Secondary metabolites produced by species of Fusarium and other soi! fW1gi were tested against so... more Secondary metabolites produced by species of Fusarium and other soi! fW1gi were tested against sorne plant parasitic nematodes. Assays were conducted in vitTO using toxin concentrations of 0.02,0.2,2,20, and 200 ppm in 4 % methanol. T2-toxin, moniliforrnin, verrucarin A and cytochalasin B significanùy reduced the viability of Meloidogyne javanica juveniles at 2 ppm or higher concentrations after 72 hours exposure at 22.5 oc. Enniatin B showed a significant increase in M. javanica mortaliry at 20 ppm. T2-toxin also showed a nematicidal effect on M. hapla and Pratylenchus neglectus at 0.2 and 2 ppm, respectively. When tested in soi! against M. javanica parasitizing tomato plants, T2-toxin and moniliformin did not affect nematode densiry. In the treated pots a larger number of galls per g of root was a1so observed. Data suggest that mycotoxins can interact with nematodes through antagonistic or synergistic effects related to the concentration levels present in the plant rhizosphere. Résumé-Observations sur les propriétés nérnaticides de certaines mycotoxines-Les métabolites secondaires produits par certaines espèces de Fusarium et d'autres champignons du sol ont été testés contre des nématodes parasites des plantes. Les essais ont été conduits in vitro avec des concentrations de 0.02, 0.2, 2, 20, et 200 ppm en solution aqueuse à 4 % de méthanol. La toxine T2, la moniliformine, la verrucarine et la cytochalasine B ont significativement réduit la viabilité des juvéniles de Meloidogyne javanica à partir de 2 ppm après 72 heures d'exposition à 22.5 oc. L'enniatine B a montré une augmentation significative de la mortalité des larves de M. javanua à 20 ppm. La toxine T2 possède également un effet nematicide sur M. hapla et Pratylenchus negleclUs à 0.2 et 2 ppm, respectivement. Testées dans le sol contre M.javanica sur tomate, la toxine T2 et la moniliforrnine n'ont pas réduit la densité des nématodes. Dans les POts traités, une plus grande quantité de galles par g de racine a été observée. Les données suggèrent que les mycotoxines peuvent interagir avec les nématodes par effets synergiques ou antagonistes, en relation avec les concentrations présentes dans la rhizosphère des plantes.
Principal components and hierarchical cluster analysis based on morphometric characters of the ty... more Principal components and hierarchical cluster analysis based on morphometric characters of the type populations of the 39 species attributed to the Xiphinema americanum-group confirmed the occurrence of five subgroups. The use of a single character is generally insufficient to characterize a species because of the wide intra-population and intra-specific variations. Hierarchical cluster analysis, although impractical for species/population identification, appears useful in the study of the relationships between species or groups of species.
ABSTRACT EU legislation restricted many chemicals for root-knot nematodes (Meloidogyne spp., RKNs... more ABSTRACT EU legislation restricted many chemicals for root-knot nematodes (Meloidogyne spp., RKNs) control. Alternative ways of plant protection were hence investigated, based on the use of microbial formulations exploiting plant parasites antagonism. RKNs are severe and widespread pests causing extensive damage to crops in greenhouse and field. Several antagonistic microorganisms are suitable for biocontrol, including the nematophagous hyphomycete Pochonia chlamydosporia that parasitizes eggs to acquire additional nourishment and face competition with other soil microorganisms. A commercial product (POCHAR) was developed by Microspore based on P. chlamydosporia with other microbial inocula that can be applied through irrigation. The aim of this study was to test POCHAR’s efficacy against RKNs on potato and its promotion effect on tomato in two field trials. Moreover, the research included trials to evaluate the best method for open-field application in crops not managed through drip irrigation, opening up the possibility to treat large areas without major technological needs. RKNs control with POCHAR represented a viable alternative to chemicals. In conclusion, the organic approach developed through the bioformulated product highlighted effective RKNs management, with a potential to sustain both plant nutrition and the related root protection needs.
