Application of Azoxystrobin Fungicide Improves Drought Tolerance in Tomato, via Enhancing Physio-Biochemical and Anatomical Feature

To investigate whether the fungicide Azoxystrobin improves the potential to maintain physio-biochemical functions under drought, tomato plants were applied with Azoxystrobin under either well-watered and deficit irrigation conditions. Drought-stressed tomato plants showed significant reductions in most tested parameters of physiology [cell membrane stability (CMS), relative water content (RWC), relative water loss (RWL) and chlorophylls], growth attributes and leaflet and main stem anatomical features, while exhibited increases in contents of proline and total phenols, activities of catalase (CAT), peroxidase (POD) and polyphenol oxidase (PPO), fresh (FW) and dry (DW) weights of roots, and leaflet spongy tissue thickness compared to well-watered control plants. Under full irrigation, Azoxystrobin treatment significantly increased RWC and chlorophyll content, POD and PPO activities, root DW, number of fruits per plant and many features of leaflet and main stem, while significantly decreased CMS and RWL, root, shoot and plant lengths, shoot and plant FW, and stem xylem tissue thickness compared to the control plants sprayed with water. However, Azoxystrobin treatment ameliorated drought stress in tomato plants and significantly increased CMS and free proline content, activities of CAT, POD and PPO, and contents of free and total phenols, and root DW and number of fruits per plant, in addition to spongy tissue thickness of leaflet, but not affected chlorophylls and carotenoids contents, root FW, plant DW and most of anatomical features compared to the stressed plants without Azoxystrobin treatment. These results support that Azoxystrobin foliar application may have a positive effect on well-watered and drought-stressed tomato plants.