Salicylic acid affects mycorrhizal features, antioxidant enzyme activities and seed yield of linseed under water-deficit stress in open-field conditions.

The research aims were to study salicylic acid (SA) effects on mycorrhiza [hyphal width (HW), vesicle diameter (VD) and mycorrhizal colonization (MC)] and interaction between them on greenness index (GI), drought tolerance index (DTI), antioxidant enzymes activities, and seed yield of linseed under drought. A factorial experiment was conducted in an open-field place with mycorrhiza [non-inoculation, Funneliformis mosseae (FM), and Rhizoglomus intraradices (RI)], SA (250 μM and non-SA), and irrigation levels [100%, 70%, and 40% field capacity (FC)] as treatments. Severe drought increased VD, MC, superoxide dismutase (SOD), ascorbate peroxidase (APX), and peroxidase activities while decreased GI, DTI, and yield. The RI-linseed had higher MC, GI, SOD, and glutathione reductase (GR) activities, but FM-linseed had greater VD and yield under drought. Inoculated linseed with both mycorrhiza showed a reduction in DTI and yield under SA than non-SA. In RI-linseed, SA increased GI, MC, HW, VD, catalase and GR, but decreased in FM-plants. Mycorrhiza (particularly RI) alleviated drought (40% FC)-caused negative effects on linseed via the improvement of SOD, APX, and GI. Regardless of other treatments, SA had negative effects on HW and VD, but SA effects varied depending on mycorrhizal species so that SA increased HW, VD, and MC in RI. Due to the positive correlation between MC and HW, SA reduces FM colonization by reducing the HW of FM. Totally, SA along with RI species can mitigate the harmful effects of drought and improve tolerance via increasing MC, HW, VD, catalase, peroxidase, and GR activities.