Archivio Journal of Plant Pathology

Abstract:

Four oomycetes (Pythium aphanidermatum, Pythium dissimile, Pythium papillatum and Phytophthora nicotianae) and three plants (Lucerne, sugarbeet and tomato) were used in order to study the effects of species diversity on zoospore encystment and pathogenicity. The plant intra-specific variation affected the number of P. aphanidermatum zoospores that encysted in the elongation zone of lucerne and tomato seedlings but not of sugarbeet. Differences in encystment were not reflected in disease severity with the exception of root reduction of lucerne seedlings. Differences in zoospore encystment between isolates of P. aphanidermatum and Ph. nicotianae were reflected to the severity of disease symptoms caused only on lucerne seedlings. The mixed inoculum experiment indicated that in most combinations the encystment density was intermediate between the observed for single oomycete inoculations. Disease symptoms of the mixed inocula varied and either resembled the symptoms caused by one oomycete or did not differ from the symptoms caused by single inoculations.