Vol. 11, Issue 3 (2022)

Author(s):
Mahendra, Reddi Kumar, CPD Rajan and Sumathi

Abstract:
A bioformulation with increased shelf life is the essential requirement in the development of formulations of biocontrol agents. To accomplish this, the current study involved isolation of Trichoderma harzianum (GRT4) and Pseudomonas fluorescens (PF4) from the groundnut rhizosphere followed by in-vitro testing of above biocontrol agents each against Macrophomina phaseolina and Sclerotium rolfsii. Finally, the effective antagonistic isolates were formulated using talc, kaolinite, gypsum (solid carrier materials) and glycerol, polyvinylpyrrolidone (PVP) and soybean oil (liquid carrier materials). After development, the formulations were stored at 4 ^oC and at room temperature for evaluating their shelf life periodically at 30, 60 and 90 d after storage. In our study, we found talc-based formulations of T. harzianum and P. fluorescens maintained higher inoculum densities (9.3 ´ 10⁷ cfu g^-1, 11.9 ´ 10⁷ cfu g^-1 & 8.4 ´ 10⁸ cfu g^-1, 10.5 ´ 10⁸ cfu g^-1) both at room temperature and at 4^oC, respectively even after 90 d of storage when compared with other solid formulations tested. In case of liquid formulations of P. fluorescens tested, glycerol amended nutrient broth maintained higher inoculum densities (6.5× 10⁸ cfu ml^-1, 10.3× 10⁸ cfu ml^-1) both at room temperature and at 4^oC respectively after 90 days of storage.