Biological functions of Trichoderma spp. for agriculture applications

Rhizoctonia solani is a pathogen that causes considerable harm to plants worldwide. In the absence of hosts, R. solani survives in the soil by forming sclerotia, and management methods, such as cultivar breeding, crop rotations, and fungicide sprays, are insufficient and/or inefficient in controlling R. solani. One of the most challenging problems facing agriculture in the twenty-first century besides with the impact of global warming. Environmentally friendly techniques of crop production and improved agricultural practices are essential for long-term food security. Trichoderma spp. could serve as an excellent example of a model fungus to enhance crop productivity in a sustainable way. Among biocontrol mechanisms, mycoparasitism, competition, and antibiosis are the fundamental mechanisms by which Trichoderma spp. defend against R. solani, thereby preventing or obstructing its proliferation. Additionally, Trichoderma spp. induce a mixed induced systemic resistance (ISR) or systemic acquired resistance (SAR) in plants against R. solani, known as Trichoderma-ISR. Stimulation of every biocontrol mechanism involves Trichoderma spp. genes responsible for encoding secondary metabolites, siderophores, signaling molecules, enzymes for cell wall degradation, and plant growth regulators. Rhizoctonia solani biological control through genes of Trichoderma spp. is summarized in this paper. It also gives information on the Trichoderma-ISR in plants against R. solani. Nonetheless, fast-paced current research on Trichoderma spp. is required to properly utilize their true potential against diseases caused by R. solani.

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Trichoderma spp. Genes Involved in the Biocontrol Activity Against Rhizoctonia solani

The incidence of fungal diseases in post-harvest fruits, in storage, or both, is still a problem today due to the large losses caused to producers and merchandisers
 of these products. Therefore, the aim of this study was to evaluate in vitro and in vivo the inhibitory effect of essential oils of basil (Ocimum basilicum), cinnamon (Cinnamomum zeylanicum),
 clove (Syzygium aromaticum), soursop (Annona muricata), ginger (Zingiber officinale), mint (Mentha piperita), oregano (Origanum vulgare), rosemary (Rosmarinus officinalis) and sage (Salvia
 officinalis) at different concentrations on a native strain of Penicillium digitatum as an organic alternative to the use of synthetic fungicides. In order to obtain the strain, fruits from
 localities producing sweet orange (Citrus sinensis Osbeck) in Puerto Rico were selected. Inhibition tests with essential oils were performed on a strain from the Guayanilla locality with
 morphological and molecular identification. Inhibition tests were performed in vitro and in vivo. The experimental design was completely randomized, and the means were compared with the Tukey
 test (p£0.05). Three in vitro inoculation methods were used with the essential oils in the culture medium at different concentrations. In addition, the fungus was treated in vivo in its
 natural environment with the oils that showed more than 90% inhibition in the in vitro methods. Cinnamon, clove and oregano leaf and bark oils inhibited 90 to 100% of P. digitatum
 development. Oils of basil, soursop, ginger, mint, rosemary, and sage inhibited little or not at all the fungal growth. There were some differences in vivo regarding in vitro methods, since
 only clove oil maintained similar levels to the in vivo and in vitro control as the treated fruits showed no contamination with P. digitatum at 7 and 14 days.

EFECTO INHIBITORIO DE ACEITES ESENCIALES EN EL CRECIMIENTO MICELIAL DE Penicillium digitatum (PERS.) SACC. AISLADO DE NARANJA DULCE (Citrus sinensis OSBECK)

Biological control agents can be an effective and safe sustainable alternative method to reduce the detrimental effects of synthetic fungicides. In the present study, an airborne microfungi Trichoderma yunnanense showed broad spectrum antifungal and plant growth promoting activities. The characterization of the fungal isolate was confirmed by morphological features, DNA sequencing and phylogenetic tree analysis. Various growth parameters such as root and shoot length (13.76 mm and 19.3 mm), root and shoot dry weight (0.048 g and 0.037 g) were enhanced in the treated plants compare to control. In treated plants. The total chlorophyll and sugar content were found to be higher than control. Trichoderma yunnanense showed higher antagonistic potentiality (50–66%) against Alternaria brassicicola, Alternaria solani, Aspergillus ochraceus but showed lower potentiality against Pencillium oxalicum (21.42%). Thus the strain of Trichoderma yunnanense possessed growth-promoting potential and potent to antagonistic activity against plant pathogenic fungi.

Biocontrol and plant growth promoting potential of Trichoderma yunnanense

Fungi belonging to the genus Trichoderma were discovered in the late 18th century and they have been utilized ever since their biocontrol potential was uncovered. Trichoderma species have greatly assisted the blooming of agricultural industries due to their aggressive characteristics against plant pathogens. Their role as a biocontrol agent is owed to their mode of mechanisms: induction of the plant’s defence system, mycoparasitism, the production of secondary metabolites, and rhizosphere competence. Meanwhile, their role as a biofertilizer became evident when studies conducted hitherto showed that they could increase plant’s nutrient uptake, improve the yield of crops, enhance plant’s tolerance to external stresses, and induce the germination of seeds. Since this genus is hyperdiverse, accurate identification of them is indispensable. In the past, Trichoderma spp. were identified via their morphological characteristics. However, the emergence of molecular technology has made the identification of Trichoderma isolates more precise, explicit and rapid. Hence, this paper briefly reviews the accumulated knowledge in respect of this genus. Nevertheless, an extensive study must be done in order to explore the potential in improving the natural strains of Trichoderma. 

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The Impact of Trichoderma spp. on Agriculture and Their Identification

Fungi are morphologically, ecologically, metabolically and phylogenetically diverse. Fungi play important roles as one of the major decomposer in ecosystems, dominated by Saprophytic fungi. The identification of fungi is important to differentiate each fungi owing to their special ability in our ecosystem. However, the identification of fungi is become very challenging for those untrained mycologists.  Essentially, the identification of fungi at the species-level is more problematic. Traditional approaches, based on the morphological or physiological features alone are unreliable because of the limited amount of morphological characters for fungi identification. Thus, a reliable molecular approach is required to identify the fungi at species-level. Here, we have successfully identified the species of 25 isolated fungi samples from the polluted areas in Kelantan and Terengganu by using the molecular identification utilizing the ITS1-5.8S-ITS2 regions. Phylogenetics tree was then constructed, using MEGA v7.0 software to illustrate the inter-relationships among the isolates. Among of 25 isolated fungi samples, 23 were identified from Ascomycota division and another two were from the Zygomycota division. From our observation, the most frequent species grew for both polluted areas were from Lasiodiplodia sp.

https://journal.unisza.edu.my/agrobiotechnology/index.php/agrobiotechnology/article/download/146/128

Siti Noraisyah Tan Jamaluddin

Papers

Molecular Identification of Isolated Fungi from Kelantan and Terengganu Using Internal Transcriber Spacer (ITS) Region