Control Of Plant Parasitic Nematodes Research Articles

SCREEN HOUSE ASSESSMENT OF NEEM-FORTIFIED CASSAVA PEEL POWDER FOR CONTROLLING NEMATODES AND YIELD IMPROVEMENT OF SUGARCANE (SACCHARUM OFFICINARUM)

Screen house trials for the assessment of Neem-fortified cassava peels for control of plant-parasitic nematodes and yield improvement of sugarcane (Saccharum officinarum) were conducted in Moor plantation, Ibadan, Southwest Nigeria. Cassava peel powder (CPP) solely and in combination with Neem Leaf Powder (NLP) or Neem Seed Powder (NSD) at 100gCPP/10 Litre soil, 90gCPP+30gNSP/10 Litre soil, 80gCPP+20gNSP/10 Litre soil, 70gCPP+30gNSP/10 Litre of soil, 90gCPP+10gNLP/10 Litre soil, 80gCPP+20gNLP/10 Litre soil, 70gCPP+30gNLP/10 Litre soil were incorporated into potted naturally infested soil in the screen house, at 14 d before planting. All treatments significantly (p<0.05) reduced plant-parasitic nematode population. Soil treatment with Cassava Peel Powder in combination with Neem Leaf Powder at 70gCPP+30gNLP/10 Litre of soil recorded the most effective control for soil and root nematodes associated with sugarcane in the two screen house trials. The soil amendment also supported the good vegetative growth and yield of sugarcane, which is an indication of its capability to improve soil fertility.

Simultaneous exposure of nematophagous fungi, entomopathogenic nematodes and entomopathogenic fungi can modulate belowground insect pest control.

Entomopathogenic nematodes (EPNs) and fungi (EPF) are well known biological control agents (BCAs) against insect pests. Similarly, the nematophagous fungi (NF) are considered good BCA candidates for controlling plant parasitic nematodes. Because NF can employ EPNs as food and interact with EPF, we speculate that the simultaneous application of EPNs and EPF might result in higher insect mortality, whereas the triple species combination with NF will reduce the EPN and EPF activity by predation or inhibition. Here we evaluated single, dual (EPN + EPF, EPF + NF, EPN + NF) and triple (EPN + EPF + NF) combinations of one EPN, Steinernema feltiae (Rhabditida: Steinernematidae), one EPF, Beauveria bassiana (Hypocreales: Clavicipitaceae), and two NF, Arthrobotrys musiformis (Orbiliales: Orbiliaceae) and Purpureocillium lilacinum (Hypocreales: Ophiocordycipitaceae) under laboratory conditions. First, we showed that EPF reduced the growth rate of NF and vice versa when combined in both rich and limiting media, suggesting a negative interaction when combining both fungi. Three different fungal applications (contact with mycelia-conidia, immersion in conidial suspension, and injection of conidial suspension) were tested in single, dual and triple species combinations, evaluating Galleria mellonella (Lepidoptera: Pyralidae) larval mortality and time to kill. When mycelia was presented, the EPF appeared to be the dominant in combined treatments, whereas in immersion exposure was the EPN. In both types of exposure, NF alone did not produce any effect on larvae. However, when A. musiformis was injected, it produced larval mortalities >70% in the same time span as EPN. Overall, additive effects dominated the dual and triple combinations, with the exception of injection method, where synergisms occurred for both NF species combined with EPN + EPF. This study illustrates how differences in species combination and timing of fungal arrival can modulate the action of BCAs when augmented in the soil. Further studies are required to fine-tune these multitrophic interactions to provide successful, sustainable and resilient pest management in agroecosystems.

Nematode-specific cadherin CDH-8 acts as a receptor for Cry5B toxin in Caenorhabditis elegans.

