Mechanical investigation to assess the peel contribution in apple fruit

Fleshy fruit are generally stored before consumption, especially apple, during which, however, several diseases and disorders can occur. Mechanical handling and transportation can in fact cause general wounding, leading to dramatic quality decay and fruit loss, with a consequent negative economic impact. Although the majority of the investigations addressed to fruit quality aspects have been to date mainly focused on flesh, is the multi-layered peel tissue complex that represents the first natural barrier of a fruit. In this study, a texture analyzer was employed to investigate the peel contribution on the general fruit firmness behavior in apple, assessing a germplasm collection composed by 65 accessions after two months of cold storage. This device generated a mechanical force-displacement profile on which a set of analytical parameters was identified. The comparative analysis between intact and peeled portions performed on each single fruit, enabled the characterization of the contribution of peel on fruit firmness. By the general representation of the phenotypic variance related to the peel effect over the apple collection assessed by multivariate statistical approach, two clusters were identified, highlighting a specific set of apple cultivars distinguished by a superior peel contribution. The parameters here isolated and employed are finally proposed as novel traits with a potential impact for breeding, and suitable for the characterization and selection of novel accessions with an enhanced postharvest resistance due to an improved fruit peel mechanical performance.