Tomato Pathogen Research Articles

Beyond the genomes of Fulvia fulva (syn. Cladosporium fulvum) and Dothistroma septosporum: New insights into how these fungal pathogens interact with their host plants.

Fulvia fulva and Dothistroma septosporum are closely related apoplastic pathogens with similar lifestyles but different hosts: F.fulva is a pathogen of tomato, whilst D.septosporum is a pathogen of pine trees. In 2012, the first genome sequences of these pathogens were published, with F.fulva and D.septosporum having highly fragmented and near-complete assemblies, respectively. Since then, significant advances have been made in unravelling their genome architectures. For instance, the genome of F.fulva has now been assembled into 14 chromosomes, 13 of which have synteny with the 14 chromosomes of D.septosporum, suggesting these pathogens are even more closely related than originally thought. Considerable advances have also been made in the identification and functional characterization of virulence factors (e.g., effector proteins and secondary metabolites) from these pathogens, thereby providing new insights into how they promote host colonization or activate plant defence responses. For example, it has now been established that effector proteins from both F.fulva and D.septosporum interact with cell-surface immune receptors and co-receptors to activate the plant immune system. Progress has also been made in understanding how F.fulva and D.septosporum have evolved with their host plants, whilst intensive research into pandemics of Dothistroma needle blight in the Northern Hemisphere has shed light on the origins, migration, and genetic diversity of the global D.septosporum population. In this review, we specifically summarize advances made in our understanding of the F.fulva-tomato and D.septosporum-pine pathosystems over the last 10 years.

RAV1 family members function as transcriptional regulators and play a positive role in plant disease resistance.

Phytopathogens pose a severe threat to agriculture and strengthening the plant defense response is an important strategy for disease control. Here, we report that AtRAV1, an AP2 and B3 domain-containing transcription factor, is required for basal plant defense in Arabidopsis thaliana. The atrav1 mutant lines demonstrate hyper-susceptibility against fungal pathogens (Rhizoctonia solani and Botrytis cinerea), whereas AtRAV1 overexpressing lines exhibit disease resistance against them. Enhanced expression of various defense genes and activation of mitogen-activated protein kinases (AtMPK3 and AtMPK6) are observed in the R. solani infected overexpressing lines, but not in the atrav1 mutant plants. An invitro phosphorylation assay suggests AtRAV1 to be a novel phosphorylation target of AtMPK3. Bimolecular fluorescence complementation and yeast two-hybrid assays support physical interactions between AtRAV1 and AtMPK3. Overexpression of the native as well as phospho-mimic but not the phospho-defective variant of AtRAV1 imparts disease resistance in the atrav1 mutant A. thaliana lines. On the other hand, overexpression of AtRAV1 fails to impart disease resistance in the atmpk3 mutant. These analyses emphasize that AtMPK3-mediated phosphorylation of AtRAV1 is important for the elaboration of the defense response in A. thaliana. Considering that RAV1 homologs are conserved in diverse plant species, we propose that they can be gainfully deployed to impart disease resistance in agriculturally important crop plants. Indeed, overexpression of SlRAV1 (a member of the RAV1 family) imparts disease tolerance against not only fungal (R. solani and B. cinerea), but also against bacterial (Ralstonia solanacearum) pathogens in tomato, whereas silencing of the gene enhances disease susceptibility.

Inactivation efficacy of low-pressure plasma treatment against seed-borne tomato pathogen Clavibacter michiganensis and effect of seed setting position and mesh sheet usage.

Clavibacter michiganensis, a gram-positive actinomycete, is a major seed-borne tomato pathogen. We investigated the inactivation efficacy of low-pressure plasma treatment against C. michiganensis inoculated on tomato seeds by placing them on a mesh sheet above the bottom dielectric glass plate. The 2- and 5-minute plasma treatment reduced C. michiganensis populations on the tomato seeds by 0.8 and 1.8 log cfu/seed, respectively. The reduction rates were similar to those of C. michiganensis on shirona (cruciferous) seeds, which have different shapes and surface structures. In contrast, the inactivation of C. michiganensis cells using plasma was more difficult than that of X. campestris cells. Additionally, it was found that placing seeds on a mesh sheet laid on the dielectric glass plate was remarkably effective in inactivating the pathogens on tomato seeds. Since the tomato seeds were susceptible to damage from plasma treatment, methods to reduce its damage need to be investigated.

