Creation Of Seedless Germplasm Between Satsuma Mandarin And Seedy Sweet Oranges Via Protoplast Fusion

China is one of the citrus origins, citrus germplasm resources are rich, and many of them often possess elite traits. However, most of them have seeds or even very seedy, thereby affecting their commercial value and international competitiveness. Seedless breeding is one of our important goals. Protoplast fusion provides an effectively complementary technique in citrus breeding which can overcome efficiently the breeding barriers of sexual crossing e.g. incomparability, male or female sterility, polyembryony etc. Futhermore, it may be possible to combine and exchange both the nuclear and cytoplasmic genomes in the hybrid progeny, especially for creation and improvement of CMS traits. Satsuma mandarin (Citrus unshiu Marc.) was verified as a CMS type. Herein, the symmetric fusion technique was adopted to create hybrid plants for further seedless breeding by transferring CMS from a CMS cultivar Citrus unshiu Marc. cv. Guoqing No. 1 into traditional seedy citrus cultivars. It is also possible to obtain somatic hybrid for triploid breeding. The main results of this research are as follows:1. The symmetric fusion was performed via electrofusion between embryogenic suspension-derived protoplasts of Guoqing No.1 Satsuma callus and mesophyll protoplasts of 'Taoye' orange (C. sinensis (L) Osbeck), 'Xinhui' orange (C. sinensis (L) Osbeck), 'Early gold' orange (C. sinensis (L) Osbeck), and 'Qingjiang' ponkan (C. reticulata (L) Osbeck) respectively. Flow cytometry analysis showed that 20 plants recovered from Guoqing No.1 Satsuma + 'Taoye' orange, all of them were tetraploids. By SSR analysis, we found that all the hybrids with recombination of nucear DNA at TAA15 locus; by CAPS analysis, we found that the mtDNA of the regenerated plants was inherited from Guoqing No.1 Satsuma; For cpDNA segregation pattern, cpSSR analysis of the plants recovered showed their cpDNA was also derived from Guoqing No.1 Satsuma. Only callus lines were obtained from the remaining fusion combinations.2. Regenerated embryoids of two fusion combinations between Chongyi (C. reticulata) and Citrange, Chongyi and Lemon were induced to regenerate shoots and roots. Flow cytometry analysis showed that among nine plants recovered from Chongyi (C. reticulata) + Lemon, four of them were diploids, two were tetraploids, and three of them were hexaploids. Eighty plants recovered from Chongyi (C. reticulata) + Citrange, were all diploids.In summary, somatic hybrids combining elite traits from both parents were regenerated. They can be used directly as scion or for triploid breeding. Somatic hybrids containing elite traits from wild tangerine hold potential as new rootstocks.