VEGETATIVE INCOMPATIBILITY IN DIAPORTHE AMBIGUA

Vegetative compatibility of strains of Diaporthe ambigua has not previ ously been examined. Single ascospore and single ascus strains, origin ating from individual apple, pear and plum rootstocks, were paired on freshly prepared oatmeal agar to determine if vegetative incompatibili ty could be detected in D. ambigua. Barrage reactions were evident as black lines along the zone of mycelial contact between expanding colon ies (vegetative incompatibility reaction). Strains from cankers within an area were of numerous vegetative compatibility groups (VCGs). Stra ins from adjacent rootstocks usually differed in VCG. D. ambigua has t he ability to outcross, and does so, despite its apparent homothallic nature. DsRNA-containing strains of D. ambigua developed a broad, clea r zone when paired with a dsRNA-containing strain from a different VCG .