Growth Patterns and Metabolic Activity of Pseudomonads in Sugar Beet Spermospheres: Relationship to Pericarp Colonization byPythium ultimum

Growth patterns of seed-inoculated fluorescent pseudomonads in the spermospheres of sugar beet in soil or sand maintained at −15 J/kg and 16 C were monitored over a 72-h time period. When incubated in soil, strains 33-2 (Pseudomonas putida), A1 (P. florescens), and ML5 (P. florescens-putida) exhibited relatively short lag phases (<4 h), with most growth occurring during the first 12 h. Strains F42 (P. putida) and PGS12 (P. aureofaciens) exhibited long lag phases (8-12 h), and their populations increased mainly between 12 and 24 h. Doubling times during the exponential growth phases were 2-3 h for all strains except P. syringae strain B728a, which had the longest doubling time (5-7 h). Most strains reached the stationary phase within 24 h after planting of seed