Specimens of Paralongidorus buchae Lamberti, Roca et Chinappen, collected in Mauritius in April 1... more Specimens of Paralongidorus buchae Lamberti, Roca et Chinappen, collected in Mauritius in April 1987, from the rhizosphere of sugar cane, were observed to be parasitised by a zoosporic fungus. Elliptical zoosporangia were present in the body with discharge tubes emergiug through the cuticle (Fig. 1, a-c).
For many years the taxonomy of the genus Pasteuria has been marred with confusion because the bac... more For many years the taxonomy of the genus Pasteuria has been marred with confusion because the bacterium could not be cultured in vitro and, therefore, descriptions were based solely on morphological, developmental, and pathological characteristics. The current study sought to devise a simple method for PCR-amplification, cloning, and sequencing of Pasteuria 16S rDNA from small numbers of endospores, with no need for prior DNA purification. Results show that DNA extracts from plain glass bead-beating of crude suspensions containing 10,000 endospores at 0.2 x 10 endospores ml(-1) were sufficient for PCR-amplification of Pasteuria 16S rDNA, when used in conjunction with specific primers. These results imply that for P. penetrans and P. nishizawae only one parasitized female of Meloidogyne spp. and Heterodera glycines, respectively, should be sufficient, and as few as eight cadavers of Belonolaimus longicaudatus with an average number of 1,250 endospores of "Candidatus Pasteuria us...
A factorial taxonomic metabarcoding study was carried out to determine the effect of root-knot ne... more A factorial taxonomic metabarcoding study was carried out to determine the effect of root-knot nematodes (Meloidogyne incognita, RKN) and the nematocide fenamiphos on the rhizosphere microbiome of tomato. Plants inoculated (or not) with RKN secondstage juveniles (J2), and treated (or not) with the nematocide, were tested in a 6 months greenhouse assay using a RKN-free soil proceeding from an organic crop. Rhizosphere soil was sampled at J2 inoculation, 3 months later (before the second nematocidal treatment), and again after 3 months. At each sampling, the RNAs were extracted and the 16S rRNA V4 regions sequenced with a Next Generation Sequencing (NGS) protocol. Changes in bacteria metagenomic profiles showed an effect of the treatments applied, with different representations of taxa in samples receiving nematodes and fenamiphos, at the two sampling times. In general, a tendence was observed toward an increase number of OTUs at 6 months, in all treatments. β-Proteobacteria were the most abundant class, for all treatments and times. When compared to soil before transplanting, the presence of tomato roots increased frequency of Actinobacteria and Thermoleophilia, reducing abundance of Solibacteres. At lowest taxonomic levels the samples clustered in groups congruent with the treatments applied, with OTUs differentially represented in relation to RKN and/or fenamiphos applications. Bacillus, Corynebacterium, Streptococcus, and Staphylococcus were more represented at 6 months in samples inoculated with RKN. The nematodes with the nematocide application increased the emergence of rare OTUs or reduced/enhanced the abundance of other taxa, from different lineages.
A novel Gram-negative pathogenic bacterium (BN) was discovered in second-stage juveniles (J2) of ... more A novel Gram-negative pathogenic bacterium (BN) was discovered in second-stage juveniles (J2) of root-knot nematodes (RKN, Meloidogyne spp.). Mature bacteria showed a peculiar rod morphology characterized by four cells sequentially joined at septa. Mature rods measured 4–5 × 0.5–0.6 μm and were characterized by the emptying and tapering of both apical cells. The data showed an electron-dense external matrix forming a coating capsule involved in host attachment. The rods were not motile and packed in parallel inside the J2 body. After J2 penetration by adhering, germinating cells, the bacterium proliferated until the host body content was completely digested, producing a lethal disease. Parasitized hosts were recognized using light microscopy by a pale creamy-brown color assumed at parasitism completion. At death, the whole nematode body was filled with cells and only a few sclerotized esophageal structures (i.e., stylet, median bulb) remained visible. The BN cells were quickly relea...
