Control of Meloidogyne incognita in tomato plants with highly diluted solutions of Thuya occidentalis and their effects on plant growth and defense metabolism

Abstract

This work aimed to control the root-knot nematode Meloidogyne incognita in tomato Solanum lycopersicum L plants with high-diluted solutions of Thuya occidentalis, and to study its effects on growth and plant defense responses. The in vivo experiment was carried out over two years (2013 and 2014) at a climatized greenhouse, whilst the in vitro experiment was carried out in the laboratory. Eight treatments were used (6, 12, 24, 50, 100, 200 and 400CH (Hahnemannian centesimal) of T. occidentalis, with water as control treatment). For the in vivo assay, in 2013 plants were inoculated with about 4850 eggs and second-stage juveniles (J2), while in 2014 they were inoculated with 5050 eggs and J2. The treatments were applied once a week, as 0.1% aqueous solutions onto the plant shoots, for 50 and 40 days respectively. For the in vitro experiment, the nematodes were directly exposed to the same 0.1% treatments. The treatments did not show nematostatic or nematicide effects in the in vitro assay, and had no influence on the hatching of the eggs. For the in vivo assay in 2013, T. occidentalis 100CH decreased the number of J2 present in the roots, whilst the dynamization of 200CH stimulated root development and increased the weight of the fruits of the first cluster. In 2014, 100CH decreased numbers of J2 in the soil. Some dynamization increased the plant's defense enzyme activity, such as peroxidase (24, 50, 200 and 400CH), polyphenoloxidase (200CH), and phenylalanine ammonia-lyase (24 and 50CH). In this study, T. occidentalis 100CH showed potential for the control of M. incognita, whilst 24 and 200CH influenced the growth of plants.