Cryopreservation of in vitro-produced basidiospores of Oncobasidium theobromae Talbot & Keane

Oncobasidium theobromae Talbot & Keane is the causal pathogen of vascular-streak dieback (VSD) of cocoa in Asia and Papua New Guinea. Disease resistance is considered the most effective for controlling VSD. Resistance screening require a regular supply of basidiospores, the only known propagules. A method was developed to produce basidiospores in vitro by exposing cultures to saturated moist air generated by a humidifier. The spores were viable and infective on cocoa. Since they readily germinate in water, the ability to preserve them in liquid nitrogen is useful for synchronising the presence of both susceptible host and infective inocula. This paper reports a study to test the viability of in vitro-produced basidiospores of O. theobromae stored in liquid nitrogen.