A METHOD FOR DETERMINATION OF BIO-POTENCY BY LETHAL DOSE TITRE-50 (LDt 50)OF LIVE ANTAGONIST AGAINST PATHOGEN

摘要

A method is proposed for determining the lethal dose titre value of 50% killing of live pathogen by using live form of biopesticides. The method consists of first determining the titre value of starter/seed culture by preparing their serial dilutions (101 to 1010) in nutrient broth, after incubation at 37°C±7°C. A control antagonist set of live antagonist titre, antagonist-pathogen interaction set and a control pathogen tube are prepared separately and their optical densities are measured using a colorimeter. The differences in optical densities of interaction set (z) and control antagonist set (y) are recorded. That antagonist titre dilution in the respective tube whose (z-y) value equals x/2 where x is optical density of control pathogen tube, determines LDtso. Alternately LDt50 is determined by preparing antagonist-pathogen interaction set and control pathogen set on agar petriplates. That antagonist titre dilution on the interaction petriplate showing a/2 number of pathogen colonies where 'a' is total number of pathogen colonies in control pathogen plate, deterfines LDt50.