Parasitic nematodes of animals and plants cause worldwide devastating impacts on people's lives and agricultural crops. The crystal protein Cry5B produced by Bacillus thuringiensis has efficient and specific activity against a wide range of nematodes. However, the action mode of this toxin has not yet been thoroughly determined. Here, a nematode-specific cadherin CDH-8 was demonstrated to be a receptor for Cry5B toxin by using Caenorhabditis elegans as a model, providing evidence that the cadherin mutant worm cdh-8(RB815) possesses significant resistance to Cry5B, and the CDH-8 fragments bind specifically to Cry5B. Furthermore, CDH-8 was identified to be required for the oligomerization of Cry5B toxin in vivo and contribute to the internalization and pore formation of Cry5B in nematode cells. This study will facilitate a better understanding of the action mode of nematicidal Cry toxins and help the design of Cry toxin-based products for the control of plant or animal parasitic nematodes.

A trait-based approach for the choice of cover crops in banana cropping systems: theoretical developments and practical applications

Cover crop-based cropping systems have gained considerable attention in recent years because of the recognized benefits of increasing agroecosystem diversity to enhance ecological functions and agroecosystem services through positive effects between species. While agronomic tools and methods to assess these services in multispecies plant communities barely exist, trait-based approaches, originally developed in the field of comparative functional ecology, provide an appropriate framework to study the effects of plant diversity on agroecosystems. We present our theoretical and applied research conducted over recent years using a trait-based approach to help improve cover crop choice to sustain agroecosystem services in banana agroecosystems of the French West Indies. We first provide a conceptual framework for assessing expected agroecosystem services from cover crops in banana agroecosystems, i.e., weed control, plant-parasitic nematode control, improvement of the nutrient cycling and avoidance of interference for resource acquisition in banana (dis-service), based on plant effect traits. Then, we experimentally characterized a collection of cover crop species to identify their resource acquisition strategies and the potential trade-offs they reveal. More practically, we characterized the cover crop species according to their potential to deliver four agroecosystem services expected from banana/cover crop systems. We constructed functional profiles of the cover crop species, and compared these profiles to cover crop ideotypes to select the best-suited species for each service. Finally, we used engineering traits to help design and optimize design and management of cover crop species mixtures. These examples from our research demonstrate that functional, trait-based approaches have strong potential to tackle agronomic issues and to resolve fundamental and applied questions related to the design of multispecies cropping systems that optimize multiple services.

Influência de manipueira sobre Meloidogyne javanica na soja

Searching alternatives for the control of plant parasitic nematodes, nematicide effect of secondary metabolites or plant residues has been studied. Thus, the manipueira, a liquid residue obtained from the industrialization of cassava (Manihot esculenta), has as its composition cyanogenic glycosides with antimicrobial properties. The objective of this study was to evaluate the potential of the manipueira applied to the soil, aiming at the control of Meloidogyne javanica in the soybean crop. The manipueira was applied at the concentrations of 0, 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100%. The experimental design was completely randomized, in an 11 × 2 factorial arrangement (concentrations of manipueira × forms of application - single and fractionated), with five replicates. Soybean plants were inoculated with 3000 eggs and J2 of M. javanica per pot. Sixty days after the first application of the manipueira, agronomic characteristics and parasitism were evaluated. The single application of the manipueira promoted greater growth and root development, as well as a reduction in the number of eggs and juveniles in the roots and in the reproduction factor of M. javanica, for all concentrations. The split application had more effect on reducing the number of galls and egg mass. The lethal manure concentrations for 50% of the soil and root nematode populations were 37.90% and 29.67%, respectively.

Comparative effects of different organic materials on nematode community in continuous soybean monoculture soil

Plant parasitic nematodes are the most devastating pest in continuous soybean monoculture, which have been managed mainly by chemical nematicides. However, safe and alternative methods need to be developed. A variety of organic materials are used for this purpose, but the control efficiency of different organic materials for nematodes has not been assessed in a comparative manner. Therefore, based on a 7-year experiment of continuous soybean monoculture, we directly compared the effects of different organic materials (maize straw combined with chemical fertilizer (F + S), poplar leaf combined with chemical fertilizer (F + L), cow manure combined with chemical fertilizer (F + C) and only fertilizer as CK) on nematode trophic groups and functional guilds under the same condition. Despite the lack of total nematode density differences, organic materials altered the soil nematode community in a soybean monoculture system. The relative abundance of plant parasites was highest in F + L treatment, followed by F + S treatment, while lowest in F + C and CK treatments. Meanwhile, bacterivores and fungivores had a higher relative abundance in CK and F + C treatments and a lower relative abundance in F + L and F + S treatments. Furthermore, significant treatment effects were also observed on the relative abundance of different functional guilds, except colonizer-persister (c-p) 5 plant parasites. The relative abundance of c-p 2 bacterivores was significantly higher in CK and F + C treatments than in F + S and F + L treatments, while the relative abundance of c-p 3 omnivore-carnivores was significantly higher in F + S and F + L treatments than in CK and F + C treatments. Organic materials treatments had a significant effect on Shannon index (H’), plant parasite index (PPI), structure index (SI) and enrichment index (EI) (P < .05), and the significant effects varied among different organic materials treatments. The results of this study suggest that the influence on the soil nematode community of organic materials is associated with their chemical composition, and so is its efficacy of controlling plant parasitic nematodes.

