Low-Temperature Storage and Cryopreservation of Grapefruit (Citrus paradisi Macfad.) Seeds

BACKGROUND: Grapefruit is an economically important fruit worldwide, but our knowledge of its seed biology is rather poor. OBJECTIVE: The present study aimed to develop techniques for banking and cryopreservation of grapefruit seeds. MATERIALS AND METHODS: Grapefruit seeds with the exotesta removed were used. Seeds were desiccated to three moisture levels between 5-9% and stored at 15°C, 4°C and -20°C for up to 24, months to investigate seed lifespan in conventional seed bank. Meanwhile seeds desiccated by silica gel or saturated salt solution and embryonic axes by flash drying were employed to develop cryopreservation protocols. RESULTS: It was confirmed that grapefruit seeds have some intermediate properties, being able to withstand removal of type II water up to 7% MC, but sensitive to -20°C storage. For cryopreservation, the excised embryonic axes had a wider moisture window between 5% and 15%, with a maximum past-thaw emergence of 95%, while seeds survived only with a maximum past-thaw emergence of 50% or 70% from a much narrow moisture window. CONCLUSION: In contrast to previous reports on another type II seed, coffee, we found that citrus seeds desiccated by silica gel had better post-thaw viability than those subjected to equilibrium desiccation with saturated salt solutions. Further investigation is required to elucidate the mechanisms that contribute to variable cryopreservation tolerance.