Key wheat genes that control plant height and grain size identified

Rothamsted scientists, together with partners at the University of Olomouc, Czechia, have uncovered how a family of genes in wheat fine-tunes the plant’s growth and grain development, a breakthrough that could help breeders produce bigger harvests.

The study focused on genes that regulate the production of gibberellins – natural plant hormones that drive growth. By examining seven versions of GA3OX genes in bread wheat (Triticum aestivum), the team found that different members of the gene family have distinct roles in shaping both plant stature and grain size.

Mutations in one set of genes, known as GA3OX2, left wheat plants severely stunted and infertile, due to extremely low gibberellin levels throughout the plant. By contrast, changes in GA3OX3 and GA1OX1 genes affected gibberellin levels mainly in developing grains. Whereas GA3OX3 mutants had lower gibberellin levels, leading to smaller and lighter grains, GA1OX1 mutants accumulated higher gibberellin levels, producing larger grains.

Intriguingly, the study also revealed that grain-related genes can influence plant height, suggesting that hormones move between tissues more widely than previously thought. Analysis of modern wheat varieties showed that breeders have already, perhaps unknowingly, selected natural versions of these genes linked with larger grain size.

The findings highlight new possibilities for crop improvement, say the researchers. By harnessing natural genetic variation in hormone pathways, plant breeders may be able to balance plant height with grain yield more precisely, a longstanding goal in agriculture.

“Our work shows how research into growth regulation pathways in wheat can guide the selection of gene variants that benefit farmers,” said Dr Stephen Pearce, a co-author of the study. “Decades of work on the gibberellin pathway led us to target these genes, which could now help develop wheat with bigger grains”.