Maintenance of Suppressiveness

Once soils suppressive to a particular nematode pest have been identified and characterised, the next challenge is to understand how they are best managed to maintain suppressiveness. Specific suppression is dependent on the presence of the host nematode and usually manifests itself in situations where nematode populations have remained at high levels for many years. Thus the use of nematode-resistant varieties, fallowing and other practices that reduce nematode populations to very low levels...

Mycorrhizal Fungi

The potential that endophytic fungi possess to regulate plant-parasitic nematode populations was first shown for endomycorrhizal fungi by Fox and Spasoff (1972). Mycorrhiza (myc gr. fungus, rhiza root) describes the symbiotic association between a fungus and the plant root. Approximately 80 of all plant species harbour one or more mycorrhizal fungi (Wang and Qiu 2006). Of the different types of mycorrhizas the arbuscular mycorrhiza (AM) are the most common and have the greatest impact on...

AMF and Cyst Nematodes

Compared with the amount of work done on Meloidogyne, few reports describe interactions between AMF and cyst forming nematodes. Tylka et al. (1991) have shown that soybean cv. Wright inoculated with a mixture of Gigaspora margarita, Glomus etunicatum, G. macrocarpum and G. mosseae responded more tolerant to Heterodera glycines infection than non-mycorrhizal plants. However, this effect was transient and only observed in greenhouse experiments but not in the field. In a greenhouse experiment,...

Monitoring the Worm Innate Immune Response Following Different Modes of Pathogen Infections

A hallmark of the innate immune response in C. elegans, as in other invertebrates, is the challenge-induced synthesis of a battery of antimicrobial peptides and proteins, which are expressed in tissues in contact with invading microorganisms. C. elegans encodes a wide diversity of candidate immune effectors, which include lysozymes, caenopores or saposin-like proteins (ssp), antimicrobial caenacins (cnc) and neuro-peptide-like proteins (nlp), thaumatins (thm), PR-1 plant antimicrobial...

General Conclusions and Future Prospects

Two root-knot nematode genomes are now completed, the potato-cyst nematode (Globodera pallida) will be finished shortly, and a draft sequence of soya bean cyst (Heterodera glycines) is also available. The number plant-parasitic nematode genomes available will increase dramatically over the next few years as sequencing cost continue to fall. Concomitantly with this, the number of microbial genomes will also increase and these will include bacteria and fungi that are pathogens of nematodes....

Attachment and Parasitism

Parasitism Trichoderma

Parasitism is probably an important mode of action and attachment is one of the initial steps of it. Trichoderma asperellum-203 and T. atroviride showed the ability to parasitize nematode eggs and J2s (Sharon et al. 2001). Mechanisms involved in the attachment and parasitism processes were investigated, with special attention to the role of the gelatinous matrix (gm) in direct nematode-fungus interactions. It was found that the gm enables fungal attachment and enhances parasitic abilities of...

Fusarium Endophytes

Fusarium Tomato Split Root

Of all plant species investigated for the occurrence of endophytic fungi, most were colonized by members of the genus Fusarium (Kuldau and Yates 2000 Bacon and Yates 2006 Macia-Vicente et al. 2008). Among them, F. oxysporum was the most cosmopolitan endophytic species isolated so far. Although some strains are known for their pathogenicity, the majority of strains in nature are non-pathogenic saprophytes. Many of these non-pathogenic F. oxysporum strains have been described as antagonists of...

Understanding the Impact of Soil Organic Matter on Suppressiveness

Organic matter has profound effects on many important soil physical and chemical properties (e.g. soil aggregation, soil water availability and nutrient cycling) it promotes biological activity and diversity through affects on the detritus food web and it plays a key role in developing healthy soils and enhancing their suppressive-ness to plant pathogens and pathogenic nematodes (Weil and Magdoff 2004 Magdoff and Weil 2004). Since levels of soil organic matter gradually decline when plant...

Endospore Cuticle Interactions

The infection of second-stage root-knot juveniles by P. penetrans endospores is initiated when viable endospores adhere to the cuticle surface of migrating nema-todes as they move through the soil. Attachment can therefore be seen as the key to the commencement of infection. Studies (Stirling 1985 Davies et al. 1988, 1990 Channer and Gowen 1992 Sharma and Davies 1996 Espanol et al. 1997 Mendoza de Gives et al. 1999 Wishart et al. 2004) have shown that different populations of endospores do not...

