Boron toxicity effects on grafted and non-grafted pepper (Capsicum annuum) plants

Grafting is a vegetative plant propagation technique. In a grafted plant, the upward supply of water and mineral nutrients as well as the downward flow of photosynthesis are modified. In this context, the objectives of this work were to find out whether the grafting of pepper plants (Capsicum annuum L. family Solanaceae) reduces leaf boron concentration of some commercial cultivars under boron toxicity and to examine the effects of grafting and scion-cultivars on the levels of phenols, flavonoids and antioxidant capacity. Ungrafted plants of the cultivars Century, Twingo, Imperial and Arlequin, as well as grafted Twingo, Imperial and Arlequin plants as scions, and Century as rootstock were used. The plants were treated with 5 mg L-1 boron for 7, 14, 21 and 28 days. After 21 and 28 days of treatment, grafting significantly reduced the boron concentration in the leaves of the scion-cultivars while it was increased by 80% in the non-grafted plants. After 21 days of boron treatment, it was found that grafting reduced the concentration of leaf phenol to 60-70% in ungrafted Century plants. In Century x Twingo there was a 33% increase in the flavonoid concentration of leaves after 7 days grafting; while in the Century x Imperial and Century x Arlequin combinations this was decreased by 75-92% compared to non-grafted Century plants. The antioxidant capacity of leaves after 21 days treatment increased in all rootstockscion combinations by 28% as measured by the FRAP and DPPH methods. In conclusion, grafting reduced boron concentration in the leaves of the tested scion-cultivars, as well as having an effect on the phenol and flavonoid concentrations and antioxidant capacity of the leaves.