Breeding of Low-chill Peach and Nectarine for Mild Winters

Abstract

Abstract Breeding low-chilling peach and nectarine cultivars began in Florida in 1953. Objectives were to produce low-chilling, early-ripening peach cultivars with fruit qualities equal to temperate-zone cultivars. Low chilling was essential for local adaptation (4). Early ripening was essential to allow production of the earliest-season peaches on the domestic market with little competition from other states and to allow harvest of the crop during the relatively dry period of late April and May. Feral selections descended from Spanish seed introductions through St. Augustine, Fla., seed importations from Okinawa, and ‘Hawaiian’, a South China clone, served as the main sources of low chilling (18). These sources were hybridized with high-chilling U.S. clones having commercial fruit qualities. Resultant seedlings were selected for best adaptation and improvement in fruit qualities above that of the low-chilling parents. Chilling requirements of progeny were near midparent values; chilling requirements of the F2 seedlings ranged from equal to the low parent to equal to the high parent (14), indicating that many genes are involved in chilling. Selections were intermated, and low-chilling progeny were hybridized with other high-chilling U.S. clones, resulting in more progenies for further selection. Commercial fruit size and satisfactory horticultural qualities were obtained after six generations of crosses and backcrosses. Clonal selections made during these six generations and in subsequent generations serve as the basis for most low-chilling cultivars currently grown in Florida, southern Texas, and southern California. Selections from this program are either grown commercially or being evaluated in many tropical and tropical highland areas of the world (11, 16, 19, 24).