MANGO - Tropical Fruits - page 264

of the young fruit is green, sometimes purplish, and, when ripe, green, yellow,
orange, yellowish-red, purplish or purplish-red. The Indian group tends to
mature with a yellow-and-red colour combination, while the Indochina-
Philippine mangos have yellow- or orange-coloured fruit. Some fruits, such as
'Nam Dok Mai', have a slight pink hue on a yellow peel when ripe.
The peel (exocarp) is thick and the fl esh (mesocarp) of ripe fruit is yellow
or orange-yellow and juicy. The pericarp can be separated into exocarp,
mesocarp and endocarp at about 14 days after anthesis. There is a period
9-14 weeks after fruit set when growth rate decreases, and this is associated
with hardening of the endocarp and accumulation of starch and sugars (Fig.
10.7). The endocarp is hard, with fi bres that may extend into the fl esh. The
period from fruit set to maturity depends upon cultivar and climate and can
range from 10 to 28 weeks. The cv. 'Saigon' grown in a hot climate is ready for
harvest in 12-13 weeks. In cool areas, where mean temperatures fall below
20°C, maturation is delayed by up to 4 weeks.
A network of latiferous canals and secretory ducts anastomoses in all
directions in the exocarp and mesocarp (Joel, 1978). Cultivars with a poorly
developed duct system are more susceptible to the Mediterranean fruit fl y
( C. capitata Wied.). The latiferous canals in mango begin to disintegrate during
ripening and the fruit becomes susceptible to fruit fl ies. The sap from the skin
contains urushiol, a toxin also found in other members of the Anacardiaceae ,
which causes an allergic skin rash on contact. Urushiol is catechol substituted
with an alkyl chain with 15-17 carbon atoms. Some individuals are more
sensitive than others.
CULTIVAR DEVELOPMENT
Genetics, cytogenetics and breeding
Cytological studies of seven species, M. indica , M. sylvatica , Mangifera calo-
neura , M. zeylanica , M. caesia , M. foetida and M . odorata , showed all to have
a chromosome number of 2n = 40 (Mukherjee, 1950). M. zeylanica and
M. odorata have been successfully crossed, indicating the possibility of
interspecifi c crosses without the problem of interspecifi c sterility. This is
supported by the uniformity of chromosome morphology. Although mango
hybridization has been carried out, very few cultivars have been developed by
controlled pollination. Hence, little genetic information is available.
Problems in breeding
Breeding is dii cult because of the small number of seeds obtained, the
complex nature of the panicle and fl ower (Fig. 10.1a, b), excessive fruit drop,