Caratterizzazione, selezione, risanamento e valutazione di cultivar locali di fagiolo comune

The general objective of this research programw as the improvement of old local landraces of common bean cultivated in traditional areas of ltaly. While the market demand of bean grain commercial varieties has been so far quite feeble, that of bean landraces raised significanfly in the last three years. A strong demand of local and typical products like these beans offers to the farmers the opportunity to improve their incomes, thus the value of the whole area of cultivation. The old bean populations owned by the farmers, often present a high genetic variability with undesirable characters like the susceptibility of various diseases. For these beans, germplasm characterization and plant selection followed by the BCMV- or bacterial- free individuals recovery are very imporîant tools to produce superior and genetically uniform seed pools. Such research activities were developed for five old bean landraces: Spagnolet nano, cultivated at Lamon (Belluno), Bianco di Bagnasco, cultivated at Bagnasco (Cuneo) (both exposed to extinction risk),Fagiolo del Purgatorio cultivated at Gradoli (Viterbo), Verdolino and Ciuoto both cultivated at Sarconi (Potenza). All these landraces are susceptible to BCMV and bacterial diseases. Seed samples were recovered from growers and submitted to different analyses; DNA analysis (SSR and AFLP marker pro files) allowed to evaluate the degree of genetic variability present in the original population of each landrace and to define the strategy of selection on the basis of its value. Cluster analysis, based on Nei's genetic distances and Jaccard's similarity index as defined by SSR and AFLP markers, respectively, showed that all populations clustered into two groups corresponding to the Andean and the Mesoamerican gene pools. The data obtained showed a genetic vari_ ability that was high in the white small seeàed Fagiolo del Purgatorio, intermediate in the Bianco di Bagnasco (large white seeds), in Verdolino (small green seeds) and in Ciuoto (small" borlotto, seeds), and almost absent in Spagnolet nano (large, ,borlotto,' seeds). This suggested to select lines for best agronomical traits in the landraces having medium and high genetic variability. Phytopathological analysis proved Bianco di Bagnasco to be BCMV free even if susceptible, Verdolino and Ciuoto infected by BCMV and BYMV in low percentages and by Pseudomonas syringae pv. phaseolicola and Xanthomonas campestris pv. phaseoli, whereas Spagnolet nano was infected by BCMV also after several generations, due to the high ability of this virus to be seed transmitted. For this last landrace we started a restoring pro_ gram to obtain virus-free plants under screen-houses to avoid aphids pests. For Verdolino and Ciuoto disease free seed lots were obtained.