Emission and crop response in almond orchards fumigated with reduced rates of Telone® C-35 and low permeability film for nematode control

Many high-value tree crops are dependent on soil fumigation for control of plant-parasitic nematodes and diseases for successful orchard replanting. Due to detrimental impacts on the environment, fumigants are under stringent regulations. The study investigated if a commercially available totally impermeable film (TIF) such as VaporSafe® and reduced fumigant rates can achieve emission reduction while providing good control of plant-parasitic nematodes and improving tree establishment. Two field trials were conducted in almond orchards on a sandy soil or a sandy loam to test the effects of Telone® C-35 (containing 63% 1,3-dichloropropene and 35% chloropicrin) on fumigant movement, nematode survival, and tree performance. In the trials, Telone® C-35 was applied at various rates: 100% (610 kg ha−1), 66%, or 33%; with three surface sealing methods: bare, standard polyethylene film (PE), and TIF. The TIF greatly reduced emissions compared to PE or bare soil with very low off-edge emissions. Both 100% and 66% rates of the fumigant promoted similar tree growth regardless of surface sealing methods. The 66% rate under TIF and PE also provided 100% control of resident nematodes as the 100% rate at or above 100 cm soil depth in both trials. Fumigation at the sandy soil site was able to reduce or eliminate the nematode population at the 120-150 cm soil depth. However, none of the treatments provided 100% control of nematodes at this depth in the sandy loam soil indicating the effects of soil texture on fumigation efficacy. Thus, TIF and reduced rates of Telone® C-35 can be used to reduce the environmental impacts of soil fumigation and fumigant expenses.

Mycorrhizas reduce tomato root penetration by false root-knot nematode Nacobbus aberrans

Arbuscular mycorrhizal fungi (AMF) are considered as a possible alternative for the biological control of plant-parasitic nematodes. The false root-knot nematode Nacobbus aberrans is an endoparasite that induces the formation of galls in plant roots and causes severe damage to crops of economic importance. The purpose of the study was to evaluate the effect of the individual and combined application of two AMF species (Rhizophagus intraradices and Funneliformis mosseae) on the tomato root penetration of N. aberrans second-stage juveniles (J2). Forty-five days after the application of AMF, 300 J2 were inoculated per plant. Tomato roots were analyzed after 4, 8 and 12days in order to quantify the nematodes that had invaded them. Plants inoculated with AMF presented a lower number of juveniles within the roots compared with non-mycorrhizal plants. No significant differences were observed between the individual and combined application of AMF regarding the number of nematode juveniles. The use of R. intraradices and F. mosseae (both individually and combined) reduced the entry of nematodes in tomato roots. The antagonistic effect of AMF on the invasion of N. aberrans J2 is reported for the first time.

Evaluation of Clonostachys rosea for Control of Plant-Parasitic Nematodes in Soil and in Roots of Carrot and Wheat.

