■ Abstract This review examines the discovery of naturally occurring phytochemicals antagonistic toward plant-parasitic and other nematodes. Higher plants have yielded a broad spectrum of active compounds, including polythienyls, isothiocyanates, glucosinolates, cyanogenic glycosides, polyacetylenes, alkaloids, lipids, terpenoids, sesquiterpenoids, diterpenoids, quassinoids, steroids, triterpenoids, simple and complex phenolics, and several other classes. Many other antinematodal compounds have been isolated from biocontrol and other fungi. Natural products active against mammalian parasites can serve as useful sources of compounds for examination of activity against plant parasites. The agricultural utilization of phytochemicals, although currently uneconomic in many situations, offers tremendous potential.

Phytochemical based strategies for nematode control.

Arbuscular mycorrhizal fungi and organic farming

The fungal biocontrol agent, Trichoderma harzianum, was evaluated for its potential to control the root-knot nematode Meloidogyne javanica. In greenhouse experiments, root galling was reduced and top fresh weight increased in nematode-infected tomatoes following soil pretreatment with Trichoderma peat-bran preparations. The use of a proteinase Prb1-transformed line (P-2) that contains multiple copies of this gene improved biocontrol activity in the greenhouse experiments compared with the nontransformed wild-type strain (WT). All the Trichoderma strains showed the ability to colonize M. javanica-separated eggs and second-stage juveniles (J2) in sterile in vitro assays, whereas P-2 also penetrated the egg masses. This protease-transformed line presented the same nematicidal and overall proteolytic activity as the WT in in vitro tests in which concentrated soil extracts from Trichoderma-treated soils immobilized the infective J2. However, the J2 immobilization and proteolytic activities of both P-2...

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Biological Control of the Root-Knot Nematode Meloidogyne javanica by Trichoderma harzianum.

The filamentous fungi Trichoderma spp. is currently developed as biocontrol agents against many plant pathogens. Recent studies have shown that these fungi are able to infect nematode eggs and juveniles. In this research, biological control of root-knot nematode (Meloidogyne javanica) by Trichoderma harzianum BI was investigated in greenhouse and laboratory experiments. Results showed that different concentrations (102–108 spores/ml) of T. harzianum BI decreased nematode infection and other parameters significantly, compared to control. T. harzianum BI was able to penetrate nematode egg mass matrix and significantly decreased nematode egg hatching level. Specific activities of resistance-related enzymes, namely peroxidase (POX), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) increased significantly in T. harzianum BI inoculated plants. Maximum activities of POX, PPO and PAL were observed at the 5, 5 and 6 days after inoculation, respectively. Chitinase activity was also increased in culture filtrates of T. harzianum BI grown on wheat bran moistened with salt solution supplemented with colloidal chitin or nematode eggs. Maximum activity of chitinase was recorded at the 4 days after inoculation, in media supplemented with colloidal chitin (1.15 U/min per ml) and nematode eggs (0.85 U/min per ml). Results suggested that direct parasitism of eggs through the increase in extracellular chitinase activity, which would be indicator of eggs infection capability, and inducing plant defense mechanisms leading to systemic resistance are two main suppression mechanisms used by T. harzianum BI against nematode.

Biological control of the root-knot nematode Meloidogyne javanica by Trichoderma harzianum

Interpretation of nematode community indices requires a reference to a relatively undisturbed community. Maturity and trophic diversity index values were compared for five pairs of certified organically and conventionally managed soils in the Piedmont region of North Carolina. Available nitrogen (nitrate, ammonium) was estimated at various lag periods relative to times of sampling for nematode communities to determine the strength of correlative relationship between nematode communities and nitrogen availability. Soils were sampled six times yearly in 1993 and 1994 to determine the best time of year to sample. Maturity values for plant parasites were greater in organically than conventionally managed soils, and differences between management systems were greater in fall than spring months. However, other maturity and diversity indices did not differ between the two management practices. Differences in crop species grown in the two systems accounted for most differences observed in the community of plant-parasitic nematodes. Indices of free-living nematodes were correlated negatively with concentrations of ammonium, whereas indices of plant-parasitic nematodes were correlated positively with concentrations of nitrate. Due to the similarity of index values between the two systems, organically managed soils are not suitable reference sites for monitoring and assessing the biological aspects of soil quality for annually harvested crops.

