Typical Root Research Articles

Efficacy of different fungicides and bio-agents against wilt and root rot complex of chickpea

The present investigation were undertaken to develop an effective strategy for the integrated management of wilt and root rot complex diseases of chickpea (Cicer arietinum L.), which is widely prevalent in moderate to high severity in different parts of Rajasthan. The pathogens were isolated from disease chickpea plants showing typical wilt and root rot symptoms collected from farmer's field of different chickpea growing areas of Rajasthan. Fusarium oxysporum f. sp. ciceri (one isolate), Fusarium solani (five isolates) and Rhizoctonia solani (six isolates) were isolated and their pathogenicity was confirmed by growing chickpea in pathogen inoculated soil. The fungicides, botanicals and biocontrol agents found effective in vitro, were further evaluated in field for two consecutive seasons as seed treatment individually as well as in combinations for suppression of wilt and root-rot complex of chickpea. It was found that combined treatments were superior in terms of better germination, lower mortality and higher yield as compared to the individual treatments. The most effective treatment was seed treatment with tebuconazole + T. harzianum followed by vitavax+T. harzianum as compared to control as well as other treatments.

Belief propagation for optimal edge cover in the random complete graph

We apply the objective method of Aldous to the problem of finding the minimum-cost edge cover of the complete graph with random independent and identically distributed edge costs. The limit, as the number of vertices goes to infinity, of the expected minimum cost for this problem is known via a combinatorial approach of Hessler and Wästlund. We provide a proof of this result using the machinery of the objective method and local weak convergence, which was used to prove the $\zeta(2)$ limit of the random assignment problem. A proof via the objective method is useful because it provides us with more information on the nature of the edge’s incident on a typical root in the minimum-cost edge cover. We further show that a belief propagation algorithm converges asymptotically to the optimal solution. This can be applied in a computational linguistics problem of semantic projection. The belief propagation algorithm yields a near optimal solution with lesser complexity than the known best algorithms designed for optimality in worst-case settings.

Outbreak Risk of Club Root Caused by Plasmodiophora brassicae on Oilseed Rape in Chile.

Oilseed rape (Brassica napus L.) plants with typical club root symptoms were detected on two farms in the La Araucanía region (37°35' to 39°37' S), southern Chile. In 2010, affected plants were found in large areas throughout three fields on a single farm and disease incidence ranged from 30 to 100%. In 2013, plants with club root were found in one field on a different farm. Disease incidence in the affected areas was 30%. In both cases, affected plants showed root swellings or distortions, but no aerial symptoms were evident. Cross-sections from symptomatic roots were observed under light and fluorescent microscope and compared to healthy roots. The presence of plasmodia with resting spores in the root tissue pointed to Plasmodiophora brassicae Woronin as the causal agent. Pathogenicity was evaluated in the greenhouse. Inoculum was prepared by grinding 10 g of fresh galled roots in sterile water. The macerated tissue was filtered through sterile cheesecloth and the spore suspensions were adjusted to 1 × 107 spores/ml. Seeds of oilseed rape cv. Imminent were germinated and 5-day-old seedlings were transplanted in 250-ml pots (4 seedlings per pot). The soil surrounding the base of each seedling was inoculated with 1 ml of spore suspension. One pot received no inoculum and was used as a control. Pots were watered regularly. After 45 days, the inoculated plants showed root swelling similar to that observed in the field, whereas no symptoms were observed on the roots of the control plants. Specific PCR detection for P. brassicae was performed with pairs of primers TC1F/TC1R and TC2F/TC2R, according to the protocol described by Cao et al. (1). Total DNA was obtained from old galled roots collected in the field and galled roots from plants of the pathogenicity test, using the E.Z.N.A HP Plant DNA mini kit (Omega Biotek). Amplicon sizes of 548 and 519 bp, respectively, were obtained for each primer set, which is consistent with that reported by Cao et al. (1). Seed contamination with P. brassicae in the same seed lot used to sow the commercial field of 2013 was evaluated using the PCR method described above. Washing protocols to collect resting spores from seed was based on Rennie et al. (2). Total DNA was extracted from the resting spores pellet that had been ground in liquid nitrogen, using E.Z.N.A HP Plant DNA mini kit. PCR was performed on undiluted and diluted (1/10, 1/100, 1/1000, and 1/10000) DNA. Total DNA from a plant with gall roots where plasmodia were observed and a plant with healthy roots were used as positive and negative control, respectively. A 548-bp amplicon was amplified in the 1/10 and 1/100 dilutions with the TC1F/TC1R primers only indicating that the pathogen may have been present in the seed lot. In Chile, club root symptoms on B. napus were described in 2008 (3), though no indication of location or incidence was given. To our knowledge, this is the first confirmed case of club root disease in an oilseed rape field. This finding could prelude new cases and possibly an outbreak of club root disease on oilseed rape, jeopardizing this important crop of southern Chile. Oilseed rape production in Chile relies on imported seed of hybrids and parental materials. Although seed contamination with P. brassicae is thought to play a minor role in the epidemiology of the disease, we cannot ignore the possibility that the occurrence of this disease in 2013 may have been associated with the use of contaminated seed.

