INHERITANCE OF PROCUMBENT HABIT FROM CIPO SWEET ORANGE IN CROSSES WITH CLEMENTINE MANDARIN

'Cipo' sweet orange [Citrus sinensis (L.) Osbeck] combines typical mid season fruit characteristics with a unique procumbent growth habit. Th is distinctive habit may be of value in breeding smaller and more proc umbent scion cultivars if the growth habit is transmitted to hybrid se edlings. Two hybrid populations were created using 'Clementine' mandar in (Citrus reticulata Bianco) as the female parent and either 'Cipo' s weet orange or 'Pineapple' (another midseason sweet orange with a more typical upright growth habit) as the male parent. The 'Clementine' x 'Cipo' cross yielded many hybrids with the procumbent habit, many with the upright habit, and some that appeared intermediate. Both hybrid p opulations were compared with nucellar seedling populations from 'Cipo ' and 'Pineapple' using two morphological characteristics that differe ntiate between the procumbent habit of 'Cipo' and the upright habit of 'Pineapple'. All the 'Clementine' x 'Pineapple' hybrids mere of uprig ht growth habit, while the 'Clementine' x 'Cipo' progeny segregated in to two groups based on growth habit (upright and procumbent). The two measured characteristics were tightly correlated in the segregating po pulation and are probably pleiotropic effects of the same genetic muta tion. The observed population distributions were as expected if the pr ocumbent habit in 'Cipo' is controlled by a single dominant allele in the heterozygous condition.