DETERMINING THE FEASIBILITY OF MEASURING GENOTYPIC DIFFERENCES IN SKIN-SET

Replicated experiments with various potato cultivars having diverse tuber skin types demonstrated that the Halderson periderm shear tester was sufficiently sensitive to measure genotypic and phenotypic differences in skin-set (periderm maturity). All genotypes had lower skin-set readings at the bud end of the tuber compared to the equatorial region and stem end. The technique employed with the shear tester objectively resolved genotypic differences in the developmental time courses for skin-set and clearly showed that the periderm of Russet Burbank tubers matured more rapidly than the periderm of other cultivars with smooth skin types. However, a consistent relationship between periderm weight and skin-set could not be established. In postharvest experiments designed to describe the phenotypic effect of temperature and relative humidity on tuber periderm maturation, we found that high relative humidity retarded the development of skin-set. The ability to detect genotypic and phenotypic differences with this technique for measuring skin-set indicates that it is feasible to further develop a standardized procedure suitable for testing diverse skin types in breeding and certified seed programs as well as for use by growers of table stock, seed, and chipping potatoes.