Poster Session: Mycology

95-P

Conidia viability and cytology in Moniliophthora roreri, the causal agent of frosty pod rot of cacao.
J. R. DIAZ VALDERRAMA (1), M. C. Aime (1)
(1) Purdue University, West Lafayette, IN, U.S.A.

Moniliophthora roreri causes frosty pod rot disease in cacao. Yield losses of close to 100% have been recorded and in many cases entire plantations have been abandoned because of the disease. Before the 1950’s frosty pod rot was confined to the north-western part of South America but recently it has spread northwards as far as Mexico and southwards into Peru. Currently frosty pod rot represents a serious threat to cacao growers in Bolivia, Brazil, and even West Africa. M. roreri is only known to reproduce via conidia, and therefore it is important to know how long spores may remain viable in the field, especially after a farm is abandoned. We have found that a small proportion of spores maintain viability for at least 14 months in vitro. Two varieties of M. roreri have been formally described, M. roreri var. roreri and M. roreri var. gileri. These are differentiated by host (the latter is confined to T. gileri, rather than T. cacao) and differences in spore size. However, our studies show that spore size in M. roreri is quite variable and is due to nuclei number, which is also quite variable. Finally, we have conducted multiple generations of single spore isolation and cytological studies as well as analyses of multiple genetic markers to infer whether this fungus is potentially outcrossing. These and other results will be discussed.