Arbuscular mycorrhizas (AM) can improve phosphorus (P) nutrition and could serve as an environmentally friendly approach for sustainable crop production under P-limiting conditions. The objectives of this study were to assess the effect of AM on different physiological traits and to quantify the responsiveness of different basil (Ocimum basilicum L.) cultivars to AM under low P availability. The basil cultivars 'Genovese', 'Sweet Basil', 'Dark Opal', and 'Erevanskii' were inoculated (AMI) using Rhizophagus irregularis. Photochemical efficiency and gas exchange were measured on AMI and non-inoculated (AMC) plants and, at harvest, the shoot biomass, shoot P concentration, root morphological traits, frequency of mycorrhizas in the roots (F%), and extent of root colonization (M%) were determined. Significant differences in F% and M% were found among the examined cultivars, with the highest found in 'Dark Opal' and the lowest in 'Erevanskii'. AMI reduced the shoot biomass and increased the shoot P concentration as well as other examined root traits in 'Genovese' and 'Erevanskii', whereas it did not affect those traits in 'Dark Opal' and 'Sweet Basil', indicating differences in responsiveness to AM. AMI positively affected the gas-exchange parameters in all examined cultivars, probably due to the increased sink capacity of a bigger root system and/or AM structures within the roots.
Keywords: basil; chlorophyll fluorescence; gas exchange; mycorrhizal responsiveness; phosphorus nutrition; root morphology.