New 'Green Revolution' Gene Discovery Sows Hope Of Drought Resilient Wheat

Researchers at the John Innes Centre in collaboration with an international team of researchers have discovered a new height-reducing gene Rht13 which means that seeds can be planted deeper in the soil giving access to moisture, without the adverse effect on seedling emergence seen with existing wheat varieties.

Varieties of wheat with the Rht13 gene could be rapidly bred into wheat varieties to enable farmers to grow reduced-height wheat in drier soil conditions.

"We have found a new mechanism that can make reduced-height wheat varieties without some of the disadvantages associated with the conventional semi-dwarfing genes. The discovery of the gene, its effects and exact location on the wheat genome, means that we can give breeders a perfect genetic marker to allow them to breed more climate-resilient wheat," said John Innes Centre group leader Dr. Philippa Borrill corresponding author of the study.

However, the Green Revolution genes bred into wheat also have a significant disadvantage: when these varieties are planted deeper to access moisture in water limited environments, they can fail to reach the surface of the soil.

The newly discovered Rht13 dwarf gene overcomes this problem of seedling emergence because the gene acts in tissues higher up in the wheat stem. So, the dwarfing mechanism only takes effect once the seedling has fully emerged. This gives farmers a significant advantage when planting deeper in dry conditions.

The discovery of the Rht13 dwarfing gene was made possible by recent advances in wheat genomic research, principally the publication in 2020 of the Pan Genome, an atlas of 15 wheat genomes collected from around the world.

Earlier studies had identified the Rht13 locus—the region of DNA—as located on chromosome 7B on the wheat genome but the underlying gene had not been identified.

In collaboration with the group of Wolfgang Spielmeyer at CSIRO Australia, researchers used RNA and chromosome sequencing to track down the new semi-dwarfing gene.

They found a one–point mutation change—a single letter change in a sequence of DNA—and this variation on the Rht13 locus encodes an autoactive NB-LRR gene, a defense related gene, that is switched on all the time.

Experiments testing the effects of the gene in a range of transgenic wheat plants confirmed that the Rht13 variation represents a new class of reduced height gene—more commonly associated with disease resistance as opposed to widely used Green Revolution genes (Rht-B1b and Rht-D1b)) which are associated with hormones and therefore affect overall growth.