Resumption of chestnut cultivation in Lombardy: starting from native genetic resources

In the past, the sweet chestnut tree (Castanea sativa Mill.) was an important multifunctional resource for mountain communities. Recent decades have seen a decline in chestnut cultivation due to the abandonment of chestnut groves and the incidence of emerging diseases and pests. To stimulate the resumption of cultivation and enhance the marketing of local varieties, the Lombardy Region has recently financed the two CASTADIVA and CASTANEVAL PSR projects, in which a strict collaboration between researchers and chestnut growers in the province of Brescia and Varese has been developed. The projects aimed at the characterization of Lombardy's chestnut germplasm by integrating analyses of genetic markers and fruit quality traits. Eleven SSRs markers were used to assess the genetic variability and divergence of five chestnut groves in the province of Brescia and seven in that of Varese, together with some wild chestnut stands, representative of the non-cultivated genetic resources in the same areas. The genetic structure analysis showed a separation into two main gene pools between the sites in the two provinces. In the province of Varese, plants with unique genotypes prevail in the cultivated chestnut groves. Among the grafted plants, the Pajè, Piliscè, Russirò, Venegona and Verdesa local varieties are distributed in seven clonal groups. Our results are likely originated/caused by different management systems of chestnut groves and germplasm in Lombardy: graft of selected genotypes or use of single genotypes with the best traits. Based on the identified genetic structure, a subset of trees from different collection sites were selected for analyses of fruit morphology and chemical composition (specific carbohydrates, moisture, fat, protein, ash and fiber) that valorize chestnut nutritional quality. The main differences in fruit chemical composition consist in content of sucrose that mainly contributes to chestnut sweetness, and raffinosaccharides that cause flatulence discomfort. The morphological and biochemical data of fruits will be discussed in relation to the genetic relationships among the sampled trees. In the frame of the CASTANEVAL project, we are also developing a chestnut micropropagation system to offer sustainable and economical tool for the conservation and multiplication of native germplasm of high local interest. The results of this study represent a tool for the conservation and leveraging of local germplasm and provide useful indications for the management of chestnut cultivation.