Abstract
Seed treatments with antagonistic bacteria could reduce the severity of crown and root rot diseases in wheat crops. The objective of this study was to evaluate the potential antagonistic activity of a bacterial consortium of three Chilean strains of Pseudomonas protegens against the wheat crown and root rot pathogens Gaeumannomyces graminis var. tritici, Rhizoctonia cerealis, and Fusarium culmorum. Two field experiments were carried out on artificially infested soil during two consecutive seasons (2016–2017 and 2017–2018) in an Andisol soil of southern Chile. Control treatments (not inoculated with fungi) were also included. Each treatment included a seed treatment of spring wheat cv. Pantera-INIA with and without the bacterial consortium. Both phytosanitary damage (incidence and severity) and agronomic components were evaluated. Bacterial populations with the phlD+ gene in the wheat plant rhizosphere during anthesis state (Z6) were also quantified. In both seasons, infection severity decreased by an average of 16.8% in seeds treated with P. protegens consortium, while yield components such as spikes m−1 and number of grains per spike increased. The use of antagonistic bacteria resulted in a total yield increase only during the first experimental season (P < 0.05). In general, accumulated rainfall influenced the antagonistic effect of the consortium of P. protegens strains, accounting for the differences observed between the two seasons. The results suggest that this P. protegens consortium applied on seeds can promote plant growth and protect wheat crops against crown and root rot pathogens in Southern Chile under field conditions.
Highlights
Wheat cultivation (Triticum aestivum) is severely affected by several soil-borne pathogenic fungi that cause diseases of economic importance
Inoculation of the bacterial consortium increased the populations of bacteria phlD+ in the rhizosphere, moving from an average of Log 3.05 colony forming units (CFU) g−1 of root to Log 5.28 CFU g−1 root in season 1, and from Log 4.46 CFU g−1 to 5.45 CFU g−1 in season 2 for untreated and treated seeds with the bacterial consortium of P. protegens, respectively (Figure 2)
Infection associated with inoculation with F. culmorum and R. cerealis did not increase the population of phlD+ bacteria with respect to the control (CNIF −Pp) or seed not treated with P. protegens (Fc −Pp and R. cerealis isolate M31S (Rc) −Pp treatments)
Summary
Wheat cultivation (Triticum aestivum) is severely affected by several soil-borne pathogenic fungi that cause diseases of economic importance. Tritici causes take-all disease of cereals, which damages roots, crown, and culms of the plant and strongly reduces crop yield (McMillan et al, 2014; Vera et al, 2014), mainly surviving as mycelium in a saprophytic manner in culms, crowns, and roots of wheat plants and other susceptible grasses This fungus produces runner hyphae, which grow superficially and cover and penetrate tissues in the root area, colonizing and destroying vascular tissues, interfering the transport of water and nutrients in the host plant (Kwak and Weller, 2013; Quan et al, 2015). A third genetic group, capable of causing severe infections in wheat plants, was identified by using RAPD (random amplification polymorphism DNA) fingerprinting while sampling 48 commercial wheat fields in the 2011–2012 season in the Araucanıa, Los Rıos, and Los Lagos regions of Chile (unpublished data)
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