Monitoring and protection of local genetic resources of sweet chestnut (Castanea sativa Mill.) by integrated analysis of cultivated and wild populations: case study of Umbria and Lombardy regions (Italy)

Genetic analysis by DNA markers is very useful for characterization and traceability of traditional cultivars and typical products. The genetic identity of products is generally referred to the cultivars and does not consider the genetic contribution of pollen from external sources. The gene flow between cultivated and wild plants is important in chestnut, because grafted cultivars, selected pollen donors, and wild trees are often located in the same areas. Indeed, the chestnut cultivar ‘Marron’ produces poor to no pollen. In “CASTADIVA” and “MULTICAST” research programmes, chestnut groves of Lombardy and Umbria regions, respectively, were characterized by genetic analysis of orchards, fruits, and wild populations. A heterogeneous situation was found in Lombardy region, where two distinct areas were investigated. Chestnut orchards of Varese area showed a great diversity, with genetically heterogeneous plantations, with few grafted genotypes and few clonal replicates. On the contrary, in Brescia area, some chestnut groves included a relatively high fraction of grafted ‘Marron’ plants, together with other local cultivars. An unconventional orchard composed of non-grafted seedling was also studied in Brescia area. A conventional management system was found in Umbria region, with chestnut orchards composed of genetically uniform trees grafted with few cultivars. The integrated analysis of mother plants, fruit embryos, and wild populations showed that the fruits from ‘Marron’ trees were genetically intermediate between mother plants and local wild populations, which act as pollen donor. On the opposite, the offspring from genetically heterogeneous orchards displayed a genetic profile similar to the respective mother plants. The in situ interaction between cultivated and wild chestnut confers a geographic and genetic signature to chestnut fruits. These results open perspectives to improve the genetic characterization and traceability of chestnut productions.