Haynaldia villosa (L.) is a wild relative species of common wheat that possesses many beneficial genes that can be used for wheat improvement. The accurate detection of H. villosa chromosomes in the genetic background of wheat is critical for transferring its beneficial genes to common wheat by chromosome engineering. The aim of the present study was to investigate the distribution patterns of two repeated DNA sequences, pSc119.2 and pAs1, as well as two rDNA multigene family sequences, 45S rDNA and 5S rDNA, in the individual chromosomes of H. villosa for the future precise identification of alien chromatin in germplasm development and breeding programs. A set of common wheat-H. villosa disomic addition 1V-7V lines was used to determine these specific signals on individual chromosomes of H. villosa. The results showed that two rDNA probes, pTa71 (45S rDNA) and pTa794 (5S rDNA), were located on 1VS and 5VS, respectively, and the signal could be discriminated exclusively in the common wheat background as effective markers of 1VS and 5VS. Furthermore, all seven chromosomes of H. villosa could be distinguished clearly by fluorescence in situ hybridization using pSc119.2 and pAs1 as probes in combination. The utilization of these cytogenetic markers of repetitive sequences, combined with other molecular markers sometimes, will make it possible for a precise identification of alien chromosomes with high efficiency.
Bacterial artificial chromosomes(BACs)or yeast artificial chromosomes(YACs)containing large inserts as probes for fluorescence in situ hybridization(FISH)have been used in the physical mapping of specific DNA sequences,especially for single-or low-copy sequences.Our earlier study identified Stpk-V,a powdery mildew resistance-related gene located on the 6VS chromosome arm of the wild grass Haynaldia villosa(tribe Triticeae),and obtained several Triticum aestivum–H.villosa alien chromosome lines carrying the Stpk-V gene.However,the precise physical location of the Stpk-V gene on chromosome 6VS is not known.In this study,we used TAC-FISH with TAC15 as the probe coupled with sequential genomic in situ hybridization(GISH)to determine the physical location of the Stpk-V gene in different T.aestivum–H.villosa 6V alien chromosome lines,including addition,substitution and translocation lines.The result indicated that the fraction length of the Stpk-V locus is 0.575±0.035 on the 6V chromosome short arm and this was confirmed by FISH using TAC15 as the probe for tracing the Stpk-V gene in other genetic stocks.The cytological mapping strategies used in this study will be of benefit for tracing the alien gene location in the course of introducing desirable traits from wild species.
