In vitro evaluation of tuberisation earliness and productive ability of new Italian potato clones

The earliness and productive ability represented by percentage of tuberized plant and number of tubers per plant of 12 new potato clones, an old Italian variety Viola Calabrese and two control cvs. Désirée and Spunta were evaluated in vitro. Tuberization was carried out on two media (Murashige and Skoog medium with and without CCC) and under two photoperiods (long day and short day). In vitro tuberization was significantly influenced by genotype, photoperiod and medium. Under inductive conditions (short day and CCC in the medium) the lower plant growth improved microtuber production achieving the highest Harvest Index (HI). Concerning earliness, two main groups were observed: a group in which tuberization resulted anticipated under short day, such as Désirée cv., and a group in which long day conditions were responsible for early tuberization, such as Spunta cv. MN 190 and ISCI 67, which had Spunta as parental type and showed similar behaviour to the reference cultivar for all factors studied.