The location and genome origin of alien chromatin in wheat founder parent Xiaoyan 6

The location of alien chromatin in Xiaoyan 6 was identified using mc-GISH analysis, genetic mapping and whole genome re-sequencing, and its possible origin was discussed. As a founder parent, Xiaoyan 6 has played an important role in distant hybridization breeding in China. Although it came from the cross between common wheat and Thinopyrum ponticum (Podp.) Barkworth and D.R. Dewey, the location of its alien chromatin has not been determined using traditional genomic in situ hybridization (GISH). In the present study, chromosome variation in Xiaoyan 6 was discovered by multicolor GISH analysis. Four alien-specific markers were developed by specific-locus amplified fragment sequencing technique. Their amplified sequences were analyzed by basic local alignment search tool with the reference genome sequences of common wheat Chinese Spring (CS) and Th. elongatum, and the whole genome re-sequencing reads of Th. ponticum and CS. Furthermore, the four markers were mapped on three different chromosomes in two RIL populations. By dissecting the mapped reads depth of the whole genome re-sequencing of Xiaoyan 6, we found that the depth of nine chromosome regions was obviously lower than the average. Among these, three regions on 1A, 3A and 7B were demonstrated as the alien introgressions in Xiaoyan 6 by multiple methods. Finally, the genetic transmission of the alien chromatin was analyzed in a set of wheat-Th. ponticum introgression lines. Some stable QTLs for morphological and physiological traits have been mapped near the alien chromatin.