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

Full Text

   

P. ANBAZHAGAN ¹, M. THERADIMANI ², V. RAMAMOORTHY ², P. VELLAIKUMAR ³, S. JULIET HEPZIBA ⁴

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

Abstract

False smut disease of rice incited by Ustilaginoidea virens is an organ-specific pathogen that causes chalkiness of grain which leads to a reduction in 1000 grain test weight and yield. The dual culture assay results revealed that each Trichoderma isolates suppress the mean mycelial growth of U. virens under in-vitro conditions. Among the nine different Trichoderma isolates, 3 isolates were selected as effective isolates viz., TKM1, TKT9 and TTN5. Among these three effective isolates, maximum mycelial growth inhibition was recorded in the isolate TKM1 with 80.18 percentage reduction over control. The SEM photographs revealed that the hyphal round off in U. virens which is mainly due to the production of volatiles through direct antagonistic activity and competition through indirect antagonistic activity in which conidial adherence of T. harzianum over the surface of the mycelial mat of U. virens was observed. In 2020, the field experiment results revealed that the minimum disease severity was recorded when the Trichoderma isolate TKM1 was sprayed during booting stage with 4.61%, 50% PE stage with 17.91% and 100% PE with 21.86%. In 2021 the disease severity varied from 9.21% to 69.59%. The lowest disease severity was recorded in the plots sprayed with propiconazole fungicide with 9.21%. However, the disease severity recorded in fungicide treated plots were statistically on par with the Trichoderma isolate TKM1 treated plots at 50% PE spray with 10.60%. The disease severity recorded in the plots sprayed with TKM1 showed non-significant relationship with the fungicide treated plots which clearly revealed that the control efficacy of both TKM1 and Propiconazole treated plots were similar with each other. Among the Trichoderma treated plots the yield gain varied from 10.01% to17.20%. The yield gain was found to be 18.35% in fungicide treated plots. The yield and yield gain obtained by the effective isolate TKM1 (yield = 6405 kg/ha and yield gain = 17.20%) was statistically on par with propiconazole treated plots and significantly showed better yield and yield gain than the control plots. In 2021 among the Trichoderma treated plots the yield gain varied from 4.10% to 10.16%. The maximum yield gain was recorded in the fungicide treated plots (12.00%).

Keywords

Antagonistic activity, control efficacy, mycoparasitism, organ-specific, propiconazole, yield gain

Full Text