Coniella eucalyptorum (Crous & M.J. Wingf.) L.V. Alvarez & Crous, Stud. Mycol.

Brahmanage, Rashika S., Wijayawardene, Nalin N., Nanayakkara, Chandrika M., Muthumala, Chaminda K., Wijesundara, Siril, Dai, Dong Q. & Ariyawansa, Kahandawa G. S. U., 2023, Eucalyptus leaf spot disease caused by Coniella eucalyptorum in Sri Lanka, Phytotaxa 630 (1), pp. 40-50 : 43-45

Coniella eucalyptorum (Crous & M.J. Wingf.) L.V. Alvarez & Crous, Stud. Mycol. 85: 15 (2016)

Index Fungorum Registration Identifier 817817, Fig. 2

Basionym: Pilidiella eucalyptorum Crous & M.J. Wingf. , in Van Niekerk, Groenewald, Verkley, Fourie, Wingfield & Crous, (2004).

Pathogenic on leaves of E. camaldulensis . Sexual morph: Undetermined. Asexual morph: Conidiomata 80−140 μm long, 150−200 μm in diameter (n= 15), solitary or aggregated, globose, brown, and dark brown to black from the top. Conidioma wall consisting of 2–3 layers of hyaline textura prismatica and 4−5 layers of brown textura angularis cells. Conidiogenous cells 12–15 × 1–2 μm (x̄ = 13 × 2 μm, n = 20), annellidic, narrowing at the tip, smooth and hyaline. Conidia 10−13 × 3−6 μm (x̄ = 12 × 5 μm, n = 30), hyaline to pale brown, becoming dark brown at maturity, smooth, broadly ellipsoidal, both sides gradually tapering, smooth-walled, and multi-guttulate with one or two prominent guttules.

Culture characteristics: Colony on PDA reaching 25 mm diameter after seven days at 25 °C, colony circular, margin wavy, flat, velvety appearance, colony from above: pale pink to brown; reverse: light brown to dark brown.

Material examined: Sri Lanka, North Central Province, Polonnaruwa District, Aralaganwila , (Latitude 7.293889 Longitude 81.2109594) on leaves of E. camaldulensis , 5 th of May 2022, Rashika S. Brahmanage, RB-LP31, ( NIFSCC-RB-LP31 , UOCCC-RB-LP31 )

GenBank accession numbers: ITS = OR141147 , LSU = OR143784 , tef1-α = OR461287

Notes: Based on the morphological characteristics, our strain (NIFSMC-RB-LP31) is similar to the holotype of Coniella eucalyptorum (CBS 112640) collected from the leaves of Eucalyptus grandis × E. tereticornis hybrid ( Alvarez et al. 2016). According to multi-gene phylogeny (ITS, LSU, and tef1-α), our strain (NIFSMC-RB-LP31) clustered with other strains of C. eucalyptorum (CBS 111023, CBS 112640, CBS 114134, and MFLU 17-0675) with 100% ML and 1.00 PP bootstrap support ( Fig. 1 ). When comparing the ITS, LSU, and tef1-α gene regions, no base pair (0%) differences were observed between our strain (NIFSMC-RB-LP31) and the holotype of C. eucalyptorum (CBS 112640). Coniella eucalyptorum was previously recorded in Australia, Brazil, Chile, Indonesia, Malaysia, Mexico, Thailand, Venezuela, and Vietnam ( Hyde et al. 2020). Therefore, we identified our fungal collection as the first geographical record from Sri Lanka.

Pathogenicity assay

Results of the pathogenicity test showed that the RB-LP31 strain (identified as C. eucalyptorum ) can cause disease on only wounded host leaves. The initial symptoms were seen on wounded leaves after two to three days of inoculations with mycelial plugs ( Fig. 3 , e 1 – e 4). Small light-brown to brown lesions emerged at the inoculation site of the leaves. Subsequently, these lesions rapidly enlarged (diameter 2 – 5.5 cm) and transformed into brown to dark brown lesions after five days of inoculation. Symptoms continuously spread, and sparse white mycelia appeared on the lesions three days post-inoculation and subsequently spread throughout the host leaf. Initial symptoms were seen on wounded leaves treated with spore suspensions of C. eucalyptorum after 10–12 days of inoculation ( Fig. 3 , a 1 – a 4), and 1–3 cm lesions appeared after 16 days of inoculation. Non-wounded leaves inoculated with both spore suspensions and mycelial plugs showed no symptoms even after 16 days of inoculation ( Fig. 3 , b and f), similar to the negative control treatments ( Fig. 3 , c, d, g, and h). Based on the morphological characteristics, we identified the re-isolated fungus as C. eucalyptorum .

Figures

FIGURE 1. Phylogram generated for Coniella species from ML and BI analyses based on a combined dataset of ITS, LSU, and tef1-α sequences. The tree is rooted with Melanconiella sp. (CBS110385). Bootstrap support values for ML ≥ 65 % and Bayesian posterior probabilities (PP) ≥ 0.95 are shown at the nodes. The strain from the current study is in red. All ex-type strains are in bold black. Some branches were shortened to fit them to the pages, and these are indicated by two diagonal lines with the number of times a branch was shortened indicated next to the lines.

FIGURE 2. Coniella eucalyptorum (NIFSMC-RB-LP31) a–b Disease symptoms on the leaves of Eucalyptus camaldulensis. c–d Appearance of Conidiomata on E. camaldulensis. e Wall of conidiomata. f Conidiogenous cell. g–i Conidia. j Above view of the culture on PDA k Reverse view of the culture e = 50 μm, f–i = 20 μm.

FIGURE 3. Pathogenicity test results for C. eucalyptorum on E. camaldulensis leaves. a1–a4 wounded leaves inoculated with C. eucalyptorum spore suspensions. b1–b2 non-wounded leaves inoculated with C. eucalyptorum spore suspensions. c1–c2 non-wounded leaves inoculated with sterile water (control). d1–d2 wounded leaves inoculated with sterile water (control). e1–e4 wounded leaves inoculated with C. eucalyptorum mycelial plugs. f1–f2 non-wounded leaves inoculated with C. eucalyptorum mycelial plugs. g1–g2 wounded leaves inoculated with sterile PDA plugs (control). h1–h2 non-wounded leaves inoculated with sterile PDA plugs (control).