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

120 S. Pereira-Lorenzo and A. M. Ramos-Cabrer
This means there is no close correlation between male sterility and quality of
the fruit but perhaps between male sterility and productivity as suggested by Liu
and Zhou (1999).
Meiosis in pollen mother cells occurs in the first week of June in Italian cultivars,
10 to 15 days before anthesis (Botta et al., 1995). Pollen viability varied
from 81.3 ± 6.1% based on fluorochromatic reaction to 58.2 ± 7.0% on hanging
drops and 50.1 ± 4.5% germination on agar media. Pistillate flowers have six to
eight styles whose tips present a hollow at full bloom. The ovary presents seven
(rarely six or eight) carpels. Each flower has 10 to 16 anatropous ovules. Bearing
mono-embryonic seeds (marron type) has been related to the high occurrence of
anomalies, such as delayed of embryo sac differentiation and the presence of supernumerary
nuclei in the embryo sac (Botta et al., 1995).
3.3. Phenology
Chestnut is a deciduous tree as corresponding to the temperate area where it is
cultivated. Castanea species are generally cold hardy. Castanea dentata and C.
mollissima have been reported to survive down to –30 °C (Andersen, 1994).
After chilling requirement, bud break begins at the end of March for Asiatic
cultivars, and interspecific hybrids (Table 6), being the most precocious, followed
by the European cultivars. Interspecific hybrids maintain their precocity contribution
origin from the Asiatic. However, some hybrid cultivars of C. sativa are as
precocious as C. crenata (Table 6) such as Garone Negro. New shoots are very
sensitive to spring frost, and this limits the use of Asiatic cultivars to orchards located
at altitudes lower than 500 m. However, European cultivars can avoid spring frost
because of their late bud break.
Flowering time is highly variable with the local climatic condition (Breisch, 1995).
Asiatic cultivars and hybrids produce the male flowering between the end of May
and the end June, while European cultivars are between mid-June to mid-July.
Table 7 show that the time of flowering for Euro-Asiatic hybrids is more precocious
than European cultivars.
Precocity is also maintained at harvest time, on the 1st September for C. crenata
and C. mollissima. Most of the cultivars of C. sativa produces in October and 1st
November, but some cultivars are as precocious as Asiatic species such as Temprana
and Pilonga which when cultivated in South Spain (Pereira-Lorenzo and Ramos-
Cabrer, 2002).
4.1. Origin of the cultivars
4. CULTIVARS
As Vavilov (1951) described; growers realised a first domestication selecting the
best nut from wild populations. With the knowledge of vegetative propagation as
grafting, a second domestication began which resulted in fixing the best genotypes.