Mass Release of Biological Control Agents

The possibility of introducing mass-produced antagonists into soil or establishing them on seeds or roots has been a major component of research on biological control of soilborne pathogens for several decades. However, any objective review of that research would have to conclude that there have been relatively few practical outcomes. By 2005, only nine bacteria and five fungi were registered with the United States Environment Protection Agency for control of soilborne diseases (Fravel 2005)....

Suppressing Nematodes with Organic Amendments

It has been known for many years that animal manures, oil-cakes, residues from leguminous crops and other materials with a low C N ratio can be added to soil to control plant-parasitic nematodes (see reviews by Muller and Gooch 1982 Rodriguez-Kabana 1986 Stirling 1991). Although there is some evidence that such amendments increase populations of microorganisms antagonistic to nematodes, the main mechanism is thought to be the release of nematicidal compounds such as ammonia during the...

AMF Mode of Action

From all the work done over the past years on the mode-of-action of the AMF x plant-parasitic nematode interaction it appears that under a wide spectrum of environmental conditions, the antagonistic activity of AMF is related to specific mechanisms of action or a combination of several mechanisms. As nematodes are generally not presented in root segments colonized by AM fungi (Diedhiou et al. 2003), competition for space and feeding sites may occur (Hussey and Roncadori 1978). This hypothesis...

The Soil Ecosystem

Soil biomass in the below-ground subsystem can be structured through food chains that originate either from the primary production of plant roots (grazing food chains), or from labile or recalcitrant litter and debris (the decomposer food chains). We review ecology theory on how such structures are inevitably interlinked, which theoretically may lead to nematode control by natural mechanisms we also give practical examples of the functional involvement of nematodes. 2.2.2.1 Food Chains and...

Molecular Markers for Ecological Studies

DNA based methods have increasingly been used for elucidating the taxonomic identity of fungi in soils (Peay et al. 2008 Anderson and Cairney 2004). Typically, DNA is extracted from soils, and specific region of ribosomal DNA is amplified by PCR and analyzed by gel electrophoresis or sequencing. Recently, Orbiliales-specific PCR primers for the internal transcribed spacer (ITS) and 28S ribosomal DNA were designed to directly detect nematode-trapping fungi without culturing in soils (Smith and...

Physical Chemical Barriers and Evasion Behavior

Metazoans are endowed with an innate immune defense that provides protection against infection and consists of five interconnected components (1) physical barriers to prevent microbial invasion (2) constitutive chemical shields to inhibit microbial growth (3) recognition systems to identify the entry of foreign microorganisms (4) inducible antimicrobial responses triggered by the recognition system (5) cellular recruitment processes to amplify and enhance defense (Akira et al. 2006). Currently,...

The Surface Coat and Excreted Secreted Antigens

The surface coat (SC) of nematodes contains various proteins, carbohydrates and lipids, as individual components or as glycoproteins mucins, glycolipids, or lipoproteins. Studies have used antisera, lectins, biotin and neoglycoproteins to characterize and localize surface components and to learn about its nature. Binding of lectins indicated the presence of specific carbohydrates on the surface and amphids of different life-stages of plant-parasitic nematodes. Carbohydrate-recognition domains...

References

Abad P, Gouzy J, Aury JM et al (2008) Genome sequence of the metazoan plant-parasitic nematode Meloidogyne incognita. Nat Biotechnol 26 909-915 Ahren D, Tunlid A (2003) Evolution of parasitism in nematode-trapping fungi. J Nematol 35 194-197 Allison SD (2006) Brown ground a soil carbon analogue for the green world hypothesis Am Nat 167 619-627 Anderson RM, May RM (1981) The population dynamics of micro-parasites and their invertebrate hosts. Philos Trans R Soc B 291 451-524 Avendano F, Pierce...