Biological control is a promising approach to reduce plant diseases caused by nematodes. We tested the effect of the fungus Clonostachys rosea strain IK726 inoculation on nematode community composition in a naturally nematode infested soil in a pot experiment, and the effect of C. rosea on plant health. The numbers of plant-parasitic nematode genera extracted from soil and plant roots decreased by 40 to 73% when C. rosea was applied, while genera of nonparasitic nematodes were not affected. Soil inoculation of C. rosea increased fresh shoot weight and shoot length of wheat plants by 20 and 24%, respectively, while only shoot dry weight increased by 48% in carrots. Light microscopy of in vitro C. rosea-nematode interactions did not reveal evidence of direct parasitism. However, culture filtrates of C. rosea growing in potato dextrose broth, malt extract broth and synthetic nutrient broth exhibited toxicity toward nematodes and immobilized 57, 62, and 100% of the nematodes, respectively, within 48 h. This study demonstrates that C. rosea can control plant-parasitic nematodes and thereby improve plant growth. The most likely mechanism responsible for the antagonism is antibiosis through production of nematicidal compounds, rather than direct parasitism.

Isolation of Antagonistic Endophytes from Banana Roots against Meloidogyne javanica and Their Effects on Soil Nematode Community.

Banana production is seriously hindered by Meloidogyne spp. all over the world. Endophytes are ideal candidates compared to pesticides as an environmentally benign agent. In the present study, endophytes isolated from banana roots infected by Meloidogyne spp. with different disease levels were tested in vitro, and in sterile and nature banana monoculture soils against Meloidogyne javanica. The proportion of antagonistic endophytes were higher in the roots of middle and high disease levels. Among those, bacteria were dominant, and Pseudomonas spp., Bacillus spp. and Streptomyces spp. showed more abundant populations. One strain, named as SA, with definite root inner-colonization ability was isolated and identified as Streptomyces sp. This strain showed an inhibiting rate of >50% in vitro and biocontrol efficiency of 70.7% in sterile soil against Meloidogyne javanica, compared to the control. Greenhouse experiment results showed that the strain SA exhibits excellent biological control ability for plant-parasites both in roots and in root-knot nematode infested soil. SA treatment showed a higher number of bacterivores, especially Mesorhabditis and Cephalobus. The maturity index was significantly lower, while enrichment index (EI) was significantly higher in the SA treatment. In conclusion, this study presents an important potential application of the endophytic strain Streptomyces sp. for the control of plant-parasitic nematodes, especially Meloidogyne javanica, and presents the effects on the associated variation of the nematode community.

Mode of action and efficacy of iprodione against the root‐knot nematode Meloidogyne incognita

AbstractThe ban and restriction on the use of several synthetic chemicals for controlling plant parasitic nematodes, and concern about their side effects necessitate the availability of effective methods of control with low toxicity to humans and non‐target organisms. Therefore, efficacy and mode of action of iprodione, a dicarboximide fungicide, was evaluated against the root‐knot nematode Meloidogyne incognita, in vitro and in vivo conditions, in comparison with the nematicides fenamiphos, fosthiazate and oxamyl at 7.00, 1.66 and 1.66 mL/5 L water, respectively. In vitro, iprodione showed nematostatic rather than nematicidal activity against second‐stage juveniles of M. incognita in contrast to fenamiphos, fosthiazate and oxamyl which were nematicidal. In the in vivo experiment with tomato, iprodione controlled M. incognita less than fenamiphos, fosthiazate and oxamyl. No visual symptoms of phytotoxicity were observed. Therefore, iprodione can be a useful chemical for controlling nematode populations if included in an Integrated Pest Management program.

Transgenic Nicotiana benthamiana plants expressing a hairpin RNAi construct of a nematode Rs-cps gene exhibit enhanced resistance to Radopholus similis

Burrowing nematodes (Radopholus similis) cause severe harm in many agronomic and horticultural crops and are very difficult to manage. Cathepsin S is one of the most important cysteine proteinases and plays key roles in nematodes and many other parasites. To evaluate the effect of in planta RNAi on the control of this nematode, a specific fragment from the protease gene, cathepsin S (Rs-cps), was cloned into the binary vector pFGC5941 in the forward and reverse orientations to construct recombinant plant RNAi vectors. Transgenic Nicotiana benthamiana plants expressing Rs-cps dsRNA were obtained and studied. The transcript abundance of Rs-cps dsRNA appeared to be diverse in the different transgenic lines. Moreover, the bioassay results revealed that Rs-cps transgenic N. benthamiana plants were resistant to R. similis and the transcription level of Rs-cps in R. similis was drastically decreased. In addition, the reproduction and hatching rate of R. similis isolated from the Rs-cps transgenic plants were also significantly reduced. Our results suggest that Rs-cps is essential for the reproduction and pathogenicity of R. similis. This is the first study to employ in planta RNAi approach to target the Rs-cps gene for the control of plant parasitic nematodes.

