A comparison of tuber shape and tissue composition of potato genotypes

Seven tuber attributes were measured for a number of cultivars and breeding lines: two shape indices for the length and flatness of the potato, one index for the narrowness of the pith, three volume parameters for the relative proportion of cortical, perimedullaryand pith zones of the potato, and specific gravity. The three index traits, specific gravity and volume of the pith zone showed highly significant genotype x year interactions. Significant genotypic and seasonal effects were usually detected for the three volume traits and specific gravity. The percentage volume of the cortical and perimedullary zones showed no genotype x year interactions. Correlations between the traits were estimated, and a factor analysis was performed based on the correlation matrix. One factor appeared to control the negative allometric relationship between the percentage volumes of the cortical and perimedullary zones, and another factor indicated the relationship between the length and flatness indices of the potato.