Abstract

Mixing fungicides with bacteria that produce antimicrobial compounds is an integrated management tool that can reduce root rot pathogens such as Gaeumannomyces graminis var. tritici (Ggt), which causes take-all disease in wheat. This study analyzed the effect of wheat seed treatments on the survival of two strains of Pseudomonas protegens when applied to the seeds alone or integrated with a fungicide a.i. fluquinconazole. Through three field experiments, under wheat monoculture and rotation, inoculated with Ggt, the effect of the bacterial combination with the fungicide seed treatment on yield components was analyzed, and above ground symptoms and root rot severity of take-all disease were determined. In addition, bacterial populations were quantified using PCR and qPCR with phiD +-specific primers in wheat roots during tillering and anthesis throughout two seasons. P. protegens did not show marked effects on the evaluated parameters. However, when combined with fungicide, they increased yield, grain quality, test weight parameters, biomass, and plant height at early stages of plant development; they also decreased the severity of the disease. Initial populations of the bacteria were not affected when seeds were co-treated with fluquinconazole, which was related to an early root colonization and protection in initial stages of development to stabilize their population during anthesis. Results suggest that the integration of P. protegens strains with fluquinconazole is an alternative management strategy for reducing take-all disease in southern Chile.