Earlier-Bolting Spinach Cultivars Respond to a Wider Spectrum of Night-Break Light for Bolting than Later-Bolting Cultivars

We investigated varietal differences in reproductive responses of spinach (Spinacia oleracea L.), a long-day plant, to 2-h night-break treatments with light of various wavelengths provided by light-emitting diodes of various colors. In the first experiment, medium-early-bolting cv. ‘Alrite’ and late-bolting cv. ‘Summer Focus’ were treated with blue, green, yellow, red, far-red, or no light. Both cultivars showed high night-break sensitivity to red, yellow, and green light and low sensitivity to blue light for bolting, but ‘Alrite’ was much more sensitive to far-red light than ‘Summer Focus.’ In the second experiment, we added medium-early-bolting cv. ‘Atlanta’ and late-bolting cv. ‘Active.’ These cultivars were night-broken by red, far-red or no light. Bolting of earlier-bolting cultivars ‘Alrite’ and ‘Atlanta’ was accelerated more by far-red night-break treatment than that of later-bolting cultivars ‘Active’ and ‘Summer Focus.’ These results suggest that earlier-bolting cultivars of spinach have a wider range of effective night-break wavelengths for bolting than later-bolting cultivars.