Differential Colonization of the Plant Vasculature Between Endophytic Versus Pathogenic Fusarium oxysporum Strains.

Plant xylem colonization is the hallmark of vascular wilt diseases caused by phytopathogens within the Fusarium oxysporum species complex. Recently, xylem colonization has also been reported among endophytic F. oxysporum strains, resulting in some uncertainty. This study compares xylem colonization processes by pathogenic versus endophytic strains in Arabidopsis thaliana and Solanum lycopersicum, using Arabidopsis pathogen Fo5176, tomato pathogen Fol4287, and the endophyte Fo47, which can colonize both plant hosts. We observed that all strains were able to advance from epidermis to endodermis within 3 days postinoculation (dpi) and reached the root xylem at 4 dpi. However, this shared progression was restricted to lateral roots and the elongation zone of the primary root. Only pathogens reached the xylem above the primary-root maturation zone (PMZ). Related to the distinct colonization patterns, we also observed stronger induction of callose at the PMZ and lignin deposition at primary-lateral root junctions by the endophyte in both plants. This observation was further supported by stronger induction of Arabidopsis genes involved in callose and lignin biosynthesis during the endophytic colonization (Fo47) compared with the pathogenic interaction (Fo5176). Moreover, both pathogens encode more plant cell wall-degrading enzymes than the endophyte Fo47. Therefore, observed differences in callose and lignin deposition could be the combination of host production and the subsequent fungal degradation. In summary, this study demonstrates spatial differences between endophytic and pathogenic colonization, strongly suggesting that further investigations of molecular arm-races are needed to understand how plants differentiate friend from foe. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Detection, Identification and Molecular Characterization of Tomato Mosaic Virus (ToMV) Isolates from Pakistan.

Tomato mosaic virus (ToMV) is one of the lethal tomato pathogens. In this study, we collected tomato leaves exhibiting interveinal chlorosis from farmer’s fields in district Lahore, Pakistan. The presence of tobamoviruses was confirmed through extracting RNA, cDNA synthesis, PCR amplification and subsequent sequencing of capsid protein (CP) gene of ToMV that contained 480 nucleotides (encoded for 160 amino acids making ~17 kDa protein) located at 5703rd to 6182nd nucleotide position in ToMV genome. In sequence analysis, Pakistani isolates shared 98.9-99.5% and 97.3-99.3% nucleotide and amino acid homologies with each other and 96-99% and 90-98.6% with other isolates respectively. In phylogenetic analysis the Pakistani isolates grouped with Iranian and Chines isolates, exhibiting higher nucleotides and amino acids identities as well. This research reveals a geographical association among Pakistani, Chines and Iranian ToMV isolates. The study suggests extensive surveys of tobamoviruses infecting field crops for their detailed genetic information.

Effectiveness of Massep (Ocimum gratissimum L.) essential oil and its nanoemulsion toward Sclerotium rolfsii, Phytophthora infestans and Alternaria solani, pathogens associated with tomato rot diseases

This study aimed to evaluate the antimicrobial potential of Massep essential oil and its nanoemulsion against Sclerotium rolfsii, Phytophtora infestans and Alternaria solani, the main pathogens of tomato. Essential oil (EO) was extracted by hydrodistillation and their chemical composition analyzed by gas chromatography coupled with mass spectrometry (GC-MS). The nanoemulsion of EO was prepared by emulsification with Tween 80 as surfactant. The antimicrobial activity of EO and its nanoemulsion was evaluated in vitro on mycelial growth. In situ tests were performed with the pure EO and the formulation on tomato fruits by direct inoculation as preventive and curative tests. Results showed that, the yield of Massep EO was 0.40%. GC-SM analysis revealed 29 compounds with Thymol (35.15%), 3,7,7-trimethyl-1,2,3-Cycloheptatriene (13.09%), γ-Terpinene (10.08%), Eugenol (9.89%) and β –Thujene (3.43%) as major components. The Massep EO formulation was "milky-white" in appearance, stable, had pH 7.4, and the average particle size of 199 nm. In vitro, Massep EO nanoemulsion significantly inhibited the mycelial growth of Sclerotium rolfsii, Phytophtora infestans and Alternaria solani, more than pure Massep EO, based on minimal inhibitory concentration (MIC). In situ, Massep EO nanoemulsion was more active than pure EO. It reduced necrosis diameter at a rate of 100%, 100% and 71.81% (curative test) respectively, against S. rolfsii, P. infestans and A. solani, at concentrations of 1000 μl/l, 1200 μl/l and 2400 μl/l. Statistical analysis revealed that, EO nanoemulsion was significantly efficiency than Pure EO.