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Nematode communities in organically and conventionally managed agricultural soils.

Aqueous extracts of neem (Azadirachta indica), castor (Ricinus communis) and pongamia (Pongamia pinnata) cakes were evaluated as substrates for mass production of the biological control agent, Trichoderma harzianum which was used in the management of Meloidogyne incognita in egg plant under fields conditions Castor cake extract at 10% gave maximum growth of mycelial mat and spore production of T harzianum compared with moderate growth in 10% pongamia cake and 5% castor cake extracts Application of plant based formulations of T harzianum to nursery beds of egg plant was effective in producing vigorous seedlings (increase in plant height and seedling weight) with the least root galling The above treatments also increased root colonization and parasitization of M incognita females by T harzianum

Evaluation of plant based formulations of trichoderma harzianum for the management of meloidogyne incognita on egg plant

Trichoderma harzianum in combination with neem, karanj and castor oil cakes was effective in increasing the growth of acid lime seedlings and reducing the population of Tylenchulus semipenetrans both in soil roots. The parasitization of citrus nematode females with T. harzianum increased in the presence of the oil cakes.

Management of the citrus nematode, tylenchulus semipenetrans, by integration of trichoderma harzianum with oil cakes

Integration of the bio-control fungus, Paecilomyces lilacinus with neem (Azadirachta indica) leaf aqueous suspensions was attempted for the management of root-knot nematode, Meloidogyne incognita on egg plant (Solanum melongena). Results revealed the suitability of neem leaf suspensions (5 and 10%) for mass multiplication of P. lilacinus. Further, significant reduction in root-knot index and final population of M. incognita were observed in the egg plant seedlings which were given root-dip treatment in neem leaf suspensions mixed with P. lilacinus spores. In addition, significant increases were observed on the colonization of P. lilacinus on the roots of egg plant and parasitization of eggs of M. incognita, indicating the complementary interaction between these two components for the sustainable management of root-knot nematodes on egg plant.

Integration of paecilomyces lilacinus with neem leaf suspension for the management of root-knot nematodes on egg plant

Studies on the management of carnation and gerbera to control root-knot nematode, Meloidogyne incognita, in commercial polyhouses using pre-plant (dazomet) and post-plant (chlorpyriphos, carbosulfan and carbofuran) chemicals in a comparison with various combinations of and with bio-agents (Paecilomyces lilacinus, Pochonia chlamydosporia) and neem cake were made. Pre-plant treatment of beds with dazomet followed by the application of neem cake (1 kg/m2, 15 days later) along with P. lilacinus or P. chlamydosporia significantly reduced populations of M. incognita and the mortality of plants, and suppressed the nematode infection for nearly 2 years. The antagonistic fungi established themselves better in the beds treated with dazomet than in untreated beds. Chlorpyriphos and carbofuran (each applied twice in 6 months) significantly reduced nematode populations in roots and soil. However, there was a build-up of nematode populations in beds treated with these two chemicals after 1 year. On a long term basis, soil management with pre-plant treatment of dazomet, followed by the application of oil cakes plus antagonistic fungi, was more effective against M. incognita than post-plant treatment with carbofuran, carbosulfan and chlorpyriphos on carnation and gerbera grown in polyhouses.

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M. Nagesh

Papers

Evaluation of plant based formulations of trichoderma harzianum for the management of meloidogyne incognita on egg plant

Management of the citrus nematode, tylenchulus semipenetrans, by integration of trichoderma harzianum with oil cakes

Integration of paecilomyces lilacinus with neem leaf suspension for the management of root-knot nematodes on egg plant

Management of carnation and gerbera to control the root-knot nematode, Meloidogyne incognita, in commercial polyhouses

Management of root-knot nematode, Meloidogyne incognita on tomato by integration of Trichoderma harzianum with neem cake