EFFICACY OF BACTERIAL SEED TREATMENTS FOR CONTROLLING PYTHIUM ROOT-ROT OF WINTER-WHEAT

Pythium root rot, caused by various Pythium spp., is a widespread dise ase of wheat. The objective of this study was to identify bacterial st rains from wheat roots in Arkansas that suppressed Pythium root rot an d to compare their efficacy with that of bacterial strains from other areas. Bacterial strains (applied as seed treatments) that suppressed Pythium root rot in growth chamber assays were evaluated further for i n vitro antibiosis against three Pythium spp. and for efficacy under f ield conditions. Pseudomonas fluorescens strain 2-79R, Burkholderia ce pacia strain 1-23, and Pseudomonas sp. strain 1-30 were the most effec tive for suppressing Pythium root rot under field conditions and signi ficantly (P = 0.10) increased yield in one experiment. Strains that we re effective in the field also expressed in vitro antibiosis to at lea st two of three Pythium spp.; however, strains expressing the highest levels of antibiosis were not effective in the field. In the field, ro ot rot suppression and yield enhancement were inconsistent across expe riments and generally small in magnitude. Therefore, these strains hav e little potential for commercial use under the conditions in which th ey were tested.