A Teosinte Branched‐B1 null mutation increases durum wheat tillering, increasing grain yield in certain environments

Abstract Wheat ( Triticum spp.) is a hardy, drought‐tolerant crop well suited to harsh environments like the Northern Great Plains. In regions with higher rainfall or irrigation, a densely planted, high‐biomass crop ideotype may be preferable. However, in moisture‐stressed climates with variable weather, crops are planted at a lower density, and lines with increased tillering potential can improve yields. Drought‐tolerant genotypes with higher tillering potential can provide a harvestable crop in poor years while maximizing yields in favorable conditions. Greater tillering potential allows plants to capitalize on timely rainfall. Teosinte Branched‐1 (TB1 ) is a transcription factor that regulates axillary meristem outgrowth in wheat. This study examines its effects on tillering, mature inflorescence morphology, and their impact on grain yield in durum wheat ( Triticum turgidum L. subsp. durum ). Reducing TB1 function through nonsense mutations in one homeolog can enhance tillering potential, boosting yield under favorable conditions. TB1 variants were analyzed in near‐isogenic line populations across 3 years and five Montana environments. Lines with mutations in both TB1 homeologs had 20% more productive tillers but reduced grain yields in some environments due to reduced spike size. Genotypes containing only the tb‐B1‐W341* nonsense mutation allele had a grain yield increase of up to 20% in environments with optimal mid‐season rainfall and did not yield significantly lower than the wildtype genotypes in any other environment. Integrating a TB‐B1 nonsense allele into durum wheat breeding programs could be useful to increase productive tillers and yield potential.