Climatic adaptation in fruit crops

Fruits have varying amounts of climatic adaptation. Most grow only in either the tropical, subtropical, or temperate zones. For example, fruits such as mango and pineapple grow best in a tropical climate without frosts, citrus grows best in a subtropical climate without hard winter freezes, and apricot grows best in a temperate, Mediterranean climate of uniformly cool winters and dry summers. However, strawberry has adaptation from the equator to the Arctic Circle and some apple genotypes will grow in low chill, subtropical climates while others will grow in high chill, temperate climates. Clearly, some fruits have more specific adaptation limitations than others as seen by their specialized areas of production. Fruit breeding is human directed evolution for desired tree and fruit characteristics. Climatic adaptation precedes breeding for commercial fruit qualities. Without climatic adaptation, the breeder may not be able to make hybrids and cannot adequately fruit and evaluate them. Once the breeder finds climatic adaptation for tree growth and fruiting, selection for more specific climatic requirements is possible, and primary attention can then be given to fruit characteristics necessary for making the crop economically viable. Adaptation factors for tree growth, flower bud formation, flowering, and fruit growth and maturation are photoperiod, light intensity, chilling and heat units, soil type, and temperature and water tolerance. These topics are discussed with examples of fruit species that respond to each, and the presence of genetic variability in that fruit species for climatic adaptation. Future prospects in breeding for adaptation are presented.