Agriculture Reference
In-Depth Information
The apple or pear tree grown today is almost invariably a compound tree
consisting of a fruiting scion grafted or budded on to a rootstock. In some cases
it is made up of three components: the scion, the rootstock and an interstock
(interstem). This latter may be used where the scion and the rootstock will not
form a strong graft union with each other, i.e. are incompatible, but will each
unite with the interstock. It is also used to achieve control of scion vigour by
the influence of an interstock cultivar which is too difficult to propagate for it
to be used as a rootstock.
The apple scion cultivars in commerce are classified as
Malus
×
domestica
Borkh. (Korban and Skirvin
). This species was considered to have orig-
inated as the result of interspecific hybridization, its main ancestor being
M.
sieversii
with contributions from
M. orientalis
,
M. sylvestris
,
M. baccata
,
M. mand-
shurica
and
M. prunifolia
. Recent work, however, suggests that
M. sieversii
was
the sole genetic ancestor of traditional European eating apples ( Juniper
et al.
,
).
Resistance to apple mildew is being introduced from
M.
×
robusta
,
M.
×
zumi
and
M. hupahensis
and to apple scab from
M.
floribunda
. Resistance to apple
scab and tolerance to very low winter temperatures are also being introduced
from
M. baccata.
Roach (
×
) considered that the original 'Paradise' rootstocks, from which
the 'Malling' ('M.') clonal rootstocks were selected, were forms of
M. pumila.
Seedlings of crab apple,
M. sylvestris
, were also commonly used as rootstocks
in Europe.
Malus
robusta
has also been used because of its tolerance of cold
winters.
M. sieboldii
(Regel) Rehder,
M. baccata
(L.) Borkh and
M. prunifolia
Borkh were generally used in Japan with a pendulous sport of the latter being
predominant (Fukuda,
×
×
micromalus
Makino were used in breeding programmes, each being crossed
with 'M.
). Additionally
M. baccata
(L.) Borkh and
M.
'(
M. pumila
) to produce rootstocks which are now commercially
available (Fischer,
).
Most
Malus
species intercross and, given the length of time over which apple
trees of different sorts have been selected, it is difficult to be certain of the
authenticity of specific names. A modern list of sections, primary species and
species hybrids ( Janick
et al.,
) and
R. Watkins (personal communication) consider
M. floribunda
and
M. micromalus
to be hybrids and therefore better designated as
M.
) is presented in Table
.
. Fischer (
×
floribunda
and
M.
×
micromalus
.
The pear cultivars grown in Europe and much of the 'western' world are
mainly of the species
Pyrus communis
L., possibly with a degree of hybridization
with
P. korschinskyi
(which may be simply a synonym) and
P. heterophylla.
In Japan,
ChinaandothertemperateFarEasterncountriesthepearcultivarsarederived
from
P. pyrifolia
(Burm.) Nakai (
P. serotina
Rehder). In the English language these
have been referred to as 'Sand pears', 'Asian pears' and 'Japanese pears', but
