Phialide

Abstract: For the morphological classification of the fungi discussed in this chapter three terms are used in the literature with overlapping meaning: black yeasts, meristematic fungi and microcolonial fungi (MCF) As will be described later, because of pleomorphic behavior the clear separation of fungi into one or the other group is impossible and fungi can just be clustered into one of those form groups according to their predominating morphological characteristics “Black yeast” is a terminus technicus subscribing a group of fungi that is quite heterogeneous from the taxonomic and phylogenetic point of view but having in common melanized cell walls and the formation of daughter cells by yeast-like multilateral or polar budding (Fig 201) The resulting daughter cells may be encapsuled in a matrix of extracellular polymeric substances (EPS) Most black yeasts additionally exhibit mycelial growth and generate conidia from simple phialides, from phialides with collarettes, from annelated phialides, on rhachides or on undifferentiated conidiogenous cells (de Hoog and Hermanides-Nijhof 1977) Conidia may be unseptated or otherwise have up to three transversal septa Also the formation of arthroconidia from fragmenting hyphae can occur in some genera Only very few species, for example, Phaeococcomyces exophialae, do not form any hyphal states The term “meristematic fungi” was introduced by de Hoog and HermanidesNijhof (1977) for fungi that form aggregates of thick-walled, melanized cells enlarging and reproducing by isodiametrical division (Fig 202) Propagules are liberated by breaking apart of aggregates as in the genus Sarcinomyces (Fig 203) or by endogenous conidiogenesis with subsequent disruption of the mother cell wall as in the genus Phaeotheca Some meristematic fungi might form blastic conidia from fairly undifferentiated cells, for example, in Capnobotryella, or even yeast-like budding cells as in Hortaea werneckii Thus, some meristematic fungi can also be Chapter 20

Abstract: Four varieties of Gibberella fujikuroi are described on the basis of mating groups, variation in ascospore and perithecial size, phialide type, and microconidial formation. The varietal type, G. fu...

Abstract: Species of Trichoderma and Hypocrea that have green conidia and sterile or fertile elongations of their conidiophores are described or redescribed and their phylogenetic position explored. The described species include T. crassum, T. fasciculatum, T. fertile, T. hamatum, T. longipile, T. oblongisporum, T. pubescens, T. spirale, T. strictipile, T. strigosum, T. stromaticum, T. tomentosum, Hypocrea aureoviridis f. macrospora, H. ceramica. and H. semiorbis. Trichoderma fasciculatum originally was described from cultures from ascospores of an unidentified Hypocrea specimen; it is considered to be a synonym of T. strictipile. The remaining species of Trichoderma considered here have not been linked to teleomorphs, and the Trichoderma anamorphs of H. aureoviridis f. macrospora and H. semiorbis have not been named. Five new species of Hypocrea are described, viz. H. cremea, H. cuneispora, H. estonica, H. strictipilosa and H. surrotunda. The phylogenetic relationships of these species were inferred based on partial RPB2 and EF-1α DNA sequence data and phenotypic characteristics, including teleomorph, anamorph, colony and growth rates. Trichoderma crassum was found to be a sister species to T. virens, based on molecular sequences and phenotypic data. Hypocrea surrotunda and H. cremea, H. cuneispora and T. longipile, T. fertile and T. oblongisporum, T. tomentosum and H. atrogelatinosa, and T. hamatum and T. pubescens, respectively, were found to be closely related phylogenetically, based on RPB2 and EF-1α gene genealogies. Anamorph and teleomorph phenotype, including conidiophore elongations, phialide morphology, conidial morphology, stroma anatomy and ascospore morphology are not useful predictors of relationships. Despite the shared phenotypic characters of these Trichoderma and Hypocrea species, they are distributed between two major clades of Trichoderma/Hypocrea. Redescriptions and a key to species of Hypocrea/Trichoderma with green conidia and conidiophore elongations are presented.

Abstract: New definitions of the form-genera Phoma Sacc. and Ascochyta Lib., based on developmental criteria, are presented. Phoma species show phialidic ontogeny. The first conidium is produced within a papillate protrusion of the undifferentiated parent cell; after a conidium secedes the basal part of the papilla remains as a collarette on the conidiogenous cell which may show two or three layers corresponding with the layers of the original papilla. The conidia secede by a three-layered septum and are in principle one-celled, although secondary septation may occur, especially in vivo (0-95%). In vitro under normal laboratory conditions the majority of conidia however always remain one-celled. The pycnidia are usually glabrous but also may be hairy or setose. Ascochyta species show annellidic ontogeny. The conidia arise as relatively thin-walled protrusions from undifferentiated parent cells. The secession of successive conidial primordia by a three-layered septum however may occur at approximately the same level, resulting in an increasing collar of periclinal annellations, which under the light microscope looks like the collarette of a phialide. After or incidentally also before secession the conidia become two(or more-) celled by invaginations of a newly produced inner wall layer (distoseptation). In this genus therefore conidial septation is an essential part of the conidium completion, which explains that in vivo as well as in vitro the conidia are always mainly two- (or more-) celled. The pycnidia are glabrous or sometimes hairy. These new generic concepts imply that most of the species usually placed in Ascochyta viz. those in Ascochyta sect. Phyllostictoides Zherbele, belong to Phoma as are many species at present placed in Phyllosticta, Diplodina and Pyrenochaeta. Pyrenochaeta mali Smith is shown to be identical with Phoma herbarum. For Pyrenochaeta acicola (Lev.) Sacc. the new name Phoma leveillei is introduced.