Production Of Triploid Citrus Germplasm By Somatic Hybridization And Genetic Analysis Of Some Regenerated Plants

Citrus occupies important position in agriculture economics in our country with the high yield and good quality being its core competitiveness. Seedlessness has always been an aim in Citrus breeding. Cell fusion technology has brought an effective method for the breeding of seedlessness Citrus: produce triploid plants via the fusion of haploid and diploid. Based on the above consideration, ‘Early Gold’ haploid callus was used to fuse with diploid mesophyll or callus protoplast of six different citrus cultivars. Moreover, the genetic composition of some regenerated plants were analysed by SSR. The results were as follow:1. Production of triploid plants by the fusion patten of haploid callus + diploid mesophyll. The fusions were performed using haploid callus line of ‘Early Gold’ sweet orange(i.e. Fa) as callus parent and six excellent diploid cultivars as mesophyll parents. However, the fusion cells gradually died during culturing processing and failed to regenerate.It has been tried many times(more than 3 times for each combination), but the regeneration still be failed. This result demonstrated that it is hard to get triploid regenerated plants by the fusion patten of haploid callus protoplast + diploid mesophyll protoplast.2. Production of triploid plants by the fusion patten of haploid callus + diploid callus. The fusions were performed respectively between haploid callus line(i.e. Fa、Ec) and diploid callus line(i.e. ‘Murcott’ tangor). The regenerated callus of Fa + MCK、Ec + MCK were obtained, The regenerated callus of Fa + MCK was proved to be mixoploid of diploid and tetraploid, and the regenerated callus and embryoid of Ec + MCK were pentaploid.3. The plants-inducing and ploidy analysis of three combinations. Via culturing and inducing, 33‘G1 + Kate’ plants、14‘G1 + Itaboria’plants、4‘G1 +MCK’plants were obtained. Ploidy traits has been analysed, all the regenerated plants were tetraploid.4. Genetic identification of the regenerated plants of three combinations. The nuclear genome and cytoplasmic genome of ‘G1 + Kate’、‘G1 + Itaboria’、‘G1 + MCK’ were analysed, and the results showed that all the regenerated plants were tetraploid somatic hybrids with nuclear genome from both two parents, and mesophyll and mitochondria genomes from G1.