Nematode Life Styles and Ecological Niches Diversity

Another conspicuous difference between FLN and PPN is the duration of their life cycle while C. elegans take approximately 3 days to complete a generation, PPN exhibit a much longer reproductive cycle, taking at least 2-4 weeks. Moreover, soil nematodes can also inhabit very different ecological niches. For example, although C. elegans has been recognized as a probable human commensal that spread around the world in association with agriculture (Thomas 2008) it is primarily found in ephemeral...

Grass Endophytes

Cool season grasses such as tall fescue (Festuca arundiaceae) and perennial ryegrass (Lolium perenne) are commonly colonized by fungal species of the genus Neotyphodium (former Acremonium). These endophytic fungi are obligate biotrophs which colonize the plant tissue intercellular (Hinton and Bacon 1988 Siegel et al. 1987). They often form close associations with the plant cell walls (Christensen et al. 2002) however, they do not invade the plant cells. Neotyphodium endophytes produce several...

The Role of the Surface Coat in Immune Evasion by Animal Parasitic Nematodes

Animal-parasitic nematodes have evolved a mutiplicity of evasive strategies to survive in immunologically competent host. The parasite's ability to exist for long periods of time in their host, has been attributed to a rapid turnover of their cuticle surface, shedding of surface antigens and membrane rigidity, which are likely to render the parasite less susceptible to immune attack (Simpson et al. 1984 Kusel and Gordon 1989). The mechanisms underlying surface antigen switching mechanisms are...

Designer BCAs

The use of molecular tools by biological control scientists has grown since the publication of Stirling's book in 1991 when the impact of these techniques was in its infancy and is now routine. As our understanding grows, with respect to the key factors that are important in determining the mode of action of biological control agents and the biochemistry of each individual strains specificity, the application of such techniques to broaden the host range and aggressiveness of potential...

Parasitic Nematode References

Academic, London Ahman J, Johansson T, Olsson M et al (2002) Improving the pathogenicity of a nematode-trapping fungus by genetic engineering of a subtilisin with nematotoxic activity. Appl Environ Microbiol 68 3408-3415 Ait Barka E, Eullaffroy P, Clement C et al (2004) Chitosan improves development, and protects Vitis vinifera L. against Botrytis cinerea. Plant Cell Rep 22 608-614 Allen MF (1992) Mycorrhizal functioning an integrative plant-fungal process....

AMF and Root Knot Nematodes

Most of the research conducted in the past on AMF x plant-parasitic nematode interactions focused on root-knot nematodes. For example, biological control of root-knot nematodes by AMF has been demonstrated on many crops (Table. 10.1). In mycorrhizal plants egg production of M. hapla was reduced up to 75 and disease severity up to 71 (Waceke et al. 2001). Other effects of AMF towards root-knot nematode infestation include reduced juvenile penetration (Sikora 1979), reduced number and size of...

Endophytic Behaviour and Biological Control

As stated above, colonisation of a plant tissue by endophytes may increase host tolerance to stress caused by pests and pathogens through a wide array of mechanisms. These would include induction of host's systemic resistance, antibiosis, reduction of palatability, or direct parasitism. Among these, parasitism of plant parasitic nematodes or pest insects are the best known effects of NEF. Many different organisms have been shown to produce a systemic activation of the plant defence mechanisms...

Transportome and Vegetative Growth

The transportome is the range of genes that an organism possesses that encode protein molecules that contribute to transport of molecules across biological membranes. The array of outer membrane bound transporters available to the bacterial cell governs the uptake of solutes and signalling molecules into the cell above ambient concentrations as well as controlling the secretion of proteins and excretion out of the cell. The outer membrane of bacterial cells is the first port of call for...

Bioenhancement Of Crop Productivity By Fungal Inoculation

Alabouvette C, Couteaudier Y 1992 Biological control of Fusarium wilts with non-pathogenic Fusarium. In Tjamos EC, Cook RJ, Papavizas GC eds Biological control of plant diseases. Plenum, New York, pp 415-426 Alabouvette C, Roucel F, Louvet J 1979 Characteristics of Fusarium wilt-suppressive soils and prospects for their utilization in biological control. In Schippers B, Gams W eds Soil-borne plant pathogens. Academic, London, pp 165-182 Alkan N, Gadkar V, Goburn J et al 2004 Quantification of...

