PRODUCTION AND USE OF CALLI FROM YELLOW BIRCH BUDS FOR IN-VITRO ASSESSMENT OF VIRULENCE OF NECTRIA-GALLIGENA ISOLATES

Field studies of perennial Nectria canker of northern hardwoods, cause d by the ascomycete fungus Nectria galligena, are time-consuming since the disease develops slowly on the stem of trees. In this report, an in vitro bioassay is described for determining and comparing the virul ence of different isolates of Nectria galligena by using calli produce d from yellow birch buds. The technique facilitates the distinction be tween highly virulent and less virulent isolates of the pathogen withi n one week following the inoculation.