Agriculture Reference
In-Depth Information
Avocados can be grown under a wide range of temperatures, although the three avo-
cado ecological races show different temperature requirements. Thus, both the Mexican
and Guatemalan genotypes originate in the tropical highlands of Central America and,
consequently, they can also be cultivated in areas with subtropical climates, although
the Mexican race seems to be more adapted to low temperatures. The West Indian
genotypes, originated from lowlands in the Pacific Central American coast are more
adapted to warmer conditions with optimum temperatures between 25°C and 28°C
and they are highly sensitive to frost. In spite of the different climatic adaptations,
avocado, in general, has shown adaptation to very different edaphoclimatic conditions
and current cultivation regions range from the tropics to higher than 35° N (Southern
Spain) or 35° S (New Zealand). Differences also occur in the tolerance to temperature
among cultivars from the same botanical race. A careful site selection should be made
in areas prone to low winter temperatures in order to reduce the risk of frost damage.
Nevertheless, freezes can sometimes take place even in important avocado growing
regions in subtropical climates; in those cases, it is recommended that pruning of dead
wood is postponed for several weeks or months to evaluate damaged branches.
Crop Management
Traditionally, commercial propagation of avocado has been performed by grafting
on seedling rootstocks. However, more recently, clonal rootstocks are increasingly
been used especially due to the development of new selections, such as Duke 7 or
Dusa, with tolerance to
Phythopthora
root rot. For a thorough review on avocado
propagation see Bender and Whiley (
2002
).
Alternate or biennial bearing is common in avocado and different crop manage-
ment practices such as the use of appropriate rootstocks, harvesting most of the
crop as soon as commercial maturity has been reached, especially in 'on' years, and
selective heavy pruning before blooming can help to reduce alternate bearing. See
Whiley (
2002
) for a review.
Reproductive Biology
One of the main limitations in avocado production worldwide is the massive
abscission of flowers and developing fruitlets that results in a fruit set that ranges be-
tween 0.001 and 0.23 % (Sedgley
1980
). Inadequate pollination itself cannot explain
these low yields and, consequently, several additional factors are also implicated.
Inflorescence and Flower Development
Reproductive growth usually occurs once per year in most cultivars following a
rest period (Davenport
1986
). Floral primordial are usually found in terminal and
subterminal buds of spring and summer growth flushes (Scora et al.
2002
).
