Browsing by Author "Reghmit, Abdenaceur"

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Biological control of arbuscular mycorrhizal fungi and Trichoderma harzianum against Fusarium oxysporum and Verticillium dahliae induced wilt in tomato plants
(Springer Science and Business Media Deutschland GmbH, 2023) Meddad-Hamza, Amel; Benzina, Farida; Meddad, Chahinez; Hamza, Nabila; Reghmit, Abdenaceur; Ziane, Hana
Background: Arbuscular mycorrhizal fungi (AMF) and Trichoderma harzianum are effective bioagents against Fusarium oxysporum and Verticillium dahliae in tomato plants. The objective of the research was to evaluate the in vivo antagonistic activity of AMF and T. harzianum against Verticillium and Fusarium wilt by enhancing the growth and resistance of tomato plants. A completely randomized experimental design was used, consisting of twelve treatments with nine replicates for each treatment. The treatments included combinations of AMF and T. harzianum inoculation, infection or non-infection by F. oxysporum and V. dahliae, while also considering individual and combined treatments. Mycorrhization rates, growth parameters, disease severity, disease progression, and the impact on disease mitigation were evaluated. Results: The study revealed the superiority of AMF over T. harzianum, resulting in a significant enhancement in the overall extent of mycorrhizal colonization in tomato plants co-inoculated with T. harzianum. Moreover, AMF treatments and the AMF + T. harzianum consortium contributed to the improvement in growth among all plants infected with V. dahliae and F. oxysporum. Both AMF and T. harzianum significantly reduced the progression of Fusarium wilt, resulting in reductions of 45.14 and 44.91%, respectively, than the untreated plants infected with F. oxysporum (initial disease severity of 75.54%). T. harzianum demonstrated greater efficacy in reducing V. dahliae infection, with a reduction of 34.45% compared to 28.26% for AMF, starting from an initial disease severity of 69.85%. Thus, T. harzianum demonstrated greater effectiveness in controlling disease, particularly Verticillium wilt. Conclusion: The target application of disease control methods in tomato plants revealed the effectiveness of both AMF and T. harzianum in mitigating Fusarium wilt. Furthermore, T. harzianum demonstrated a higher level of effectiveness against Verticillium wilt. These findings emphasize the potential of AMF and T. harzianum as sustainable alternatives in agriculture, providing a viable option to decrease dependence on fungicides.
Recherche de certaines souches fongiques antagonistes productrices de molécules bioactives isolées de la rhizosphère de l'olivier et évaluation de leurs potentiels de lutte contre la verticilliose de l’olivier
(Université M'Hamed Bougara Boumerdes : Faculté des Sciences, 2022) Reghmit, Abdenaceur; Tihar-Benzina, Farida(Directeur de thèse)
En Agriculture, les agents phytopathogènes sont souvent responsables des dégâts et des pertes agronomiques et économiques considérables sur plusieurs cultures. Les traitements chimiques, bien que nocifs, mais ils restent largement utilisés. Afin de limiter ces maladies, l’utilisation de souches de Trichoderma spp. a montré ses effets antagonistes contre plusieurs espèces de champignons phytopathogènes et leur capacité à contrôler ces maladies et offre des perspectives prometteuses pour une agriculture durable et respectueuse de l’environnement. Une collection de 20 isolats de Trichoderma spp. appartenant à différentes espèces sont été isolés à partir des sols rhizosphériques de l’olivier issus de quatre régions du nord Algérien: Boumerdes, Bouira, Bejaia et Tipaza. Ces dernières ont été identifiées par des moyens phénotypique et moléculaire. L’isolement à partir des branches et rameaux présentant les symptômes caractéristiques de la verticilliose vasculaire de l’olivier ont permis de sélectionner 11 isolats fongiques affiliés à l’espèce V.dahlaie dont 6 espèces sont assignés au pathotype non défoliant alors que le reste composent le pathotype défoliant. La croissance mycélienne des isolats antagonistes de Trichoderma spp. et de phytopathogènes de V. dahlaie a été évaluée dans différentes conditions physico-chmiques. Ces derniers ont montré une croissance optimale sur les milieux organiques spécifiquement le milieu PDA, sous une température de 25°C et à un pH=8 cependant le cycle alternatif de la lumière et d'obscurité (12h de lumière /12h d'obscurité) favorise mieux la croissance mycélienne du V.dahliae. Par ailleurs, les isolats de Trichoderma spp. ont montré une croissance optimale sur le milieu PDA à un pH 5 et à.0.2 M en NaCl les qualifiant d’halotolérants. Des tests ont été menés pour évaluer l’effet antagoniste in vitro de tous les isolats de Trichoderma spp. par confrontation directe, indirecte ainsi que l’effet des filtrats de cultures. Les résultats montrent que tous les isolats de Trichoderma ont une activité antagoniste contre les isolats de V. dahliae. Dans la confrontation directe, les isolats T12 et T9 ont donné les meilleurs pourcentages d’inhibitions moyens de 68.86% et 59.96% respectivement. Cependant, les tests de confrontation indirecte in vitro ont montré une réduction de la croissance radiale comprise entre 55.26 et 65.93%. De même, Les filtrats de culture ont plus ou moins inhibé la croissance mycélienne des isolats de V. dahliae. La plus importante inhibition a été obtenue avec le filtrat T7 qui a montré un pourcentage d’inhibition moyen de 48.15% à la dose 20%. Les souches de Trichoderma spp. possèdent un vaste répertoire de métabolites secondaires et des composés volatiles (VOCs). D’autre part, les activités chitinolytiques et protéolytiques les plus élevées sont obtenues par les deux isolats T2 et T6 avec une activité de 0.043 U/ml et 0.019 U/ml respectivement. Les résultats montrent également la capacité des isolats de Trichoderma de solubiliser le phosphate, de produire l’ammoniaque, de fixer l’azote et de synthétiser des phytohormones telles que l’AIA et l’acide gibbérellique à des degrés différents. La souche T11 a montré une meilleure production d’AIA et d’acide gibbérellique avec une concentration de 21.15 ?g/ml et 7.87µg/ml respectivement. Les analyses par GC-MS et par HPLC ont permis d’identifier de nombreuses molécules possédant des capacités PGP et antifongique. L’essai de biocontrôle effectué sur l’olivier (variété Chemlal) a décelé une efficacité très intéressante de Trichoderma aureoviridae (T2), Trichoderma harzianum (T9) et T. harzianum(T12) à l’égard de V. dahalie. Cette constatation est basée sur la diminution significative de la gravité de la maladie par rapport au témoin (> 67%). Les données enregistrées ont également montré que Trichoderma aureoviridae (T2) à enregistré le pourcentage le plus élevé de réduction de la maladie (83,81%). Cette étude a montré que l’action des souches de Trichoderma testées ne se limite pas seulement à la protection de la plante mais aussi à la stimulation de la croissance de l’olivier.