Signaling Pathways

Following exposure to pathogen microorganisms, the epithelial layer of mucosal surfaces is confronted with the task of recognizing pathogen-associated molecular patterns. The mechanisms by which C. elegans recognizes pathogens have yet to be elucidated. Nevertheless, the genetic pathways operating in the worm's response to microbial challenges have been extensively characterized in recent years see reviews Ewbank 2006 Gravato-Nobre and Hodgkin 2005 Kim and Ausubel 2005 Schulenburg and Boehnisch...

For Managing Plant Parasitic Nematodes

Abstract Biological control of plant-parasitic nematodes can be accomplished either by application of antagonistic organisms, conservation and enhancement of indigenous antagonists, or a combination of both strategies. The application of biological control has been inconsistent in suppressing nematode populations because the efficacy of antagonists is influenced by other soil organisms and the host-plant. Integration of biological control with nematicides, solarization, organic amendments, and...

Trichoderma as a Biological Control Agent

Edna Sharon, Ilan Chet, and Yitzhak Spiegel Abstract Trichoderma species are free-living fungi that are common in soil and root ecosystems. Some strains establish root colonization and enhance growth and development, crop productivity, resistance to abiotic stresses and uptake and use of nutrients. Trichoderma species can antagonize and control a wide range of economically important plant pathogenic fungi, viruses, bacteria and nematodes. Root-knot nematodes, Meloidogyne spp., are sedentary,...

Nematophagous Fungi

The so-called nematophagous fungi are a phylogenetically diverse non-related group of fungi which is able to infect and kill nematodes, at any developmental stage e.g. eggs, juveniles or sessile females . The biology and infective processes of the different groups of nematophagous fungi have been extensively reviewed Lopez-Llorca et al. 2006, 2008 Lopez-Llorca and Jansson 2006 , and therefore we will only give here a brief description. According to their mode of infecting nema-todes,...

How Molecular Approaches Are Shaping Our Knowledge of Nematode Control in Natural Ecosystems

The drivers of biological control mechanisms in nature, their impact on selected populations, on the nematode community and on the soil community as a whole are still not clearly understood. To fully understand the ecology of nematode control mechanisms in natural systems, we must be able to address key questions what is the identity of the nematodes and what is their fundamental niche how are they distributed in soil and how diverse are their populations Similar questions on the organisms they...

Monitoring Biocontrol Agents in Soil

Many different groups of organisms are known to parasitise or prey on nematodes, but one of the main problems in working with biological control systems is the difficulty of detecting and quantifying some of these groups in soil. This applies particularly to the predatory and parasitic fungi. Nematode-trapping fungi can be quantified using sprinkle plates and soil dilution plates, but these time-consuming methods tend to detect species that grow well in culture and their efficacy is affected by...

State of the Pasteuria Sequencing

As discussed above, the last decade has seen the sequencing of eukaryotic and prokaryotic organisms and with the development of more efficient sequencing technologies the sequencing of organisms has become increasingly routine. Comparing the genomes of different organisms can often lead to insights into their evolutionary history and help to answer questions regarding how organisms with similar developmental processes and genetics have very different life forms, and conversely, how very similar...

BottomUp Control

Heterodera

Bottom-up control occurs when a nematode population size is kept below a certain level by resource limitation, i.e., food availability. What would initially appear to be a simple concept potentially involves several mechanisms. Plant-parasitic nema-todes are obligate parasites which have co-evolved with their host plants during this process, both nematodes and plants have also interacted and co-evolved with a range of other rhizosphere organisms. The outcomes of this coevolving network are...

Trichoderma Biocontrol Activity Against Root Knot Nematodes

Trichoderma asperellum-203 and T. atroviride IMI 206040 both fungi were previously defined as strains of T. harzianum exhibited biocontrol activity against M. javanica in soil Sharon et al. 2001 . Several other Trichoderma species and isolates 3 isolates of T. asperellum 44, GH11 and 34 T. harzianum 248 T. hamatum 382 have been also evaluated as biocontrol agents against M. javanica and M. incognita. Those Trichoderma isolates had shown biocontrol activity against plant pathogenic fungi....