ECOLOGICAL ADAPTATION AND THE EVOLUTION OF MODERN AVOCADO CULTIVARS

The geographic area in which the avocado originated, stretching from Mexico through Guatemala and probably to Pacific coastal Costa Rica, presents a diverse set of environments. The three races that gave rise te modern avocado cultivars-Antillean (West Indian), Guatemalan and Mexican-accordingly are adapted te quite distinct environmental conditions. The apparent Mexican-Guatemalan hybrids that originated around Atlixco in Puebla State, Mexico, exemplified by 'Fuerte', showed remarkable adaptation when moved to the Mediterranean-type subtropical microcIimates cornmon in southern California, permitting a commercial industry to develop and later be transferred to other parts of the world with similar climates, such as South Africa, Israel and Chile. Selection from the material originally brought from Mexico and Central America permitted California to develop commercial cultivars exemplified by 'Hass', 'Fuerte' and 'Reed', among others, that lead the world in the area planted. Guatemalan cultivars are adapted te elevated situations in Central America, yielding well under cool conditions and forming an important dietary staple. The Antillean race, 'which probably originated aIong the Pacific coast in Central America, yields well in lowland tropical situations and warm subtropical areas such as southern Florida. Planting Guatemalan and Antillean avocados side-by-side in Florida ea¡'ly in this century produced a new group of hybrid cultivars with quality superior to that of most Antillean cultivars, adaptation te sea level locations, and an extended range of season of maturity that permitted Florida te market fruit into the autumn and winter, well past the season of pure Antillean cultivars. The best of these hybrids, 'Booth 7', 'Booth 8', 'Lula', 'Choquette' and a few others have been exported te warm locations about the tropical world for commercial planting. Thus, selection of avocado germplasm imported from Mexico and Central America into California and Florida produced a group of cultivars that are of significant commercial importance in the world.