Pestalotiopsis piraubensis V.P. Abreu & O.L. Pereira, sp. nov.
Index Fungorum number: IF 556023; MycoBank number: MB 556023; Facesoffungi number: FoF 04861; Fig. 1
Etymology – Name refers to the city of Piraúba, state of Minas Gerais, Brazil, where the fungus was collected.
Holotype – VIC 44199
Asexual morph: Culture obtained by direct isolation from diseased guava fruits (Fig. 1a). On MEA, conidiomata sporodochial, globose, solitary, semi-immersed, black, exuding globose, dark brown to black conidial masses (Fig. 1d–e). Conidiophores indistinct, reduced to conidiogenous cells. Conidiogenous cells discrete, cylindrical or spathulate, hyaline, smooth-walled, 4–10 × 1.5–3 μm. Conidia fusoid, ellipsoid, straight to slightly curved, 4-septate, 25–33.5×5–7.5 μm, basal cell conic, hyaline, smooth and thin-walled, 4.5–7.5 μm long; three median cells doliiform, 15.5–20.5 μm long, minutely verruculose, concolourous, pale brown, septa darker than the rest of the cell (second cell from the base 5–7.5 μm long; third cell 4.5–6.5 μm long; fourth cell 5–7 μm long); apical cell 3.5–6 μm long, hyaline, cylindrical to subcylindrical, thin- and smooth-walled; with 1–3 tubular apical appendages, arising from the apical crest, unbranched, filiform, flexuous 12–25.5 μm long; basal appendage single, tubular, unbranched, centric, 2–6.5 μm long (Fig. 1f–h). Sexual morph: Not observed.
Culture characteristics – Colonies on MEA attaining 43 mm diam after 7 days at 25 °C, with a regular edge, whitish to pale yellow-coloured, with dense aerial mycelium and dark brown to black conidial masses (Fig. 1b). Colonies on PDA attaining 68 mm diam after 7 days at 25 °C, with irregular edge, whitish to pale yellow-coloured, with sparse aerial mycelium on the central surface and dark brown to black conidial masses (Fig. 1c).
Pathogenicity test – The inoculation method used consisted of the wounding of the detached fruits and on these, the mycelium plug, with the mycelial part facing the surface of the fruit was added. Causing fruit rot disease, seven days after the inoculation of healthy ripe guava fruits.
Material examined – Brazil, Minas Gerais, Piraúba, in a commercial orchard, on fruits of Psidium guajava L. (Myrtaceae), 20 January 2014, V.P. Abreu & O.L. Pereira (VIC 44199, holotype), ex-type living culture COAD 2165.
GenBank numbers – MH627381 (ITS), MH643773 (tub2), MH643774 (tef1-α).
Notes – Pestalotiopsis spp. were previously considered opportunistic pathogens that affect stressed plants (Coyier and Roane 1987). Pirone (1978) reported different species of Pestalotiopsis causing leaf spots on a range of ornamentals. However, in recent years, there has been an increase in reports of these pathogens causing widespread damage to several economically important crops (Keith et al. 2006; Ko et al. 2007; Rodrigues et al. 2014; Rosado et al. 2015; Solarte et al. 2018). Therefore, the increase of guava planting areas has contributed to the emergence of several diseases, and there is no data on the environmental requirements of Pestalotiopsis infection on guavas in Brazil, nor any studies on field epidemiology for these diseases or post-harvest management. The topology of the concatenated tree was similar to that of individual trees, thus, only the concatenated tree is presented here (Fig. 2). Molecular data showed that Pestalotiopsis piraubensis COAD 2165 did not group with any other species reported in the literature. Morphologically, P. piraubensis differs from P. trachicarpicola for presenting larger conidia. Pestalotiopsis piraubensis has 1–3 apical appendages and the other species have 2–4 (mostly 3). Pestalotiopsis kenyana and P. biciliata differ from P. piraubensis by having conidiomata pycnidial in culture on PDA. P. photinicola presents smaller conidia (18–24 ×4–5 μm) than P. piraubensis. Although most of the morphological characteristics did not differ so much, the most striking feature of P. piraubensis was the size of the conidiogenous cells, which was much smaller (4–10×1.5–3 μm diam), when compared to the other species. Phylogenetic analyses and morphological comparisons support the introduction of P. piraubensis as a new species within this genus. Besides that, this study may be helpful for further studies on the management of guava diseases.
Figure 1 – Pestalotiopsis piraubensis (VIC 44,199, holotype) a disease symptom on the fruit of Psidium guajava in a commercial orchard in the city of Piraúba, state of Minas Gerais, Brazil. b Colony on MEA (Malt Extract Agar) after 7 d at 25 ºC with a photoperiod of 12 h in the dark in Petri dishes (90×15 mm) (COAD 2165). c Colony on PDA (Potato Dextrose Agar) after 7 d at 25 ºC with a photoperiod of 12 h in the dark in Petri dishes (90×15 mm) (COAD 2165). d Conidioma sporulating on PDA. e Conidial masses. f Conidia (1–3 apical appendages). Scale bars: e=50 µm, f–h=20 µm
Figure 2 – Phylogram generated from Bayesian Inference analysis based on combined ITS, tub2 and tef1 sequence data for several closely related species in Sporocadaceae. Sequence data of type cultures, ex-type or ex-epitype obtained from Maharachchikumbura et al. (2014), Chen et al. (2017a, b), Akinsanmi et al. (2017), Liu et al. (2017) were included in this study. The combined genes sequence analysis included 61 taxa, which comprise total 1994 characters (557 characters for ITS, 830 characters for tub2, 607 characters for tef1-α), and outgroup taxon Neopestalotiopsis saprophytica MFLUCC 12–0282. Bayesian posterior probability are indicated at the nodes, and values≥0.95 are in bold. Isolate numbers are indicated after species names. The
ex-type or ex-epitype strains are in bold and black. The newly generated sequence is indicated in bold and blue