Dothideomycetes » Macrovalsariaceae

Macrovalsaria

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

 

Macrovalsaria Petr., Sydowia 15(1-6): 298 (1962) [1961]

Saprobic on dead twigs, wood, bamboo and culms of a wide range of hosts. Sexual morph: Ascostromata dark brown to black, immersed to erumpent, solitary to a few in a group, carbonaceous, oblate, sphaeroid to subsphaerical, with a central ostiole. Peridium comprising brown and small-celled textura angularis. Asci 8–spored, bitunicate, fissitunicate, cylindro-clavate, with a short fine pedicel, apically rounded with a small ocular chamber. Paraphyses unbranched, tapering upwards, apically free. Ascospores uniseriate to irregularly uniseriate, 1– septate, brown, elliptical-fusoid, slightly constricted at septum, with skull cap-like germ apparatus at the lower end, transverse striation near the center of lower cell with longitudinal striations from transverse striation to the end cell, surface smooth, granular to verrucose. Asexual morph: Undetermined.

 

Type species Macrovalsaria leonensis (Deighton) Petr. 1962

 

Notes – Petrak & Deighton (1962) introduced the genus Macrovalsaria with M. leonensis (≡ Valsaria leonensis Deighton, in Petrak & Deighton 1952) as the type species. The genus Macrovalsaria has a global distribution in the tropics. Sivanesan (1975) examined the type specimen of M. megalospora (≡ Sphaeria megalospora Mont.) and several other specimens including M. leonensis (Deighton) Petr. (the generic type), and synonymised all of them under Macrovalsaria megalospora which is the primogenital epithet. The unique characteristic of the genus Macrovalsaria is the brown, uniseptate ascospores that are constricted at the septum and the skull cap-like germ apparatus at the base (Sivanesan 1975, Hyde et al. 2000). The asexual morph is unknown. Phylogenetic analysis carried out by Li & Zhuang (2009) based on 28S rDNA showed that the genus Macrovalsaria is related to Botryosphaeriales and in their analysis, two strains of M. megalospora clustered in the Lasiodiplodia. Cultures and sequences are available but not for the type species. In another study, Doilom et al. (2017) described Macrovalsaria megalospora from Tectona grandis in northern Thailand, provided voucher specimens and placed their voucher specimens to Dothideomycetes incertae sedis based on morphology and phylogenetic analysis. We re-studied the specimen of Macrovalsaria leonensis from PDD collected by Deighton under the code PDD 14987. The ascospores illustrated are re-drawn from Chacón et al. (2014) to show the diagnostic characters of the ellipsoidal ascospores namely, the helmet-like cover with striae toward one end and the occurrence of single septum. We carried out phylogenetic analysis with the strains provided by Li & Zhuang (2009) as well as those of Doilom et al. (2017). The strains of M. megalospora provided by Li & Zhuang (2009) clustered in the Lasiodiplodia which is inconclusive as the analysis was based only on 28S large ribosomal subunit RNA gene regions. In depth analysis using TEF (data not shown) and ITS sequences of the reference specimen of M. megalospora provided by Doilom et al. (2017) shows that M. megalospora forms an independent lineage close to Valsariaceae and closely related families in the Dothideomycetes (Fig. 20) in the order Pleosporales. The new family Macrovalsariaceae is introduced to accommodate the monotypic genus Macrovalsaria typified by M. leonensis. Macrovalsariaceae has dark brown to black ascostromata, cylindro-clavate with a short fine pedicel asci and elliptical to fusoid with skull cap-like germ apparatus at the lower end ascospores.