Effect of fruit shading and cold storage on tocopherol biosynthesis and its involvement in the susceptibility of Star Ruby grapefruit to chilling injury

• Tocopherol content in the flavedo of grapefruit increase during fruit maturation. • TAT1 and genes of the tocopherol-core pathway are up-regulated during fruit maturation. • Light avoidance reduces γ-tocopherol and expression of GGDR and tocopherol-core pathway genes. • Cold up-regulated genes involved in precursors supply but repressed those of the core pathway. • Changes in tocopherols during storage appears to be cold-mediated and not related to CI tolerance. The aim of this study was to investigate the role of tocopherols in the susceptibility of Star Ruby grapefruit to postharvest chilling injury (CI). Fruit exposed to normal sunlight (NC, non-covered) and deprived of light (C, covered) in the last stages of development were used. Tocopherol contents increased in the flavedo of both NC and C fruit during development, concomitantly with the up-regulation of TAT1 and most genes of the tocopherol-core pathway. Fruit shading reduced total contents by repressing γ-tocopherol accumulation, associated to a down-regulation of GGDR and VTE1 and, to a lesser extent, of VTE2 , VTE3a and VTE4 . During cold storage, total and α-tocopherol contents increased in NC and C fruit, and no direct relationship between tocopherol accumulation and CI tolerance was found. Cold stress up-regulated most genes involved in the synthesis of tocopherol precursors and down-regulated those of the tocopherol-core pathway, but changes seemed to be cold-mediated and not related to CI development.