Agriculture Reference
In-Depth Information
(mandarins) or green-yellow (lemons, limes and grapefruit). Albedo is a white and
spongy tissue, which separates flavedo from the segments. Juice is located into
vesicles attached to the segment dorsal walls. Seeds are ovate to roundish in shape,
mono- or poly-embryonic, with cotyledons colour ranging from white (oranges and
grapefruit) to green (mandarins).
Although some taxonomists have combined all
Citrus
into a single citrus spe-
cies, recent studies suggest that there are only three major affinity groups within
Citrus
, the
C. medica
group (
C. medica
,
C. aurantifolia
and
C. limon
), the
C. reticu-
lata
group (
C. reticulata
,
C. sinensis
,
C. paradisi
,
C. aurantium
and
C. jambhiri
),
and the
C. maxima
group (
C. maxima
). There is a fourth group with no commercial
importance (
C. halimii
group).
There are six citrus groups of economic interest: sweet orange [
C. sinensis
(L.)
Osb.], common mandarin (
C. reticulata
Blanco), Satsuma mandarin (
C. unshiu
Marc.), grapefruit (
C. paradisi
Macf.), lemon (
C. limon
Burm. f.) and lime (
C. auran-
tifolia
L.). An additional group of hybrids is under consideredation. For detailed infor-
mation on these citrus groups see the reviews by Agustí (
2003
), Donadio et al. (
1995
),
Hodgson (
1967
), Jackson (
1991
), Saunt (
2000
), and Vacante and Calabrese (
2009
).
Sweet Oranges
Sweet orange may be separated into three groups: (1) the common oranges, (2)
the navel oranges, and (3) the pigmented (blood) oranges. The common oranges
(Fig.
6.1a
) are more important commercially and are mainly processed for juice
production. Navel oranges (Fig.
6.1b
) are the second most widely planted group
and are mainly marketable for fresh consumption. The third group, blood oranges
(Fig.
6.1c
), is a very much less important group and plantings are limited to areas
with Mediterranean-type climates. Sweet oranges ripen from early in autumn to late
in spring. The most important sweet orange cultivars are described below.
Common Oranges
'Valencia' is most likely of Chinese origin, but is so named because it resembles
a similar cultivar growing in Valencia, Spain. It is the most important late-season
sweet orange. Fruit usually matures from March to May in the northern hemisphere
(NH) and from September to November in the southern hemisphere (SH). Fruit
remain on the tree without important loss of internal quality, but may regreen on
the tree and can reduce flowering the following spring inducing the tree to alter-
nate bearing. Fruits are of medium size, spherical to oblong, orange-yellowish and
commercially seedless (fewer than nine per fruit). Juice is of excellent quality be-
cause of its high concentration of total soluble solids (TSS) and is keenly sought
for processing into juice. There are several cultivars of 'Valencia', such as 'Frost',
'Midknight' and 'Delta' that differ in fruit shape, peel thickness and date of maturty.