Running a typical ROOT HEP analysis on Hadoop MapReduce

We evaluate how a typical ROOT High Energy Physics (HEP) analysis can be executed on Hadoop MapReduce. We take into account several aspects and we propose a method to perform the analysis in a completely transparent way to ROOT, the data and the user: the goal is to let ROOT run without any modifications and to store the data in its original format. The solutions which has been found to solve the encountered problems can be easily ported to any HEP code, and in general to any code working on binary data relying on independent sub-problems like HEP particle collision events. We tested the method by running an analysis code for the top quark pair production cross section measurement with the ATLAS experiment at the Large Hadron Collider in the CERN laboratory.

Cytogenetic characterization of Agrobacterium rhizogenes transformed root lines of Rauvolfia serpentina

Genetically transformed root cultures of Rauvolfia serpentina, have been developed following transformation with agropine strains of Agrobacterium rhizogenes. Characterization of Ri transformed root lines on the basis of morphology, karyotype analysis, T-DNA gene integration pattern and ajmalicine content in R. serpentina has been described in the present study. The transformed root lines were morphologically similar and exhibited typical hairy root phenotype. The somatic metaphase plates of the transformed root lines showed 2n = 22 chromosomes which is the diploid chromosome number of the species. The karyotype of both non-transformed and transformed roots showed 20 chromosomes with median to nearly median primary constriction and one pair of chromosomes had two constrictions, one at the median region and the other at the sub terminal region. Based on the pattern of TL and TR gene insertion the Ri transformed root lines can be divided into six types. Complete integration of TL-DNA was noted in 11 root lines induced with strain A. rhizogenes LBA 9402 belonging to Type I and II it is noteworthy that none of the root lines showed presence of aux1 and aux2, which are part of TR-DNA. Variable integration of TL-DNA was characteristic of several R. serpentina root lines. The Ri transformed root lines showed significant variability (p ≤ 0.05) in ajmalicine content (0.004 ± 0.001 to 0.229 ± 0.014 mg g−1 DW) after 4 weeks of culture on solid modified MS medium. Thus, we can conclude that the Ri transformed root lines of R. serpentina are morphologically and cytologically stable however variable pattern of TL and TR-DNA genes integration as well as ajmalicine content was noted among the different root lines. Thus, genetically variant transformed root lines of R. serpentina with high ajmalicine content can be selected for scale up studies.

High-sensitivity CRDS absorption spectroscopy of acetylene between 5851 and 6341 cm−1

The absorption spectrum of acetylene has been recorded at room temperature (297 K) using high-sensitivity cavity ring-down spectroscopy (αmin ∼ 5×10−11 cm−1) in the 5851 and 6341 cm−1 interval corresponding to a region of very weak absorption. A list of about 10,700 absorption features with estimated absolute line intensities was constructed. The smallest intensities are of the order of 5×10−29 cm molecule−1. The line list includes about 2500 absorption lines of ethylene present at the ppm level in the acetylene sample and identified on the basis of a high-resolution Fourier transform spectrum specifically recorded. A total of more than 2700 lines of 12C2H2 were rovibrationally assigned in comparison with accurate predictions provided by a global effective operator model. Overall, the present effort adds about 2260 new assignments to the set of about 500 assigned transitions available in the literature. The new assignments correspond to 45 new bands and 17 already-known bands, for which additional J lines were assigned. Spectroscopic parameters were derived for the upper vibrational levels from a band by band fit of the line positions (typical root mean square deviation values are of the order of 0.001 cm−1). A few of the analysed bands were found to be affected by rovibrational perturbations, which are discussed. The new data will be valuable to refine the parameters of the global effective Hamiltonian and dipole moments of 12C2H2.

