Rapid evaluation of peat-base legume inoculant using immunomagnetic beads for cell retrieval and fluorescent nucleic acid probes for viability analysis

Abstract

Problems associated with traditional methods of evaluating legume inoculants using the most-probable-number plant nodule grow-out test include technician time, expense, growth chamber space, and the length of time (30 days) required to conduct the tests. Through the use of specific monoclonal antibodies, a biotin-labelled intermediate antibody, and streptavidin-labelled magnetic micro-beads, we were able to rapidly remove and purify rhizobial cells from peat inoculants used as quality control samples in the Canadian Legume Inoculant and Pre-Inoculated Seed Testing Program. Viability of the recovered cells was evaluated with a commercial kit employing differential fluorescent nucleic acid probes allowing viability to be rapidly determined via visual examination with a fluorescence microscope. Total elapsed time for complete evaluation of an inoculant was about 90 minutes.