Development of fruit quality traits and comparison of the fruit structure of two Vaccinium corymbosum (L.) cultivars

• Development of most blueberry quality traits is initiated in the early growth stage.
• ‘Earliblue’ and ‘Patriot’ differ in the fruit growth rate and the onset of the softening process.
• ‘Earliblue’ and ‘Patriot’ have common but also specific desirable quality traits.
• Differences concern fruit firmness and size, size of picking scar, skin thickness and number of sclereids.

Given their flavour values and high antioxidant content, highbush blueberry fruits are increasingly appreciated by consumers, and the area of cultivation of the species is constantly growing. Mature fruits of various cultivars differ in many quantitative morphological and sensory traits. The structure of the fruits of two Vaccinium corymbosum cultivars ‘Earliblue’ and ‘Patriot’ was compared in three developmental stages using light microscopy and scanning electron microscopy. Special attention was paid to the initiation and rate of development of the most important traits associated with the fruit quality, in particular those that have an impact on fruit firmness and shelf life. It was found that the analysed cultivars were characterised by a varied rate of fruit development, and initiation of many quality traits in fruit micromorphology and anatomy took place in an early stage of development (hypanthium stage). The mature fruits of ‘Patriot’ exhibited a smaller size of the picking scar and higher firmness; they were also larger and heavier than ‘Earliblue’. In turn, the ‘Earliblue’ fruits had a thicker skin and a greater number of stone cells. Moreover, the fruits of both cultivars were characterised by presence of a small number of stomata and shallow microcracks as well as waxy bloom, which had a similar form in both cultivars, and by similar distribution of various forms of tannin and anthocyanin deposits. Cellular structure of fruits has an impact on the firmness and shelf life of blueberries.