Food security is a critical global challenge amidst growing populations, shifting environmental conditions and climate change. As a key staple crop, wheat provides a fifth of global calories and protein, making its sustainable production crucial. However, wheat yields are often limited by nitrate availability. Previous research indicates nitrate impacts reproductive development of shoot apical meristems (SAMs), influencing the rate of development and ear morphology, impacting grain yields. Previous research also suggests that strigolactones are upregulated in response to nitrate deficiency, potentially affecting shoot architecture and development. In this study, I aimed to explore the role of strigolactones in wheat’s reproductive development and yield formation under nitrate stress. I hypothesised that strigolactones mediate reproductive responses to nitrate stress by examining changes in SAM development and gene expression in response to varying nitrate levels in wild-type (WT) and strigolactone mutant wheat in the UK model Cadenza. My findings revealed distinctly different reproductive responses between moderate and severe nitrate stress. Under severe nitrate deficiency, SAM development in primary shoots accelerated, while under moderate limitation, multiple tillers emerged, but their reproductive development was deprioritised. Strigolactone signalling was found to be essential for these responses. In strigolactone signalling mutants (d14), primary SAM development did not accelerate under nitrate stress, and reproductive development in higher-order tiller SAMs was not delayed. Under severe nitrate deficiency, strigolactone signalling led to the upregulation of FT2, VRN1, FUL2, and FUL3, and the downregulation of TFL1, promoting faster reproductive development. Conversely, under moderate stress, strigolactones suppressed these genes in higher-order tillers, delaying their development, effectively deprioritising them. These results highlight the critical role of strigolactones in redistributing reproductive efforts and regulating wheat’s response to nitrate availability, offering insights into potential targets for optimising reproductive development. This knowledge is essential for enhancing wheat yields in nitrate-limited environments, supporting sustainable agriculture and global food security.
