Salinity sensitivity and mycorrhizal responsiveness of polyphenolics in ‘Siam Queen’ basil grown in soilless substrate

Authors: Scagel, Carolyn; Lee, Jungmin

Submitted to: Scientia Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/30/2020
Publication Date: 7/27/2020
Publication URL: https://handle.nal.usda.gov/10113/6887876
Citation: Scagel, C.F., Lee, J. 2020. Salinity sensitivity and mycorrhizal responsiveness of polyphenolics in ‘Siam Queen’ basil grown in soilless substrate. Scientia Horticulturae. 269. https://doi.org/10.1016/j.scienta.2020.109394.
DOI: https://doi.org/10.1016/j.scienta.2020.109394

Interpretive Summary: Quality of basil products is linked to phenolic composition. Phenolic composition of basil was assessed when grown with different levels of salinity from sodium chloride (NaCl) or calcium chloride (CaCl2). Plants were also inoculated or not with an arbuscular mycorrhizal fungus (AMF), to determine whether AMF alter the effects of salinity on phenolics. The effects of salinity on polyphenolic profiles varied only slightly between salt types. Salinity altered phenolic accumulation at lower salinity levels than those that influenced biomass yield. Salt-treated plants had lower concentrations of most measured polyphenolic compounds but enhanced accumulation of two polyphenolics (quercetin-rutinoside and a cinnamic acid derivative). In salt-treated plants AMF increased FW and accumulation of several polyphenolics, but did not completely mitigate the negative effects of salinity on biomass yield or phenolic composition. Decreasing availability and rising costs of high quality water for irrigation results in more frequent use of saline water sources in many crop production systems. Our data highlights the importance of considering the effects of salinity on both crop productivity and quality.

Technical Abstract: The effects of salinity from NaCl or CaCl2 on phenolic composition in basil (Ocimum basilicum L. ‘Siam Queen’). Plants in no-salt controls and salinity treatments were also inoculated or not with the arbuscular mycorrhizal fungus (AMF), Rhizophagus irregularis, to determine whether AMF alter the effects of salinity on phenolics. Salinity had no influence on plant fresh weight (FW) at 41 d, but by 75 d plants treated with salt had lower FW than no-salt controls. Salinity decreased accumulation of several polyphenolics. At both harvests, non-inoculated plants treated with salt had lower concentrations of caffeic acid (P5), chicoric acid (P7), caffeic acid derivative (P8), and rosmarinic acid (P11) than no-salt controls. Salt-treated plants also had lower concentrations of caffeic acid derivative (P1), caftaric acid derivative (P2), cinnamyl malic acid (P3), and feruloyl tartaric acid (P4), but only at 75 d. Salinity from both salts enhanced accumulation of quercetin-rutinoside (P9) but only CaCl2 enhanced accumulation of cinnamic acid derivative (P10). Salinity altered plant phenolic profiles in non-inoculated plants at 75 d, when minor polyphenolics were more prevalent in no-salt controls than in plants treated with salt. In general, phenolic concentrations in no-salt controls were more responsive to AMF at 41 d than at 75 d and phenolic concentrations in salt-treated plants was generally more responsive to AMF at 75 d than at 41 d. In salt-treated plants AMF increased FW and accumulation of several polyphenolics, but did not completely mitigate the negative effects of salinity on FW or phenolic composition. Our results indicate that salinity can alter polyphenolic composition of ‘Siam Queen’ basil even when it has no influence on productivity (FW). While basil productivity may be more sensitive to NaCl than CaCl2 as plants age, the effects of these two salts on phenolics appear to be very similar. This highlights the importance of considering the effects of salinity on both crop productivity and quality.