Vardi, A., Department of Fruit Tree Breeding and Molecular Genetics, Institute of Horticulture, Agricultural Research Organization, P.O. Box 6, 50250 Bet Dagan, Israel
Neumann, H., Department of Fruit Tree Breeding and Molecular Genetics, Institute of Horticulture, Agricultural Research Organization, P.O. Box 6, 50250 Bet Dagan, Israel
Frydman-Shani, A., Department of Fruit Tree Breeding and Molecular Genetics, Institute of Horticulture, Agricultural Research Organization, P.O. Box 6, 50250 Bet Dagan, Israel
Yaniv, Y., Department of Fruit Tree Breeding and Molecular Genetics, Institute of Horticulture, Agricultural Research Organization, P.O. Box 6, 50250 Bet Dagan, Israel
Spiegel-Roy, P., Department of Fruit Tree Breeding and Molecular Genetics, Institute of Horticulture, Agricultural Research Organization, P.O. Box 6, 50250 Bet Dagan, Israel

Conventional citrus breeding faces many obstacles such as a prolonged period of juvenility, as well as incompatibility and polyembryony. Little published information is available on inheritance of juvenility, self-incompatibility, or parthenocarpy. Satsuma mandarin, known to possess obligatory parthenocarpy, was crossed with 20 different cultivars. Zygotic hybrids were grown in an insect-proof screen house. The procedure employed - induction of root restriction, removal of lateral shoots, limb bending, and optimum fertigation - resulted in an apparent reduction in the duration of the juvenile period. Chances of cross-pollination were very slight. Data on age of flowering, pollen fertility, fruit set, and number of seeds per fruit were analyzed. The genetic analyses of the different populations point to the possibility of polygenic inheritance of juvenility, support the self-incompatibility model proposed by Soost (1965, 1969), and suggest that the S allele of Satsuma differs from the two S alleles of Ellendale and one of the S alleles of Clementine. In addition, we suggest that obligatory parthenocarpy in Citrus depends on three dominant complementary genes.