Genetic Diversity and Distinctiveness of Common Beans (Phaseolus vulgaris L.) Between Landraces and Formal Cultivars Supporting Ex Situ Conservation Policy: The Borlotti Case Study in Northern Italy

The common bean (Phaseolus vulgaris L.) arrived in Europe in the sixteenth century from the American continent and spread across the old continent as a result of adaptation to different climatic and geographical conditions, as well as selection for different cultivation techniques and eating habits. This expansion gave rise to a huge number of landraces, which have now been largely replaced by more productive cultivars. To avoid losing this genetic diversity heritage, it is essential to characterize the genetic resources at risk of extinction for correct in situ/ex situ conservation and as a first step toward promoting and relaunching their exploitation. In this article, we report the study of a group of Borlotti beans, both landraces and modern cultivars, which are typically cultivated in Northern Italy. The aim was to explore the variability within the assembled Borlotti panel to assess whether landraces have maintained their morphological and genetic identity over time during on-farm cultivation. In particular, we investigated whether it is possible to distinguish between landraces and commercial accessions, a topic that has so far been understudied, but in the field of conservation, it is particularly important because it allows for the prioritization of preserving genetic resources. We found distinctive traits among the various accessions, with only a few landraces maintaining their identity, many of which should more properly be defined as obsolete cultivars. Taken together, these data indicate that it is possible to establish a priority scale for in/ex situ conservation by comparing landraces and cultivars using morphological and genetic data. Furthermore, thanks to geographical isolation, on-farm conservation has proven to still be successful in maintaining the identity of landraces.