Penerapan Sistem Olah Tanah dan Pemulsaan Pada Tebu untuk Pengendalian Nematoda Parasit Tumbuhan Dominan

Conventional tillage system practices for a long time can reduce soil qualities because of soil erosion, soil compaction and depleting of soil organic matter. Conservation tillage such as No-tillage system can be applied as an alternative technique to rehabilitate soil degradation problems.. This research is a part of a long term study of soil rehabilitation that was conducted from 2010 till now, in PT GMP, Central Lampung. Sampling of nematodes was done on April 2013 when the second ratoon RGM 00-838 variety of sugarcane was 9 months old. The aim of this research was to study the effect of tillage and mulching systems on the abundance of several dominant plant parasitic nematodes. Split plot experimental design was applied on this research. Tillage system as the main plots consisted of intensive tillage and no-tillage systems, while mulching system as the sub-plots consisted of no-mulch and mulching with 80 ton ha-1 of fresh bagasee. Nematodes were collected from 0-20 cm deep of soil and extracted by sieving and centrifugation with sugar solution methods at the Plant Pest and Disease Laboratory, University of Lampung. The results of this research showed that there were eleven plant parasitic and seven free-living nematode genera inhabited the PT GMP sugarcane plantation. The three plant parasitic nematode genera dominant were Hoplolaimus, Xiphinema, and Hemicriconemoides. No-tillage system effectively reduce the abundance of Xiphinema and , mulching with bagasse reduced the abundance of Hemicriconemoides. Meanwhile, mulching on No-tillage system more effective to reducing the abundance of Hoplolaimus compared to intensive tillage system. This results suggested that the No-tillage with bagasse mulching system was one of alternative techniques to control plant parasitic nematodes pest of sugarcane plantation. Keywords : Tillage, mulching, sugarcane, plant parasitic nematodes, abundance.

Control and Management of Plant-Parasitic Nematodes in Integrated Production of Garden Strawberries (Fragaria×Ananassa Duchesne Ex Rozier)

AbstractArable soils are one of the most valuable natural resources and their long-term sustainable management is a determining factor in the integrated production of strawberries. It is well known that the current large-fruited garden strawberry (Fragaria × ananassa Duchesne ex Rozier) cultivars are more susceptible to many species of plant-parasitic nematodes and other plant pathogens. The aim of this study was to evaluate the effects of some cultural practices as potential methods for control of nematodes in the integrated production of strawberries. The investigation of the nematode populations was carried out in the region of western Balkan Mountains in Bulgaria (43°33'22.3"N 22°47'03.4"E), with cultivar ‘Maya’. In the surveyed area, plant protection products were applied under an approved scheme complying with the requirements for integrated fruit production (IOBC, IFP). Nematode populations were identified and classified to trophic level. The following genera of plant-parasitic nematodes were identified: Pratylenchus crenatus, P. neglectus, P. thornei, Tylenchorhynchus sp., and Paratylenchus spp. The density and species composition of plant parasitic nematodes were significantly reduced at the end of the study period comparing to the beginning of the study. From the results, it is clear that the integrated production can be defined as an economically feasible production of high quality fruits, giving priority to environmentally safe methods of pest control.

