Gibbago
Citation: Pem D et al. (2019) Mycosphere Notes 275-324: A morphotaxonomic revision and typification of obscure Dothideomycetes genera (incertae sedis). Mycosphere 10(1), 1115–1246
Gibbago E.G. Simmons, Mycotaxon 27: 108 (1986)
Saprobic or pathogenic on leaves and wood. Sexual morph: Undetermined. Asexual morph: Conidiophores straight or curved, mostly unbranched or rarely branched, pale brown, septate and solitary or 2–4 loosely fasciculate, erect, simple with a single apical conidiogenous locus which proliferate by means of a secondary conidiophore that arises immediately below the apical cell of the existing conidiophore, septate, slightly pigmented. Conidiogenous cells swollen at the apex, holoblastic, polyblastic, sympodial, hyaline to medium or dark brown, with occasionally 1–5 apical proliferations. Conidia formed singly at the tip of conidiogenous cell, sometimes catenate, pale to dark brown with the densely pustular wall, mostly ovoid to oblong, rounded at the base and round to conical at the apex, initially solitary, ellipsoid, beakless, pigmented, becoming transversely and longitudinal septate, with apical cells swelling slightly and producing secondary conidia similar to initial ones with distinct constriction at the median septum (Simmons 1986).
Type species – Gibbago trianthemae E.G. Simmons
Notes – The monotypic genus Gibbago was introduced by Simmons for the type species Gibbago trianthemae. The latter was isolated from leaves of Trianthema portulacastrum. The genus is characterized by loosely fasciculate, erect conidiophores, polyblastic, sympodial conidiogenous cells and ellipsoid, beakless, transversely and longitudinally septate brown conidia. Its sexual morph has never been reported. We have re-studied the isotype specimen of Gibbago trianthemae under the code NY00945973. The genus Gibbago was accommodated in Pleosporaceae by Simmons (1986) based on its morphological similarities with the genus Alternaria, Embellisia, Ulocladium and Stemphylium and this was followed by Wijayawardene et al. (2014). Only ITS sequence data is available for the putative strains of Gibbago trianthemae GT-VM and NFCCI 1886. In a previous study by Ariyawansa et al. (2015b), the strains Gibbago trianthemae GT-VM and NFCCI 1886 formed a distinct lineage basal to Paradendryphiella and Pleospora with low boostrap support. In our study, after nucleotide blast using the Basic Local Alignment Search Tool, DNA sequence of strains of Gibbago trianthemae were highly similar to species in the family Pleosporaceae. In the phylogenetic analyses of the ITS sequences, the two strains Gibbago trianthemae GT-VM and NFCCI 1886 formed a independent clade basal to Exserohilum and Setosphaeria with moderate bootstrap support (Fig. 1). We therefore, transfer Gibbago to Pleosporaceae following Ariyawansa et al. (2015b).
Figure 1 – Phylogram generated from maximum likelihood analysis based on ITS sequence data retrieved from the GenBank. Related sequences were referred to Wanasinghe et al. (2018). Sixteen-one taxa are included in the genes sequence analyses which comprise 618 characters after alignment. Neocamarosporium chichastianum (CBS 137502), Neocamarosporium goegapense (CPC 23676) are used as the out-group taxon. Maximum likelihood (ML) analysis was conducted in the CIPRES Science Gateway V. 3.3. The best sorting RAxML tree with a final likelihood value of -5725.732510 is presented. Estimated base frequencies were as follows: A = 0.231229, C = 0.247168, G = 0.234507, T = 0.287096; substitution rates AC = 1.411986, AG = 1.991610, AT= 1.292870, CG = 0.994088, CT = 3.032473, GT = 1.000000; gamma distribution shape parameter α = 1.220238; proportion of invariant 0.455010. ML bootstrap values ≥ 50% are given as the first set of numbers and approximate likelihood-ratio test (aLRT) ≥ 0.90 values as the second set of numbers above the nodes. Voucher/strain numbers are given after the taxon names, the one from type material are indicated in bold face. Sequence of interest is indicated in red. The bar length indicates the number of nucleotide substitutions per site.
References
Ariyawansa HA, Thambugala KM, Manamgoda DS, Jayawardena R et al. 2015b – Towards a natural classification and backbone tree for Pleosporaceae. 71, 85–139.
Simmons EG. 1986 – Alternaria themes and variations (22-26). Mycotaxon 25(1), 287–308.
Wijayawardene NN, Crous PW, Kirk PM, Hawksworth DL et al. 2014b – Naming and outline of Dothideomycetes–2014 including proposals for the protection or suppression of generic names. Fungal Diversity 69, 1–5.
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