Chestnut

Abstract

The genus Castanea, chestnuts and chinkapins, belongs to the family Fagaceae, which includes other important timber producing genera such as Quercus and Fagus. The genus Castanea is divided into three geographically delimited sections with at least seven consistently recognized interfertile species: 4 species in Asia (C. mollissima, C. henryi, C. seguinii, and C. crenata), two or more species in North America (C. dentata, C. ozarkensis, and C. pumila) and one in Europe and Turkey (C. sativa). The two most important diseases of chestnut are ink disease (Phytophthora) and chestnut blight (Cryphonectria). Resistance to these is the major objective for rootstock breeding in Europe and scion breeding in North America. In both cases, the source of resistance was Asian species. European breeding programs developed resistant hybrid rootstocks, which are propagated by stooling, cuttings, or in vitro culture. A major pest of chestnut is the gall wasp Dryocosmus kuriphilus whose control is based on the spread of parasitoids but also on the selection of resistant cultivars. For nut production, the most important breeding objectives include the following: good horticultural traits, product quality, suitability to storage and processing, and ease of peeling. For timber, important characters include wood quality, rapid growth, and nonchecking of wood (ring-shake). Molecular maps have been developed, which has expanded the genetic knowledge of the chestnut. An efficient genetic transformation protocol for C. sativa through the coculture of somatic embryos with different strains of Agrobacterium tumefaciens has been described.