Trichoderma harzianum as a biocontrol agent for 𝘗𝘺𝘵𝘩𝘪𝘶𝘮 𝘢𝘱𝘩𝘢𝘯𝘪𝘥𝘦𝘳𝘮𝘢𝘵𝘶𝘮, a causal organism of damping-off of tomato

Abstract

Soil-borne fungal diseases in plants cause a severe reduction in the quality and quantity of plant products in agricultural lands. Damping-off disease, which occurs mainly due to the attack of 𝘗𝘺𝘵𝘩𝘪𝘶𝘮 sp., is one such disease affecting most species of crop plants, specially the Solanaceae crops including tomato. Methods of prevention and disease control include the use of fungicides, reduction in seedling density and biological control. 𝘛𝘳𝘪𝘤𝘩𝘰𝘥𝘦𝘳𝘮𝘢, a soil-borne fungus, has been found to be a successful biocontrol agent against a number of soil-borne pathogenic fungi over a period of years.

𝘛𝘳𝘪𝘤𝘩𝘰𝘥𝘦𝘳𝘮𝘢 sp. was isolated from garden soil mixed with decomposing plant material, by the dilution plate method on Potato Dextrose Agar medium (PDA). Based on colony, morphological characteristics and growth rate measurements on 2% Malt Extract Agar (MEA), the species was identified as 𝘛𝘳𝘪𝘤𝘩𝘰𝘥𝘦𝘳𝘮𝘢 𝘩𝘢𝘳𝘻𝘪𝘢𝘯𝘶𝘮. The causal organism was isolated on water agar from root tips of diseased seedlings, collected from a seedling bed of tomato (cultivar: Thilina, V/2/3/K.U.N/OO3). Based on colony and morphological characteristics, the fungus was identified as 𝘗𝘺𝘵𝘩𝘪𝘶𝘮 𝘢𝘱𝘩𝘢𝘯𝘪𝘥𝘦𝘳𝘮𝘢𝘵𝘶𝘮.

The biocontrol ability of 𝘛𝘳𝘪𝘤𝘩𝘰𝘥𝘦𝘳𝘮𝘢 𝘩𝘢𝘳𝘻𝘪𝘢𝘯𝘶𝘮 against 𝘗𝘺𝘵𝘩𝘪𝘶𝘮 𝘢𝘱𝘩𝘢𝘯𝘪𝘥𝘦𝘳𝘮𝘢𝘵𝘶𝘮 was tested in comparison to 0.02% Captan [1,2,3,6-Tetrahydro-N-(trichloromethylthio) phthalimide 3a,4,7,7a-Tetrahydro-2-[(trichloromethyl)thio]-lH-isoindole-1,3(2H)-dione], a recommended contact fungicide to control the disease. Linear growth measurements of 𝘗. 𝘢𝘱𝘩𝘢𝘯𝘪𝘥𝘦𝘳𝘮𝘢𝘵𝘶𝘮 on PDA plates were taken in the presence of treatments (𝘛. 𝘩𝘢𝘳𝘻𝘭𝘢𝘯𝘶𝘮 or fungicide). The inhibition in growth of 𝘗. 𝘢𝘱𝘩𝘢𝘯𝘪𝘥𝘦𝘳𝘮𝘢𝘵𝘶𝘮 was significant (P = 0.05 level) in 𝘛. 𝘩𝘢𝘳𝘻𝘪𝘢𝘯𝘶𝘮 treated plates compared to the fungicide treatment and the control.

In vivo effect of 𝘛. 𝘩𝘢𝘳𝘻𝘪𝘢𝘯𝘶𝘮 against damping off development was tested using tomato plants in a moisture chamber at room temperature (27 ± 1°C). The treatments were addition of a spore suspension (106) of 𝘛. 𝘩𝘢𝘳𝘻𝘪𝘢𝘯𝘶𝘮, fungicide (0.02%) and reducing the number of seeds planted. The number of diseased seedlings was counted 10 days and 14 days after planting and percentage disease incidence was calculated. There was a 88.8% reduction in disease incidence by 𝘛. 𝘩𝘢𝘳𝘻𝘪𝘢𝘯𝘶𝘮; which was significant at P = 0.05 level. Treatment with 𝘛. 𝘩𝘢𝘳𝘻𝘪𝘢𝘯𝘶𝘮 was 30.6% more effective than the fungicide used (Captan) and 18.4% more effective than reduced seedling density.

Results obtained from the current study showed that damping-off disease of tomato caused by 𝘗𝘺𝘵𝘩𝘪𝘶𝘮 𝘢𝘱𝘩𝘢𝘯𝘪𝘥𝘦𝘳𝘮𝘢𝘵𝘶𝘮 can be significantly reduced by the biocontrol agent 𝘛𝘳𝘪𝘤𝘩𝘰𝘥𝘦𝘳𝘮𝘢 𝘩𝘢𝘳𝘻𝘪𝘢𝘯𝘶𝘮.