The role of plant parasitic nematodes on productivity reduction of banana and tomato in East Kalimantan, Indonesia

Suyadi, Rosfiansyah. 2017. The role of plant parasitic nematodes on productivity reduction of banana and tomato in East Kalimantan, Indonesia. Asian J Agric 1: xxxx. Plant parasitic nematode is one of the most limiting factor of agricultural ecosystem productivity in East Kalimantan, but their occurrence in agricultural field as a crop’s pest generally undistinguished, due to their microscopic size and their existence wrapped in the roots or soil particles. However, plant parasitic nematodes might cause yield loss up to 75%, without showed any disease symptom on crop morphologically. Perennial crop and annual crop under intensive cultivation usually experience high yield loss due to plant parasitic nematodes, if crop protection management was not implemented properly. This research aimed to determine the role of plant parasitic nematodes in reducing crop’s productivity in East Kalimantan, in relation to agricultural practices implemented by farmers. A descriptive research and comparative analyses were implemented to determine the role of plant parasitic nematode on yield reduction of banana and tomato as the indicator of productivity. Based on the field observation related to pest management in East Kalimantan, it was determined that plant parasitic nematode existence was neglected by farmers and no significant effort was implemented to control plant parasitic nematodes population. Therefore, low productivity of agricultural ecosystem in East Kalimantan was reported by Statistical Office, and it was not only caused by soil fertility problems, in some crops it was also the impact of population outbreak of plant parasitic nematodes. The first ranking three genera of plant parasite nematodes observed in East Kalimantan were Meloidogyne, Radhopholus, and Rotylenchulus, respectively. Meloidogyne and Rotylenchulus were major pest on vegetables, and caused yield loss &gt;50% on tomato. While, genus of Radhopholus was the major pest on banana, and caused yield loss &gt;75% on banana.

Off-tarp emissions, distribution, and efficacy of carbonated fumigants in a low permeability film tarped field

Carbonated fumigants have been shown to distribute quickly and uniformly in sandy soils and improve pest control efficacy for annual crops. Low permeability films, such as VaporSafe® (TIF), could further improve fumigant dispersion by effectively retaining the fumigant in soil; however, there is a concern that the TIF can lead to higher off-tarp edge emissions. An orchard field trial was conducted to determine the off-tarp emissions, distribution, efficacy, and fate of carbonated Telone® C35 [63.4% 1,3-dichloropropene (1,3-D), 34.7% chloropicrin (CP)] that was shank-injected at 46cm soil depth. Treatments included carbonated fumigants at full- or 2/3 rates and a full rate of regular (nitrogen-pressurized) fumigants covered with standard polyethylene (PE) film, TIF, or no surface seal. Fumigant emissions at the regular tarp edge (25cm from the shank line) peaked at 3.98μgm−2s−1 for 1,3-D and 0.05μgm−2s−1 for CP. The addition of a TIF tarp extension (to 85cm from the shank line) reduce peak off-tarp emissions to <1 and <0.03μgm−2s−1 for 1,3-D and CP, respectively. Fumigant concentration under TIF was usually at least twice that under PE regardless of carbonation. Carbonation at 345KPa with 1.5% of dissolved CO2 did not significantly improve fumigant dispersion in soil profile compared to the conventional nitrogen pressurization. In a citrus nematode bioassay, only the 2/3 rate of carbonated fumigation treatment sealed with PE failed to control nematodes at 25cm away from shank line. This research indicates that a 60-cm TIF extension can effectively reduce off-tarp edge emissions in strip fumigation treatments. While the adaptability of carbonation of fumigants is still questionable, further research efforts are needed in finding effective solutions to control plant parasitic nematodes, which remain a challenge in orchard fumigation.

The discovery of fluazaindolizine: A new product for the control of plant parasitic nematodes

Fluazaindolizine is a new highly effective and selective product for the control of plant parasitic nematodes. Specificity for nematodes coupled with absence of activity against the target sites of commercial nematicides suggests that fluazaindolizine has a novel mode of action. The discovery, structure-activity development and biological properties for this new class of nematicides are presented.

Biological Control of Meloidogyne incognita by Spore-forming Plant Growth-promoting Rhizobacteria on Cotton.

