Improvement of Subtropical Fruit Crops: Citrus
IMPROVEMENT OF SUBTROPICAL FRUIT CROPS: CITRUS HAMILTON P. ÏRAUB, Senior Iloriiciilturist T. RALPH ROBCNSON, Senior Physiolo- gist Division of Frnil and Vegetable Crops and Diseases, Bureau of Plant Tndusiry MORE than half of the 13 fruit crops known to have been cultivated longer than 4,000 years,according to the researches of DeCandolle (7)\ are tropical and subtropical fruits—mango, oliv^e, fig, date, banana, jujube, and pomegranate. The citrus fruits as a group, the lychee, and the persimmon have been cultivated for thousands of years in the Orient; the avocado and papaya were important food crops in the American Tropics and subtropics long before the discovery of the New World. Other types, such as the pineapple, granadilla, cherimoya, jaboticaba, etc., are of more recent introduction, and some of these have not received the attention of the plant breeder to any appreciable extent. Through the centuries preceding recorded history and up to recent times, progress in the improvement of most subtropical fruits was accomplished by the trial-error method, which is crude and usually expensive if measured by modern standards. With the general accept- ance of the Mendelian principles of heredity—unit characters, domi- nance, and segregation—early in the twentieth century a starting point was provided for the development of a truly modern science of genetics. In this article it is the purpose to consider how subtropical citrus fruit crops have been improved, are now being improved, or are likel3^ to be improved by scientific breeding. Each of the more important crops will be considered more or less in detail.
[Show full text]