The difficulties in assessing the distinctness characters in lucerne plants have recently led to reject the registration to the EU database of registered plant varieties for several new varieties with valuable agronomic characteristics. The tendency of lucerne plants to grow during winter and its fall dormancy can be efficient discrimination tools for the varieties during registration tests and could be an interesting agronomic characteristic to evaluate cultivar adaptability to different climatic conditions.

The information about the dormancy of lucerne are limited and the dormancy class of many Italian varieties is still unknown. The aim of our study was to validate the method proposed by the International Union for the Protection of New Varieties of Plants (UPOV) for the assessment of the dormancy class and to classify an adequate number of Italian cultivars. The experiment was carried out during three consecutive Distinctness, Uniformity and Stability (DUS) trials, lasting 18 months each, from 2016 to 2019 at the experimental farm of the CREA-DC located in Palermo, Italy. The method was based on the linear regression analysis to evaluate the functional relationship between the fall dormancy class (FDC) and the natural plant height (NPH) measured during the different DUS trials in five growth stages. Seven varieties, representing the fall dormancy classes (FDC) 2, 4, 5, 6, 7, and 9 (UPOV), were used as control varieties and twenty-one varieties under DUS testing were evaluated to assess their dormancy class. A Principal Component Analysis (PCA) was performed using the data matrix varieties x NPH. The models obtained were used to estimate the fall dormancy class of the candidate varieties and the results were compared with the visual dormancy class. The first principal component and the fall dormancy class had a significant linear relationship in all the years of the trial. NPH4 and NPH15 showed to be a useful tool for the discrimination of lucerne cultivars with different dormancy ratings.