Alien Gene Introgression in the Genomics Era of Wheat

Wheat has a narrow genetic basis due to the allopolyploid origin of its genome. However, it has numerous wild relatives usable for expanding the genetic variability of the genome. Traditionally, laborious cytological analyses have been employed to detect homoeologous recombination. This has limited alien gene introgression to a relative small scale. Here, we report the study towards efficient application of ph1b mutant and high-throughput genotyping technology in the homoeologous recombination-based alien gene introgression involving Aegilops speltoides (2n=2x=14, genome SS) and Thinopyrum elongatum (2n=2x=14, genome EE). These two wild species contain the genes for resistance to rust, scab, and tan spot diseases and tolerance to salt and waterlogging. We genotyped the individual B-S and B-E homoeologous pairs using wheat 90K SNP arrays and then developed PCR-based molecular markers from the SNPs located in the distal, middle, and proximal regions for each of the chromosome arms based on the high-throughput genotyping results. The SNP-derived PCR markers have been effectively used to detect B-S and B-E recombinants from the large recombination populations. Meiotic recombinants involving multiple chromosomal regions of the individual B-S and B-E homoeologous pairs have been recovered and delineated using the newly developed user-friendly molecular markers. All recovered recombinants have been verified and physically demarcated by GISH. The recombinants with the Ae. speltoides/Th. elongatum-derived genes of interest will be selected for germplasm development. This molecular marker-mediated approach enables the meiotic homoeologous recombination-based alien gene introgression on a large scale and enhances the utilization of alien genes in wheat improvement.