Effect of inoculum preparation and formulation on survival and biocontrol efficacy of Pseudomonas fluorescens F113

Sugarbeet seeds used by farmers are often pelleted using an EB-(TM)-based m is. During the pelleting process, the seeds are dried immediately after app lication of the mix. In this work, the effects of inoculum preparation and formulation on survival and biocontrol efficacy of Pseudomonas fluorescens F113Rif were investigated using a 1:1 EB(TM)/vermiculite mix and sugarbeet seeds pelleted with this material. Growing F113Rif Cor 3 d (28 degrees C) w ithin the EB(TM)/vermiculite mis amended with nutrients (sucrose asparagine broth), instead of adding the cells to the unamended mix immediately befor e drying the mis or the pelleted sugarbeet seeds, resulted in improved surv ival of the strain in the mis or on the seeds, respectively, during subsequ ent storage. A slower drying (20 h instead of 3 h) of the F113Rif-inoculate d EB(TM)/vermiculite mix to 11% w/w water content enhanced strain survival in the mis during storage, bur the drying conditions studied had no effect on inoculant survival on the seed during storage when pelleted seeds were d ried to 10% w/w water content. Biological control of damping-off disease of sugarbeet (caused by Pythium spp.) in soil microcosms was achieved when F1 13Rif was inoculated in the unamended mis 3 d before pelleting the seeds, b ut not when nutrient-amended mix was used. Inoculum preparation and drying of the formulation are keg factors to consider when optimizing the use of a commercial EB(TM)/vermiculite seed formulation for delivery of a biocontro l Pseudomonas inoculant.