EPICUTICULAR WAX MORPHOLOGY AND COMPOSITION ARE RELATED TO GRAPEFRUITCHILLING INJURY

Differences in chilling injury (CI) susceptibility between 'Marsh' gra pefruit (Citrus paradisi Macf.) from interior and exterior tree canopy positions were analyzed to investigate the hypothesis that epicuticul ar wax morphology and composition influence CI development during low- temperature storage. The sun-exposed surface of fruit from the exterio r canopy had significantly more CI and larger wax platelets than the s haded surface of the same fruit. Interior canopy fruit had significant ly less CI and smaller wax platelets than exterior canopy fruit. Hydro carbons, primarily n-alkanes, were significantly more abundant in the epicuticular wax on the surfaces of sun-exposed and exterior fruit com pared with surfaces of shaded and interior fruit, respectively. Result s of this study suggest that epicuticular wax plays a role in the deve lopment of external CI symptoms on grapefruit.