Pseudocoleophoma rhapidis Kular. & K.D. Hyde, 2022

Kularathnage, Nuwan D., Wanasinghe, Dhanushka N., Senanayake, Indunil C., Yang, Yunhui, Manawasinghe, Ishara S., Phillips, Alan J. L., Hyde, Kevin D., Dong, Wei & Song, Jiage, 2022, Microfungi associated with ornamental palms: Byssosphaeria phoenicis sp. nov. (Melanommataceae) and Pseudocoleophoma rhapidis sp. nov. (Dictyosporiaceae) from south China, Phytotaxa 568 (2), pp. 149-169 : 158-162

Pseudocoleophoma rhapidis Kular. & K.D. Hyde , sp. nov.

Index Fungorum number: IF559350; Facesoffungi number: FoF 10620, FIGURE 4

Etymology:—referring to the host genus, Rhapis .

Pathogenic, associated with leaf spots of Rhapis excelsa (Thunb.) A. Henry , appearing as scattered, brown spots. Sexual morph: Undetermined. Asexual morph: coelomycetes. Conidiomata 150–225 × 225–300 µm (x̅ = 200 × 280 µm, n = 10), pycnidial, solitary, scattered, immersed, covered with transparent epidermal tissues, uniloculate, subglobose, black, ostiolate. Ostiole apapillate. Pycnidial wall 20–25 µm wide, consisting of 4–7 layers of brown, thick-walled, compressed cells of textura angularis. Conidiophores reduce to conidiogenous cells. Conidiogenous cells 7–10 × 13–17 µm (x̅ = 9 × 15 µm, n = 20), phialidic, hyaline, smooth-walled, doliiform. Conidia 20–25 × 10–15 µm (x̅ = 22 × 13 µm, n = 20), oblong to obovoid, hyaline, aseptate, smooth, thin-walled.

Colony characters— Colonies on PDA incubating at 25 °C in dark, attenuated 2 cm after 2 weeks, circular, flat, smooth margin, slightly raised in the middle, white, without pigments in the media; reverse off-white. Cultures not sporulate within 30 days.

Material examined— China, Guangdong Province, Guangzhou city, Zhongkai University of Agriculture and Engineering (23°06’28.4”N 113°16’51.6”E), as leaf spots of Rhapis excelsa (Arecaceae) , 20 May 2021, N.D. Kularathnage, NDK 30-1 ( ZHKU 21-0010 , holotype), ex-type living culture ZHKUCC 21-0124 ; ibid. NDK 30-2, ( ZHKU 22-0004 , isotype), ex-type living culture ZHKUCC 22-0004 .

Disease Symptoms—Leaf-spots were observed on most of the leaves and mainly seen at the leaf margin and along the veins. The border of the spots was sometimes surrounded by a black line. Conidiomata were scattered in leaf-spots.

Notes—The combined ITS, LSU, SSU and tef- 1 α multilocus analysis showed that our Pseudocoleophoma strain, P. rhapidis is phylogenetically closely related to P. bauhiniae and P. flavescens . However, P. rhapidis forms a distinct subclade with moderate support, sister to P. bauhiniae . The comparison of the DNA sequence of ITS, LSU, SSU, and tef-1α loci of Pseudocoleophoma rhapidis with P. bauhiniae revealed base pair differences of 18/526, 5/859, 12/1026 and 72/928 respectively.

Pseudocoleophoma rhapidis was collected from leaf spots on Rhapis excelsa while P. bauhiniae and P. flavescens were collected from decaying pods of Bauhinia sp. and soil of a potato ( Solanum tuberosum L.) field respectively ( Jayasiri et al. 2019, Li et al. 2020). Pseudocoleophoma rhapidis differs from P. bauhinia in having oblong, aguttulate, large conidia while P. bauhinia has elongate, guttulate, small conidia. Pseudocoleophoma flavescens has small conidiomata and small conidia while P. bauhinia has large conidiomata and conidia ( TABLE 4 ). Our species is the first report of a Pseudocoleophoma species collected from China. Based on morphology and phylogeny, we introduce this strain as a new species, Pseudocoleophoma rhapidis .

Pathogenicity tests for Pseudocoleophoma rhapidis

The inoculated leaf tissues began to show symptoms ten days after inoculation. Initial symptoms were small, circular, brown spots that expanded slowly ( FIGURE 5 ). None of the control plants showed any disease symptoms. Disease symptoms on the host inoculated with mycelial plugs appeared later than on leaves inoculated with a conidial suspension. Leaf spots on inoculated plants were smaller than on naturally infected plants. The temperature was 15–25 °C during the test with no rainfall.

The pathogen was re-isolated from the leaf spots resulting from inoculation by both methods. The culture characteristics of the re-isolated strains were consistent with the inoculated strain and ITS sequences of those strains were identical to the inoculated strain, thus fulfilling Koch’s postulates. Conidiomata similar to the holotype were observed in microscope examination of leaf spots.

Figures

FIGURE 4. Pseudocoleophoma rhapidis (ZHKU 21-0010, holotype). a Habitat. b Leaf spots on Rhapis excelsa. c Conidiomata on substrate. d Cross-section of conidiomata. e, f Conidiogenous cells and conidia. g Conidia. h, i Colony on PDA (i from the bottom). Scale bars: d = 100 µm, e–g = 25 µm.

FIGURE 5. Pathogenicity test results of Pseudocoleophoma rhapidis inoculated into healthy, Rhapis excelsa plants. Infected leaves with disease symptoms at ten days post-inoculation with a Mycelial plug. b Conidial suspension. Close up of leaf-spots on leaves inoculated with c–e Conidial suspension. e Mycelial plug.