CONIDIOGENESIS IN CERATOCYSTIS ULMI,CERATOCYSTIS PICEAE,AND GRAPHIUM PENICILLIOIDES

Conidiogenous cells of both the synnematous and mononematous conidiophores in Ceratocystis ulmi and C. piceae develop by sympodial proliferation. Holoblastic conidia are produced on nodules or short denticles from the synnematous conidiogenous cells and on well-defined denticles from the mononematous conidiogenous cells. Graphium penicillioides is characterized by percurrent proliferation of the conidiogenous cells and the conidia are holoblastic and annellidic. A comparison of the type material of G. penicillioides with the lectotype specimen of C. piceae indicates that G. penicillioides is not the conidial state of C. piceae. The method of conidial development in C. ulmi and C. piceae is distinct from that of G. penicillioides, the lectotype species of Graphium; these conidial states are, therefore, placed in a new hyphomycete genus, Pesotum, as the Pesotum state of Ceratocystis ulmi and C. piceae, respectively.