Interspecific hybridization of chestnut.

Chestnut (Castanea spp.) is a tree species mainly distributed in the northern Hemisphere in natural stands, orchards and coppices. As a multipurpose tree, chestnut is used to produce timber, nuts, tannins, and other related products; and also it is a valuable asset in landscapes and in material and unmaterial cultural heritage. Insterspecific hybridization was first done in 1894 in the USA and later, in the 1920s, in Europe and Japan. In the USA, blight resistant Chinese and Japanese species were used as the donor in a backcrossing program with the American chestnuts (C. dentata) as the recurrent parent, which has successfully produced blight resistant timber chestnuts. In Europe, Japanese chestnut trees were introduced as origen of resistance to ink disease (Phytophthora spp.) to produce largest clonal collection of hybrids used to produce nuts and timber, so as rootstocks for local cultivars. The difficult-to-peel pellicles of the Japanese chestnut cultivars was overcome with the newly released Japanese chestnut hybrid 'Porotan', which includes the easy-peel pellicle trait controlled by a single recessive gene (P/p) from chinesse chestnut (C. mollissima). After more than 100 years of chestnut hybridisation, new technologies and the recently reported genome sequence will allow to face new threats to maintain the rich genetic and cultural heritage of chestnut.