A study was carried out on the effect of the root endophytic fungus Pochonia chlamydosporia on pl... more A study was carried out on the effect of the root endophytic fungus Pochonia chlamydosporia on plant systemic signal of defense related genes during fungal or nematode parasitism. Different biotic stress factors were examined, inoculating roots of dicot and monocot hosts with the endophyte, and measuring the expression of defense genes in leaves. A first greenhouse assay was carried out on expression of PAL, PIN II, PR1 and LOX D in leaves of tomato cv Tondino inoculated with Phytophthora infestans (CBS 120920), inoculating or not the roots of infected plants with P. chlamydosporia DSM 26985. In a second assay, plants of banana (Musa acuminata cv Grand Naine) were artificially infected with Fusarium oxysporum f. sp. cubense Tropical race 4 (TR4) and inoculated or not with DSM 26985. In a further experiment, banana plants were inoculated or not with P. chlamydosporia plus juveniles of the root knot nematode (RKN) Meloidogyne incognita. A similar assay was also carried out in vitro wi...
Fungi and bacteria associated to phytoparasitic nematodes Globodera rostochiensis and Meloidogyne... more Fungi and bacteria associated to phytoparasitic nematodes Globodera rostochiensis and Meloidogyne spp. in Algeria were identified and characterized. Trichoderma spp. showed the highest prevalence in the cysts of G. rostochiensis. A number of isolates were identified through PCR amplification and the sequencing of the internal transcribed spacer (ITS)1-2 and Rpb2 gene regions. The most represented species were T. harzianum and T. afroharzianum. The latter and T. hirsutum were reported for the first time in Algeria. Fusarium spp., including F. oxysporum and F. solani, comprised a second group of fungi found in cysts. Taxa associated to females of Meloidogyne spp. included T. harzianum, Fusarium spp. and other hyphomycetes. To assess the efficacy of Trichoderma spp., two assays were carried out in vitro with the culture filtrates of two T. afroharzianum and T. harzianum isolates, to check their toxicity versus the second stage juveniles of M. incognita. After 24–48 h exposure, a mortal...
Climate changes include the intensification of drought in many parts of the world, increasing its... more Climate changes include the intensification of drought in many parts of the world, increasing its frequency, severity and duration. However, under natural conditions, environmental stresses do not occur alone, and, in addition, more stressed plants may become more susceptible to attacks by pests and pathogens. Studies on the impact of the arbuscular mycorrhizal (AM) symbiosis on tomato response to water deficit showed that several drought-responsive genes are differentially regulated in AMcolonized tomato plants (roots and leaves) during water deficit. To date, global changes in mycorrhizal tomato root transcripts under water stress conditions have not been yet investigated. Here, changes in root transcriptome in the presence of an AM fungus, with or without water stress (WS) application, have been evaluated in a commercial tomato cultivar already investigated for the water stress response during AM symbiosis. Since root-knot nematodes (RKNs, Meloidogyne incognita) are obligate endoparasites and cause severe yield losses in tomato, the impact of the AM fungal colonization on RKN infection at 7 days post-inoculation was also evaluated. Results offer new information about the response to AM symbiosis, highlighting a functional redundancy for several tomato gene families, as well as on the tomato and fungal genes involved in WS response during symbiosis, underlying the role of the AM fungus. Changes in the expression of tomato genes related to nematode infection during AM symbiosis highlight a role of AM colonization in triggering defense responses against RKN in tomato. Overall, new datasets on the tomato response to an abiotic and biotic stress during AM symbiosis have been obtained, providing useful data for further researches.
A study was carried out for identification and detection of Phytophthora spp. from soil and plant... more A study was carried out for identification and detection of Phytophthora spp. from soil and plant samples, collected from Solanaceous crops in Egypt and Italy. The samples were screened with specific and universal primers of Phytophthora 18S, ITS1–ITS2 and 28S regions, followed by PCR product sequencing. The Phytophthora spp. detected were P. infestans (Egypt) and P. parasitica (Italy). A molecular beacon probe was also developed based on the avr3a gene of P. infestans to detect a variant associated with virulence traits. The probe was suitable for avr3a allele identification from P. infestans and also from P. parasitica PCR products.
