INTERNAL DAMAGE IN POTATO-TUBERS - A CRITICAL-REVIEW

Literature describing the effects of genotype, development and environ ment on internal damage in potato tubers is re-examined with particula r reference to methods used to determine susceptibility. While there a re many reports illustrating genotypic differences, these are by no me ans all reliable and even those which employ acceptable methods suffer from comparisons under a relatively limited range of circumstances. C hanges in susceptibility with development and storage are not consiste nt and have not been extensively investigated. More information is ava ilable 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 ef fect is not large and is primarily observed for the potassium-deficien t range of concentrations. Relationships between internal damage and t uber properties are reconsidered and the strength of evidence for thei r roles evaluated. The relevance of tuber water status is given partic ular attention because there is strong evidence that it is of major im portance. A more quantitative approach to its characterization is requ ired for the information to be of practical value. In the light of the effects of applied potassium, variation in tuber potassium in relatio n to internal damage is explored. Its relationship with other tuber pr operties such as dry matter, water status, polyphenol oxidase and tyro sine concentration is examined together with the potential for these a s mechanisms underlying external factors.