The influence of cultivar and mechanical damage on the relationship between inoculum concentration of Phoma exigua var. foveata on potato tubers and gangrene development

Abstract

In an experiment to examine the influence of cultivar and tuber damage on the relationship between inoculum concentration and potato gangrene development, the extent to which cultivars differed in their response to increased inoculum concentration depended on the type of damage which the tubers received. There was considerable variation in cultivar response in terms of lesion frequency when tubers were inoculated by damaging them on a commercial grader, whereas when they were uniformly wounded or left undamaged cultivar differences were small. The relationship between the number of detectable wounds on tubers and gangrene incidence was not consistent for the three cultivars. Lesion size was shown to increase linearly with increasing concentrations of pycnidiospores when tubers of cultivars of different susceptibilities were point‐inoculated.