Agriculture Reference
In-Depth Information
long life cycle and heterozygosity of the crop (Knight and Schnell, 1993). The
objectives of mango breeding are to develop regular-bearing dwarf trees that
have an extended cropping season, good cropping in the wet tropics, attractive
fruit of good size (300-500 g), free from internal breakdown and good keeping
and eating quality without fi bre. Active breeding programmes are carried out
in many countries in the world, including India, the USA, Israel and Australia
(Galán Saúco, 1996). Rating scales for important characteristics, such as size,
shape, colour, fi rmness, fi bre content, fl avour, disease resistance and yield,
have been developed. Characteristics are rated on 1 to 5 or 1 to 10 scales (least
desirable to most desirable) in merely descriptive terms (Knight, 1985).
More recent objectives of mango improvement include resistance to
diseases, such as anthracnose
and powdery mildew, both devastating to fruit
yields, and tolerance to environmental conditions such as soil salinity and
cold temperatures. There is some variation in the degree of fruit susceptibility
to anthracnose disease. Genetic transformation of mango is possible, using
Agrobacterium
as the transformant.
Cultivars
There are hundreds of named mango cultivars throughout the tropics and
subtropics (Table 10.3). Each country or region also has their own selected
cultivars (Table 10.4). Preferences for cultivars vary in dif erent regions of the
world. The most important commercial cultivars are derived from selections
among open-pollinated seedling populations. Many excellent cultivars have
been developed through introduction and selection by cooperation between
researchers, growers, nurserymen and hobbyists. Seedlings can be produced
by mass cross-pollination of a collection of mixed cultivars selected for known
desirable characteristics among mono- and polyembryonic races (Whiley
et al.
,
1993). Only seeds from the monoembryonic cultivars are used as the female
parent and planted for later evaluation. Polyembryonic lines are dii cult to
use as the female parent, as there is no assurance that a sexual seedling will be
produced.
It is without doubt that India, with more than 1000 named cultivars and
with dif erent regions growing specifi c cultivars, has provided most of the
germplasm for cultivar development. Florida has developed a large number of
cultivars, using mainly Indian cultivars, which have shown wide geographic
adaptability. 'Haden' was a major cultivar in the early mango industry in
Florida. It may be a parent of other cultivars, including 'Irwin' and 'Lippens'.
Other well-known Florida cultivars include 'Keitt', 'Sensation' and 'Tommy
Atkins' (Campbell and Campbell, 1992). Most mango varieties planted in the
Americas, the Canary Islands and many African countries were developed
in Florida. The Florida varieties are also dominant in international trade and
include 'Tommy Atkins', 'Haden', 'Kent', 'Keitt' and 'Van Dyke'.
