Influence of canopy position on the microstructural parameters of 'Forelle' pears and its link to mealiness

'Forelle' is the second most exported pear (Pyrus communis L.) cultivar from South Africa, but the fruit has the potential to become mealy. The variables that affect and lead to mealiness are not clearly understood, although it is thought that the position of the fruit in the canopy plays a large role in the fundamental mechanism involved. It has previously been shown that pears that become mealy have a predisposition to mealiness before ripening, in that the porosity in the neck region is larger for these fruit, than for fruit that will not become mealy. In order to test if this predisposition can be linked to the canopy position, the fruit were harvested from seven different trees and five different canopy positions, which included outer canopy fruit on the eastern and western sides, middle canopy fruit on the eastern and western sides and inner canopy fruit. The neck region was sampled with a 5.5 mm core sampler directly after harvest and scanned at 3 mu m resolution in the General Electric Phoenix NanoTom located at the Central Analytical Facilities at Stellenbosch University. The outer canopy fruit on the western side exhibited a lower connectivity of the pore space and smaller cell sizes, while the inner canopy fruit exhibited a higher connectivity of the pore space and larger cells. The connectivity of the pore spaces was positively correlated with the cell sizes, and negatively correlated with the total pore space. These observations were, however, not statistically significant and were repeated with a larger sample of fruit in 2017. The fruit harvested in 2017 showed statistically significant differences in density between the fruit in the outer canopy that became mealy and non-mealy, already at harvest. These results indicate that there are microstructural differences in freshly harvested fruit at different canopy positions and that these microstructural differences influence the ultimate mealiness of the ripened fruit.