Differential plant response to toxins and elicitor proteins released by the potato and tomato pathogens Alternaria solani and Alternaria alternata

Early blight of potato and tomato, caused principally by Alternaria solani, results in extensive damage to foliar tissues. Symptoms are seen as expanding necrotic lesions. Lesions are sometimes surrounded by a halo of chlorotic tissue, however the basis for presence or absence of the distinctive halo have not been determined. To dissect the basis for lesion development a series of Alternaria-associated toxins and potential elicitor proteins were tested in potato and tobacco. Infiltration of leaves demonstrated that, while most of the pure toxins did not have a visible effect, two anthraquinones, bostrycin and altersolanon A, elicited a strong necrosis-mediated response. Extracts of solid and liquid cultures of A. solani yielded anthraquinones that also elicited a necrotic response. Two potential elicitor proteins were identified and cloned from the potato brown spot and early blight pathogens Alternaria alternata and A. solani, respectively. Agrobacterium-mediated infiltration and expression of the A. alternata xyloglucanase cel12-A and A. solani Hrip1 revealed that cel12-A had no apparent effect, whereas Hrip1 induced expanding tissue death and development of chlorotic halos. Development of chlorotic halos was dependent on leaf age, with older leaves exhibiting halos. It is proposed that specific toxin and elicitor production, in conjunction with tissue susceptibility mediate the outcomes of early blight symptoms.

Efficacy of microbial consortia and natural compounds as seed treatment for tomato pathogen management

Efficacy of microbial consortia and natural compounds as seed treatment for tomato pathogen management

The efficacy of Iranian Pythium oligandrum isolates in biocontrol of soil-borne fungal pathogens of tomato

The efficacy of Iranian Pythium oligandrum isolates in biocontrol of soil-borne fungal pathogens of tomato

Activity of Aqueous Extracts from Native Plants of the Yucatan Peninsula against Fungal Pathogens of Tomato In Vitro and from Croton chichenensis against Corynespora cassiicola on Tomato.

Plant extracts are a valuable alternative to control pathogens of horticultural crops. In the present study, four species of pathogenic fungi were isolated from leaf spots on Solanum lycopersicum and identified by traditional and molecular techniques as Alternaria alternata ITC24, Corynespora cassiicola ITC23, Curvularia lunata ITC22, and Fusarium equiseti ITC32. When 11 aqueous extracts from eight native plants of the Yucatan Peninsula were tested against the four fungi in vitro, the extract from Croton chichenensis roots was most active, inhibiting mycelial growth (79-100%), sporulation (100%), and conidial germination (71-100%) at 3% (w/v). A logarithmic-diagrammatic scale of the pathosystem C. cassiicola-S. lycopersicum was established and used to assess disease severity on inoculated tomato plants in a greenhouse after treatment with the aqueous extract from C. chichenensis roots at 12% (w/v). After 21 days, the disease severity was 57% lower than on the control without extract applied. This dose of the extract was not phytotoxic to tomato leaves and was compatible with the beneficial organisms Bacillus subtilis CBCK47 and Trichodema asperellum Ta13-17. The antifungal efficacy of C. chichenensis is highly promising for incorporation into integrated disease management of tomato crops.

Karyotype variation, spontaneous genome rearrangements affecting chemical insensitivity, and expression level polymorphisms in the plant pathogen Phytophthora infestans revealed using its first chromosome-scale assembly.

