Why red grapefruit is more resistant to chilling injury than yellow grapefruit

Grapefruit are widely recognized by their extreme sensitivity to develop chilling injury (CI) during postharvest storage at low temperature. Moreover, many varieties and mutants of grapefruits exhibit important differences in both external and internal coloration, from yellow to deep red, due to a distinctive accumulation of pigments, in particular of the red carotene lycopene. Thus, in this study the genetic variability in external peel coloration of grapefruits has been used to elucidate the potential relationship between carotenoid content and composition, and development of CI. CI increased progressively after 2 weeks storage at 2?C in fruit of the yellow Marsh (M) grapefruit but in the red Star Ruby (SR) CI symptoms were exclusively restricted to yellow areas of the fruit peel. Moreover, CI was absent in red peel tissue, even after prolonged cold storage, in which lycopene content was 14-times higher than in yellow tissue. Resistance to CI in red, lycopene-accumulating tissues was also observed in M grapefruits treated with CPTA (an inhibitor of lycopene cyclization) which increased total carotenoids (x7) and lycopene content (x32). In addition, SR grapefruits growing under shaded conditions developed an intense external red coloration and accumulated large amount of lycopene, and were highly resistant to CI upon subsequent postharvest cold storage. To further explore the mechanisms involved in the resistance to CI induced by lycopene, activity and gene expression of different members of the antioxidant enzymatic system (SOD, AT, GR, APX) as well as expression of ethylene biosynthetic and signaling genes were analyzed in yellow and red peel tissue of grapefruit, and the potential relationship with the development of CI will be presented and discussed. ? Original title, complete list of authors, and sourcesResistance to chilling injury in red, lycopene-accumulating, tissue of cold-stored grapefruitsJ. Lado1,2, M.J. Rodrigo1, P. Cronje 3, L. Zacarias11Instituto de Agroquimica y Tecnologia de Alimentos, Consejo Superior de Investigaciones Cientificas, Avenida Agustin Escardino 7, 46980 Paterna, Valencia, Spain2Instituto Nacional de Investigacion Agropecuaria, Camino a la Represa s/n Salto, Uruguay3Citrus Research International, Department of Horticultural Science, Stellenbosch University, South Africa V Postharvest Unlimited, ISHS International Conference, 10-13 June 2014, Cyprus, http://web.cut.ac.cy/postharvest/The picture is by prowellness.es ?