Long days promote somatic embryogenesis in spinach

As has been previously shown, the genotype at the individual plant level has a strong effect on the regeneration capacity of spinach, and this effect quite often masks the impact of other factors, including the light environment. Therefore, apical sections of the lateral roots of the same seedling (line) were exposed in parallel to both long day (LD, 16-h photoperiod) and short day (SD, 8-h photoperiod) conditions to assess the effect of photoperiod on somatic embryo (SE) regeneration. The root sections in most lines responded with significantly higher frequencies of regeneration and mean SE numbers with LD compared to roots of the same origin with SD, while 7 of 40 lines were only able to regenerate when exposed to LD. Moreover, in all lines cultured with SD, regeneration was delayed by approximately 4 weeks. Obtained SEs were further grown and multiplied, providing material for the evaluation of the effect of light intensity on regeneration capacity. Maximal regeneration capacity was recorded at 100 μmol m−2 s−1 in all lines tested. The present research confirmed the previously observed strong effect of genotype on regeneration capacity and undoubtedly showed a significantly better response in explants exposed to LD than to SD. These results could contribute to better understanding the process of SE induction in spinach and further improve the efficiency of this process.

► The photoperiod strongly affects spinach regeneration capacity in vitro.
► Somatic embryogenesis was more efficient with long days than with short days.
► Some lines were only able to regenerate with long days.
► Regeneration was delayed with short days by approximately 4 weeks.
► Maximal regeneration capacity was achieved at 100 μmol m−2 s−1.