Abstract
SummaryThe capacity of the bread wheat (Triticum aestivum) genome to tolerate introgression from related genomes can be exploited for wheat improvement. A resistance to powdery mildew expressed by a derivative of the cross‐bread wheat cv. Tähti × T. militinae (Tm) is known to be due to the incorporation of a Tm segment into the long arm of chromosome 4A. Here, a newly developed in silico method termed rearrangement identification and characterization (RICh) has been applied to characterize the introgression. A virtual gene order, assembled using the GenomeZipper approach, was obtained for the native copy of chromosome 4A; it incorporated 570 4A DArTseq markers to produce a zipper comprising 2132 loci. A comparison between the native and introgressed forms of the 4AL chromosome arm showed that the introgressed region is located at the distal part of the arm. The Tm segment, derived from chromosome 7G, harbours 131 homoeologs of the 357 genes present on the corresponding region of Chinese Spring 4AL. The estimated number of Tm genes transferred along with the disease resistance gene was 169. Characterizing the introgression's position, gene content and internal gene order should not only facilitate gene isolation, but may also be informative with respect to chromatin structure and behaviour studies.
Highlights
Using interspecific hybridization to widen a crop’s gene pool is an attractive strategy for reversing the genetic bottleneck imposed by domestication and for compensating the genetic erosion, which has resulted from intensive selection (Feuillet et al, 2008)
The flow karyotype derived from the DAPI-stained chromosomes of the DT4AL-TM line included a distinct peak (Figure S1) corresponding to the 4AL telosome (4AL-TM), which enabled it to be sorted to an average purity of 86.2%
DNA of all 45 000 sorted 4ALTM telosomes was amplified by DNA multiple displacement amplification (MDA)
Summary
Using interspecific hybridization to widen a crop’s gene pool is an attractive strategy for reversing the genetic bottleneck imposed by domestication and for compensating the genetic erosion, which has resulted from intensive selection (Feuillet et al, 2008). Introgression events have involved the transfer of a substantially sized donor chromosome segment, which, along with the target, probably bears gene(s), which impact negatively on the host’s fitness (a phenomenon called ‘linkage drag’) (Gill et al, 2011; Qi et al, 2007; Zamir, 2001). The prime means of reducing the length of an introgressed segment is to induce recombination with its homoeologous region (Niu et al, 2011) The success of this strategy is highly dependent on the conservation of gene content and order between the donor segment and its wheat equivalent
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