New Species and Records of Carbonaceous Ascomycetes from Guyana, Including a New Potential Pathogen of Greenheart

Dillon Raynel Husbands, Purdue University

Abstract

Greenheart (Chlorocardium spp.) is Guyana’s most marketable timber species. Greenheart wood is one of the densest in the world and it is regarded as durable due to near immunity to decay, resistance to termite damage and its ability to withstand biodegradation in saline conditions for extensive periods, thus greatly coveted for dock and harbor applications. The seeds of greenheart are known to contain volatile secondary compounds that are believed to provide defense against predation by other organisms. During 2010–2016, an unusual Xylaria sp. was documented growing from morbid seeds of both C. rodiei and C. venenosum in both natural and logged forests of central Guyana. Combined teleomorphic and molecular characteristics indicate that the fungus represents a new species and is described here as Xylaria karyophthora . Despite more than a decade of silvicultural research with special emphasis on greenheart regeneration, there are no reported cases of seed pathogens of greenheart until 2002 when Xylaria stromata were observed fruiting on Chlorocardium seeds of the Iwokrama Forest Reserve. Visual observations indicated that ca. 80% of dispersed seeds were infected with Xylaria stromata at all sampled sites. The exact time of introduction of this fungus is unclear, although our examination of these historical records would indicate that it was sometime after 1980 but before 2000. The discovery of this putative pathogenic Xylaria on greenheart underscores the need for continued and strategic documentation of fungal diversity in Guyana. These documentation efforts can contribute immensely to the development of a database for resident macromycete diversity that will provide a knowledge base to help recognize other potential phytopathogens, as well as endemic beneficial species. This thesis is therefore organized into three chapters with each contributing to the overall information on new species and records of ascomycetes from Guyana. Chapter I presents a historical review and commentary on key silivcultural and mycofloristic research in relation to the emergence of Xylaria karyophthora in Guyana. It highlights the strong emphasis of these silvicultural studies on greenheart regeneration and the absence of pathogen associated constraint to seed germination and recruitment. Further, a timeframe of these studies and the emergence of Xylaria karyophthora is also provided. Chapter 2 presents Xylaria karyophthora: A new seed-inhabiting fungus of greenheart from Guyana. It includes information on the macromorphological, micromorphological, cultural, DNA sequence data and a preliminary distribution data for this fungus. Chapter 3 documents other species of carbonaceous fungi from Guyana. Illustrations, descriptions, molecular data and notes on three species representing two families, Xylariaceae and Bertiaceae, are presented here. Xylaria tuberoides ( Xylariaceae) and Bertia tropicalis (Bertiaceae) are new record from Guyana and Phylacia cf. poculiformis (Xylariaceae) is re-described from new materials from Guyana.

Degree

M.S.

Advisors

Aime, Purdue University.

Subject Area

Botany

COinS