Antagonistic Potential of Trichoderma viride and T. harzianum Against Some Dermatophytic Fungi

In this study, Trichoderma viride and T. harzianum were used as biological control agents to assess their antagonistic potential against some dermatophytic fungi (Microsporum gypseum, M. fulvum, Trichophyton rubrum, T. interdigitale) which causes ring worm in human. For this purpose dual culture method was used. Trichoderma viride and T. harzianum showed highest percentage inhibition of radial growth (PIRG) against Trichophyton interdigitale (92% & 60% respectively). Colony over growth was also observed with Trichoderma viride. The outcomes of the study indicate that Trichoderma viride was excellent antagonist to prevent the growth of dermatophytic fungi whereas T. harzianum exhibited moderate PIRG between 45-60% against Microsporum gypseum, M. fulvum, Trichophyton rubrum, T. interdigitale.


INTRODUCTION
Soils that are rich in keratinous materials are the most conductive for the growth and occurrence of keratinophilic fungi. Keratinophilic fungi along with dermatophytes are responsible for various cutaneous mycoses. Dermatophytoses allude to superficial fungal infection of keratinized tissues bring about keratinophilic dermatophytes. The infection is often called as ring worm or "tinea". Biological control of pathogen by microorganisms is an alternative of chemical treatment method. An interesting alternative approach to treat mycosis caused by dermatophytes such as T. rubrum, T. interdigitale, Microsporum gypseum and M. fulvum, may be the use of antagonistic fungi such as Trichoderma. Trichoderma spp. is occurred worldwide in the soil (Domsch et al., 1980;Christensen, 1981). Its antagonistic activity against plant pathogen has been studied widely and it"s extensively used as BCAs in the world (Khetan, 2001;Tronsmo & Hjeljord, 1998).
The success of Trichoderma strains as BCAs is due to their high reproductive capacity, ability to survive under very unfavorable conditions, efficiency in the utilization of nutrients, capacity to modify the rhizosphere, strong aggressiveness against phytopathogenic fungi and efficiency in promoting plant growth and defense mechanisms. Trichoderma viride and T. harzianum were found to be an antagonist to many plant pathogens. Antagonists perform against pathogens through parasitism, antibiosis or competition. They produce toxic metabolites and inhibit pathogen by antibiosis (Dandurand & Knudsen, 1993).

Screening by dual cultured method:
Trichoderma viride and T. harzianum obtained from Rajasthan Agriculture Research Institute (RARI) Durgapura, Jaipur and were used in present study for their antagonistic activity against Microsporum gypseum, M. fulvum, Trichophyton rubrum and T. interdigitale. For this purpose dual culture method was used which based on percentage inhibition of radial growth (PIRG). A 3mm diameter size were cut from the margins of 7 days old vigorously growing cultures of dermatophytic fungi and antagonistic fungi and placed on 1 cm away from the periphery of 9cm petri plates containing PDA medium on opposite side of each other on same petri plate. As a control dermatophytic fungi were similarly placed on PDA medium without Trichoderma spp. These petri plates were incubated at 28ºC for 7 days. Antagonistic activity of Trichoderma spp. were determined by measuring the percentage inhibition of radial growth (PIRG) of dermatophytic fungi using the formula (Edgington, et al., 1971).

PIRG
100 Rr R

 
Where R -Indicates the radius of dermatophytic fungi in control plates r -Indicates the radius of dermatophytic fungi in dual cultured plates Investigation were continue to record the number of days needed for the colony overgrowth. In dual culture, assessment of colony interactions grading were done based on intermingling and inhibition zone (Skidmore & Dickinson 1976) identified 5 separate modes of interaction colony overgrowth and were assigned values on 0-5 scale for each type of interaction where "0" indicates no inhibition. In present study, antagonistic relationships among Trichoderma spp. and dermatophytic fungi ranged from grade 2 -4 (Table 1& Fig. 2). However, grade 3 was observed as the most commonly experienced type of colony interaction, followed by grade 4. Trichoderma harzianum showed grade 2 interaction against M. fulvum.

DISCUSSION
Trichoderma has been reported as potential biocontrol agent due to their ability to inhibit the prevalence of diseases caused by soil borne pathogens (Calvet et al., 1990;Elad et al., 1993;Ashrafizadeh et al., 2005;Dubey &Suresh, 2007). In present study, two isolates of Trichoderma were assessed in vitro for screening antagonistic potential against Microsporum gypseum, M. fulvum, Trichophyton rubrum and T. interdigitale. The result revealed that Trichoderma viride demonstrated strongest antagonistic activity to inhibit the growth of above mention dermatophytic fungi. Begum et al. (2008) observed that Trichoderma virens and Trichoderma harzianum inhibit the growth of Colletotrichum truncatum. The study was based on culture filtrate test and high PIRG value in dual culture method. Trichoderma harzianum exhibited different isolates and abilities to attack Sclerotium rofsii (Jinantara, 1995;Henis et al., 1983).Trichoderma viride was found best antagonist based on two criteria high PIRG value and minimum colony overgrowth time. Etabarian (2006) observed decreased/ minimized the colony area of Macrophomia phaseoli by using Trichoderma viridie (MO) as antagonistic in dual culture and cellophane method. Omero et al. (2004) investigated that Trichoderma virens NRRL 26672 was the most effective against T. rubrum NCPF118. T. virens NRRL 26672 developed with T. rubrum NCPF118 hyphae as a carbon source, showed upgraded discharge of active extracellular chitinases and b-glucosidases which affecting sporulation and lysis on T. rubrumNCPF118 hyphae. Rahman et al. (2009) were found that highest PIRG value with T. harzianum IMI-392432 using dual culture method as compare to T. virens IMI-392430, T. pseudokoningiiIMI-392431 and T. harzianum IMI-392433.Cherif et al. (2009)

CONCLUSION
Conclusively, T. viride was found to be more potent antagonist than T. harzianum againt all the fungi tested. Our findings have led to the possibility that Trichoderma spp. might be suitable to control the activity of dermatophytic fungi.