Agriculture Reference
In-Depth Information
Apple rootstock
×
site interactions
In relative terms rootstock effects on scion growth and cropping are fairly
consistent over a wide range of environments. Rootstock
site interactions,
although often statistically significant, are usually small compared with root-
stock effects especially when a wide range of rootstocks is being tested. They
may, however, be important where they reflect site variations in major disease
or climatic stresses and in rootstock tolerance of these. Parry (
×
) found
that even within the limited confines of English apple growing areas trees on
'MM.
' varied more in relation to soil type than those on 'M.
a', and on
sites with replant disease the vigour of trees on 'M.
a' was reduced more than
on other rootstocks. Other site
×
rootstock interactions could not be attributed
to any specific cause.
Apple rootstock
×
scion interactions
In broad terms the direction of rootstock effects is consistent over the range of
scion cultivars with respect to vigour of growth, cropping, fruit size, etc. There
are, however, numerous reports of significant rootstock
×
scion interactions;
for example, Parry (
) found large differences between effects of rootstocks
on the cropping efficiency of 'Cox' and on that of 'Worcester Pearmain', and
Barritt
et al.
(
a) found that as rootstock vigour increased, the incidence of
biennial bearing of 'Golden Delicious' and of 'Granny Smith' increased but
that of 'Redchief Delicious' decreased.
Pear scion cultivars
European-type pear scion cultivars
The dominant cultivars of European pears (
Pyrus communis
) were selected in
the eighteenth and nineteenth centuries. A relatively small number of 'sports'
have also been selected from these.
'Williams'BonChretien'('Bartlett')wasbredbyStair,inBerkshire,England,
distributed by Williams of Middlesexand taken to America in
. It was later
distributed under the name of 'Bartlett' in the USA and became the leading
cultivar there both for fresh consumption and, especially, for canning. It is
primarily grown in Washington State and California and is also widely grown
in the most important Italian pear growing region, the lowlands of Emilia-
Romagna and Veneto. The fruits are medium-large, yellow blushed with
brownish-red and of excellent quality. 'Bartlett' is a prolific and heavy cropper,
requires a shorter growing season than most major pear cultivars (
days
