High light accelerates potato flowering independently of the FT-like flowering signal StSP3D

Little is known on the environmental control of potato flowering. With recent developments in potato breeding, and the growing interest in true potato seed production, more knowledge on potato flowering is required. This research aims to elucidate the effect of the daily light integral (DLI: the accumulated light throughout a day) on potato flower initiation time and investigate which mechanisms underlie this control. We grew potato plants in climate chambers to compare flower initiation under different DLIs in short and long days. We measured the time until the first appearance of the flower buds and the number of leaves formed before the inflorescence. Furthermore, gene expression changes of the potato flowering time gene StSP3D were measured, and potato plants silenced in StSP3D were used to determine whether DLI mediated flowering time was regulated through StSP3D. Additionally, we determined sucrose and starch concentrations and measured the transcription levels of StTPS1, a gene involved in sugar mediated flowering control. Increasing DLI clearly accelerated flowering in potato. The role of carbohydrates (sucrose and starch) and StTPS1 in DLI-accelerated flowering was inconclusive. Although StSP3D was upregulated under high DLI, transgenic lines silenced in StSP3D also showed accelerated flowering under higher DLIs. We therefore conclude that high DLI accelerates potato flowering and this acceleration happens independently of StSP3D upregulation.