TEOSINTE BRANCHED1 regulates height and stem internode length in bread wheat

Regulation of plant height and stem elongation has contributed significantly to improvement of cereal productivity by reducing lodging and improving distribution of assimilates to the inflorescence and grain. In wheat, genetic control of height has been largely contributed by the Reduced height-1 alleles that confer gibberellin insensitivity; the beneficial effects of these alleles are associated with less favourable effects involving seedling emergence, grain quality, and inflorescence architecture that have driven new research investigating genetic variation of stem growth. Here, we show that TEOSINTE BRANCHED1 (TB1) regulates height of wheat, with TB1 being expressed at low levels in nodes of the main culm prior to elongation, and increased dosage of TB1 restricting elongation of stem internodes. The effect of TB1 on stem growth is not accompanied by poor seedling emergence, as transgenic lines with increased activity of TB1 form longer coleoptiles than null transgenic controls. Analysis of height in a multiparent mapping population also showed that allelic variation for TB1 on the B genome influences height, with plants containing the variant TB-B1b allele being taller than those with the wild-type TB-B1a allele. Our results show that TB1 restricts height and stem elongation in wheat, suggesting that variant alleles that alter the expression or function of TB1 could be used as a new source of genetic diversity for optimizing architecture of wheat in breeding programmes.