Production Practices and Quality Assessment of Food Crops. Vol. 1

9.3. Hybrids
Chestnut breeding in Europe began with the production of hybrids resistant to the
ink disease (Phytophthora spp.) to substitute the indigenous species. Initially,
seedlings from Asiatic species C. crenata and C. mollissima were introduced between
1917 and 1940 (Elorrieta, 1949; Fernandez et al., 1993) as a way to combat the
ink disease, which was threatening the European chestnut orchards. Resistance of
the Asiatic species was confirmed later, but these species were in many respect
inferior to the European species C. sativa; i.e. less vigour, lower quality of the
nuts, bad affinity with the local cultivars, sensitive to early spring frost and summer
drought, difficulty in adapting to climatic characteristics of some areas in Europe
(Elorrieta, 1949; Fernandez-Lopez, 1996). In Spain, a program of hybridisation
between C. crenata with C. sativa were carried out by Gallastegui (1926) with
the aim of combine the best characteristics of both species.
Between 1942 and 1958 (Urquijo, 1944, 1957; Fernandez et al., 1993), first
generations of hybrids were obtained using C. sativa as female progenitor, and C.
crenata or C. mollissima as male. Between 1953 and 1958, 40 clones of second
and third generation of open pollination hybrids were selected by resistance to ink
disease and, amongst these, some as rootstocks to local cultivars and some as
direct producers (Urquijo, 1944). A new selection by resistance to ink disease was
developed between 1954 and 1965 with over 10000 seedlings coming from a few
families whose exact origin is unknown but were supposed hybrids.
Most of the hybrids were transfered to the CTIFL between 1959 and 1962. In
1989 a new program began to identify the mixture of hybrids clones with the aim
of selecting the best material.
Results showed that some clones were interesting for timber, nut production or
as rootstocks (Fernandez et al., 1992, 1993; Fernandez-Lopez, 1996; Pereira-Lorenzo
and Fernandez-Lopez, 2001).
Asiatic species were introduced in France in 1925 and they showed a high
tolerance to ink disease but poor adaptation to soil and weather conditions.
Schad et al. (1952), beginning a breeding program to create and select interspecific
hybrids obtained from open or controlled crossing. Some of the French clones
became very popular as direct nut producers (Bergougnoux et al., 1978; Breisch,
1995) but occasionally incompatible with clones of C. sativa (Breisch, 1995;
Pereira-Lorenzo and Fernandez-Lopez, 1997; Craddock and Bassi, 1999). A new
hybridisation program has been initiated in France to obtain resistant, vigorous clones
that produce high quality nuts (Guedes-Lafargue and Salesses, 1999).
9.4. Pest and diseases
Chestnut, an Ancient Crop with Future 151
Most of the studies about the ink disease on chestnut during recent years were
focused in the better knowledge on the species identification, pathogenicity and
climatic and human factors predisposing trees to ink disease infection (Vanini and
Vettraino, 2001). Recently, molecular studies allow more rapid and objective
identification of Phythophthora taxa, between them those which affecting chestnut
(Cacciola et al., 2001).