Genetic Improvement of Sweet Chestnut in Sicily (Castanea sativa Mili.) by the Selection of Superior Autochthonous Genotypes

Abstract

In Sicily, the chestnut (Castanea sativa Mill.) grows in limited areas of the South eastern Mt. Etna volcano and of the Northern Mountains, namely Madonie and Nebrodi. In the Island, chestnut can be considered as a neglected species, because of the modest importance recognized to it for horticultural and forestry exploitation. Recently, the Sicilian regional government founded the 'Horticultural Forestry' project to promote the cultivation of chestnut as possible fruit tree for local city farmer markets, where typical products are usually sold. The project was developed in five steps, carried out during three years by the Dipartimento di Colture Arboree of Palermo University: identification of the main growing areas; selection, during the ripening season, of the most vigorous and highly productive trees observed in each area; selection of the best genotypes, among the accessions collected, on the basis of the carpological traits, choosing the ones that presented the best fruits. The morphological characterization of husks and fruits was done referring to the UPOV descriptors list. Only 47 accessions, among hundreds of accessions observed, were chosen on the basis of the carpological traits and were studied in situ. Husk and fruit traits were recorded in the laboratory and analysed statistically, leading to a further selection of only 25 'superior' accessions. These genotypes were analysed at the molecular level using six microsatellite or SSR (Simple Sequence Repeat) primer pairs (ENICs: 4, 15, 32 and 38, CsCat: 4 and 6). SSR markers enabled the discrimination of 23 genotypes and showed low genetic distance among them. Further observations, carried out on both tree and fruit traits, led to the selection of Il 'superior' genotypes, having important carpological traits (big fruit size, absence of adherence of the seed coat to the kernel; absence of penetration of the seed coat into the embryo; mono embryonic fruit, etc.). This study could be a good start to compare autochthonous genotypes to weli know international cultivars, under the prevailing environmental conditions of the main Sicilian growing areas.