Improvement of techniques for potato blackspot evaluation and some errors associated with measurements

Potato blackspot is a sub-epidermal blackening of tissue that results when bruising forces rupture cells of susceptible tubers. Degree of blackspot susceptibility is measured by bruising tubers and assessing the amount of discoloration that develops. Since the rate of color development is influenced by temperature, all testing was done at 21 C. Blackspot intensity was evaluated by visual inspection and by use of a photo reflectometer. A high correlation exists between reflectometer measurements and visual observations.