Agriculture Reference
In-Depth Information
There are two groups of limes: 'Tahiti' and 'Mexican' limes. The former includes
the 'Persian' and 'Bearss' limes, the latter includes the 'West Indian' and 'Key'
limes.
Lime trees are very vigorous, thorny, with upright and spreading growth habit.
Leaf lamina of 'Tahiti' lime is large and elliptical, whereas that of 'Mexican' lime is
small and nearly round. Margin is serrated and petiole almost non-existent for both
types. Flowering occurs in two major peaks, but may occur continuously producing
several crops a year. Petals of 'Tahiti' lime are purple, whereas those of 'Mexican'
lime are white. Fruits are spherical to elliptical. 'Tahiti' lime does not produce seeds
since it is a triploid and produces no viable pollen; 'Mexican' lime has 10-15 seeds
per fruit.
The fruit of 'Tahiti' lime (Fig.
6.1h
) is greenish-yellow or pale yellow when fully
mature, very juicy and extremely acidic. The rind is very thin with distinctive rind
oil aroma.
The fruit of 'Mexican' lime is greenish-yellow or yellow when mature, but it is
often harvested earlier while still dark green in colour. The flesh is tender, greenish-
yellow, very juicy and highly acidic.
Citrus Rootstocks
With citrus seedlings, the trees have an extended juvenile period, in which trees
are unable to flower and, thus, are non-productive and excessively vigorous. Seed-
lings are also susceptible to many soil-related problems, such as calcium, salin-
ity, drought, nematodes and some root rot diseases mainly
Phtophthora
spp. To
overcome these problems, most citrus trees consist of two parts: the cultivar that
is budded on a rootstock. The combination integrates favourable attributes of both
of them, and, although there is not perfect rootstock even for a specific situation,
rootstock selection is a major consideration to the success of the plantation.
Today the range of rootstocks is ample. Some are natural species, but man-made
hybrids are increasingly being used. The most important rootstocks are listed above,
together with their main agronomical characteristics (Table
6.1
) and tolerance to
disease (Table
6.2
). For additional information refer to reviews by Agustí (
2003
),
Castle (
1987
) and Saunt (
2000
).
Sour orange (
C. aurantium
L.), sweet orange, and rough lemon (
C. jambhiri
Lush.) rootstocks were widely used but they are now in decline because of the
susceptibility to citrus Tristeza virus (CTV) and to
Phytophthora
root rot. Neverthe-
less, sour orange is an excellent rootstock that has been and will probably continue
to be the main rootstock used worldwide. Sweet orange is a good rootstock tolerant
to many virus diseases including CTV, but has been replaced by other high quality-
inducing rootstocks.
Cleopatra mandarin (
C. reshni
Hort. ex Tan.) is of minor importance worldwide.
However, increasing interest is being shown in some citrus producing countries
because its high calcium, salinity and CTV tolerance.
