Molecular Cytogenetic Identification Of Progenies Derived From Wheat-Th.Ponticum Octoploid SNTE20

Thinopyrum ponticum(Podp.)Barkworth [Syn.](2n=10x=70)is a perennial plant of the genus Thinopyrum,which is closely related to the wheat genus.It has excellent traits such as vigorous growth and resistance to various wheat diseases.Wheat-Th.ponticum octaploid SNTE20 obtained by crossing common wheat with Th.ponticum is an important bridge for transferring the excellent genes of Th.ponticum to wheat.In our laboratory,numbers of new wheat-Th.ponticum germplasms with excellent agronomic traits were selected from the offsprings between SNTE20 and common wheat Jimai22.In this study,morphology,cytogenetic and molecular biology were used to identify them.Based on the main agronomic traits,their chromosomal composition and structural variations were analyzed,and the specific IT markers of Th.ponticum was obtained.Markers laid the foundation for their further utilization in wheat genetic improvement.The following main results were obtained:1.Identification of substitution lines.Using the Th.ponticum genomic DNA as a probe and Yannong15 genomic DNA as a block for GISH analysis,it was found that two chromosomes in the root tip cells of B18255-4 had obvious hybridization signals,indicating that it contained two Th.ponticum chromosomes;for the same cell,FISH analysis revealed that B18255-4 deleted a pair of 1B chromosomes,so it was a disomic alien substitution line with a pair of 1B chromosomes absent.Compared with the parental chromosomes,it was found that the hybridization signals on the 5AL and other chromosomes changed significantly,indicating that the chromosome substitution was accompanied by structural variation.Out of the 840 pairs of IT primers,14 specific IT markers belonging to the homeologous group 1 were obtained,and it is speculated that the alien chromosomes in B18255-4 originated from the homeologous group 1 of Th.ponticum.2.Identification of translocation lines.Using the genomic DNA of Th.ponticum as a probe and the genomic DNA of Yannong 15 as a blocker,B18164-6 was subjected to GISH identification.The results showed that there were alien signals at the ends of two chromosomes;FISH identification was then performed on the same cell to find the translocation occurred on 7DL,it is speculated that the alien fragments originated from the homeologous group 7 of Th.ponticum.Compared with the parent chromosomes,the 5AL and other chromosomes of B18164-6 have obvious signal changes,indicating that their chromosomes have undergone structural changes.3.Identification of introgression lines.Using Th.ponticum genomic DNA as a probe and Yannong 15 genomic DNA as a blocker,16 germplasms were identified by GISH,but no foreign signals were found,indicating that they were introgression lines.The results of FISH identification and comparison with the parent chromosome suggestedthat except for B18234-2,the remaining 15 introgression lines have different degrees of signal differences,indicating that there had different degrees of chromosome structural variations.Through molecular markerassisted identification,seven specific IT markers derived from the second and third homeologous groups were detected among 6 materials such as B18235-12.The differences in FISH banding patterns on the chromosomes of different germplasms indicated that they are different introgression lines.