Effects of melatonin on root knot nematode: in situ estimation of physiological responses in tomato

Abstract

This research was conducted in 2020 to investigate the influence of melatonin (10, 50 and 100 mu M) given in three methods (immersion, irrigation and foliar spraying), on some physiological aspects of tomato seedlings exposed to root knot nematodes. The seedlings were inoculated with 1000 infective juveniles of Meloidogyne incognita [(Kofoid and White) Chitwood]. Dualex (R) optic sensor was used to in situ measure total chlorophylls, flavonols and anthocyanins contents and nitrogen balance index (NBI). Results indicated that while no significant effects were observed on chlorophyll content, melatonin ameliorated the adverse effects of M. incognita on chlorophyll depending on the concentration and mode. Flavonols were at the highest in the irrigated plants and the lowest in the immersed ones, between 06-1.1, exhibiting a significant difference. NBI was affected by the method the melatonin was applied, and immersing boosted it, while irrigation caused a significant decrease. Irrigation resulted in significantly higher anthocyanins compared to the other two methods. One observation was that applying melatonin in the low and medium concentrations to the nematode containing soil increased the anthocyanins. Melatonin merits a value in developing a response against the nematode but needs further elucidation.