Cryopreservation in artichoke: towards a phytosanitary qualified germplasm collection

Artichoke is of great economic significance in the Mediterranean basin. Although Italy has the richest primary cultivated gene pool, only a limited number of varietal types are vegetatively propagated to fit market demand. This could lead to the erosion of genetic resources. The development of cryopreservation procedures for the ex situ conservation of the genetic resources of artichoke is advisable not only to counter genetic erosion, but also to develop a certified phytosanitary germplasm collection. In this study, several parameters were tested in order to set up a simple and efficient procedure for the cryopreservation of artichoke shoot tips, based on vitrification/onestep cooling, which was successfully applied to two spring cultivars 'Grato 1' and 'Campagnano'. Cold acclimation prior to cooling was essential for tissue recovery and regrowth. The size of the shoot tips was also critical, and medium size tips (3-4mm in length) proved to be the best responding starting material. The best survival percentage of cryopreserved shoot tips was 61% for 'Grato1' and 55% for 'Campagnano'. Cryopreserved shoot tips developed directly into plantlets, which proved to be stable in terms of chromosome numbers. The cryopreservation procedure was notably effective in eliminating the endemic Artichoke Latent virus (ArLV) from both cultivars, irrespective of the shoot tip size used, which were up to 10 times the size used in meristem cultures for virus elimination. All plantlets analyzed for ArLV by RT-PCR were virus-free eight months after regeneration. An analysis of ArLV elimination and chromosome numbers of cryopreserved artichoke plants is presented here for the first time.