EPICUTICULAR WAX MORPHOLOGY AND COMPOSITION ARE RELATED TO GRAPEFRUIT CHILLING INJURY

Differences in chilling injury (CI) susceptibility between 'Marsh' grapefruit (Citrus paradisi Macf.) from interior and exterior tree canopy positions were analyzed to investigate the hypothesis that epicuticular wax morphology and composition influence CI development during low-temperature storage. The sun-exposed surface of fruit from the exterior canopy had significantly more CI and larger wax platelets than the shaded surface of the same fruit. Interior canopy fruit had significantly less CI and smaller wax platelets than exterior canopy fruit. Hydrocarbons, primarily n-alkanes, were significantly more abundant in the epicuticular wax on the surfaces of sun-exposed and exterior fruit compared with surfaces of shaded and interior fruit, respectively. Results of this study suggest that epicuticular wax plays a role in the development of external CI symptoms on grapefruit.