Agriculture Reference
In-Depth Information
'M.
'. 'Cox' apples of any given size on 'M.
' have lower Ca content than
those on 'M.
', 'MM.
' and, especially, 'M.
'. The effect can be up to
' have correspondingly higher levels of
bitter pit and senescent breakdown (Blasco and Jackson,
mg/
g. Fruits from trees on 'M.
; Blasco,
).
This effect is compatible with the observation that an 'M.
' interstock can
lower Ca concentration in the xylem sap ( Jones,
). The effect on xylem
sap content was shown below as well as above the interstock, implying effects
via root behaviour.
Scion cultivars differ greatly in fruit Ca concentration. Volz
et al.
(
)
showed apple Ca concentration in mg/
on different ages of fruiting wood of 'Royal Gala' whereas that of 'Braeburn',
'Granny Smith' and 'Fuji' ranged from
g fresh wt to range from
.
to
.
.
-
.
,
.
-
.
and
.
-
.
, respec-
tively. Johnson (
), after adjusting for fruit weight, found 'Gala' fruits to
have
)
showed that at any given fruit mass 'Mutsu' apples contained much more Ca
than those of 'Cox' (
c
.
.
mg/
g compared with
.
for 'Jonagold'. Similarly, Perring (
%moreina
g apple). Testoni and Pizzocaro
(
) found 'Starking' to have
.
mg Ca/
g fresh wt in comparison with
for 'Golden Delicious'. The relationship between the calcium concentra-
tion in the fruit of a cultivar and the incidence of Ca-related storage disorders
is not absolute but holds in many cases, e.g. 'Gala' is generally considered
resistant and 'Cox' fairly prone to bitter pit. Fruit Ca concentrations do not
necessarily reflect those in leaves. Van der Boon (
.
) found 'James Grieve'
apple trees to have lower concentrations of Ca in the fruits though more in the
leaves than 'Cox'. Johnson (
) found 'Gala' to have much lower leaf Ca
but higher fruit Ca than 'Jonagold'. Lang (
)
attributed the lower concentrations of Ca in 'Cox' than in 'Gala' apples to a
more severe malfunction of the xylem in the fruit pedicel of 'Cox' as the season
progresses, with an increasing proportion of fruit in which the xylem is totally
non-conducting.
There is evidence for two genes, Bp-
) and Lang and Ryan (
, that control Ca accumu-
lation and distribution, respectively, within apple fruits and control resistance
to bitter pit (Korban and Swiader,
and Bp-
).
Other nutrients and fruit eating-quality
High nitrogen levels can result in decreasing fruit firmness at harvest and to
an increase in breakdown during storage (Sharples,
). High N fertilizer
rates can also reduce the concentration of alcohol-insoluble solids and malate
but increase the concentration of sugar (Richardson,
). Fruits with high N
content are more likely to be affected by cork spot and bitter pit and to develop
more scald, bitter pit, internal browning and internal breakdown after storage
