Citrus Rootstock Germplasm Creation Via Somatic Hybridization Of Wild Tangerines With Citrange And Lemon

Wild relatives often possess many elite traits which are seldom in cultivated species. They are very important to increase genetic diversity and improve cultivated species. However, the characters, such as polyembryony, long juvenility, pollen and/or ovule sterility in citrus greatly hinder the utilization of wild species. Somatic hybridization provide the means to overcome these barriers and introduce desirable agronomical traits into breeding materials from species, especially wild relatives that could not otherwise be crossed, and combine the nuclear and cytoplasmic genomes of plants from different genetic origins rapidly. This technique allows the transfer of genes that are not available as cloned DNA sequences, agriculturally interesting genes and cytoplasmic genes. Therefore, to transfer elite traits of wild to cultivated species by somatic hybridization is of basilic practical significance. The goal of this study is to produce somatic hybrids of wild tangerines with Citrange (Poncitrus trifoliata Raf.×Citrus sinensis Osb.) and lemon (C.limon) via protoplasts electrofusion, which can create new rootstock germplasm transferred with wild tangerines' elite traits. The main results of this study are followed:1. Well-cultured callus of wild tangerines were adjusted, and rapid-growing and well-dispersed suspension cultures which were easy for the isolation of protoplasts were established. Regenerated embryoids and planlets of two combinations of Chongyi (C. reticulata) and Citrange, Chongyi and Lemon were obtained by the procedures, including isolation of protoplasts, purification, electrofusion and culture. The regenerated embryoids of the combination of Chongyi and Lemon growed rapidly, but it was hard to get induced shoots. Whereas, it takes more time to get embryoids regenerated from the other combination of Chongyi and Citrange and it was easy to get induced planlets. These showed that there were great differences in regeneration ability between different combinations.2. Four planlets of the combination of Chongyi and Citrange were all diploid and the results of SSR (Simple Sequence Repeat) showed that the nuclear DNA of these plantlets characterized with the bands different from two parents'. Four embryoids were chosen randomly from Chongyi + Lemon. Two of them were diploid, and the other two were tetraploid. SSR indicated that two diploid embryoids were regenerated directly from protoplasts of Chongyi and two tetraploid embryoids are allotetraploid somatic hybrids with sum bands of two parents', and one of the allotetraploid embryoids have a new band which exist neither in Chongyi nor in Lemon.In summary, somatic hybrids which may transfer wild tangerines' elite traits to cultivated species were obtained via somatic hybridization. The somatic hybrids, especially the allotetraploids with both parents' nuclear DNA, hold potential as new rootstocks.