|Riassunto in Inglese:|
The application of cryogenics to plant material is an innovative technique for preservation and recovery of pathogen-free germoplasm. “Cryoconservation” is a key issue in the collection and storage of plant biodiversity for the safeguard of species undergoing genetic erosion, and to maintain new cultivars obtained by breeding. Cryoconservation allows the long-term storage of plant material at low cost, in a small space and in absolute sanitary and genetic safety, and could replace conventional germoplasm collections. In turn, “cryotherapy” achieves eradication of plant viruses by cryogenic treatment of shoot tips. The technique has been applied on several plant species, succeeding in eradication of many viruses as Plum Pox Virus (PPV) and Potato Virus Y (PVY). Cryotherapy stands as an effective alternative to thermotherapy and meristem culture for plant pathogen eradication.
Artichoke (Cynara scolymus) is considered highly valuable vegetal crop, whose germoplasm characters of the different varieties have to be preserved. The lack of controlled nurseries for plantlets triggers use of infected propagative material and virus diffusion, representing the main concern for artichoke health status. Artichoke Latent Virus (ALV) and Artichoke Italian Latent Virus (AILV) affecting artichoke crops cause severe losses of yield and quality of the product.
In this work a protocol for cryopreservation of artichoke shoot tips was developed applying the vitrification technique (Sakai et al., 1990). The procedure involves the following steps: preculture of shoot tips on high sucrose medium, osmoprotection, dehydration with vitrification solution, rapid cooling by plunging in liquid nitrogen, warming, unloading of vitrification solution and plating on a suitable regrowth medium. Vitrification is the crucial treatment, but previous and following steps have been proved to be key factors for the success of the procedure as well. Therefore, each of these phases has been addressed separately, in order to find the best condition (time, temperature…) in terms of shoot regrowth. Timing has proved to be particularly critical. The development of the protocol represents the first approach to the issue; following experiments will check the genetic stability of the cryopreserved material, eventually tailor the protocol on different artichoke varieties, and exploit cryotherapy for virus eradication.