Effect of Nosodes on Lettuce, Parasitized or Not by Meloidogyne enterolobii.

BACKGROUND: Nosodes are homeopathic preparations (HPs) obtained from tissues or substances associated with the targeted disease or from culture of the pathogenic agent. Nosodes are thought to modulate host resistance, easing symptoms or promoting cure. A few studies have been published about control of plant-parasitic nematodes with HPs, but none with nosodes. Conceptually, nosodes prepared from nematode infective stages might interact with the plant's pathogen-recognition system and initiate or modulate plant resistance to nematodes. OBJECTIVE: Our goal was to investigate whether nosodes prepared from second-stage juveniles (J2) of Meloidogyne enterolobii can affect the moderate resistance already existing in the lettuce cultivar 'Elisa'. METHODS: Nosodes at the Hahnemannian concentrations (cH) 6, 18, 30 and 42 were applied on lettuce plants through irrigation, with a constant daily dosage. The nosode treatment started at the seedling stage, before nematode inoculation with 3,000 eggs + J2 per plant. A series of absolute and relative controls, and 10 replicates per treatment, were employed. At harvest, variables related to plant growth and nematode reproduction were assessed. RESULTS: The nosode at 6, 18, and 30cH reduced (p <0.05) the nematode reproduction factor and root density. The nosode effect was cH-dependent since nematode reproduction was favored by treatment with 42cH. The nosode also affected (p <0.05) lettuce roots, which presented higher or lower fresh weight and volume depending on the cH applied and the condition-parasitized or not. CONCLUSION: Nosodes obtained from Meloidogyne J2 may affect plant parasitism by nematodes, possibly by interfering with plant resistance. The nature-positive or negative-and intensity of the nosode effect depends on the cH applied to the plants. Further studies are necessary to identify which cH values are more effective in reducing nematode reproduction without causing negative side effects on plant growth.

Effect of Homeopathic Preparations on Lettuce, Parasitized or Not by Meloidogyne enterolobii.

BACKGROUND: There are relatively few scientific works on the use of homeopathy to manage plant pathogens, particularly nematodes. A handful of studies focused on Meloidogyne spp. parasitizing vegetables have brought contradictory results on nematode control and enhancement of plant tolerance to parasitism. OBJECTIVE: Our goal was to assess the effect of Cina-a well-known anti-nematode ingredient-on Meloidogyne enterolobii parasitizing lettuce. METHODS: Cina was applied daily on nematode-inoculated plants, from the seedling stage until harvest. We tested an evenly spaced range of Hahnemannian concentrations (c), which were applied though irrigation with a constant dose of the ingredient. Several absolute and relative controls were employed to allow the assessment of the effect of Cina on nematode reproduction and lettuce growth. RESULTS: Cina affected growth of non-parasitized plants, both positively and negatively; this effect was modulated by the c applied and the thermal stress suffered by the plants in one of the assays. The effect of Cina on the growth of nematode-parasitized plants was neutral or negative. Cina reduced nematode reproduction by 25-36%. CONCLUSION: Based on the moderate negative effect of Cina on M. enterolobii reproduction, it seems this ingredient may be useful as a complementary strategy for Meloidogyne control. But Cina did not enhance the tolerance of lettuce to Meloidogyne spp.