disease of the coconut characterized by elliptic lesions with defined dark borders varying in size from 3 to 5 mm (Cardoso et al. 2003). In January of 2018, leaves with symptoms of pestalotia spot were obtained from ten year old coconut plants "dwarf variety" in a commercial planting in the city of Neópolis (10°20'S/36°42'W), Sergipe, Brazil. Disease incidence was 80% on 60 plants observed. Twenty samples of symptomatic tissues were collected and disinfested for 2 min in 1% sodium hypochlorite, washed in sterile water, placed on PDA (potato dextrose agar), and incubated at 25 ± 1°C with a 12-h photoperiod for 4 days. Five isolates were obtained, and pure cultures deposited in Phytopathogen Collection of the Federal University of Alagoas, accession numbers: COUFAL0240 to COUFAL0244. Seven day old colonies grown on PDA at 25°C, were whitish with aerial mycelium on the surface and abundant production of black conidiomata. Conidia were fusiform, straight to slightly curved with five cells, three median cells with brown coloring being the second and third being darker and the apical and basal cells, hyaline. Fifty conidia were measured and varied in size from 20.02-24.26 x 5.37-7.50 μm. The conidia presented two to four apical appendages and one basal appendage (Fig. S1). The morphological characteristics coincide with the Neopestalotiopsis foedans (Sacc. & Ellis), Maharachchikumbura et al. (2014). Molecular identification was conducted using partial nucleotide sequences from the ITS (ITS1/ITS4) region (GenBank no. MT605375 to MT605379) and from the genes TUB2 (Bt2a/Bt2B) (no. MT634202 to MT634206) and TEF-1α (526F/1567R) (no. MT634197 to MT634201). Besides that, the isolates grouped with the ex-type N. foedans species (CGMCC 3.9123) in a phylogenetic tree of Bayesian inference using concatenated sequences (Fig. S2). The pathogenicity was confirmed on seedling from coconut plants "dwarf variety" maintained in a greenhouse. Four plants were used, being one as a control. Spore suspensions of 106 conidia mL-1 was prepared from a 7 days old culture (cultivated at 25ºC). Inoculations were performed by spraying the conidial suspension on two whole leaves per plant (wounded and unwounded). In the control, sterilized distilled water was used. Plants were incubated at 25 ± 1°C and 100% relative humidity. Ten days after inoculation, depressed and necrotic lesions were observed in 100% on the inoculated leaves with wound. No symptoms observed on unwounded leaves, nor in the control treatment. To complete Koch's postulates, the N. foedans fungus was successfully re-isolated from the symptomatic leaves and identified phenotypically in optical microscope. Neopestalotiopsis foedans has already been reported in Calliandra haematocephala (Hassk), Neodypsis decaryi (Jum.), Rhizophora mangle (L.), Thuja occidentalis and Psidium guajava (L.) (Saccardo, 1882; Maharachchikumbura et al. 2014, Solarte et al. 2018). However, this is first report of N. foedans causing leaf spot in coconut in the world. The pestalotia spot is commonly observed in Brazil in C. nucifera and should be considered an important disease for this culture, as this can significantly reduce its photosynthetic area.
Keywords: Causal Agent; Crop Type; Etiology; Fungi; Subject Areas; Tropical plants.