Protective and curative effect of neem (Azadirachta indica) formulations on the development of root-knot nematode Meloidogyne javanica in roots of tomato plants

Two types of neem formulations, crude and refined, were tested. The crude form was neem leaves and neem cakes (a by-product left after the extraction of oil from neem seed) and one of the neem-refined products was "aza". The protective and curative soil application of these formulations significantly reduced the number of egg masses and eggs per egg mass on tomato roots. Protective application of neem crude formulations (leaves and cake) did not reduce the invasion of juveniles whereas aza at 0.1% w/w did. Curative application of neem formulations significantly reduced the number of egg masses and eggs per egg mass as compared with the control. (c) 2006 Elsevier Ltd. All rights reserved.

Response of free eggs on infective juvenile root-knot nematode Meloidogyne javanica through neem (Azadirachta indica A. Juss) amended soil

Air-dried and 3 mm pore size sieved soil was amended with neem crude formulations (leaves and cake) @ 3% w/w and a refined product, aza @ 0.05 and 0.1 w/w. Three days after treatment, 500 eggs of M. javanica held in 2 ml water were added in each dish. In another experiment, soil was amended with neem crude formulations @ 10. 5, 2.5 and 1% w/w and refined formulation aza @ 0.025, 0.05, 0.1 and 0.5% w/w. Three days after amendment 1000 plus minus 21 freshly hatched J2 held in 3 ml water were added to the amended soil. Untreated soil was kept as control. Comparison of treatments means showed that all the neem formulations caused significant reduction of hatching. Neem crude formulations were more effective in reducing hatching as compared to commercial product aza. Among the crude formulations, neem leaves were most effective in reducing hatching. In other experiment all the doses of neem crude and refined formulations differed significantly with control in reducing the mobility of juveniles. It was observed that by increasing the dose of the formulations the mobility was reduced accordingly.

Comparative effect of root-knot nematode on severity of Verticillium and Fusarium wilt in cotton

The effect of root-knot nematode (RKN) (Meloidogyne incognita) on Verticillium dahliae and Fusarium oxysporum f.sp. vasinfectum in cotton (Gossypium hirsutum) was investigated. Two different inoculation methods were used, one in which inoculum was added to the soil, so that nematode and fungal inoculum were in close proximity; the other, inoculation into the stem, whereby the two inocula were spatially separated. Invasion of the roots by RKN enhanced disease severity, as measured by the height of vascular browning in the stem, following inoculation with either wilt pathogen. The effect of RKN on Fusarium wilt was more pronounced than that on Verticillium wilt. Nematode-enhanced infection by F. oxysporum is a well known effect but there are few reports of enhanced infection by Verticillium due to RKN. Relative resistance of a number of cotton cultivars to both wilt diseases, as measured by height of vascular browning, was similar to the known field performance of the cultivars. The use of vascular browning as an estimate of disease severity was therefore validated.

Enhancement of germination of spores of Verticillium dahliae and Fusarium oxysporum esp vasinfectum in vascular fluid from cotton plants infected with the root-knot nematode

Root-knot nematode [RKN] (Meloidogyne incognita) can increase the severity of Verticillium (V dahliae) and Fusarium (F oxysporum f.sp. vasinfectum) wilt diseases in cotton (Gossypium hirsutum). This study was conducted to determine some of the physiological responses caused by nematode invasion that might decrease resistance to vascular wilt diseases. The effect of RKN was investigated on spore germination and protein, carbohydrate and peroxidase content in the xylem fluids extracted from nematode-infected plants. Two cotton cultivars were used with different levels of resistance to both of the wilt pathogens. Spore germination was greater in the xylem fluids from nematode-infected plants than from nematode-free plants. The effect on spore germination was greater in the Fusarium-resistant cultivar (51%). Analysis of these fluids showed a decrease in total protein and carbohydrate levels for both wilt-resistant cultivars, and an increase in peroxidase concentration. Fluids from nematode-free plants of the Verticillium-resistant cultivar contained 46% more peroxidase than the Fusarium-resistant cultivar. The results provide further evidence that the effect of RKN on vascular wilt resistance is systemic and not only local. Changes in metabolites in the xylem pass from the root to the stem, accelerating disease development.

