Yield reduction historically associated with the Aegilops ventricosa 7DV introgression is genetically and physically distinct from the eyespot resistance gene Pch1

Marianna Pasquariello, Simon Berry, Christopher Burt, Cristobal Uauy & Paul Nicholson 

Theoretical and Applied Genetics March 2020 - volume 133: 707–717

Key message

Yield penalty and increased grain protein content traits associated with Aegilops ventricosa 7D introgression have been mapped for the first time, and they are physically distinct from the eyespot resistance locus Pch1.

Abstract

Wheat wild relatives represent an important source of genetic variation, but introgression of agronomically relevant genes, such as for disease resistance, may lead to the simultaneous introduction of genetically linked deleterious traits. Pch1 is a dominant gene, conferring resistance to eyespot and was introgressed to wheat from Aegilops ventricosa as part of a large segment of the 7D^V chromosome. This introgression has been associated with a significant yield reduction and a concomitant increase in grain protein content. In this study, we evaluated both traits and their relationship to the location of the Pch1 gene. We found that both QTLs were clearly distinct from the Pch1 gene, being located on a different linkage group to Pch1. In addition, we found that the QTL for increased grain protein content was strong and consistent across field trials, whereas the yield penalty QTL was unstable and environmentally dependent. The yield and grain protein content QTLs were genetically linked and located in the same linkage group. This finding is due in part to the small size of the population, and to the restricted recombination between wheat 7D and Ae. ventricosa 7D^v chromosomes. Although recombination in this interval is rare, it does occur. A recombinant line containing Pch1 and 7D_KASP6, the marker associated with increase in grain protein content, but not Xwmc221, the marker associated with the yield penalty effect, was identified.

See https://link.springer.com/article/10.1007/s00122-019-03502-1

Figure 1: Physical and genetic map of chromosome 7D in the HS × HS/VPMD7D population (a, b) aligned to the LOD profile of the QTL interval mapping analysis of 4 years trials combined data for yield and GPC, and of two years trials for TGW (c). QTL positions are shown to the right of the genetic maps by bars that indicate areas on the map with a LOD score greater than the significance threshold of 2.3. c Shows line RVPM003 which possesses the Ae. ventricosa alleles for 7D_KASP6 (peak marker for GPC) and Xbarc97 (Pch1) but has the Hobbit sib allele at Xwmc221 (associated with positive yield)