Internal damage in potato tubers: A critical review

Literature describing the effects of genotype, development and environment on internal damage in potato tubers is re-examined with particular reference to methods used to determine susceptibility. While there are many reports illustrating genotypic differences, these are by no means all reliable and even those which employ acceptable methods suffer from comparisons under a relatively limited range of circumstances. Changes in susceptibility with development and storage are not consistent and have not been extensively investigated. More information is available on soil-related factors, particularly potassium fertilizer, for which there is fairly compelling evidence of a significant reduction in susceptibility with increasing rate of application. However, the effect is not large and is primarily observed for the potassium-deficient range of concentrations. Relationships between internal damage and tuber properties are reconsidered and the strength of evidence for their roles evaluated. The relevance of tuber water status is given particular attention because there is strong evidence that it is of major importance. A more quantitative approach to its characterization is required for the information to be of practical value. In the light of the effects of applied potassium, variation in tuber potassium in relation to internal damage is explored. Its relationship with other tuber properties such as dry matter, water status, polyphenol oxidase and tyrosine concentration is examined together with the potential for these as mechanisms underlying external factors.