Influence of Canopy Depth on Susceptibility of ‘Marsh’ Grapefruit to Chilling Injury1

Abstract

‘Marsh‘ grapefruit ( Citrus paradisi Macf.) harvested from the exterior canopy of the tree were more susceptible to chilling injury (CI) at 4.4°C than grapefruit harvested from the interior canopy of the same tree. No differences were found in the levels of total soluble carbohydrates, reducing sugars, and sucrose in the peels of the fruit from the 2 canopy depths. An unusual pattern of CI, remarkably similar to the pattern of citrus rust mite [ Phyllocoptruta oleivora (Ashm.)] damage, was observed in several of the exterior canopy fruit. Although the fruit had no visible rust mite damage at harvest, fruit remaining on the tree developed the characteristic bronzing associated with rust mite injury within 2 to 3 weeks after the test fruit were harvested. It is suggested that environmental and biotic factors predispose grapefruit to CI.