Biological control relying on soil microorganisms may offer feasible and sustainable perspectives... more Biological control relying on soil microorganisms may offer feasible and sustainable perspectives in many agrosystems for management of soil pests such as root-knot nematodes (RKNs, Meloidogyne spp.). The rhizosphere environment shows a complex of soil microbial communities, including beneficial organisms such as specialized bacterial pathogens and/or of rhizosphere fungi. New advanced technologies like Next Generation Sequencing (NGS) may enlarge our knowledge about the biodiversity and role of these rhizosphere communities. The numbers of microbial species usually range around 10 3-10 4 taxonomic units g-1 of soil. This dimension suggests that the nematode antagonists known today represent only a fraction of the total number potentially available. The soil microbiome activity may lead to soil suppressivity, a stable nematode control effect related to species undetected or undescribed. Known parasitic microorganisms like the bacterium Pasteuria penetrans show specific and density-dependent links with the host. Other species such as the nematophagous fungus Pochonia chlamydosporia can also induce plant growth promotion effects. NGS transcriptomic data indicate that it can elicit a plant response to many biotic and abiotic stresses. In conclusion, the biodiversity of antagonists and the mechanisms they exert in nematode regulation have yet to be fully explored. However, new high-throughput analytical technologies may fill this gap. Experimental assays for RKN management and/or plant growth promotionindicate that biological management of nematodes is a promising alternative to chemicals. However, this approach requires detailed knowledge about the composition, role and effects of the microbial community present in soil and/or about the right and accurate aggregate of biological entities to apply.
The role of nematology in food security is discussed. Nematology began with the classification of... more The role of nematology in food security is discussed. Nematology began with the classification of species. The onset of monocultures required effective nematode management tools. Recently, more complex approaches to management include ecology, natural sciences and genomics, with important fallouts in crop protection. The food security goal is to satisfy any dietary need for the healthy life of all but this message has not spread globally. Benefits achievable through crop technologies are not equally distributed and food security is not yet assured for several million people. Many social, political or economic factors are involved, and nematology may only partially contribute to achieve this goal. However, the scientific knowledge produced can contribute to solving some food security issues. Fundamental conditions are free access to education and science, as well as support for independent production of knowledge, improving regional and international cooperation and research.
Trees are crucial for sustaining life on our planet. Forests and land devoted to tree crops do no... more Trees are crucial for sustaining life on our planet. Forests and land devoted to tree crops do not only supply essential edible products to humans and animals, but also additional goods such as paper or wood. They also prevent soil erosion, support microbial, animal, and plant biodiversity, play key roles in nutrient and water cycling processes, and mitigate the effects of climate change acting as carbon dioxide sinks. Hence, the health of forests and tree cropping systems is of particular significance. In particular, soil/rhizosphere/root-associated microbial communities (known as microbiota) are decisive to sustain the fitness, development, and productivity of trees. These benefits rely on processes aiming to enhance nutrient assimilation efficiency (plant growth promotion) and/or to protect against a number of (a)biotic constraints. Moreover, specific members of the microbial communities associated with perennial tree crops interact with soil invertebrate food webs, underpinning ...
Applied microbiology and biotechnology, Jan 5, 2017
The molecular mechanisms active during the endophytic phase of the fungus Pochonia chlamydosporia... more The molecular mechanisms active during the endophytic phase of the fungus Pochonia chlamydosporia are still poorly understood. In particular, few data are available on the links between the endophyte and the root response, as modulated by noncoding small RNAs. In this study, we describe the microRNAs (miRNAs) that are differentially expressed (DE) in the roots of tomato, colonized by P. chlamydosporia. A genome-wide NGS expression profiling of small RNAs in roots, either colonized or not by the fungus, showed 26 miRNAs upregulated in inoculated roots. Their predicted target genes are involved in the plant information processing system, which recognizes, percepts, and transmits signals, with higher representations in processes such as apoptosis and plant defense regulation. RNAseq data showed that predicted miRNA target genes were downregulated in tomato roots after 4, 7, 10, and 21 days post P. chlamydosporia inoculation. The differential expression of four miRNAs was further valida...
