Agriculture Reference
In-Depth Information
exposed to sunlight will produce, on average, larger fruits than those on more
vigorous rootstocks which have a larger proportion of shaded canopy. This is
true in some cases; for example, Silbereisen (
) found that fruits of 'Golden
Delicious' and 'Cox's Orange Pippin' on 'M.
'
when the trees were grown in planting systems appropriate to their vigour even
though the average annual orchard yields were higher on 'M.
' were larger than those on 'M.
'. Similarly,
Gyuro
et al.
(
) found the percentage of fruits (averaged over 'Jonathan',
'Golden Delicious' and 'Starking') of more than
mm diameter to be
,
') and vigorous (seedling)
rootstocks, respectively. However, within each category of rootstock vigour, i.e.
very dwarfing, dwarfing, semi-dwarfing, semi-vigorous and vigorous, there are
clear differences between individual rootstocks in their effects on fruit size and
many cases in which the more dwarfing rootstocks do not give the larger fruits.
For example, trees on 'M.
and
on dwarfing ('M.
'), semi-vigorous ('M.
' (semi-dwarfing) and 'M.
' (dwarfing) generally
give larger fruits than those on 'M.
' which is very dwarfing (van Oosten,
).
Secondly, rootstocks can influence fruit size through their effects on the
number of fruits in relation to the size and photosynthetic potential of the tree.
In general, as this ratio is increased fruit size is reduced, hence the widely used
practice of fruit thinning to increase the size of the remaining fruits. Trees on
some very dwarfing rootstocks which have a higher yield per unit volume than
those on 'M.
a; Palmer
et al.
,
', e.g. on '
' and 'M.
', can give much smaller fruits (van
Oosten,
a).
There are also effects of rootstock on fruit size which cannot be explained by
differences in either proportion of shaded canopy or cropping level. Callesen
(
'
than when on 'Bemali' rootstock even though the trees on the latter were
of similar size and were lower yielding. 'Gala' trees on 'Mark' rootstock can
give smaller fruits than when on 'M.
) reported larger fruits when on the rootstocks 'M.
EMLA' and 'Jork
' even after taking
cropping levels in relation to tree size into account (Barritt
et al.
,
EMLA' and 'Bud.
b; Perry,
) also found that trees of 'Summerland McIntosh'
on 'Mark' rootstock had significantly smaller fruits than the same cultivar on
'M.
). Hampson
et al.
(
EMLA' and 'Jork
' even when all the trees were of very similar size, and
thoseon'M.
EMLA'and'Jork
'hadhigheryields,thoughnotsignificantlyso.
Colour
Rootstock influences on fruit colour appear to be mainly a secondary effect of
their effects on the vigour of tree growth and within-tree shade. Gyuro
et al.
(
) recorded fruit colour of apples of 'Jonathan' and 'Starking Delicious'
in the outer, middle and inner zones of trees on 'M.
', 'M.
' and seedling
rootstocks and on their own roots (Table
.
). In each case the fruits from
the outer zone, defined as
m from the external surface, had the greatest
