Efficacy of bacterial seed treatments for controlling Pythium root rot of winter wheat.
Bacterial strains that suppress Pythium root rot were isolated from wheat roots in Arkansas, USA, and were compared with bacterial strains from other areas. Strains (applied as seed treatments) that suppressed Pythium disease in growth chamber assays were further evaluated for in vitro antibiosis against 3 Pythium spp. (P. irregulare, P. torulosum and P. graminicola) and for efficacy under field conditions. Pseudomonas fluorescens strain 2-79R, Burkholderia cepacia strain 1-23 and Pseudomonas sp. strain 1-30 were the most effective for suppressing Pythium root rot in the field conditions, and significantly increased yield in one experiment. Strains that were effective in the field also expressed in vitro antibiosis to at least 2 of 3 Pythium spp. However, strains expressing the highest levels of antibiosis were not effective in the field. In the field, root rot suppression and yield enhancement were inconsistent across experiments and were generally small in magnitude.