Study On Chromatin Elimination/introgression During Early Stage And Regenerated Somatic Hybrid Calli In Wheat

Plant somatic hybridization not only allows bypassing normal crossfertilization but also increases our ability to investigate the mechanism of chromatin elimination and introgression between relatively remote species. This technique has successfully allows for the improvement of a crop species by the transfer of agronomical relevant traits. For wheat, works carried out in our laboratory had generated many intra-, interspecies and generic somatic hybrid plants. The system of wheat introgression lines has established by transferring exogenous chromatin from other cereals by somatic hybridization in our laboratory. In this work, preliminary report describes a somatic hybrid route to introgression involved in wheat and Elytrigia intermedium (Host) Nevski, which will be more efficient than sexual crossing.Prior to fusion, callus-derived protoplasts of E.intermedium were irradiated with ultraviolet light (UV, 380μW/cm~2) for 0s, 30s and 1min respectively, and then were fused with suspension-derived protoplasts of common wheat by PEG (Neomycin phosphate transferase) method. Seventeen somatic hybrid cell lines from total 178 regenerated clones were verified by peroxidase/esterase isoenzymes, cytological observation, RAPD (Randomly amplified polymorphism DNA), SSR (Simple Sequence Repeat) and GISH (Genomic in situ hybridization) analysis. The phenotypes of them all were resembled to wheat, and a few chromatins of E. intermedium were observed to introgression into genomics of wheat.Fashions of chromatin elimination of E.intermedium in early stage and regenerated calli of wheat somatic hybridization was analysised by cytological and GISH method. The results showed that donor chromatin were mainly eliminated in interphase through micronucleus formation in early stage somatic hybridization, other patterns of chromatin elimination of donor in early stage of wheat including micronucleus formation in anaphase, micronucleus formation in multi-nucleus and segregation of parents. The lagging chromosomes, chromosome bridges, nucleus efflux and abnormal nucleus were also expressed in some symmetric and asymmetric somatic hybrid clones. Interestingly, desynchronized cell cycle and a random chromosomes distribution in dividing cells were noticed in asymmetric somatic hybrid cell lines. Two-four micronucleus without main nucleus was found in 2 weeks-culture by UV treatment for 1min, which meant that this micronucleus might be lost gradually during the following cell division.In conclusion, the main period of donor chromatin elimination and introgression took place during the early stage, in other word, were from 5 to 15 days after fusants were cultured.