Microsatellite and morphological characterization of three Rostrato di Val Chiavenna (Sondrio, Italy) maize (Zea mays L.) accessions

Beaked corn represents one of the most characteristics and neglected group of Italian maize landraces. These genotypes, classified in the “Rostrata” group, were mostly grown in northern Italy, on the left bank of the Pò river, until the end of the Second World War and then subjected to strong genetic erosion because of the subsequent introduction of improved genotypes and hybrids of US origin. These materials are experiencing a revival period for cultivation, commercial exploitation and an increased number of farmers is seeking particular genotypes for the production of niche products. In Valchiavenna (Sondrio, Lombardia, Italy) maize cultivation has historical importance for polenta preparation and is characterized by the presence of at least three accessions of “Mais Rostrato Val Chiavenna”, one conserved since 1982 in germplasm bank (here named as R17_BG) and two in situ (here named as R17_M; R17_T), with distinctive morphological traits at both ear and plant level. In the present study, these accessions have been characterized at the morphological and genetic level with 10 SSR markers and compared to other landraces of the Rostrata group. SSR analysis revealed from 3 to 11 alleles per locus evidencing a good level of heterosis and absence of allele fixation for landraces. Both phylogenetic and STRUCTURE analysis evidence that the three “Mais Rostrato Val Chiavenna” are different entities with a distinct genetic origin. Historical investigation revealed that the morphology most close to the “original” Mais Rostrato di Val Chiavenna is that of R17_T, dating back to the XIX century. These observations, coupled with morphological and genetic results may corroborate that R17_T corresponds to the original “Mais Rostrato Val Chiavenna”.