Determination of shelf-life of  Trichoderma asperellum in solid- and liquid-based formulations

Trichoderma has gained attention as a promising bio-control agent owing to its effectiveness against a wide array of soil-borne plant pathogens. Successful introduction of bio-control agents to farmers is hindered mostly by unavailability of commercial preparation of Trichoderma bio-inoculate with a considerably higher shelf-life. The objectives of this investigation was to study the shelf-life of T. asperellum in selected liquid- and solid-based formulations and to find the suitability of cattle manure as a multiplication medium. Different carrier material including liquids and solids were tested for preparation of a commercial biological formulation of T. asperellum. The liquid carrier media tested in the present study were 1% sucrose, 1% peptone water, 1% tryptone broth, 1% tryptone soy broth and sterilized distilled water. Talc powder was tested as the solid carrier material. Cattle manure was incorporated with talc-Trichoderma formulation to check the suitability of cattle manure as a multiplying substrate. The initial spore count of each liquid formulation was maintained at 1.0x10⁶ cfu/ml. At the end of 4th week, the mean viable spore counts of the tryptone broth, peptone water and tryptone soy broth used were 7.15x10⁶ cfu/ml, 7.26x10⁵ cfu/ml and 7.30x10⁵ cfu/ml, respectively. From the 4th week onwards, the viable spore count of those three formulations could not be calculated due to heavy contaminations. In the 1% sugar solution and sterilized distilled water, spores were countable only till the end of 8th week of preparation and the counts were 2.5x10⁴ cfu/ml and 2.6x10³ cfu/ml, respectively. A talc-based formulation was prepared by mixing T. asperellum spore suspension (1.0x10⁸ CFU/ml) with talc powder at three different levels (v/w); 30ml/100 g (T1), 40 ml/100 g (T2) and 50 ml/100 g (T3). Three months after storage, all the three treatments (T1, T2 and T3) yielded mean spore counts of 0.92x10⁸ cfu/g, 1.11x10⁸ cfu/g and 1.21x10⁸ cfu/g, respectively. Talc powder inoculation with cattle manure was done at four different rates, i.e. 10 g/kg cattle manure (C1), 15 g/kg cattle manure (C2), 20 g/kg cattle manure (C3) and 25 g/kg cattle manure (C4). Cattle manure was identified as a potential multiplying substrate of the talc-based formulation of T. asperellum.