Personalised external aortic root support (PEARS) in Marfan syndrome: analysis of 1–9 year outcomes by intention-to-treat in a cohort of the first 30 consecutive patients to receive a novel tissue and valve-conserving procedure, compared with the published results of aortic root replacement

ObjectiveAmong people with Marfan syndrome who have a typical aortic root aneurysm, dissection is a characteristic cause of premature death. To pre-empt Type A dissection, composite root replacement with a...

Simultaneous multiplexed quantification of nicotine and its metabolites using surface enhanced Raman scattering.

The detection and quantification of xenobiotics and their metabolites in man is important for drug dosing, therapy and for substance abuse monitoring where longer-lived metabolic products from illicit materials can be assayed after the drug of abuse has been cleared from the system. Raman spectroscopy offers unique specificity for molecular characterization and this usually weak signal can be significantly enhanced using surface enhanced Raman scattering (SERS). We report here the novel development of SERS with chemometrics for the simultaneous analysis of the drug nicotine and its major xenometabolites cotinine and trans-3'-hydroxycotinine. Initial experiments optimized the SERS conditions and we found that when these three determinands were analysed individually that the maximum SERS signals were found at three different pH. These were pH 3 for nicotine and pH 10 and 11 for cotinine and trans-3'-hydroxycotinine, respectively. Tertiary mixtures containing nicotine, cotinine and trans-3'-hydroxycotinine were generated in the concentration range 10(-7)-10(-5) M and SERS spectra were collected at all three pH values. Chemometric analysis using kernel-partial least squares (K-PLS) and artificial neural networks (ANNs) were conducted and these models were validated using bootstrap resampling. All three analytes were accurately quantified with typical root mean squared error of prediction on the test set data being 5-9%; nicotine was most accurately predicted followed by cotinine and then trans-3'-hydroxycotinine. We believe that SERS is a powerful approach for the simultaneous analysis of multiple determinands without recourse to lengthy chromatography, as demonstrated here for the xenobiotic nicotine and its two major xenometabolites.

Laser Microdissection Coupled to Transcriptional Profiling of Arabidopsis Roots Inoculated by Plasmodiophora brassicae Indicates a Role for Brassinosteroids in Clubroot Formation

The clubroot disease caused by the obligate biotrophic protist Plasmodiophora brassicae on host plants of the Brassicaceae family is characterized by enhanced cell division and cell expansion. Since a typical root section of an infected plant always includes different stages of the pathogen as well as uninfected cells, we were interested in investigating specific developmental stages of the pathogen and their effect on host transcriptional changes. We extended previous microarray studies on whole roots by using laser microdissection and pressure catapulting (LMPC) to isolate individual cells harboring defined developmental stages of the pathogen. In addition, we compared the central cylinder of infected plants with that of control plants. We were especially interested in elucidating the stage-specific hormonal network. The up-regulation of genes involved in auxin and cytokinin metabolism and signaling was confirmed. In addition, we found evidence that brassinosteroid (BR) synthesis and signal perception genes were in many cases up-regulated in enlarged cells and the central cylinder. This was confirmed by quantitative PCR. Treatment of wild-type plants with the BR biosynthesis inhibitor propiconazole reduced gall formation, and the analysis of the BR receptor mutant bri1-6 revealed less severe gall formation than in the respective wild type. Our results identify novel hormone pathways involved in clubroot development. Using LMPC to generate pools of homogeneous cell type populations combined with transcriptome analysis has been very useful to elucidate the regulation of gall growth by this obligate biotropic pathogen in a cell- and stage-specific manner.

Form matters: morphological aspects of lateral root development

The crucial role of roots in plant nutrition, and consequently in plant productivity, is a strong motivation to study the growth and functioning of various aspects of the root system. Numerous studies on lateral roots, as a major determinant of the root system architecture, mostly focus on the physiological and molecular bases of developmental processes. Unfortunately, little attention is paid either to the morphological changes accompanying the formation of a lateral root or to morphological defects occurring in lateral root primordia. The latter are observed in some mutants and occasionally in wild-type plants, but may also result from application of external factors. In this review various morphological aspects of lateral branching in roots are analysed. Morphological events occurring during the formation of a typical lateral root are described. This process involves dramatic changes in the geometry of the developing organ that at early stages are associated with oblique cell divisions, leading to breaking of the symmetry of the cell pattern. Several types of defects in the morphology of primordia are indicated and described. Computer simulations show that some of these defects may result from an unstable field of growth rates. Significant changes in both primary and lateral root morphology may also be a consequence of various mutations, some of which are auxin-related. Examples reported in the literature are considered. Finally, lateral root formation is discussed in terms of mechanics. In this approach the primordium is considered as a physical object undergoing deformation and is characterized by specific mechanical properties.

