The sweet orange is not only the most widely planted tree fruit worldwide; it is by far the most economically significant crop to Florida. Since the discovery of the original sweet orange, advantageous mutations have been identified, clonally propagated, and introduced. Though the list of sweet orange varieties presents a range of traits and characteristics, genetic variation of the sweet orange genome remains quite narrow. Tremendous expansion of orange plantings and the development of multiple market channels resulted in efficiencies, but also has contributed to the creation of a monoculture. Sweet orange varieties have proven particularly susceptible to HLB.
Breeding sweet oranges is a complex task. Dr. Ed Stover, USDA, shared that “the process is impeded by the high degree of apomixis in sweet orange, and low survival of embryos from sexual recombination (Hearn, 1994). When true hybrids are produced from sweet orange crossed with sweet orange, they reportedly do not closely resemble sweet-orange, displaying traits more like those of mandarins (C. reticulata) or pummelos (C. maxima) (Hearn, 1977) and some breeders reported no sweet-orange-like hybrids despite several attempts (Furr, 1969). There have been some instances in which crosses not including sweet orange have produced hybrids similar to the sweet orange (Hearn, 1994).”