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

8.4. Micropropagation
Several in vitro propagation methods have been developed since 1980s when applied
to chestnut (Viéitez and Viéitez, 1980 a and b; Viéitez et al., 1983). It is useful
for propagating hybrids for forest and rootstocks and is used in France and Spain
as a commercial technique (Breisch, 1995; Miranda-Fontaíña, 2001). Main problems
are the high cost of the facilities, skilled technicians and the variability of rootings
between clones.
Basically, in vitro culture has been used in the propagation of axillary shoot or
buds (Chevre et al., 1983; Sánchez and Viéitez, 1991; Sánchez et al., 1997a and
b; Ballester et al., 2002). However, potential of somatic embryogenesis has been
pointed out for chestnut micropropagation and as a tool in genetic engineering
programmes (Xing et al., 1999; Ballester et al., 2002).
In vitro culture is based on the establishment of axillary shoot or buds from
juvenile and mature material (Viéitez and Viéitez, 1980a; Sánchez et al., 1997a
and b). After several subcultures of in vitro multiplication, some micro-cuttings
are induced to root. Acclimatisation from the in vitro culture system to soil, seedlings
are grown in greenhouse under fog system.
8.5. Cuttings
Chestnut has been considered traditionally difficult to obtain hardwood cuttings
(Viéitez et al., 1987; Viéitez and Ballester, 1988). Techniques involving rejuvenation
by hard pruning over mother plants, the use of softwood cutting in spring
under fog system and hormones inductions have increased the percentage of rooting.
Some nurseries are trying to incorporate these methods to substitute layering method
in propagating hybrids for forest or rootstocks (Ponchia and Howard, 1988; Chapa
et al., 1990; Gautan and Howard, 1991; Fernandez et al., 1992; Jinks, 1995). Clonal
variation in rooting capability must be taken in account, because it can vary between
16% and 90% in hybrid clones (Fernandez et al., 1992).
9.1. Variability
Chestnut, an Ancient Crop with Future 149
9. BREEDING
Important efforts are being made in studying chestnut variability using morphology
characteristics based on Breviglieri’s (1955) ‘Scheda Castanografica’, after in the
UPOV chestnut guideline (1988) and, more recently, applied to the Spanish cultivars
(Pereira-Lorenzo et al., 1996a) and different chestnut species (Oraguzie et
al., 1998).
The first molecular markers based studies in chestnut were by isoenzymes
(Sawano et al., 1984) over 16 clones (10 Japanese, 3 Chinese, and 2 hybrids).
Wen and Norton (1992) studied four isoenzyme system and identify 22 Chinese
cultivars. Genetic analysis with isoenzymes were performed by Bonnefoi (1984),
Malvolti and Fineschi (1987), Fineschi et al. (1990a and b) and Huang et al. (1994a).