Natural isolates of the potato and tomato pathogen Phytophthora infestans exhibit substantial variation in virulence, chemical sensitivity, ploidy, and other traits. A chromosome-scale assembly was developed to expand genomic resources for this oomyceteous microbe, and used to explore the basis of variation. Using PacBio and Illumina data, a long-range linking library, and an optical map, an assembly was created and coalesced into 15 pseudochromosomes spanning 219 Mb using SNP-based genetic linkage data. De novo gene prediction combined with transcript evidence identified 19,981 protein-coding genes, plus about eight thousand tRNA genes. The chromosomes were comprised of a mosaic of gene-rich and gene-sparse regions plus very long centromeres. Genes exhibited a biased distribution across chromosomes, especially members of families encoding RXLR and CRN effectors which clustered on certain chromosomes. Strikingly, half of F1 progeny of diploid parents were polyploid or aneuploid. Substantial expression level polymorphisms between strains were identified, much of which could be attributed to differences in chromosome dosage, transposable element insertions, and adjacency to repetitive DNA. QTL analysis identified a locus on the right arm of chromosome 3 governing sensitivity to the crop protection chemical metalaxyl. Strains heterozygous for resistance often experienced megabase-sized deletions of that part of the chromosome when cultured on metalaxyl, increasing resistance due to loss of the sensitive allele. This study sheds light on diverse phenomena affecting variation in P. infestans and relatives, helps explain the prevalence of polyploidy in natural populations, and provides a new foundation for biologic and genetic investigations.

Formulation, characterization and antimicrobial activity of Rhus coriaria aqueous crude extract

Currently used copper-based pesticides and fungicides caused bacteria and fungi to develop resistance. Therefore, other environmentally friendly methods are being encouraged. Successful biopesticide usage is greatly reliant on suitable development of formulation. Four different surfactants (Emereen 1810, Emereen 1604, Emereen 1820 and Tween 20) were used to formulate Rhus coriaria aqueous extract. Stability, thermostability, particle size distribution, surface tension, shelf life were tested. The formulation was evaluated for its efficacy in controlling two of the most destructive fungi (Fusarium oxysporum (Acc No. KM039054) and Colletotrichum boninense (Acc No. KM039057) and two common bacteria (Xanthomonas vesicatoria (Acc No. KU661975) and Ralstonia solanacearum (Acc No. KT783476) in vitro and in vivo. From the four surfactants Emereen 1820 showed to be the best surfactant and was stable after six months of storage. A surface tension value of nanoemulsion solution was 27.174 mN/m, while particle size was 70.44 nm. Even after incubation and storage for up to twelve months, the formulation was stable and effective as well as efficient as compared to common commercial fungicides and antibiotics. Results indicate that R. coriaria nanoemulsion can effectively be used for the management of tomato pathogens as an eco-friendly approach.

EVALUATION OF ANTIFUNGAL POTENTIAL AND PHYTOCHEMICAL ANALYSIS OF A MEDICINAL HERB, Centaurium erythraea

Medicinal herbs are promising source of biologically active phytochemicals, many of which possess antifungal activities against phytopathogens. This research presents in vitro antifungal activity and analysis of a medicinally important herb Centaurium erythraea Rafn extracts against a highly problematic pathogen of tomato namely Fusarium oxysporum f. sp. lycopersici (FOL). In-vitro results prominently disclosed that the extracts showed good percentage growth inhibition (PGI) against FOL. Methanolic extract of C. erythraea at 200 mg mL-1 showed growth inhibition 93.3% while the synthetic fungicide benomyl showed highest growth inhibition of 90.2% at the same concentration. Phytochemical analysis indicated that methanolic extracts of this plant possess phytochemicals of all the major classes such as alkaloids, steroids, terpenoids, saponins etc. This study concludes that the extracts of C. erythraea are the best alternatives to fungicides to control Fusarium wilt pathogen of tomato.

Of its five acyl carrier proteins, only AcpP1 functions in Ralstonia solanacearum fatty acid synthesis.

The fatty acid synthesis (FAS) pathway is essential for bacterial survival. Acyl carrier proteins (ACPs), donors of acyl moieties, play a central role in FAS and are considered potential targets for the development of antibacterial agents. Ralstonia solanacearum, a primary phytopathogenic bacterium, causes bacterial wilt in more than 200 plant species. The genome of R. solanacearum contains five annotated acp genes, acpP1, acpP2, acpP3, acpP4, and acpP5. In this study, we characterized the five putative ACPs and confirmed that only AcpP1 is involved in FAS and is necessary for the growth of R. solanacearum. We also found that AcpP2 and AcpP4 participate in the polyketide synthesis pathway. Unexpectedly, the disruption of four acp genes (acpP2, acpP3, acpP4, and acpP5) allowed the mutant strain to grow as well as the wild-type strain, but attenuated the bacterium’s pathogenicity in the host plant tomato, suggesting that these four ACPs contribute to the virulence of R. solanacearum through mechanisms other than the FAS pathway.

