In vitro propagation of Italian cultivars of Vitis vinifera and evaluation of genetic stability of the micropropagated plants

Because of its geographic, historical and cultural complexity, Italy has always been a country rich in biodiversity and agronomic genetic resources. Despite the wine-producing industries are nowadays addressing to select and employ relatively few and very productive grapevine varieties, well-known in the international market, there is still a wide heritage of so-called “minor cultivars”, strictly linked to a specific geographic area. This requires pointed actions for exploitation and promotion of the regional genotypes and their in situ and ex situ conservation. The aim of the present study was to set up effective protocols to micropropagate grapevine varieties typically cultivated in Modena and Reggio Emilia provinces (Northern part of Italy), for the ex situ conservation of germplasm. Six varieties have been studied: three genotypes of Lambrusco (L. salamino, L. Sorbara and L. Marani), one cultivar with white berries, Trebbiano modenese, used for the production of Balsamic Vinegar of Modena, Malbo gentile and Ancellotta. Winter branches with dormant buds were forced in a growth chamber at about 25°C, for a 12 h photoperiod. The developed green shoots were used as explants sources, consisting in nodal segments with a single axillary bud. Explants were placed in culture on Murashige and Skoog medium (MS) and MS half strength (MS ½), added with sucrose (30 g L-1), agar (6 g L-1) and 1.1 mg L-1 of benzyladenine (BA). The genetic stability of the micropropagated plantlets was evaluated after three subcultures, analyzing nine microsatellite loci, commonly used as genetic markers of grapevine varieties and accessions. MS ½ demonstrated to prevent vitrification in three cultivars, L. Sorbara, Malbo gentile, Trebbiano modenese, and to increase the percentage of productive explants in L. Sorbara. A reduced concentration of BA (0.55 mg L-1), applied during the following multiplication phase, proved to promote shoots elongation in all genotypes, except Malbo gentile and L. Salamino. Three media with different indol butirryc acid (IBA) concentration and presence/absence of Activated Carbon (AC) were tested for rooting. Good results, in terms of percentage of rooted shoots, were obtained for each cultivar in all the tested culture conditions, although some modifications seemed to improve the root development: L. Sorbara showed an increase of rooted shoots when it was cultured on MS ½ and the addiction of AC in the culture medium prevented shoot browning in Malbo gentile, Trebbiano modenese and Lambrusco Marani. In vitro growing plantlets of the six cultivars showed the same profile as the adult trees from which explants have been taken, confirming the genetic stability of the micropropagated material.