Loss-of-function of StFKF1 delays flowering and tuberization under long-day conditions in potato.

UNLABELLED: As key components of the diurnal oscillation pathway, FKF1 family genes are well known to promote flowering under inductive photoperiods in model plants, yet their biological function in potato flowering and tuberization under specific photoperiodic conditions remains poorly understood. In this study, we provide initial insights into the biological role of StFKF1 in modulating floral transition, and lay a foundation for exploring its potential involvement in tuber formation in potato. Transcript profiling showed that StFKF1 exhibits a distinct diurnal expression pattern under light/dark cycles. We successfully generated homozygous StFKF1 knockout mutants using the CRISPR/Cas9 gene-editing system. Under long-day conditions, the mutant displayed significantly delayed flowering compared with the wild type, which was consistent with theoretical predictions. Contrary to the expectation of earlier tuberization, StFKF1 knockout led to delayed tuber formation. Furthermore, the mutant showed reduced single-plant yield, while tuber number per plant remained statistically unchanged. Gene expression analysis indicates that the florigen gene StSP3D and tuberigen gene StSP6A presented predictable expression alterations in the mutant. Notably, StGI was significantly upregulated in StFKF1 knockout lines, which may represent a component of a working hypothesis to explain the unexpected delayed tuberization phenotype. This study provides evidence suggesting that StFKF1 influences the timing of flowering and tuber initiation, as well as the expression patterns of key regulatory genes, under long-day conditions, thereby contributing to a theoretical foundation for understanding developmental transitions in this specific environmental context. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11032-026-01709-x.