NEW SPECIES AND RECORDS OF XYLARIACEAE AND THEIR ALLIES FROM GUYANA WITH EMPHASIS ON ELUCIDATING THE BIOLOGY AND ECOLOGY OF XYLARIA KARYOPHTHORA, A PUTATIVE PATHOGEN OF GREENHEART (CHLOROCARDIUM SPP.) SEEDS

Over the last two decades, mycoflorostic studies undertaken in Guyanese forests have uncovered hundreds of new fungal species and genera. One of the recovered fungal families was the Xylariaceae, although most were not identified to species. Members of this family play ecological roles as decomposers, endophytes, and pathogens of vascular plants and grass species. In addition, this group is increasingly recognized as a significant source of novel metabolic products with potential for applications in medicine, agriculture, and industrial biofuel. Given its potential, we took a more targeted approach to the documentation of this group. Our sampling efforts drawing on more than two decades of field collections yielded ca. 90 species in 12 genera, including a putative pathogen, Xylaria karyophthora of the seeds of Chlorocardium spp (Greenheart). Despite the significance of Greenheart to the Guyanese economy, little is known about the biology and ecology of this fungus. Due to the lack of available resources to study this fungus, our objectives were two-fold: first, to sequence and annotate the genome of X. karyophthora to provide a resource for genome-centric explorations, and to use this genome to infer the biology and ecology of this fungus. We focused on identifying and characterizing secretomes, viz. carbohydrate-active enzymes (CAZymes) and secondary metabolites biosynthetic gene clusters (SMBGCs) to infer the nutritional strategy of this fungus. Our results suggest that X. karyophthora has the capacity to act as both an endophyte and a pathogen. To make further inferences about the population, we used SSR markers to elucidate the genetic diversity and population structure of X. karyophthora. X. karyophthora populations have high genetic diversity, potentially exploiting both outcrossing and inbreeding reproductive strategies, and demonstrate a pattern consistent with human-mediated spread. This work will contribute information on new species and records of Xylariaceous fungi and their allies from Guyana with particular emphasis on unraveling the epidemiology, genetic diversity, and population structure of X. karyophthora.