Meloidogyne spp. in Eucalypts - Reproduction and Damage to Seedling Growth.

Eucalypts are cultivated worldwide, but little is known about their status as hosts of root-knot nematodes (RKN) (Meloidogyne spp.). Moreover, information is scarce regarding the nature of the damage caused by RKN to eucalypt seedlings and trees. To investigate these aspects, we separately inoculated Meloidogyne enterolobii, M. javanica and M. incognita in seedlings of the world's most cultivated eucalypts: Eucalyptus dunni, E. grandis, E. cloeziana, E. camaldulensis, E. saligna, Corymbia citriodora, and the hybrid E. grandis × E. urophylla. After six months of greenhouse cultivation, we assessed nematode reproduction and variables that expressed the seedlings' shoot and root growth. We observed a diverse pattern of host statuses to RKN among the eucalypts, and all three Meloidogyne species reduced (p < 0.05) the root system mass, volume and length of E. grandis, E. saligna and the hybrid E. grandis × E. urophylla. Our results reaffirm previous reports indicating that RKN can delay the growth of seedlings in nurseries, who should thus adopt appropriate sanitary measures to avoid RKN establishment and spread. Moreover, the damage caused by RKN to eucalypts after just six months of cultivation suggests that the growth of eucalypt trees may be affected over the course of several years of cultivation.

First Report of Meloidogyne Morocciensis Infecting Hops (Humulus Lupulus).

Humulus lupulus (Cannabaceae) is a climbing herbaceous plant with perennial production, intended mainly for the brewing industry. H. lupulus is widely cultivated in temperate regions; hop cultivars have shown good adaptation in regions of Brazil. In a hop-growing area in São Mateus, the state of Espírito Santo, leaf wilting and galling of the root system was observed. Soil and root samples were taken to the laboratory and processed, and the nematodes extracted from the Meloidogyne genus were identified by morphology, morphometry, and biochemical analysis. According to the results, the species identified in the hop roots was Meloidogyne morocciensis. This is the first report of H. lupulus as host of M. morocciensis.

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.