HPLC analyses of seed storage proteins reveal polymorphism in Italian common bean (Phaseolus vulgaris L.) ecotypes

Phaseolin (PHAS) and phytohemagglutinin (PHA) represent the main seed protein fractions in common bean. Currently, several ecotypes of common bean cultivated in marginal areas exist, above all in Southern Italy regions. Such germplasm could be lost due to the genetic uniformity of new cultivars. Moreover, the first step to obtain community recognition and denomination requires the full characterization of the available germplasm. In the present study, PHAS and PHA extracted in saline solutions from nine ecotypes of common bean 'di Controne' (Campania region) were analysed by anionic and cation exchange-high performance liquid chromatography (AE- and CE-HPLC), SDS-PAGE and IEF. The results obtained by AE- HPLC have allowed us either to standardize a high resolution, cost-effective and time-saving biochemical methodology or to compare the studied ecotypes with some cultivars of common bean most widely grown in Italy. The elution profiles of the nine ecotypes, already analyzed at the morpho-physiological and molecular levels, allowed us to differentiate the ecotypes either from a qualitative point of view (presence/absence of one or more peaks) or a quantitative one. For instance, the ecotypes of common bean 'di Controne' could be clearly differentiated from some commercial cultivars of dwarf and/or climbing bean. In contrast, the analysis of the electrophoresis patterns supplied less information.