Agriculture Reference
In-Depth Information
Fig. 6.4
Physiological citrus fruit disorders.
a
splitting
in 'Nova' mandarin.
b
peel pitting
in
'Marsh' grapefruit.
c
Puffing
in Satsuma fruit.
d
Creasing
in Clementine mandarin.
e
Albedo
breakdown in a Clementine fruit showing
creasing
.
f
Navel rind stain.
g
and
h
peel senescence in
Clementine mandarin.
i
Navel fruit abscission
pulp expansion takes place, the fruit splits. Although the albedo may alleviate pulp
pressure because of its sponginess, the flavedo tissues are more rigid and will
eventually crack. This appears to be the reason for the negative correlation found
between peel thickness or peel resistance to puncturing and the number of fruits
affected by
splitting
.
The application of calcium nitrate sprays at the beginning of the cell enlarge-
ment stage significantly reduces the proportion of fruit affected by
splitting
, but
the response is often erratic. Best results are obtained with the application of a
mixture of GA
3
and 2,4-dichlorophenoxyacetic acid; the treatment significantly
reduces fruit
splitting
and the repetition of the treatment improves the response.
Treatments do not increase peel thickness but significantly increase peel resistance
to puncturing.
Cold Pitting (Peel Pitting)
Cold pitting
or
peel pitting
is a physiological disorder usually related to post-harvest
storage conditions, but in some cases, as for 'Fortune' mandarin and 'Marsh' grape-
fruit (Fig.
6.4b
),
peel pitting
appears before harvesting.
Pre-harvest
peel pitting
starts on fruit as discrete areas forming sunken reddish-
brown to black lesions that tend to coalesce producing larger depressions of affected
areas. The incidence of this disorder varies among the years.