Observation of cell size and cell number to determine the difference between small- and large-fruited grape genotypes

The cell area of large- ('Autumn Royal' and 'B95-168') and small-genotype ('Thompson Seedless' and 'Flame Seedless') grapes [Vitis vinifera] was recorded from pre-bloom through berry maturity. Cell area was determined by acquiring a digital image with the use of an epiflourscent microscope. Then using a computer program, the mean cell area was determined for each sampling date. Through calculation, cells per longitudinal cross-section were also determined. At veraison there was a large difference in berry size between the large- and small-genotype berries, but there was no significant difference in cell size, making cell count the contributing factor to larger berry size. Shortly after veraison, the large-genotype berries showed rapid cell growth, adding to berry size differences between the large- and small-genotypes. The results suggest that cell division earlier in berry development and cell enlargement later in berry development both contribute to larger fruit size.