Back to the Roots of Wheat Breeding: How Heading Date Connects to Underground Plant Development

An untapped promising potential to increase the stagnating yields of modern wheat and to enhance the productivity for its use as food, feed, and an increasingly important bioenergy resource is believed to lie in the plants’ “hidden half”, the root system. In wheat, root traits have been associated with higher productivity and yields, improved nutrient acquisition and increased adaptation to abiotic stresses. They furthermore serve as key components in the plants’ response towards soil-borne plant pathogens, such as Fusarium fungi, that can cause severe yield losses and seed quality reductions. However, the roots have widely been ignored by scientists and breeders, mainly due to the notorious difficulty in obtaining appropriate measurements. Concise knowledge about the genetic background of root development is therefore strongly required, along with reliable diagnostic molecular markers for genomics-based selection of improved, resilient root systems in breeding programs.

We phenotyped an extremely diverse collection of 215 international hexaploid wheat lines in a comprehensive greenhouse screen for basic seedling growth traits. Using genome-wide genotyping data from the 90K Illumina Infinium SNP array, we identified common chromosome regions linking root mass and heading date phenotypes. Our results give interesting insights into relationships between these two traits, discriminating between linkage and pleiotropy, and provide breeders a means to maintain heading characters while maximizing root diversity. With this respect our findings also provide a valuable basis for genomics-based selection approaches to improve overall resilience in novel high-yielding wheat varieties with extended root systems.