Secondary metabolites produced by species of Fusarium and other soi! fW1gi were tested against so... more Secondary metabolites produced by species of Fusarium and other soi! fW1gi were tested against sorne plant parasitic nematodes. Assays were conducted in vitTO using toxin concentrations of 0.02,0.2,2,20, and 200 ppm in 4 % methanol. T2-toxin, moniliforrnin, verrucarin A and cytochalasin B significanùy reduced the viability of Meloidogyne javanica juveniles at 2 ppm or higher concentrations after 72 hours exposure at 22.5 oc. Enniatin B showed a significant increase in M. javanica mortaliry at 20 ppm. T2-toxin also showed a nematicidal effect on M. hapla and Pratylenchus neglectus at 0.2 and 2 ppm, respectively. When tested in soi! against M. javanica parasitizing tomato plants, T2-toxin and moniliformin did not affect nematode densiry. In the treated pots a larger number of galls per g of root was a1so observed. Data suggest that mycotoxins can interact with nematodes through antagonistic or synergistic effects related to the concentration levels present in the plant rhizosphere. Résumé-Observations sur les propriétés nérnaticides de certaines mycotoxines-Les métabolites secondaires produits par certaines espèces de Fusarium et d'autres champignons du sol ont été testés contre des nématodes parasites des plantes. Les essais ont été conduits in vitro avec des concentrations de 0.02, 0.2, 2, 20, et 200 ppm en solution aqueuse à 4 % de méthanol. La toxine T2, la moniliformine, la verrucarine et la cytochalasine B ont significativement réduit la viabilité des juvéniles de Meloidogyne javanica à partir de 2 ppm après 72 heures d'exposition à 22.5 oc. L'enniatine B a montré une augmentation significative de la mortalité des larves de M. javanua à 20 ppm. La toxine T2 possède également un effet nematicide sur M. hapla et Pratylenchus negleclUs à 0.2 et 2 ppm, respectivement. Testées dans le sol contre M.javanica sur tomate, la toxine T2 et la moniliforrnine n'ont pas réduit la densité des nématodes. Dans les POts traités, une plus grande quantité de galles par g de racine a été observée. Les données suggèrent que les mycotoxines peuvent interagir avec les nématodes par effets synergiques ou antagonistes, en relation avec les concentrations présentes dans la rhizosphère des plantes.
Principal components and hierarchical cluster analysis based on morphometric characters of the ty... more Principal components and hierarchical cluster analysis based on morphometric characters of the type populations of the 39 species attributed to the Xiphinema americanum-group confirmed the occurrence of five subgroups. The use of a single character is generally insufficient to characterize a species because of the wide intra-population and intra-specific variations. Hierarchical cluster analysis, although impractical for species/population identification, appears useful in the study of the relationships between species or groups of species.
ABSTRACT EU legislation restricted many chemicals for root-knot nematodes (Meloidogyne spp., RKNs... more ABSTRACT EU legislation restricted many chemicals for root-knot nematodes (Meloidogyne spp., RKNs) control. Alternative ways of plant protection were hence investigated, based on the use of microbial formulations exploiting plant parasites antagonism. RKNs are severe and widespread pests causing extensive damage to crops in greenhouse and field. Several antagonistic microorganisms are suitable for biocontrol, including the nematophagous hyphomycete Pochonia chlamydosporia that parasitizes eggs to acquire additional nourishment and face competition with other soil microorganisms. A commercial product (POCHAR) was developed by Microspore based on P. chlamydosporia with other microbial inocula that can be applied through irrigation. The aim of this study was to test POCHAR’s efficacy against RKNs on potato and its promotion effect on tomato in two field trials. Moreover, the research included trials to evaluate the best method for open-field application in crops not managed through drip irrigation, opening up the possibility to treat large areas without major technological needs. RKNs control with POCHAR represented a viable alternative to chemicals. In conclusion, the organic approach developed through the bioformulated product highlighted effective RKNs management, with a potential to sustain both plant nutrition and the related root protection needs.
