Agriculture Reference
In-Depth Information
with the increasing globalization of their production the name 'Nashi', which
is Japanese for a pear grown in Japan, is now preferred (Kajiura,
). It
is possible that the 'Nashi' may have some genetic influence from other wild
pears, e.g.
P. hondoensis
Kik. & Nakai, and from the Chinese white pear,
P.
×
bretschneideri
Rehder (Kajiura,
). In northern China and Japan the much
more cold-tolerant
P. ussuriensis
Maxim., hybrids of
P. ussuriensis
and
P. pyrifolia
and
P.
bretschneideri
Rehder are grown, and in warmer areas of southern
China (Pieniazek,
×
) and northern India (Mukherjee
et al.
,
) selections
of
P. pashia
D. Don are cultivated.
The main clonal rootstocks for
P. communis
are clonal selections of quince
(
Cydonia oblonga
L.). Quince has been used as a rootstock for pears for cen-
turies, different clones inducing differing degrees of dwarfing. Quince is easy
to propagate by layering or by cuttings but is not winter-hardy in areas of very
cold winters, is intolerant of calcareous soils and is incompatible with some
important cultivars such as 'Bartlett' ('Williams'') although it can be used for
these with an interstock of, for example, 'Beurre Hardy' or 'Old Home'.
Pyrus
clonal selections have been made but most are difficult to propagate vegeta-
tively. Seedlings of the main scion cultivars of
P. communis
are very widely used
as rootstocks, especially in North America.
The most commonly used rootstocks for Nashi pears in Japan are seedlings
of
P. pyrifolia
with some use also of
P. dimorphophylla
and
P. betulifolia
(Kajiura,
). In south China
P. calleryana
is used and in northern China
P. betulifolia
and
P. ussuriensis
(Lombard and Westwood,
);
P. pashia
is used in northern
India and southern China (Bell
et al.
,
). The distribution of
Pyrus
species
is given in Table
.
.
The place of cultivars in apple and
pear production
Historically apples and pears have been high-value crops which can repay
considerable expenditure on orchard and post-harvest management practices
if these improve yield, quality and marketability. There has also been ready
movement of germplasm, and development and transference of technologies
of production, over the centuries as well as in recent times. In modern times
there has been a concentration of production in climatically-favoured areas
following the opportunities for nationwide and global marketing based on
the development of transport and storage technologies. This latter trend has
been accompanied by an enormous decline in the number of cultivars that
are grown on a commercial scale. Way
et al.
(
) reported that whereas more
than
apple scion cultivars are documented, only a few dozen are now
of major importance. This trend towards concentration on a relatively few
