Stone Cell Frequency and Cell Area Variation of Crisp and Standard Texture Southern Highbush Blueberry Fruit

Sclerified stone cells with a thick and lignified secondary cell wall are known to vary in number among cultivars of northern highbush blueberry ( Vaccinium corymbosum ) and rabbiteye blueberry ( Vaccinium virgatum ), and may contribute to fruit texture. Variation in cell size can also contribute to differences in fruit firmness. Fruit from nine southern highbush blueberry [SHB ( V. corymbosum interspecific hybrids)] cultivars determined by sensory and instrumental analysis to vary in fruit texture were harvested at mature green and ripe blue developmental stages. Paraffin embedded 12-μm sections were stained with Safranin O and Aniline Blue and microstructure was examined by light microscopy. Stone cells within ≈1.2 mm of the epidermis were counted and cell area was measured in the epidermal layer and three layers beneath the epidermis of the fruit. There was a significant difference in cell area among genotypes and cell layers for mature green fruit and among texture types, genotypes, and cell layers for ripe blue fruit. The average number of stone cells in a single berry ranged from zero to 95 among cultivars. Significant differences in the number of stone cells just below the epidermal layer did not correspond to standard or crisp fruit texture.