Specimens of Paralongidorus buchae Lamberti, Roca et Chinappen, collected in Mauritius in April 1... more Specimens of Paralongidorus buchae Lamberti, Roca et Chinappen, collected in Mauritius in April 1987, from the rhizosphere of sugar cane, were observed to be parasitised by a zoosporic fungus. Elliptical zoosporangia were present in the body with discharge tubes emergiug through the cuticle (Fig. 1, a-c).
For many years the taxonomy of the genus Pasteuria has been marred with confusion because the bac... more For many years the taxonomy of the genus Pasteuria has been marred with confusion because the bacterium could not be cultured in vitro and, therefore, descriptions were based solely on morphological, developmental, and pathological characteristics. The current study sought to devise a simple method for PCR-amplification, cloning, and sequencing of Pasteuria 16S rDNA from small numbers of endospores, with no need for prior DNA purification. Results show that DNA extracts from plain glass bead-beating of crude suspensions containing 10,000 endospores at 0.2 x 10 endospores ml(-1) were sufficient for PCR-amplification of Pasteuria 16S rDNA, when used in conjunction with specific primers. These results imply that for P. penetrans and P. nishizawae only one parasitized female of Meloidogyne spp. and Heterodera glycines, respectively, should be sufficient, and as few as eight cadavers of Belonolaimus longicaudatus with an average number of 1,250 endospores of "Candidatus Pasteuria us...
A factorial taxonomic metabarcoding study was carried out to determine the effect of root-knot ne... more A factorial taxonomic metabarcoding study was carried out to determine the effect of root-knot nematodes (Meloidogyne incognita, RKN) and the nematocide fenamiphos on the rhizosphere microbiome of tomato. Plants inoculated (or not) with RKN secondstage juveniles (J2), and treated (or not) with the nematocide, were tested in a 6 months greenhouse assay using a RKN-free soil proceeding from an organic crop. Rhizosphere soil was sampled at J2 inoculation, 3 months later (before the second nematocidal treatment), and again after 3 months. At each sampling, the RNAs were extracted and the 16S rRNA V4 regions sequenced with a Next Generation Sequencing (NGS) protocol. Changes in bacteria metagenomic profiles showed an effect of the treatments applied, with different representations of taxa in samples receiving nematodes and fenamiphos, at the two sampling times. In general, a tendence was observed toward an increase number of OTUs at 6 months, in all treatments. β-Proteobacteria were the most abundant class, for all treatments and times. When compared to soil before transplanting, the presence of tomato roots increased frequency of Actinobacteria and Thermoleophilia, reducing abundance of Solibacteres. At lowest taxonomic levels the samples clustered in groups congruent with the treatments applied, with OTUs differentially represented in relation to RKN and/or fenamiphos applications. Bacillus, Corynebacterium, Streptococcus, and Staphylococcus were more represented at 6 months in samples inoculated with RKN. The nematodes with the nematocide application increased the emergence of rare OTUs or reduced/enhanced the abundance of other taxa, from different lineages.
A novel Gram-negative pathogenic bacterium (BN) was discovered in second-stage juveniles (J2) of ... more A novel Gram-negative pathogenic bacterium (BN) was discovered in second-stage juveniles (J2) of root-knot nematodes (RKN, Meloidogyne spp.). Mature bacteria showed a peculiar rod morphology characterized by four cells sequentially joined at septa. Mature rods measured 4–5 × 0.5–0.6 μm and were characterized by the emptying and tapering of both apical cells. The data showed an electron-dense external matrix forming a coating capsule involved in host attachment. The rods were not motile and packed in parallel inside the J2 body. After J2 penetration by adhering, germinating cells, the bacterium proliferated until the host body content was completely digested, producing a lethal disease. Parasitized hosts were recognized using light microscopy by a pale creamy-brown color assumed at parasitism completion. At death, the whole nematode body was filled with cells and only a few sclerotized esophageal structures (i.e., stylet, median bulb) remained visible. The BN cells were quickly relea...
