Accelerating the transfer of resistance to fusarium head blight in wheat Triticum aestivum

Release of cultivars resistant to Fusarium Head Blight (FHB) from our wheat breeding program is hindered more by incidental flaws of resistant lines than by a lack of improved resistance. To increase the number of resistant lines to select among, we are experimenting with enhancing the fixation of three quantitative trait loci (QTL) for FHB resistance. This is achieved by hemizygosity of the chromosome segments that carry the QTL loci (3BS, 6BS and 5AS) in F 1, followed by their reversion to euploidy upon inbreeding. Elite hemizygous parents were developed by combining a non-reciprocal translocation between 3BL and 6BL and atelocentric for 5AL in crosses with elite hard red spring wheat lines. Hemizygotes were tracked with DNA markers and confirmed by their chromosome pairing (iii + it + 18ii). Based on meiotic and test cross data, 3BS, 6BS and 5AS all showed rapid euploid reversion. Reversion was driven by cosegregation of 3BS and 6BS due to preferential "V" alignment of trivalents at meiotic metaphase and by natural selection in favour of euploid plants and gametes. Populations to fix FHB resistance are to be recovered from crosses of improved hemizygotes with triple QTL derivatives from the breeding program. Since hemizygous hybrids only will be advanced, their segregating progeny will go on to fix the targeted FHB QTL. With QTL recovery guaranteed, resources and crossing plans can focus on improving overall merit.