Evaluation of the pathogenicity of <i>Phoma exigua</i> var <i>exigua</i> on Californian thistle

Abstract

Pathogenicity of isolates of Phoma exigua var exigua Desm on detached wounded Californian thistle (Cirsium arvense (L) Scop) leaves was determined by measuring lesion development after inoculation with conidial solutions (1 x 10⁵ spores/ml) Results showed significant lesion development by all six test isolates compared to control treatments but inconsistent lesion development was observed between isolates and between assays The six isolates also gave greater (P<005) lesion development than the control treatment 18 days after inoculation of wounded Californian thistle leaves on whole plants with no significant differences in lesion development between isolates For whole plants and detached leaves lesion development correlated with the recovery of P exigua var exigua from lesion sites