Informatics Publishing Limited

R. Jayalakshmi ¹, G. Sobanbabu ², R. Oviya ¹, S. T. Mehetre ³, R. Kannan ⁴, M. Paramasivam ⁵, V. P. Santhanakrishnan ⁶, K. K. Kumar ⁶, M. Theradimani ¹, V. Ramamoorthy ¹

Affiliations
1 Department of Plant Pathology, Agricultural College and Research Institute, Tamil Nadu Agricultural University, Madurai, Tamil Nadu, IN
2 Department of Plant Pathology, Agricultural College and Research Institute, Tamil Nadu Agricultural University, Madurai, Tamil Nadu, IN
3 Nuclear Agriculture and Biotechnology Division, Bhabha Atomic Research Centre, Mumbai, IN
4 Department of Plant Pathology, Agricultural College and Research Institute, Tamil Nadu Agricultural University, Killikulam, Tamil Nadu, IN
5 Pesticide Toxicology Laboratory, Department of Agricultural Entomology, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, IN
6 Department of Plant Biotechnology, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, IN

Abstract

Gliotoxin is a potent antibiotic showing antifungal activity against various phytopathogenic fungi. It is produced by Q strains of Trichoderma virens and gliotoxin non-producing strains of T. virens are designated as P strains. There is no detailed study on effect of gliotoxin on suppression of damping off of tomato caused by Pythium aphanidermatum and its phytotoxicity effect on tomato plants. Thus, the present study was carried out to assess the effect of gliotoxin on inhibition of mycelial growth of P. aphanidermatum, its phytotoxicity effect on tomato and its role on the suppression of damping off of tomato. Culture filtrates of Q strains of T. virens containing gliotoxin highly inhibited the mycelial growth of P. aphanidermatum compared to that of P strains of T. virens. Purified gliotoxin but not bis-thiomethyl gliotoxin effectively inhibited the mycelial growth of P. aphanidermatum. Tomato seeds treated with purified gliotoxin did not inhibit the germination of seeds, its ischolar_main and shoot length even at higher concentration that is at 1000 ppm (fivefold inhibitory concentration against P. aphanidermatum). Foliar spray of gliotoxin on tomato plants did not show any phytotoxic effect at lower concentration but showed scorching effect at higher concentration. Seed treatment with gliotoxin producing Q strains of T. virens showed greater suppression of damping-off tomato compared to P strains of T. virens. This study clearly showed that gliotoxin producing T. virens could be used in suppression of damping-off disease incidence in tomato.

Keywords

Bio-control, damping-off, gliotoxin, Trichoderma virens

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R. OVIYA ¹, S. THIRUVUDAINAMBI ², V. RAMAMOORTHY ³, R. THAMIZH VENDAN ⁴, S. VELLAIKUMAR ⁵

Affiliations
1 Department of Plant Pathology,, IN
2 Department of Plant Pathology., IN
3 Department of Plant Pathology ., IN
4 Department of Agricultural Microbiology ,, IN
5 Department of Biotechnology, Agricultural College and Research Institute, Tamil Nadu Agricultural University, Madurai – 625104, Tamil Nadu, India ., IN

Abstract

Fusarium oxysporum f. sp. cepae causing basal rot disease of onion is a destructive phytopathogen resulting in 30-50% yield loss and remains as a major constraint in onion productivity. The management of disease through application of fungicide is not feasible and economically viable. Hence, the present study is focused on investigation of effective Trichoderma sp. and identifying the effective volatile organic compounds produced by it against the basal rot pathogen in onion. A total of ten Trichoderma spp. were isolated from rhizospheric soil of healthy onion plants and tested against virulent Fusarium oxysporum f. sp. cepae isolate FCIM1. The Trichoderma isolate (TIM2) showed 77.40% inhibition on mycelial growth of pathogen followed by the isolate (TIV1) with 70.36% inhibition. The molecular identification of effective Trichoderma isolate through the analysis of the rDNA of Internal Transcribed Spacers (ITS) region revealed isolate TIM2 as Trichoderma hamatum. The GC-MS analysis of Trichoderma hamatum unravelled the important volatile organic compounds like Methyl stearate, n-Hexadecanoic, Eicosane, 9-cyclohexy, Heptadecane, Dodecane, 2-cyclohexyl, to 2H-Pyran-2-one, 6-pentyl, 5-Hydroxymethylfurfural, Tetrapentacontane, 1-Dodecanol, 2-Propenoic acid, pentadecyl ester, Benzene, (2-methylbutyl) and 1,2-Dimethyltryptamine with peak area and retention time. These bioactive compounds exert a strong antifungal activity against Fusarium oxysporum f. sp. cepae. The scanning electron micrographs of Fusarium paired with effective Trichoderma (TIM2) showed the swollen hyphae with cell wall damage which is clear evident of antagonistic interaction of volatile compounds produced by Trichoderma hamatum.

Keywords

Dodecane, Trichoderma hamatum, Internal Transcribed Spacers, rhizospheric soil, volatile organic compound

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