Has Selection for Heading Date Inadvertently Reduced Root Variation in European Wheat?

Improving the roots of modern bread wheat varieties is considered to be one key factor in breaking yield barriers and improving adaptation to extreme abiotic stress conditions in the face of climate change. However, wheat roots have been insufficiently characterized to date, and further molecular investigations that develop diagnostic markers and thereby enable breeders a genomics-based selection of improved root systems are strongly required.

We performed comprehensive greenhouse phenotyping for basic seedling growth traits in an extremely diverse collection of 215 international wheat lines. Subsequent GWAS and haplotype network analysis identified rare haplotype variants, significantly associated with root mass, containing loci with high similarity to rice candidate genes for root traits. Strong linkage disequilibrium with molecular markers associated to heading date indicates an inadvertent co-selection of specific root variants during wheat breeding.

Our results may provide breeders the possibility for genomics-based exchange of co-localized haplotypes in order to maintain specific heading characters while maximizing root variation.