Potential of some bioagents in fungal diseases controlling and productivity enhancement of tomatoes

The impact of bioformulations on the development of fungal diseases and the productivity of tomatoes was studied. Microorganisms of the genera Azotobacter, Bacillus, Pseudomonas, Streptomyces, and Trichoderma were used as bioagents. Their protective effect was compared with the effectiveness of chemical fungicides. The majority of bioformulations actively inhibited the spore germination of tomato pathogens Alternaria solani and Phytophthora infestans. In greenhouse experiments, biological preparations provided a protective effect at the level of 33.2%–70.1% against early dry spot and 34.3%–65.5% against late blight of tomatoes. The use of bioformulations in the field experiments effectively controlled tomato diseases and improved productivity and fruit quality. The highest protective effect against early dry spot was observed with the use of bioformulations Avercom, Biophosphorin, Haupsin, Planriz, and Trichodermin. Biophosphorin, Azotobacterin, Azostrept, and Haupsin were more effective against phytophthora. Usage of bioformulations provided the 19%–66% increase of healthy fruit harvest of different varieties of tomatoes.

The Effects of Cucumber Mosaic Virus and Its 2a and 2b Proteins on Interactions of Tomato Plants with the Aphid Vectors Myzus persicae and Macrosiphum euphorbiae.

Cucumber mosaic virus (CMV), a major tomato pathogen, is aphid-vectored in the non-persistent manner. We investigated if CMV-induced volatile organic compounds (VOCs) or other virus-induced cues alter aphid–tomato interactions. Y-tube olfactometry showed that VOCs emitted by plants infected with CMV (strain Fny) attracted generalist (Myzus persicae) and Solanaceae specialist (Macrosiphum euphorbiae) aphids. Myzus persicae preferred settling on infected plants (3 days post-inoculation: dpi) at 1h post-release, but at 9 and 21 dpi, aphids preferentially settled on mock-inoculated plants. Macrosiphum euphorbiae showed no strong preference for mock-inoculated versus infected plants at 3 dpi but settled preferentially on mock-inoculated plants at 9 and 21 dpi. In darkness aphids showed no settling or migration bias towards either mock-inoculated or infected plants. However, tomato VOC blends differed in light and darkness, suggesting aphids respond to a complex mix of olfactory, visual, and other cues influenced by infection. The LS-CMV strain induced no changes in aphid–plant interactions. Experiments using inter-strain recombinant and pseudorecombinant viruses showed that the Fny-CMV 2a and 2b proteins modified tomato interactions with Macrosiphum euphorbiae and Myzus persicae, respectively. The defence signal salicylic acid prevents excessive CMV-induced damage to tomato plants but is not involved in CMV-induced changes in aphid–plant interactions.

Epiphytic and endophytic microorganisms associated to different cultivar of tomato fruits in greenhouse environment and characterization of beneficial bacterial strains for the control of post-harvest tomato pathogens

Several bacterial and fungal diseases affect greenhouse-grown tomato crops, causing severe annual yield losses worldwide. The need to reduce chemical compound applications has encouraged the search of alternative approach for the control of tomato diseases, including the use of biological control agents. The presence of total and beneficial microbial populations was investigated on the surface and in the pulp of seven cultivars of tomato fruit coming from eleven greenhouses in the Pachino district (south-east of Sicily), recognized by the European Community with the “Protected Geographical Indication” label. Principal component analysis (PCA) showed that epiphytic and endophytic microbial populations clustered into groups according to the areas of origin. Approximately 240 tomato fruit–associated bacterial isolates were selected and a high percentage of them showed antagonistic activity against Clavibacter michiganensis subsp. michiganensis, Pseudomonas syringae pv. tomato, Xanthomonas euvesicatoria pv. perforans, Botrytis cinerea and Alternaria alternata. Analysis of the 16S rRNA gene sequences revealed a predominance of bacteria in Bacillus and Pseudomonas genera, followed by Citrobacter and Enterobacter. The presence of these genera differed according to the geographical areas of tomato samples, whereas their antagonistic capabilities varied according to the five tomato pathogens. The in vitro effectiveness of eight representative bacterial strains belonging to Pseudomonas, Bacillus and Enterobacter genera was confirmed in in vivo assays, carried out on tomato fruit artificially inoculated with A. alternata and B. cinerea. Altogether, these results revealed differences in population density of native microbiota of “Pomodoro di Pachino” fruits and allowed the selection of antagonistic bacterial strains that can be applied in field and in postharvest conditions as alternatives to chemical compounds.

