andrea.gonzalezmunoz@kaust.edu.sa

Aegilops tauschii, the D genome progenitor of bread wheat, has a broad natural genetic diversity useful to improve stress tolerance traits in bread wheat through breeding and genome engineering. Trichomes are specialized structures on the aerial parts of the plant that can provide protection against pests, pathogens and drought and radiation stress, among others. Causal genes or alleles for trichome variation in wheat have not been cloned, possibly due to a complex genetic regulation of this quantitative trait.

We focused on trichome-regulating gene discovery in Ae. tauschii using a sequenced diversity panel of 493 non-redundant accessions and a genomic resource of 46 high-quality genome assemblies generated through the Open Wild Wheat Consortium (www.openwildwheat.org; Cavalet-Giorsa et al., 2023). We phenotyped the diversity panel for leaf edge trichome density and performed k-mer-based genome-wide association studies (kGWAS).

Significantly associated k-mers were mapped to multiple reference assemblies, revealing variation and novelty in the linkage disequilibrium (LD) blocks detected in comparison to using a single reference. LD blocks in chromosome arms 4DS, 4DL and 5DL were found predominantly associated in cis when mapped to accessions with high leaf edge trichome density and contain expressed candidate genes controlling trichome variation in this wild wheat relative.

These findings in Ae. tauschii correlate with quantitative trait loci described previously in rye (Secale cereale), barley (Hordeum vulgare) and the bread wheat D genome, suggesting a potential genetic conservation of this trait across Triticeae.

We will discuss these findings and our progress towards candidate gene isolation.

Cavalet-Giorsa, González-Muñoz, Athiyannan et al., (2023). Origin and evolution of the bread wheat D genome, bioRxiv, https://doi.org/10.1101/2023.11.29.568958.