The control of root-knot nematodes (Meloidogyne spp.) by Pseudomonas oryzihabitans and its immunological detection on tomato roots

Pseudomonas oryzihabitans, a bacterium associated with the entomopathogenic nematode Steinernema abbasi, was evaluated for its potential to colonise roots and thereby control a field population of root-knot nematodes. Immunological techniques were developed to detect root colonisation of P. oryzihabitans on tomato roots using a specific polyclonal antibody raised against vegetative bacterial cells. In vitro, bacterial cell filtrates were also shown significantly to inhibit juveniles hatching. In a glasshouse pot experiment, there were 22 and 82% fewer females in roots of plants treated with suspensions containing 10(3) and 10(6) cells ml(-1) of P oryzihabitans, respectively. In addition, there were significantly fewer egg masses produced; however, the numbers of eggs per egg mass did not differ significantly. The relationship between root colonisation and nematode control is discussed.

Techniques for image analysis of movement of juveniles of root-knot nematodes encumbered with Pasteuria penetrans spores

Root-knot nematodes (Meloidogyne spp.) are the most significant plant-parasitic nematodes that damage many crops all over the world. The free-living second stage juvenile (J2) is the infective stage that enters plants. The J2s move in the soil water films to reach the root zone. The bacterium Pasteuria penetrans is an obligate parasite of root-knot nematodes, is cosmopolitan, frequently encountered in many climates and environmental conditions and is considered promising for the control of Meloidogyne spp. The infection potential of P. penetrans to nematodes is well studied but not the attachment effects on the movement of root-knot nematode juveniles, image analysis techniques were used to characterize movement of individual juveniles with or without P. penetrans spores attached to their cuticles. Methods include the study of nematode locomotion based on (a) the centroid body point, (b) shape analysis and (c) image stack analysis. All methods proved that individual J2s without P. penetrans spores attached have a sinusoidal forward movement compared with those encumbered with spores. From these separate analytical studies of encumbered and unencumbered nematodes, it was possible to demonstrate how the presence of P. penetrans spores on a nematode body disrupted the normal movement of the nematode.

CaPrx, a Coffea arabica gene encoding a putative class III peroxidase induced by root-knot nematode infection

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The activity of amino acids produced by Paenibacillus macerans and from commercial sources against the root-knot nematode Meloidogyne exigua

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effects of a lectin-like protein isolated from Acacia farnesiana seeds on phytopathogenic bacterial strains and root-knot nematode

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Characterization of LeMir, a Root-Knot Nematode-Induced Gene in Tomato with an Encoded Product Secreted from the Root1

A tomato gene that is induced early after infection of tomato (Lycopersicon esculentum Mill.) with root-knot nematodes (Meloidogyne javanica) encodes a protein with 54% amino acid identity to miraculin, a flavorless protein that causes sour substances to be perceived as sweet. This gene was therefore named LeMir (L. esculentum miraculin). Sequence similarity places the encoded protein in the soybean trypsin-inhibitor family (Kunitz). LeMir mRNA is found in root, hypocotyl, and flower tissues, with the highest expression in the root. Rapid induction of expression upon nematode infection is localized to root tips. In situ hybridization shows that LeMir is expressed constitutively in the root-cap and root-tip epidermis. The LeMir protein product (LeMir) was produced in the yeast Pichia pastoris for generation of antibodies. Western-blot analysis showed that LeMir expression is up-regulated by nematode infection and by wounding. LeMir is also expressed in tomato callus tissue. Immunoprint analysis revealed that LeMir is expressed throughout the seedling root, but that levels are highest at the root/shoot junction. Analysis of seedling root exudates revealed that LeMir is secreted from the root into the surrounding environment, suggesting that it may interact with soil-borne microorganisms.

Plants reported resistant or tolerant to root knot nematode infestation /

Contribution from Bureau of Plant Industry.