Ready-to-use injectable calcium phosphate bone cement paste as drug carrier

Current developments in calcium phosphate cement (CPC) technology concern the use of ready-to-use injectable cement pastes by dispersing the cement powder in a water-miscible solvent, such that, after injection into the physiological environment, setting of cements occurs by diffusion of water into the cement paste. It has also been demonstrated recently that the combination of a water-immiscible carrier liquid combined with suitable surfactants facilitates a discontinuous liquid exchange in CPC, enabling the cement setting reaction to take place. This paper reports on the use of these novel cement paste formulations as a controlled release system of antibiotics (gentamicin, vancomycin). Cement pastes were applied either as a one-component material, in which the solid drugs were physically dispersed, or as a two-component system, where the drugs were dissolved in an aqueous phase that was homogeneously mixed with the cement paste using a static mixing device during injection. Drug release profiles of both antibiotics from pre-mixed one- and two-component cements were characterized by an initial burst release of ∼7–28%, followed by a typical square root of time release kinetic for vancomycin. Gentamicin release rates also decreased during the first days of the release study, but after ∼1week, the release rates were more or less constant over a period of several weeks. This anomalous release kinetic was attributed to participation of the sulfate counter ion in the cement setting reaction altering the drug solubility. The drug-loaded cement pastes showed high antimicrobial potency against Staphylococcus aureus in an agar diffusion test regime, while other cement properties such as mechanical performance or phase composition after setting were only marginally affected.

A new biotechnological source of rosmarinic acid and surface flavonoids: Hairy root cultures of Dracocephalum kotschyi Boiss

Hairy root induction in Dracocephalum kotschyi Boiss was investigated as a method of producing rosmarinic acid and surface flavonoids, plant secondary metabolites well-known for their antioxidant and anticancer activities. The transformation of D. kotschyi hairy root lines induced by infection with Agrobacterium rhizogenes LBA 9402 was confirmed by PCR detection of rolC and aux1 genes, and their capacity to grow and biosynthesize rosmarinic acid and surface flavonoids was studied. Two types of morphology, typical hairy root and callus-like were observed in the induced root lines. The rolC and aux1 genes were detected in the genome of both morphological types of root lines, although aux1 was more frequently observed in callus-like roots. Our results showed the capacity of the obtained hairy root lines to produce rosmarinic acid and methoxylated flavonoids. Rosmarinic acid content in hairy root lines ranged from 10 to 1500μg/g DW, which at its peak was 15 times higher than in the intact control roots. Surface flavonoids were identified in most hairy root lines, some of which showed a surface flavonoid content higher than the roots of the whole plant but generally lower than the plant leaves.

Extremely low fine root biomass in Larix sibirica forests at the southern drought limit of the boreal forest

Mongolia's Larix sibirica forests at the southern fringe of the Eurosiberian boreal forest belt are exposed not only to very low winter temperatures, but also to frequent summer droughts. It is not completely known how Siberian larch adapts to these stressors. We examined whether (i) these forests differ in their fine root bio- and necromass from more humid boreal forests further in the North and (ii) inter-annual fluctuations in fine root biomass are related to tree vitality. In two exceptionally dry summers, we found only 4–5g DM m−2 of fine root biomass (in 0–20cm depth), which is far less than typical conifer fine root biomass figures from boreal forests (c. 200–400gm−2) and the lowest forest fine root biomass reported worldwide; in a moist summer, fine root biomass was 20 fold higher. In contrast to fine root biomass, both necromass and non-tree root mass were high in all three years. From the large increase of fine root biomass in the moist summer and the generally high root necromass, we conclude that drought-induced fine root dieback was the likely cause of the very small amount of live root mass in the dry summers. Larch fine roots seem to be more drought-sensitive than shoots, since marked needle loss did not occur under the extreme conditions.

