Induction of Systemic Resistance in Tomato (Solanum lycopersicom L.) Against Damping-off Disease by Using a Mixture of Mycorrhizae

Khrieba, M.I., M.F. Azmeh, W. Chouman, I. Ghazal, and A.K. Ali. 2021. Induction of Systemic Resistance in Tomato (Solanum lycopersicom L.) Against Damping-off Disease by Using a Mixture of Mycorrhizae. Arab Journal of Plant Protection, 39(1): 61-68. The effect of vesicular-arbuscular mycorrhiza (VAM) in improving the activity of the enzyme peroxidase and its role in controlling tomato damping-off caused by Pythium ultimum was studied in a pot experiment during the 2013 growing season. Five treatments were compared with a non-treated control (C): in treatment 1, soil was infested only with Pythium (Py), in treatment 2, soil was infested with mycorrhiza only (My), in treatment 3 soil was infested with Pythium and mycorrhiza at sowing (My+Py), in treatment 4, soil was infested with Pythium and two weeks after sowing with Mycorrhiza (Py-My) and in treatment 5, soil was infested with mycorrhiza and two weeks after sowing with Pythium (My-Py). The results showed that peroxidase concentration in plant tissues 14 days after seed germination in the My treatment (361.91 μmole/mg) significantly exceeded the other treatments. In the treatment where mycorrhiza was added before the pathogen 67 Arab J. Pl. Prot. Vol. 39, No. 1 (2021) peroxidase activity reached 183.73 μmole/mg, which was 41% significantly higher than the My+Py treatment in which the pathogen and mycorrhizal inoculant were added together at sowing (108.27 μmole/mg). The peroxidase concentration increased significantly 28 days after seed germination in the My treatment (687.52 μmole/mg) as compared with the Py treatment (10.52 μmole/mg). Results also showed that in the treatment My-Py, where the mycorrhyzal inoculum was added before the pathogen, peroxidase activity (458.27 μmole/mg) was significantly higher than in the treatment Py+My, when the pathogen was added simultaneously with the vesicular-arbuscular mycorrhizal inoculum (98.67 μmole/mg). Furthermore, results showed that 35 days after seed germination, the enzyme concentration was significantly higher in the My-Py treatment (763.39 μmole/mg) as compared with My+Py treatment (143.5 μmole/mg). Keywords: Vesicular-arbuscular mycorrhiza, VAM, Pythium ultimum, peroxidase, tomato, Syrian coast, induced resistance.