The development of improved citrus and scion rootstock cultivars has been limited by several factors, including complex reproductive biology, extended juvenility, and a lack of support and continuity of long-termed conventional breeding programs (Gmitter et al., 1991). Most commercially important scion and rootstock cultivars have arisen from the selection of bud-sport mutations within existing clones or by chance seedling selections. However, there are a few important scion and rootstock cultivars that were developed by conventional breeding. Such scion cultivars are mandarin hybrids developed by USDA breeders, primarily tangelos (mandarin x grapefruit hybrids) and tangors (mandarin x sweet orange hybrids) including ‘Minneola’, ‘Orlando’, ‘Nova’, ‘Page’, ‘Robinson’, ‘Fairchild’, ‘Sunburst’ (Saunt, 1990), and more recently ‘Fall Glo’ and ‘Ambersweet’ (C.J. Hearn, personal communication). Important rootstock cultivars developed by conventional breeding include Swingle citrumelo (grapefruit x trifoliate orange hybrid) and Carrizo and Troyer citranges (sweet orange x trifoliate orange hybrid). Because of renewed interest and the development of improved breeding parents, sexual hybridization will play an increasingly important role in citrus cultivar improvement. The integration of emerging biotechnologies with conventional breeding methods will facilitate and expedite citrus cultivar improvement.

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