Proceedings of the XLVII Italian Society of Agricultural Genetics - SIGA Annual Congress

Verona, Italy - 24/27 September, 2003

ISBN 88-900622-4-X

Poster Abstract - 5.39

VARIATION IN ITALIAN ACCESSIONS OF PHASEOLUS COCCINEUS

A. ACAMPORA, M. CIAFFI, A.R. PAOLACCI, O.A. TANZARELLA

Dipartimento di Agrobiologia e Agrochimica, Università della Tuscia, Via S. Camillo De Lellis, 01100 Viterbo

tanzarel@unitus.it

Phaseolus coccineus, seed proteins, molecular markers, runner bean

P. coccineus, or runner bean, is one of the five cultivated species of Phaseolus which were introduced from Central America in the 16^th century. During the last decades there has been a progressive decrease of the common bean cultivation area, that from more than 400,000 ha in the 40’s has dropped to about 11,000 ha, the situation for P. coccineus is even worst. Moreover, a single variety, Bianco di Spagna, is grown in most of the very limited cultivation area of P. coccineus in Italy, whereas several local types are grown on very limited and marginal areas. This situation has determined a dramatic erosion of the genetic variation in the Italian germplasm of P. coccineus. A tendency to rediscover traditional and abandoned foods is spreading among consumers and the market is appreciating some previously neglected agricultural products, among them also some local varieties of common bean. Also P. coccineus has the potentiality of being included among valuable traditional foods. A key step for its promotion is represented by the assessment of the genetic variation existing in Italian germplasm, including the stored collections and the cultivated materials. It would be important, in particular, the evaluation of the nutritional characteristics, which are mostly related to the protein composition of the seeds.

The aim of this paper was the assessment of genetic variation in P. coccineus using molecular and biochemical markers. Some of the 53 available accessions, from different Italian regions, were collected directly from farmers, others from different Italian Institutions, most of them were furnished by IPK, Gatersleben, Germany. The total proteins of ten seed for each of 27 accessions of P. coccineus were analysed by SDS-PAGE electrophoresis. The electrophoretic patterns showed a wide variation both within and between the analysed accessions, as expected in an allogamous species. Some genotypes, in particular, showed the lack of the phaseolin fraction, the most important and abundant seed storage protein of Phaseolus, and of the fraction corresponding to the lectins, that are important both negatively, as antinutritional factors, and positively, for conferring aspecific resistance to insects. The variation within and between the Italian accessions of P. coccineus has also been assessed using different molecular markers. Among ten screened RAPD markers, only three were able to detect variation between single genotypes of different Italian accessions and were selected for further analyses, also some combinations of AFLP primers showed a very low level of variation. Only one of seven analysed ISSR markers detected polymorphism among the Italian accessions. Finally, IRAP and REMAP, two markers based on retrotransposons previously applied in barley (Kalendar et al., 1999. Theor. Appl. Genet. 98:704-711), have been developed in P. coccineus on the basis of the conserved LTR region sequence of the Tpv-2 family of retrotransposons, which has been studied in P. vulgaris (Garber et al., 1999. Plant Mol. Biol., 39:797-807). Some of the analysed primer combinations, in particular of IRAP, produced several polymorphic bands. Also some accessions from Central America were comprised in the analyses with the different markers. The polymorphism resulted much higher than between Italian accessions, suggesting a low level of genetic variation in the Italian germplasm of P. coccineus.