Inoue, M.Situmorang, A.Kelly, J.H.Chen, W.Zhou, H.Ferrario, C.C.Gregis, V.Vajani, A.Shaaf, S.Biswas, A.Alqusumi, R.Waters, M.T.Tucker, M.R.Zhang, D.Watts-Williams, S.J.Janiak, A.Marzec, M.Chmielewska, B.Rossini, L.Yoneyama, K.et al.Byrne, M.2025-10-142025-10-142025Journal of Experimental Botany, 2025; 76(18)0022-09571460-2431https://hdl.handle.net/2440/147766Advance Access Publication 26 June 2025. OnlinePublStrigolactone (SL) mutants display a range phenotypes, such as increased branching, reduced stature and a loss of SLs exuded from roots into soil. SL biosynthesis is complex and divergent between plant species. Recently, mutants defective in specific SL biosynthesis genes have shown a loss of exuded SLs, but no obvious change in branching (tillering). This means that functional specification may exist between certain SL sub-types. It has been suggested that the LATERAL BRANCHING OXIDOREDUCTASE (LBO) enzyme acts in a sub-pathway of SLs that is specific for branching. Here we report that barley plants mutants in hvlbo have increased tillering, but normal production of SLs detected in roots and root exudates. This finding supports the idea that SLs have functional or tissue-specific differences and that the LBO pathway has specificity for bud outgrowth rather than exudates.en© The Author(s) 2025. Published by Oxford University Press on behalf of the Society for Experimental Biology. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (https://creativecommons.org/licenses/bync/ 4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.barleybiosynthesisbranchingcroproot exudateStrigolactonetilleringyieldJournal article10.1093/jxb/eraf285743319Situmorang, A. [0000-0003-1879-3355]Kelly, J.H. [0000-0002-9472-678X]Chen, W. [0000-0001-7681-3962] [0000-0002-0727-4341]Tucker, M.R. [0000-0003-4661-6700]Zhang, D. [0000-0003-3181-9812]Watts-Williams, S.J. [0000-0003-3467-0662]Brewer, P.B. [0000-0003-4871-9260]