Far-red timing uncovers cultivar-dependent yield and bolting responses in vertical-farm spinach (Spinacia oleracea L.)
- 1Horticultural Innovation Centre, School of Natural and Social Sciences, Scotland’s Rural College (SRUC)
Abstract
Far-red light (FR; 700–750 nm) is increasingly incorporated into controlled-environment lighting because it can improve photosynthetic efficiency when combined with shorter photosynthetically active wavelengths, principally red and blue. In long-day leafy crops such as spinach, however, FR may also promote the transition from vegetative to reproductive growth and thereby reduce marketable yield. Most studies have evaluated FR fraction, intensity, or end-of-day exposure, whereas the developmental timing of FR has rarely been tested, particularly in spinach. Here we evaluated six commercial spinach cultivars (Amador, Harp, Renegade, Responder, Rubino, and Santa Cruz) in an indoor vertical farm under a common red–green–blue background (PPFD 260–264 µmol m –2 s –1 , 12-h photoperiod, 24 °C) and four FR timing treatments: no FR (control), FR throughout production (FullFR), FR during early development only (EarlyFR), and FR during late development only (LateFR). Far-red was supplied additively on the constant PAR background (i.e., supplemented, not substituted for PAR photons). LateFR matched or slightly exceeded control in marketable fresh weight (244 vs. 224 g; not significant) without increasing flowering incidence whereas far-red supplied during early development reduced fresh weight (158 g) and increased flowering. The magnitude of the timing response differed among cultivars: switching from EarlyFR to LateFR recovered 0% fresh weight in Amador but 106–107% in Renegade and Rubino, with the largest penalties occurring in otherwise bolt-resistant cultivars. EarlyFR also increased total chlorophyll and reduced the chlorophyll a/b ratio. These results show that FR response in spinach is strongly conditioned by developmental stage and cultivar. Although LateFR received more total far-red than EarlyFR, it behaved like the control, indicating that the penalty was set by far-red timing rather than dose. Treatment differences in bolting and yield tracked an estimated phytochrome photostationary-state deficit during early development: a phytochrome-deficit model markedly outperformed a cumulative-dose model (ΔAIC = 33), and the deficit × cultivar interaction was strong ( p < 0.001), with bolt-resistant cultivars losing most yield when far-red coincided with the early developmental window. We therefore propose that FR should be treated as a genotype-dependent management variable rather than as a fixed spectral input, with late application and bolt-resistant cultivars offering the most favorable combination for vertical-farm spinach production. Framed within the breeder’s equation, the close match between the trial and production environment and the scope for shorter breeding cycles indoors suggest that genotype and far-red timing can be optimized jointly to accelerate genetic gain.
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BibTeX
@article{mcgovern2026farred,
title = {{Far-red timing uncovers cultivar-dependent yield and bolting responses in vertical-farm spinach (Spinacia oleracea L.)}},
author = {Christopher McGovern and Milena Adrio and Hadi Aliki and Ruth Vichos and Wayne Powell and Rajiv Sharma},
journal = {Frontiers in Plant Science},
year = {2026},
month = oct,
doi = {10.3389/fpls.2026.1934445},
url = {https://www.frontiersin.org/articles/10.3389/fpls.2026.1934445/full},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Far-red timing uncovers cultivar-dependent yield and bolting responses in vertical-farm spinach (Spinacia oleracea L.)
AU - Christopher McGovern
AU - Milena Adrio
AU - Hadi Aliki
AU - Ruth Vichos
AU - Wayne Powell
AU - Rajiv Sharma
PY - 2026
DA - 2026/10/13
JO - Frontiers in Plant Science
DO - 10.3389/fpls.2026.1934445
UR - https://www.frontiersin.org/articles/10.3389/fpls.2026.1934445/full
AB - Far-red light (FR; 700–750 nm) is increasingly incorporated into controlled-environment lighting because it can improve photosynthetic efficiency when combined with shorter photosynthetically active wavelengths, principally red and blue. In long-day leafy crops such as spinach, however, FR may also promote the transition from vegetative to reproductive growth and thereby reduce marketable yield. Most studies have evaluated FR fraction, intensity, or end-of-day exposure, whereas the developmental timing of FR has rarely been tested, particularly in spinach. Here we evaluated six commercial spinach cultivars (Amador, Harp, Renegade, Responder, Rubino, and Santa Cruz) in an indoor vertical farm under a common red–green–blue background (PPFD 260–264 µmol m –2 s –1 , 12-h photoperiod, 24 °C) and four FR timing treatments: no FR (control), FR throughout production (FullFR), FR during early development only (EarlyFR), and FR during late development only (LateFR). Far-red was supplied additively on the constant PAR background (i.e., supplemented, not substituted for PAR photons). LateFR matched or slightly exceeded control in marketable fresh weight (244 vs. 224 g; not significant) without increasing flowering incidence whereas far-red supplied during early development reduced fresh weight (158 g) and increased flowering. The magnitude of the timing response differed among cultivars: switching from EarlyFR to LateFR recovered 0% fresh weight in Amador but 106–107% in Renegade and Rubino, with the largest penalties occurring in otherwise bolt-resistant cultivars. EarlyFR also increased total chlorophyll and reduced the chlorophyll a/b ratio. These results show that FR response in spinach is strongly conditioned by developmental stage and cultivar. Although LateFR received more total far-red than EarlyFR, it behaved like the control, indicating that the penalty was set by far-red timing rather than dose. Treatment differences in bolting and yield tracked an estimated phytochrome photostationary-state deficit during early development: a phytochrome-deficit model markedly outperformed a cumulative-dose model (ΔAIC = 33), and the deficit × cultivar interaction was strong ( p < 0.001), with bolt-resistant cultivars losing most yield when far-red coincided with the early developmental window. We therefore propose that FR should be treated as a genotype-dependent management variable rather than as a fixed spectral input, with late application and bolt-resistant cultivars offering the most favorable combination for vertical-farm spinach production. Framed within the breeder’s equation, the close match between the trial and production environment and the scope for shorter breeding cycles indoors suggest that genotype and far-red timing can be optimized jointly to accelerate genetic gain.
SN - 1664-462X
ER -