Assessment and analyses for the interpretation of potato late blight response in field studies

Potato seedlings and cultivars were successfully subjected to moderate to heavy late blight pressure in field plots to which a race complex of the pathogen was applied. Multiple assessments through the course of the epidemics revealed differences in overall disease susceptibility or resistance. Differences were also demonstrated in disease response patterns among potato lines with similar overall disease ratings. Use of principal component and cluster analyses established discrete groupings of potato lines. This provides a basis for a more objective interpretation of the results in identifying both overall disease response and pattern (slow or fast) of response of potato cultivars and breeding lines.