A study was carried out on the effect of the root endophytic fungus Pochonia chlamydosporia on pl... more A study was carried out on the effect of the root endophytic fungus Pochonia chlamydosporia on plant systemic signal of defense related genes during fungal or nematode parasitism. Different biotic stress factors were examined, inoculating roots of dicot and monocot hosts with the endophyte, and measuring the expression of defense genes in leaves. A first greenhouse assay was carried out on expression of PAL, PIN II, PR1 and LOX D in leaves of tomato cv Tondino inoculated with Phytophthora infestans (CBS 120920), inoculating or not the roots of infected plants with P. chlamydosporia DSM 26985. In a second assay, plants of banana (Musa acuminata cv Grand Naine) were artificially infected with Fusarium oxysporum f. sp. cubense Tropical race 4 (TR4) and inoculated or not with DSM 26985. In a further experiment, banana plants were inoculated or not with P. chlamydosporia plus juveniles of the root knot nematode (RKN) Meloidogyne incognita. A similar assay was also carried out in vitro wi...
Fungi and bacteria associated to phytoparasitic nematodes Globodera rostochiensis and Meloidogyne... more Fungi and bacteria associated to phytoparasitic nematodes Globodera rostochiensis and Meloidogyne spp. in Algeria were identified and characterized. Trichoderma spp. showed the highest prevalence in the cysts of G. rostochiensis. A number of isolates were identified through PCR amplification and the sequencing of the internal transcribed spacer (ITS)1-2 and Rpb2 gene regions. The most represented species were T. harzianum and T. afroharzianum. The latter and T. hirsutum were reported for the first time in Algeria. Fusarium spp., including F. oxysporum and F. solani, comprised a second group of fungi found in cysts. Taxa associated to females of Meloidogyne spp. included T. harzianum, Fusarium spp. and other hyphomycetes. To assess the efficacy of Trichoderma spp., two assays were carried out in vitro with the culture filtrates of two T. afroharzianum and T. harzianum isolates, to check their toxicity versus the second stage juveniles of M. incognita. After 24–48 h exposure, a mortal...
Climate changes include the intensification of drought in many parts of the world, increasing its... more Climate changes include the intensification of drought in many parts of the world, increasing its frequency, severity and duration. However, under natural conditions, environmental stresses do not occur alone, and, in addition, more stressed plants may become more susceptible to attacks by pests and pathogens. Studies on the impact of the arbuscular mycorrhizal (AM) symbiosis on tomato response to water deficit showed that several drought-responsive genes are differentially regulated in AMcolonized tomato plants (roots and leaves) during water deficit. To date, global changes in mycorrhizal tomato root transcripts under water stress conditions have not been yet investigated. Here, changes in root transcriptome in the presence of an AM fungus, with or without water stress (WS) application, have been evaluated in a commercial tomato cultivar already investigated for the water stress response during AM symbiosis. Since root-knot nematodes (RKNs, Meloidogyne incognita) are obligate endoparasites and cause severe yield losses in tomato, the impact of the AM fungal colonization on RKN infection at 7 days post-inoculation was also evaluated. Results offer new information about the response to AM symbiosis, highlighting a functional redundancy for several tomato gene families, as well as on the tomato and fungal genes involved in WS response during symbiosis, underlying the role of the AM fungus. Changes in the expression of tomato genes related to nematode infection during AM symbiosis highlight a role of AM colonization in triggering defense responses against RKN in tomato. Overall, new datasets on the tomato response to an abiotic and biotic stress during AM symbiosis have been obtained, providing useful data for further researches.
A study was carried out for identification and detection of Phytophthora spp. from soil and plant... more A study was carried out for identification and detection of Phytophthora spp. from soil and plant samples, collected from Solanaceous crops in Egypt and Italy. The samples were screened with specific and universal primers of Phytophthora 18S, ITS1–ITS2 and 28S regions, followed by PCR product sequencing. The Phytophthora spp. detected were P. infestans (Egypt) and P. parasitica (Italy). A molecular beacon probe was also developed based on the avr3a gene of P. infestans to detect a variant associated with virulence traits. The probe was suitable for avr3a allele identification from P. infestans and also from P. parasitica PCR products.
