Abstract
An approach to manage seed-transmitted Fusarium crown-foot-root rot (FCR, Fusarium spp.) and common root rot (CRR, Bipolaris sorokiniana) on wheat, avoiding environmental risks of chemicals, is seed treatments with microbial metabolites. F. sambucinum strain FS-94 that induces resistance to tomato wilt was shown by this study to be a source of non-fungitoxic wheat-protecting metabolites, which were contained in a mycelium extract purified by gel-chromatography and ultrafiltration. Plant-protecting effect of the purified mycelial extract (PME) was demonstrated in vegetation experiments using a rolled-towel assay and by small-plot field trials. To elucidate mechanisms putatively underlying PME protective activity, tests with cultured Triticum aestivum and T. kiharae cells, particularly the extracellular alkalinization assay, as well as gene expression analysis in germinated wheat seeds were used. Pre-inoculation treatments of seeds with PME significantly decreased the incidence (from 30 to 40%) and severity (from 37 to 50%) of root rots on seedlings without any inhibition of the seed germination and potentiation of deoxynivalenol (DON), DON monoacetylated derivatives and zearalenon production in FCR agents. In vegetation experiments, reductions in the DON production were observed with doses of 0.5 and 1 mg/mL of PME. Pre-sowing PME application on seeds of two spring wheat cultivars naturally infected with FCR and CRR provided the mitigation of both diseases under field conditions during four growing seasons (2013–2016). PME-induced ion exchange response in cultured wheat cells, their increased survivability, and up-regulated expression of some defensins’ genes in PME-exposed seedlings allow the suggestion of the plant-mediated character of disease-controlling effect observed in field.
Highlights
Root rots caused by soil fungi result in yield losses of various cereals including wheat, which is a crop of great economic importance for many grain-producing regions worldwide [1,2,3,4,5,6,7,8]
FS-94 induced systemic resistance to the vascular wilt of tomato [33], and briefly reported the inhibition of some rot- or blotch-causing wheat pathogens by the metabolites of this fungus under controlled and field conditions [34,35]. Continuing these investigations, in the current work we examine the effect of FS-94 metabolites on FCR and common root rot (CRR) agents more entirely, analyze previous studies and report new findings of laboratory and field experiments on wheat protection using the seed treatments with the extract obtained from FS-94 mycelium
Along with hyperparasitism and competition, antibiosis is implemented as a powerful strategy for plant disease managing, which are based on natural mechanisms involved in microbe-microbe and plant-microbe interactions
Summary
Root rots caused by soil fungi result in yield losses of various cereals including wheat, which is a crop of great economic importance for many grain-producing regions worldwide [1,2,3,4,5,6,7,8]. Seed treatments with biocontrol microorganisms or their biomolecules conjointly with other management procedures (healthy seeds, resistant cultivars, rotation with appropriate non-host crops, correct selection of fertilizers) might be an approach for improving the systems of integrated wheat protection from FCR and CRR without increasing the chemical impact in cereal-growing regions [19]. To implement this approach, biocontrol microorganisms, potential biopesticides or resistance inducers, which would effectively reduce the diseases on wheat plants after application on seeds should be available [31,32].
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