Uptake of water from a Kandosol subsoil. II. Control of water uptake by roots

To test for the presence of an impediment to water flow at the soil-root interface. Wheat plants were grown in repacked and undisturbed field soil. Their transpiration rate, E, was varied in several steps from low to high and then back to low again, while the hydrostatic pressure in the leaf xylem, ψ xylem, was measured non-destructively and continuously. These measurements were compared to a mathematical model that calculated ψ xylem by assuming that the hydraulic resistance across the plant was constant and that the radial flow of water to unit length of a typical plant root generated gradients in pressure in the soil water. For the repacked soil, the radial flow model could not match the experiment during the falling phase of E, unless it was assumed that either an additional, constant, interfacial resistance between the soil and the roots had developed when E was large and ψ xylem was rapidly falling, or that the resistance within the plant had changed. For the undisturbed field soil, the radial flow model did not agree with the experiment. Plausible agreement was achieved when plant water uptake was accounted for using a distributed sink model in HYDRUS-1D, with E integrated across the rootzone. This approach was based on the measured large variation in the vertical distribution of roots. There was no strong evidence of large drawdowns of soil water in the rhizosphere, even when ψ xylem was falling rapidly when E was large and the soil was moderately dry. Thus, there seems to have been an additional impediment to water flow from soil to plant, either within the plant, or at the interface between the two.

Development of a simple root model to study the effects of single exudates on the development of bacterial community structure

The plant root interface is a hot spot for microbial activities. Root exudates are the key compounds that drive microbial performance. However quality and amount of root exudates are highly dynamic in time and space, thus a direct influence of a single compound on a microbial community composition is fairly impossible to study in nature. Therefore it was the aim of this project to develop an artificial root model (ARM), and investigate the influence of three compounds which have often been described as root exudates acting as model compounds for carbohydrates, organic acids and amino acids (glucose, malic acid and serine) on the development of bacterial communities and time on the ARM based on 16S rRNA derived TRFLP pattern. The ARM consisted of a slide covered with low melting agarose, where 8 different compounds which have been described as typical root exudates were embedded. The ARMs were incubated in soil for 2, 5, 9 and 20days, before the analysis of the developed bacterial community structure was done. The bacterial community composition was in good agreement after 9days of incubation of the ARM in soil with the root associated microflora of Arabidopsis thaliana shortly before flowering. The single compounds of the exudates mix had different effects on the development of ARM derived bacterial communities. Whereas the experiments where glucose was omitted gave no significant differences in the development of bacterial communities over time compared to the ARM where the standard mixture of exudates had been applied, there was a pronounced effect visible mainly after two days of incubation of the ARM in the experiments where no malic acid was added to the exudate mixture. At later time points ARMs with standard exudates' mixture and those where malic acid had been omitted, the bacterial community composition did not differ. The experiments where serine was omitted mainly induced shifts in the bacterial community composition compared to the ARM with standard exudates' mixture at the latest sampling time point (20days of incubation).

Synthesis of In-Flight Strains Using Flight Parameters for a Fighter Aircraft

This paper describes the methodology for synthesis of structural strains during flight using recorded flight parameters of a fighter aircraft. This technique can be applied to regenerate data in the event of data loss due to faults in transmission or recording or due to faulty strain gauges. In such a case, flight parameters recorded during the flight can be employed to synthesize the strain response at the structural locations for which the data loss is observed. Artificial neural networks are used in this study to model and synthesize structural strain response using a prescribed set of flight parameters. The approach is demonstrated through the examples of typical wing root and fin root fittings of a fighter aircraft. The neural network model is developed using available data of an instrumented aircraft. The results provide not only the proof-of-concept but also indicate the acceptable efficacy of the model in terms of the accuracy of predictions. Accuracy of predictions is used to identify a more suitable set of flight parameters for efficient implementation of this model. Predicted strain responses for a number of flights are shown to be within 7% of the measured data for the entire flight duration.

Characterization of root rot disease of kiwifruit in the Black Sea region of Turkey

Forty-two kiwifruit orchards from Rize and Samsun provinces (Black Sea region, Turkey) exhibiting symptoms of root rot disease were examined between 2009 and 2010. Twenty-four fungal isolates recovered from affected roots were included in this study. Morphological characteristics of all isolates were recorded on potato dextrose agar, malt extract agar and Spezieller Nahrstoffarmer agar. The effect of temperature on radial colony growth was also evaluated at 5, 10, 15, 20, 25, 30, and 35 °C. Histone H3 gene (HIS) was amplified with primers CYLH3F and CYLH3R and the amplified fragments were sequenced. The HIS phylogeny grouped all the isolates into six well-supported clades which were in agreement with phenotypical characteristics. Isolates were identified as “Cylindrocarpon” pauciseptatum, Cylindrocladiella parva, Ilyonectria liriodendri, I. torresensis, I. robusta and I. europaea, I. liriodendri being the most frequent species. All of them are reported for the first time on kiwifruit in Turkey, with the exception of I. liriodendri. Pathogenicity tests with selected isolates showed that 10 out of 11 isolates tested were able to induce typical root rot disease symptoms, affecting plant development and leading to the death of some plants. This study shows the high diversity of root rot pathogens found in kiwifruit trees in the Black Sea region of Turkey, being the first step towards a better understanding and management of the disease in local conditions.