Efficacy of native Trichoderma asperellum in managing Alternaria solani causing early blight of Solanum lycopersicum Mill

The biocontrol efficacy of Trichoderma asperellum strain M23 (bioagent) was tested against early blight pathogen (Alternaria solani strain NO4) of tomato. These fungi were co-inoculated on tomato plants (variety UC82B and Ibadan local) at different spore concentrations, viz., 1.0 × 105, 1.0 × 107 and 1.0 × 109 while untreated plant served as control. The effect of these treatments was studied based on growth parameters, biomass and symptoms observed on disease incidence scale of 1–7. The pathogen exerted varying effects on the tomato plants as Ibadan local was more susceptible compared to UC82B. The bioagent M23 exhibited significant growth stimulatory effect (p < 0.05) on the two varieties of tomato. The antagonistic effect of M23 against NO4 was confirmed on the growth, biomass accumulation (phytomass) and fruit weight of tomato plants co-inoculated with the pathogen and the antagonist. This study demonstrated the potentials of Trichoderma asperellum not only as biocontrol agent against early blight of tomatoes but also as growth stimulatory agent for the crop.

Antifungal Volatilomes Mediated Defense Mechanism against Fusarium oxysporum f. sp. lycopersici, the Incitant of Tomato Wilt.

In this study, the volatilomes of naturally growing plant leaves were immobilized in a suitable substrate to enhance vapors’ diffusion in the soil to eradicate the Fusarium wilt pathogens in Tomato. Volatilomes produced by Mentha spicata leaves immobilized in vermiculite ball was found to be effective and exhibit 92.35 percent inhibition on the mycelial growth of Fusarium oxysporum f. sp. lycopersici (FOL). Moreover, the volatilomes of M. spicata immobilized vermiculite balls were tested based on the distance traveled by the diffused volatilomes from the ball and revealed that the volatilomes of M. spicata traveled up to 20 cm distance from the center of PVC (Polyvinly chloride) chamber showed maximum reduction in colony growth of FOL at 12th day after inoculation. Tomato plants inoculated with FOL revealed increased expressions of defense gene, pathogenesis related protein (PR1) with 2.63-fold after 72 h and the gene, transcription factor (WRKY) increased with 2.5-fold after 48 h on exposure to the volatilomes of M. spicata vermiculite balls. To the best of our knowledge, this is the first report on development of volatilomes based vermiculite ball formulations. This result indicated that the volatilomes of M. spicata are promising phyto-fumigants for management of Tomato Fusarial wilt.

Electrolytic Disinfection of Irrigation Water for Intensive Crop Production in Greenhouses as Demonstrated on Tomatoes (Solanum lycopersicum Mill)

Shortage of water availability and awareness of the need for sustainable resource management have generated a significant increase in the use of recycled water for irrigation and processing of crops and harvest products, respectively. As a result, irrigation systems face the challenge of neutralizing plant pathogens to reduce the risk of their dispersal and the subsequent occurrence of diseases with potentially high economic impacts. We evaluated the efficacy of an innovative electrolytic disinfection system based on potassium hypochlorite (KCLO) to inactivate major pathogens in hydroponically grown tomatoes: Fusarium oxysporum (Synder and Hans), Rizocthonia solani (Kühn), Tobacco mosaic virus (TMV) and Pepino mosaic virus (PepMV). The electrolytically derived disinfectant was prepared on-site and added to the recirculating fertigation solution once a week for 60 min in an automated manner using sensor technology at a dosage of 0.5 mg of free chlorine/L (fertigation solution at pH 6.0 ± 0.3 and ORP 780 ± 31 mV). Tomato fruit yield and pathogen dispersal were determined for 16 weeks. At the applied dosage, the disinfectant has been shown to inhibit the spread of plant pathogenic fungi and, remarkably, plant viruses in recirculating fertigation solutions. Phytotoxic effects did not occur.