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 andtraceability of traditional varieties and typical products. The genetic identityof products is generally referred to the cultivars and does not consider thegenetic contribution of pollen from external sources. The gene flow betweencultivated and wild populations is important in chestnut, because graftedcultivars, selected pollen donors, and wild trees are often located in the sameareas. Indeed, the chestnut cultivars "Marrone" produce poor o nonepollen.In "Multicast" and "CASTADIVA" research programmes, chestnutgroves of Umbria and Lombardy regions, respectively, were characterizedby genetic analysis of orchards, fruits, and wild populations. The newlystarted "CASTANEVAL" programme will continue the study in Lombardyregion. Genetic data depict the structure of the regional cultivated chestnut.A conventional management system was found in Umbria region, withchestnut orchards composed of genetically uniform trees grafted with fewcultivars. A more heterogeneous situation was found in Lombardy region,where two distinct areas were investigated. Chestnut orchards of Varesearea showed a great genetic diversity, with genetically heterogeneousplantations, numerous grafted genotypes and few clonal replicates. On thecontrary, in Brescia area, chestnut groves included a relatively high fractionof grafted "Marrone" plants, together with other local cultivars. The integratedanalysis of mother plants, fruit embryos, and wild populations showed thatthe fruits from "Marrone" trees were genetically intermediate between motherplants and local wild populations, which act as pollen donor. On the opposite,the offspring from genetically heterogeneous orchards displayed a geneticprofile similar to the respective mother plants. The in situ interaction betweencultivated and wild chestnut confers a geographic and genetic signature tochestnut fruits. These results open perspectives to improve thecharacterization and traceability of chestnut productions.