Agriculture Reference
In-Depth Information
significance, and the pigmented cultivars of which 'Rio Red', 'Star Ruby' and
'Redblush' are of commercial importance. Other cultivars such as 'Duncan' (white
grapefruit), 'Henderson', 'Hudson', 'Ray Ruby', 'Flame' and 'Burgundy' are of a
great lesser importance.
The 'Marsh' grapefruit has an unknown origin. This cultivar still predominates
in all citrus producing countries. The tree is vigorous and very productive. The fruit
is large, with yellow and thick rind. The flesh has a high juice content of sweet fla-
vour of rather high acidity. 'Marsh' grapefruit has typically just two or three seeds
per fruit, but is rarely seedless. The fruit matures in November in the NH, but can
remain on the tree for several months without noticeable quality deterioration.
'Rio Red' originated as a selection of a seedling of 'Ruby Red' grapefruit. Bud-
wood of this selection was irradiated and propagated and a mutation selected for its
deep red colouration. 'Rio Red' trees are vigorous with an open growth habit. The
rind is thick, with deeply blushed areas. Flesh is light red in colour, soft, and with an
excellent juice content. Seed content is low, usually one to three per fruit.
Irradiating seed from the 'Hudson' cultivar produced 'Star Ruby'. 'Star Ruby'
trees are less vigorous than most cultivars and, in general, are less productive and
bear smaller fruit. Pruning is of great importance to increase the yield, fruit size
and internal fruit quality of this cultivar. The rind is thin, smooth and fine, and
appropriately pigmented. Flesh has high juice content, is very sweet, and deeply
pigmented. 'Star Ruby' is almost seedless, rarely having more than one or two seeds
in a minority of fruit. However, it is the most problematic of all grapefruit trees to
grow well. This cultivar is susceptible to root rot (
Phytophthora
spp
.
), sunburn,
chlorosis and micronutrient deficiency and is quite cold sensitive. Fruit matures
from mid-October to early November (NH) but can hang on the tree up to March
without appreciable quality deterioration.
'Redblush' originated as a bud mutation of 'Thompson', which, in turn, is a pink
mutation of 'Marsh'. It is also named 'Ruby Red', and 'Henninger'. This cultivar
is widely grown worldwide. Good internal and rind pigmentation. Apart from the
colour, 'Redblush' is virtually identical to 'Marsh' and has few seeds.
Lemons
The Mediterranean lemon we know today is very likely to be a hybrid of citron.
Lemon cultivars are grouped in three types: Sicilian, Verna, and
Femminello
. Lem-
on trees are very sensitive to low temperatures and to fungal and algal diseases, thus
it is not well adapted to humid subtropical or tropical regions. However they do
grow well under the Mediterranean climate. Lemon trees tend to grow, flower, and
produce fruit continuously throughout the year, but in Mediterranean climate trees
have two major flowering periods, in spring and summer. Depending on several
factors, the fruit is harvested either in autumn, winter or summer. The principal,
invernale
or
limoni
crop is harvested from December to May (NH), the
verdelli
or
maiolini
crop from June to September, and the
primofiore
from September to No-
vember; an extra-crop,
bianchetti
, from April to June, exists for Femminello type.
