Synergistic Role of Selenium and Boron in Enhancing Salinity Tolerance and Secondary Metabolite Accumulation in Oregano.

The present work was performed in greenhouse conditions, and 10 ppm Se, 10 ppm B, and 100 mM salinity treatments were used. The results showed significant variations in the agronomic traits of oregano among the treatments and harvests. The 10 ppm Se×10 ppm B treatment showed improvements over other properties for morphological and yield properties with protein, essential oil, and Zn contents, and B×salinity outperformed other treatments, with variations in branch number enhancement. The analysis revealed that salinity treatment could effectively enhance Na and Ca contents. B treatment significantly improved Mn (12,443.51-18,739.77 ppm), Mg (406.85-632.79 ppm), Fe (61.43-885.06 ppm), Cu (5.02-9.32 ppm), and B (37.67-114.28 ppm) element contents. The highest K content was found from Se treatment. The effects of the Se, B, and salinity treatments showed effectively after second and third harvests of the oregano for the many examined properties. Fresh and dry weight values showed variability between 1.60-6.00 g/plant and 0.54-2.42 g/plant, respectively. Principal coordinate analysis indicated that most of the properties took place in the groups 1 (1st harvests of plant height and protein content, 2nd harvests of protein content and fresh and dry weight, 3rd harvest of fresh weight and total fresh and dry weight values) and 2 (branch number and essential oil contents, Na, and Zn). The heat-map analysis divided into two main clusters as A and B. A2, A4, and A5 treatments took place in the B group. Treatment of 10 ppm Se×10 ppm B showed better values compared to other treatments. Thus, this treatment may be beneficial for oregano cultivation under non-saline conditions.