Somatic Hybridization Between Citrus sinensis and Poncirus trifoliata

Citrus and Poncirus belong to the family Rutaceae. Citrus includes many commercially important fruit species such as sweet orange (C. sinensis), mandarin (C. reticulata), lemon (C. limon), grapefruit (C. paradisi), and is grown in over 100 countries in tropical and subtropical areas spreading over approximately 40° latitude. On the other hand, Poncirus includes only one species of trifoliate orange. (P. trifoliata), which is a deciduous shrub widely grown in Japan and China. It is an important rootstock which possesses cold hardiness, and is resistant to phytophthora, nematode, and tristeza virus (Saunt 1990). The morphology of Citrus and Poncirus is very different; however, their genomes are similar and the chromosome number is 2n = 18. These two genera are sexually compatible and the most widely grown sexual hybrid is Troyer citrange, which has become a very important rootstock in many countries.