Optimization of Tomato Shoot Architecture by Combined Mutations in the Floral Activators FUL2/MBP20 and the Repressor SP

Shoot determinacy is a key trait affecting productivity in tomato, quantitatively governed by genes within the flowering pathway. Achieving an optimal balance of flowering signals is essential for shaping plant architecture and maximizing yield potential. However, the genetic resources and allelic diversity available for fine-tuning this balance remain limited. In this work, we demonstrate the potential for directly manipulating shoot architecture by simultaneously targeting the flowering activating <i>FRUITFULL</i>(<i>FUL</i>)-like genes, <i>FUL2</i> and <i>MADS</i>-<i>BOX PROTEIN 20</i> (<i>MBP20</i>), and the flowering-repressing gene <i>SELFPRUNING</i> (<i>SP</i>). Loss of <i>MBP20</i> in the <i>sp</i> background leads to additional inflorescences, while determinacy is largely maintained. However, additional mutation of <i>FUL2</i> results in mainly indeterminate plants, which have faster sympodial cycling, leading to more compact growth and increased flower production. Our results provide a path to quantitative tuning of the flowering signals with a direct impact on shoot architecture and productivity.