Trichoderma spp. isolates from the rhizosphere of healthy olive trees in northern Algeria and their biocontrol potentials against the olive wilt pathogen, Verticillium dahliae
(Springer, 2021) Reghmit, Abdenaceur; Benzina‑tihar, Farida; López Escudero, Francisco Javier; Halouane‑Sahir, Fatma; Oukali, Zahia; Bensmail, Souhila; Ghozali, Nourelhouda
Trichoderma species are known for their ability to control many plant diseases. In this study, fifteen (T1–T15) indigenous strains of Trichoderma spp. isolated from rhizosphere soils of olive in northern Algeria were investigated for their biocontrol potential against eleven strains of Verticillium dahliae, the causal agent of wilting on olive (Olea europea cv. europea L.). Direct and indirect confrontation assays were performed to investigate if isolates of Trichoderma affect mycelium growth. In addition, gas chromatography–mass spectroscopy (GC–MS) was applied to identify the volatile organic compounds (VOCS) produced by the T2 isolate. Besides, Trichoderma isolates were screened for the production of extracellular enzymes on solid medium including chitinases, proteasesand cellulases. Results showed that Trichoderma isolates demonstrated an effective potential in reducing mycelium growth against V. dahliae in vitro. T12 was the highest antagonistic of the Trichoderma isolates by direct confrontation assay method. This isolate exhibited an average inhibition rate of 68.86% against V. dahliae isolates, whereas the evaluation of volatile metabolites effect revealed that inhibition percentage of radial growth varies between 55.26 and 65.93%. Importantly, results showed the presence of 33 compounds detected in the methanolic and hexanic fraction of T2 isolate, including important volatile compounds with antifungal activities such as Undecane, Octadecane, Eicosane, 13-Docosenamide, (Z), Hexadecanamide, 9-Octadecenamide, (Z), Cyclopentanone, 2-methyl, Tetradecanoic acid, propyl ester, Tetradecanoic acid, oleic acid, and n-Hexadecanoic acid. Interestingly, all isolates tested showed chitinolytic, proteolytic and cellulolytic activity. T2 and T12 were the effective Trichoderma isolates showing high chitinase production on solid medium. Besides that, isolates T2 and T6 demonstrated the highest chitinolytic and proteolytic activity with values 0.043 µmol/ml/min and 0.019 µmol/ml/min, respectively. Overall, the isolates, T2, T6, and T12 are the most effective agents against olive wilt pathogen V. dahliae in vitro. Hence, they could be further investigated for biocontrol of olive wilt in vivo
Volatile organic compounds activities of Trichoderma species isolated from olive grove soil against the wilt pathogen, Verticillium dahliae
(Springer Nature, 2024) Reghmit, Abdenaceur; Benzina-Tihar, Farida; Sahir-Halouane, Fatma
Production of volatile organic compounds (VOCs) is one of the modes of actions of Trichoderma spp. They inhibit pathogenic fungi/bacteria, promote plant growth, and also affect interactions of plants with pathogens. However, the study of VOCs emitted by Trichoderma species associated with olive roots and its benefits are still limited. In the present study, two strains of Trichoderma collected from olive grove soil were evaluated for their antagonistic activity against five strains of Verticillium dahliae named (Vd1 to Vd5) by indirect confrontation assay. In addition, identification and quantification of volatile compounds produced by each strain were assessed through gas chromatography-mass spectrometry (GC–MS). The extraction of metabolites was performed from filtrates using liquid–liquid extraction. Extracts obtained were taken for analysis through GC–MS. Results of indirect confrontation assay showed a high inhibitory activity against V.dahliae. Trichoderma asperellum (T4) and Trichoderma harzianum (T12) exhibited an average inhibition rate of 64.49% and 61.59% respectively. Besides, 98 volatile compounds were detected through GC–MS analysis, including important volatile compounds with antifungal activities, such as D-limonene, octadecanoic acid methyl ester, hexadecanoic acid, toluene, phenylethyl alcohol, benzene derivatives, several phenolic isomers, citral, eicosane and 13-docosenamide. Other volatile compounds revealed antibacterial activity, providing growth promotion, or antioxidant activity, such as oleic acid. Importantly, 7-epi-nemorosone was detected for the first time as new molecule produced by Trichoderma harzianum (T12). This molecule provides anticancer and antioxidant activity. Overall, these strains with various activities are considered as excellent source for discovery of bioactive molecules with eventual application in different biological fields. However, they could be beneficial mainly for suppressing plant pathogens and stimulation of plant growth.