|Riassunto in Inglese:|
Artichoke (Cynara scolymus L.) is a perennial vegetable crop cultivated mainly in Countries bordering the Mediterranean basin, where Italy, Spain, and Egypt account for about 80% of its global production.
This crop is affected by many diseases that may cause severe economic losses, i.e, a significant decrease in the quantity and quality of artichoke yield. Among other pathogens, more than 20 viruses are known to infect artichoke causing serious concern to the artichoke industry. Some of them are very damaging and considered quarantine organisms in the European Union (EU) (i.e, Tomato spotted wilt virus – TSWV).
Vegetative propagation by crown segments and offshoot facilitates the spread of viral infections from one plant to another seriously compromising yield and quality of production. For this reason, European regulations for the commercialization of propagation material foresee the absence of the most dangerous pathogens, including Artichoke latent virus (ArLV), from propagation material.
The risk of introduction of undesirable microorganisms to a country through imported germplasm is high as disease symptoms may be absent in young propagation material and their visual inspection may not reveal the presence of systemic pathogens such as viruses.
In view of above it is crucial for artichoke implantation of new fields to have available virus-free plantlets of the main artichoke varieties grown in different productive regions and to have diagnostic protocols to assess the presence of viral pathogens especially when the new plantlets have been produced by in vitro propagation. In fact, given the international rules issued to set up the commercialization and sanitary requirements necessary for the safe movement of germplasm world-wide, the presence/absence of the damaging systemic pathogens must be ascertained in transported plant material.
In the last years the Italian Ministry of Agricolture financially supported a national Project on artichoke (CarVarvi) with the aim to stimulate nursery activity in the sector of artichoke trade and to establish harmonized guidelines for the production of pathogen-tested artichoke plantlets free from the most dangerous systemic pathogens. Our Research Center joined this project working on two main workpakages:
• To establish suitable diagnostic protocols to be applied for the detection of the main viral agents in artichoke germoplasm;
• To compare the efficacy of different techniques for the in vitro production of virus-free artichoke plantlets.
To reach these objectives, in the last years we have set up and successfully applied different diagnostic methods (one step RT-PCR, tissue imprinting molecular hybridization with DNA probe) in detecting the most important viruses both in vivo and in vitro cultured artichoke germplasma. More recently a dedicated Customarray® (4x2K) chip was developed including the design and synthesis of 40-mer oligonucleotide probes specific for the detection of each of fourteen viruses known to induce severe damage in artichoke.
We, also, describe the results obtained in eliminating viruses from different artichoke cultivars using two techniques: in vitro termotherapy and meristem shoot culture. Both techniques allowed to obtain healthy artichoke plantlets even if in different extent according to: i) the characteristics of the virus to be eliminated; ii) the variety of artichoke under study; and iii) the technique used for the virus elimination.
Recently we decided to evaluate the potential of cryotherapy, an innovative technique, for producing a collection of artichoke germplasm free from systemic pathogens. A shoot tip vitrification protocol for artichoke cryopreservation has been established and successfully applied for maintaining artichoke germoplasm at ultra-low temperature. The potential shown by artichoke to regenerate after cold treatment allows to hypothesize the application of cryogenics for virus eradication from infected germplasm.