Biological control relying on soil microorganisms may offer feasible and sustainable perspectives... more Biological control relying on soil microorganisms may offer feasible and sustainable perspectives in many agrosystems for management of soil pests such as root-knot nematodes (RKNs, Meloidogyne spp.). The rhizosphere environment shows a complex of soil microbial communities, including beneficial organisms such as specialized bacterial pathogens and/or of rhizosphere fungi. New advanced technologies like Next Generation Sequencing (NGS) may enlarge our knowledge about the biodiversity and role of these rhizosphere communities. The numbers of microbial species usually range around 10 3-10 4 taxonomic units g-1 of soil. This dimension suggests that the nematode antagonists known today represent only a fraction of the total number potentially available. The soil microbiome activity may lead to soil suppressivity, a stable nematode control effect related to species undetected or undescribed. Known parasitic microorganisms like the bacterium Pasteuria penetrans show specific and density-dependent links with the host. Other species such as the nematophagous fungus Pochonia chlamydosporia can also induce plant growth promotion effects. NGS transcriptomic data indicate that it can elicit a plant response to many biotic and abiotic stresses. In conclusion, the biodiversity of antagonists and the mechanisms they exert in nematode regulation have yet to be fully explored. However, new high-throughput analytical technologies may fill this gap. Experimental assays for RKN management and/or plant growth promotionindicate that biological management of nematodes is a promising alternative to chemicals. However, this approach requires detailed knowledge about the composition, role and effects of the microbial community present in soil and/or about the right and accurate aggregate of biological entities to apply.
The role of nematology in food security is discussed. Nematology began with the classification of... more The role of nematology in food security is discussed. Nematology began with the classification of species. The onset of monocultures required effective nematode management tools. Recently, more complex approaches to management include ecology, natural sciences and genomics, with important fallouts in crop protection. The food security goal is to satisfy any dietary need for the healthy life of all but this message has not spread globally. Benefits achievable through crop technologies are not equally distributed and food security is not yet assured for several million people. Many social, political or economic factors are involved, and nematology may only partially contribute to achieve this goal. However, the scientific knowledge produced can contribute to solving some food security issues. Fundamental conditions are free access to education and science, as well as support for independent production of knowledge, improving regional and international cooperation and research.
Trees are crucial for sustaining life on our planet. Forests and land devoted to tree crops do no... more Trees are crucial for sustaining life on our planet. Forests and land devoted to tree crops do not only supply essential edible products to humans and animals, but also additional goods such as paper or wood. They also prevent soil erosion, support microbial, animal, and plant biodiversity, play key roles in nutrient and water cycling processes, and mitigate the effects of climate change acting as carbon dioxide sinks. Hence, the health of forests and tree cropping systems is of particular significance. In particular, soil/rhizosphere/root-associated microbial communities (known as microbiota) are decisive to sustain the fitness, development, and productivity of trees. These benefits rely on processes aiming to enhance nutrient assimilation efficiency (plant growth promotion) and/or to protect against a number of (a)biotic constraints. Moreover, specific members of the microbial communities associated with perennial tree crops interact with soil invertebrate food webs, underpinning ...
Applied microbiology and biotechnology, Jan 5, 2017
The molecular mechanisms active during the endophytic phase of the fungus Pochonia chlamydosporia... more The molecular mechanisms active during the endophytic phase of the fungus Pochonia chlamydosporia are still poorly understood. In particular, few data are available on the links between the endophyte and the root response, as modulated by noncoding small RNAs. In this study, we describe the microRNAs (miRNAs) that are differentially expressed (DE) in the roots of tomato, colonized by P. chlamydosporia. A genome-wide NGS expression profiling of small RNAs in roots, either colonized or not by the fungus, showed 26 miRNAs upregulated in inoculated roots. Their predicted target genes are involved in the plant information processing system, which recognizes, percepts, and transmits signals, with higher representations in processes such as apoptosis and plant defense regulation. RNAseq data showed that predicted miRNA target genes were downregulated in tomato roots after 4, 7, 10, and 21 days post P. chlamydosporia inoculation. The differential expression of four miRNAs was further valida...
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Papers by A. Ciancio