Palmeiromyces chamaeropicola D.R.S. Pereira & A.J.L. Phillips, Phytopath. Mediterr. 59(2): 360 (2020) (Figure 1)
MycoBank number: MB 834639; Index Fungorum number: IF 834639; Facesoffungi number: FoF11394;
Etymology: Named for Chamaerops humilis, the host genus from which it was collected.
Holotype: AVE-F-11 Leaf spots sunken, circular to broadly ellipsoidal, 3–7 × 2–3 mm (mean ± SD = 4.67 ± 1.06 × 2.52 ± 0.51 mm), identical on both leaf surfaces, brown-grey to yellowish centre, later becoming greyish and fragile, with a dark-brown border (ca. 1 mm wide), surrounded by a conspicuous yellow or brown to red-brown halo, occasionally coalescing, randomly distributed. Mature leaf spots contain several immersed ascomata. Ascomata pseudothecial, amphigenous, subepidermal, immersed to erumpent, scattered or clustered in groups of two or three, globose to subglobose, dark-brown, up to 90 μm diam., ostiolate. Ostiole circular, up to 21 μm diam., aperiphysate. Peridium thin-walled, composed of cells forming a textura angularis, outer layer composed of thick-walled, dark-brown to brown cells, inner layers composed of thin-walled, hyaline cells. Pseudoparaphyses absent, but pseudoparenchymatous, cellular hamathecium remnants present. Asci bitunicate, outer wall up to 2 μm thick, fissitunicate, pyriform to obovoid, slightly curved, broader at the base, well-developed ocular chamber, smooth-walled, hyaline, 8-spored, 21.4–57.9 × 8.2–19.1 μm (mean ± SD = 33.22 ± 9.69 × 14.20 ± 3.75 μm, n = 11). Ascospores biseriate, broadly ellipsoidal to subcylindrical, with rounded ends, occasionally slightly curved, hyaline, smooth- and thin-walled, guttulate, medianly 1-septate, not to slightly constricted at the sep- ta, 9.5–21.9 × 2.8–5.5 μm (mean ± SD = 17.31 ± 3.23 × 4.05 ± 0.72 μm, n = 50); mean ± SD ascospore length/ width ratio = 4.30 ± 0.58 (n = 50).
Material examined: PORTUGAL, Oeiras, National Sports Centre of Jamor, on leaf spots of Chamaerops humilis (Arecaceae), 20 September 2018, Alan J.L. Phil- lips (holotype AVE-F-11, ex-type living culture CDP 001).
GenBank Numbers: ITS: MT068628; LSU: MT076194.
Distribution: Oeiras, Portugal.
Host: Chamaerops humilis.
Notes: Palmeiromyces chamaeropicola was found associated with leaf spots of C. humilis, but pathogenicity has not been tested. Nevertheless, there is evidence that this species represents an obligate biotroph causing a previously undescribed disease on C. humilis. Phylogenetically, P. chamaeropicola is closely related to genera in Teratosphaeriaceae (Figure 2). Morphology of the sexual morph, ascospores with a peculiar mode of germination, lack of an asexual morph and very slow growth in culture correspond to genera in Teratosphaeriaceae (Crous et al., 2007). However, ascospores of P. chamaeropicola lack mucous sheaths, which is a characteristic of Teratosphaeriaceae (Crous et al., 2007; Quaedvlieg et al., 2014).
Figure 1. Palmeiromyces chamaeropicola (CDP 001, ex-type). a, Leaf spots on segments of Chamaerops humilis. b and c, Appearance of ascomata on host leaf surface. d, e and f, Asci and cellular hamathecium remnants. g, Immature ascospores (black arrows indicate remnants of cellular hamathecium). h, i and j, Mature ascospores. k, l, m and n, Germinating ascospores (k, after ca. 6 h incubation; l, after ca. 12 h incubation; m, after ca. 24 h incubation; n, after ca. 48 h incubation). o. Three-month-old colony on 1/2 PDA. Scale bars: a = 10 mm, b = 0.5 mm, c = 30 μm, d, e and f = 5 μm, g, h, i and j = 2.5 μm, k, l, m and n = 5 μm, o = 1 mm.