Exploiting the combination of natural and genetically engineered resistance to cassava mosaic and cassava brown streak viruses impacting cassava production in Africa.

Cassava brown streak disease (CBSD) and cassava mosaic disease (CMD) are currently two major viral diseases that severely reduce cassava production in large areas of Sub-Saharan Africa. Natural resistance has so far only been reported for CMD in cassava. CBSD is caused by two virus species, Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV). A sequence of the CBSV coat protein (CP) highly conserved between the two virus species was used to demonstrate that a CBSV-CP hairpin construct sufficed to generate immunity against both viral species in the cassava model cultivar (cv. 60444). Most of the transgenic lines showed high levels of resistance under increasing viral loads using a stringent top-grafting method of inoculation. No viral replication was observed in the resistant transgenic lines and they remained free of typical CBSD root symptoms 7 month post-infection. To generate transgenic cassava lines combining resistance to both CBSD and CMD the hairpin construct was transferred to a CMD-resistant farmer-preferred Nigerian landrace TME 7 (Oko-Iyawo). An adapted protocol allowed the efficient Agrobacterium-based transformation of TME 7 and the regeneration of transgenic lines with high levels of CBSV-CP hairpin-derived small RNAs. All transgenic TME 7 lines were immune to both CBSV and UCBSV infections. Further evaluation of the transgenic TME 7 lines revealed that CBSD resistance was maintained when plants were co-inoculated with East African cassava mosaic virus (EACMV), a geminivirus causing CMD. The innovative combination of natural and engineered virus resistance in farmer-preferred landraces will be particularly important to reducing the increasing impact of cassava viral diseases in Africa.

Enhanced resistance against Thielaviopsis basicola in transgenic cotton plants expressing Arabidopsis NPR1 gene

Black root rot, caused by Thielaviopsis basicola, is an important disease in several crops including cotton. We studied the response of Arabidopsis NPR1 (AtNPR1)-expressing cotton lines, previously shown to be highly resistant to a diverse set of pathogens, to a challenge from T. basicola. In four different experiments, we found significant degree of tolerance in the transgenic lines to black root rot. Although transformants showed the typical root discoloration symptoms similar to the wild-type control plants following infection, their roots tended to recover faster and resumed normal growth. Better performance of transgenic plants is reflected by the fact that they have significantly higher shoot and root mass, longer shoot length, and greater number of boll-set. Transcriptional analysis of the defense response showed that the roots of AtNPR1-overexpressing transgenic plants exhibited stronger and faster induction of most of these defense-related genes, particularly PR1, thaumatin, glucanase, LOX1, and chitinase. The results obtained in this investigation provide further support for a broad-spectrum nature of the resistance conferred by overexpression of AtNPR1 gene in cotton.

The importance of root-produced volatiles as foraging cues for entomopathogenic nematodes

Entomopathogenic nematodes (EPNs) are tiny parasitic worms that parasitize insects, in which they reproduce. Their foraging behavior has been subject to numerous studies, most of which have proposed that, at short distances, EPNs use chemicals that are emitted directly from the host as host location cues. Carbon dioxide (CO2) in particular has been implicated as an important cue. Recent evidence shows that at longer distances several EPNs take advantage of volatiles that are specifically emitted by roots in response to insect attack. Studies that have revealed these plant-mediated interactions among three trophic levels have been met with some disbelief. This review aims to take away this skepticism by summarizing the evidence for a role of root volatiles as foraging cues for EPNs. To reinforce our argument, we conducted olfactometer assays in which we directly compared the attraction of an EPN species to CO2 and two typical inducible root volatiles. The combination of the ubiquitous gas and a more specific root volatile was found to be considerably more attractive than one of the two alone. Hence, future studies on EPN foraging behavior should take into account that CO2 and plant volatiles may work in synergy as attractants for EPNs. Recent research efforts also reveal prospects of exploiting plant-produced signals to improve the biological control of insect pests in the rhizosphere.