In the past decade, increased attention has been placed on biological control of plant-parasitic nematodes using various fungi and bacteria. The objectives of this study were to evaluate the potential of 662 plant growth-promoting rhizobacteria (PGPR) strains for mortality to Meloidogyne incognita J2 in vitro and for nematode management in greenhouse, microplot, and field trials. Results indicated that the mortality of M. incognita J2 by the PGPR strains ranged from 0 to 100% with an average of 39%. Among the PGPR strains examined, 212 of 662 strains (or 33%) caused significantly greater mortality percent of M. incognita J2 than the untreated control. Bacillus was the major genus initiating a greater mortality percentage when compared with the other genera. In subsequent trials, B. velezensis strain Bve2 reduced M. incognita eggs per gram of cotton root in the greenhouse trials at 45 days after planting (DAP) similarly to the commercial standards Abamectin and Clothianidin plus B. firmus I-1582. Bacillus mojavensis strain Bmo3, B. velezensis strain Bve2, B. subtilis subsp. subtilis strain Bsssu3, and the Mixture 2 (Abamectin + Bve2 + B. altitudinis strain Bal13) suppressed M. incognita eggs per gram of root in the microplot at 45 DAP. Bacillus velezensis strains Bve2 and Bve12 also increased seed-cotton yield in the microplot and field trials. Overall, results indicate that B. velezensis strains Bve2 and Bve12, B. mojavensis strain Bmo3, and Mixture 2 have potential to reduce M. incognita population density and to enhance growth of cotton when applied as in-furrow sprays at planting.

Plant-parasitic nematodes: towards understanding molecular players in stress responses.

Background Plant–parasitic nematode interactions occur within a vast molecular plant immunity network. Following initial contact with the host plant roots, plant-parasitic nematodes (PPNs) activate basal immune responses. Defence priming involves the release in the apoplast of toxic molecules derived from reactive species or secondary metabolism. In turn, PPNs must overcome the poisonous and stressful environment at the plant–nematode interface. The ability of PPNs to escape this first line of plant immunity is crucial and will determine its virulence. Scope Nematodes trigger crucial regulatory cytoprotective mechanisms, including antioxidant and detoxification pathways. Knowledge of the upstream regulatory components that contribute to both of these pathways in PPNs remains elusive. In this review, we discuss how PPNs probably orchestrate cytoprotection to resist plant immune responses, postulating that it may be derived from ancient molecular mechanisms. The review focuses on two transcription factors, DAF-16 and SKN-1, which are conserved in the animal kingdom and are central regulators of cell homeostasis and immune function. Both regulate the unfolding protein response and the antioxidant and detoxification pathways. DAF-16 and SKN-1 target a broad spectrum of Caenorhabditis elegans genes coding for numerous protein families present in the secretome of PPNs. Moreover, some regulatory elements of DAF-16 and SKN-1 from C. elegans have already been identified as important genes for PPN infection. Conclusion DAF-16 and SKN-1 genes may play a pivotal role in PPNs during parasitism. In the context of their hub status and mode of regulation, we suggest alternative strategies for control of PPNs through RNAi approaches.

Occurrence and Control of Plant-parasitic Nematodes in Irrigation Water – A Review

A literature study was carried out to determine what is currently known about the contamination of irrigation water with plant-parasitic nematodes, and what control measures are currently available. Contamination sources of irrigation water with plant-parasitic nematodes were investigated, including wells, boreholes, collected rainwater, ponds, lakes, dams, rivers, municipal water, runoff water, irrigation canals and drainage water in soilless culture. Only when the origin of irrigation water was a capped borehole was the risk of contamination with plant-parasitic nematodes low. The plantparasitic nematodes of economic importance to grapevine reported to be found in irrigation water were Meloidogyne spp., Xiphinema spp., Tylenchulus semipenetrans, Trichodorus sp., Criconemoides xenoplax and Pratylenchus spp. The different sampling techniques used for the detection and monitoring of plant-parasitic nematodes and the sampling time and location are listed. The survival and infection potential reported for each species of plant-parasitic nematode found in irrigation water was noted. Serious nematode parasites of grapevines, such as Meloidogyne javanica, can survive for 16 to 32 days, M. incognita, for up to 14 days, Pratylenchus, for up to 70 days, T. semipenetrans, for up to 128 days, and X. index, for up to 13 days in irrigation water. All reported techniques used for the management of nematodes in irrigation water are listed and possible future research into the control of plant-parasitic nematodes in irrigation water is discussed. From this review, substantial evidence was obtained of the danger of introducing plant-parasitic nematodes to grapevine production sites by means of irrigation water.