EFFECT OF CULTURAL CONDITIONS ON BIOMASS PRODUCTION OF POTENTIAL TRICHODERMA BIOCONTROL AGENTS FROM TOBACCO RHIZOSHEREK.L.M. Mallikarjuna Rao, K. Siva Raju and H. RavisankarAbstract Physiological and environmental requirements have to be studied in depth to utilize the locally isolated Trichoderma strains as biocontrol agents. In the present study, the effect of cultural conditions on the biomass production of Trichoderma isolates from tobacco rhizosphere which were capable of antagonizing Sclerotium rolfsii and Pythium aphanidermatum infecting tobacco were reported. The isolate ThDt1 and ThDt2 showed significantly higher biomass production at pH 4 and 5 compared to other isolates. The isolates ThJt1 and TvHt2 showed maximum biomass production at pH 6 and 7 when compared to other isolates and at other pH levels. The isolates showed maximum growth between 30 and 35oC. At 6 days of incubation, the isolate ThJt1 produced maximum biomass on succinic acid and it was at a par with the glucose, fructose, sucrose and citric acid whereas the isolate TvHt2 produced maximum biomass on sucrose and it was at a par with glucose, fructose, citric acid and succinic acid. Ammonium forms of nitrogen supported the maximum growth of the isolates whereas urea showed least support. At 6 days of incubation, the isolate ThJt1 produced maximum biomass on ammonium nitrate whereas the isolate TvHt2 produced maximum biomass on ammonium nitrate and was at a par with calcium ammonium nitrate, sodium nitrite, potassium nitrate and ammonium sulphate. Glutamic acid supported the significantly higher biomass production when compared to glycine. The local isolates ThJt1 and TvHt2 showed superiority over the commercial isolate ThC in biomass production in different cultural conditions. The isolates ThJt1 and TvHt2 utilized different carbon and nitrogen sources and broad spectrum of pH and temperature tolerance can be used as biocontrol agents in different tobacco growing areas because of their versatility.
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