Effect of natural grass fallow on Fusarium root and crown rot of wheat

Tzenko Vatchev, Ivo Yanashkov

Abstract: The present study have investigated the effect of short-term grass fallow on general disease suppressiveness of two soil types – Luvic Vertisol and Eutric Fluvisols, against Fusarium root and crown rot of wheat. For this purpose, average soil samples were collected from agricultural fields, either cultivated uninterruptedly for over the last 25 years or uncultivated for four and seven years, respectively for both soil types and divided into portions corresponding to number of treatments. The individual soil portions were either left uninoculated or were separately inoculated with pure cultures of three pathogenic fungi that cause the disease – Fusarium culmorum, F. graminearum or F. oxysporum, developed on autoclaved (30 min at 121°С) barley grains. The level of disease suppression of each soil was estimated on the basis of root and crown rot disease index on wheat plants, cultivar Laska 5 in greenhouse pot experiments. High disease incidence and severity were recorded in both pathogeninoculated Luvic Vertisol and Eutric Fluvisols. Slight reduction – between 9% and 25%, in disease intensity was observed in soil samples collected from currently uncultivated areas as compared to those collected from cultivated lands. Although statistically proven, these levels of disease suppression in both soil types under grass fallow were not to be considered practically significant. In additional experiments conducted with the most aggressive species among the three pathogens, F. culmorum, significantly more severe root and crown rot was recorded in thermally sterilized (240°С for 2 h) soil portions in comparison to the natural, unsterilized soils. These results clearly demonstrate the biological nature of disease suppression towards Fusarium root and crown rot of wheat in Luvic Vertisol and Eutric Fluvisols, but as well as that short-term grass fallow does not increase the natural soil suppression against the disease to useful levels from practical point of view. It was concluded that future application of natural grass fallow as a method to control soil borne diseases of agricultural crops should be preceded by assessment of the potential impact on each individual pathosystem.

Keywords: agro-technical control method; Fusarium root and crown rot; grass fallow; wheat

Date published: 2017-09-13