ORIGINAL PAPER Improved lint yield under field conditions in cotton over- expressing transcription factors regulating fibre initiation Shiming M. Liu . Jenny C. Koebernick . Sally-Ann Walford . Greg A. Constable . Warwick N. Stiller . Danny J. Llewellyn Received: 18 June 2020 / Accepted: 7 September 2020 Ó Springer Nature Switzerland AG 2020 Abstract Only a few transcription factors (TFs) regulating which cells of the ovule epidermis differ- entiate into lint fibres have been identified in cotton (Gossypium hirsutum L.). In this study, the effect on lint yield and fibre quality of over-expressing three TFs in cotton, GhHD-1, GhMYB25 and GhMYB25- Like, and their double and triple combinations, were evaluated in field experiments over two seasons. The expression of single or stacked TFs were all driven either by an ovule-specific promoter, FBP 7, or a constitutive promoter, Stunt 7, in a Coker 315 background. TF type, either singly or in combination, was found to be the most significant factor affecting lint yield. Among 64 transgenic lines tested, seven were higher yielding than null segregant lines in one or both seasons and were all from the sets with single and double over-expressed TF combinations. A reduced yield was associated with the set of triple combina- tions. The two most stable high yielding lines across the seasons recorded 12–22% higher yields than the nulls, although were not competitive to locally adapted commercial controls. Over-expression of TFs singly or in combination did not significantly alter fibre length and strength, but sometimes increased fibre micronaire. There were positive rela- tionships between lint yield and lint percentage and lint yield and fibre density amongst the transgenic lines. Our preliminary results suggest that manipulat- ing TF expression, either singly or in pairs, can increase the density of fibres initiated on developing seeds and fibre yields under field conditions while maintaining overall fibre quality. Keywords Cotton  Fibre quality  Field trial  Genetic manipulation  Transcription factors  Yield components Introduction Four species of cotton are grown commercially (Gossypium hirsutum L., G. barbadense L., G. arboreum L. and G. herbaceum L.), but G. hirsutum represents the bulk of world production ( [ 96%) and Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11248-020-00214-x) con- tains supplementary material, which is available to authorized users. S. M. Liu (&)  G. A. Constable  W. N. Stiller CSIRO Agriculture and Food, Narrabri, NSW 2390, Australia e-mail: Shiming.liu@csiro.au J. C. Koebernick Auburn University, 202 Funchess Hall, 350 S. College St, Auburn, Al 36849, USA S.-A. Walford  D. J. Llewellyn CSIRO Agriculture and Food, Canberra, ACT 2601, Australia 123 Transgenic Res https://doi.org/10.1007/s11248-020-00214-x