Evaluation of Some Bacillus spp. Strains for the Biocontrol of Fusarium graminearum and F. culmorum in Wheat

Abstract Fusarium graminearum Schwabe - teleomorph Gibberella zeae (Schwein.) Petch. and F. culmorum (W.C.Smith) Sacc. are the most important head-blighting pathogens of wheat in many regions of the world, including Romania. The strategies developed for the control of Fusarium spp. infections on cereals include agrotechnical practices, resistant cultivars, and fungicides use. However, the toxicity of fungicides and the low efficacy of such products to control members of the Fusarium head blight (FHB) Complex led to the development of additional strategy that can be used as part of an integrated management of FHB (directed against fungal growth and/or mycotoxins biosynthesis and accumulation). The use of biocontrol agents is an important strategy for integrated management of fungal diseases in many economically important plat species. It was shown that Bacillus spp strains could suppress various soil borne diseases, their efficacy being associated with their antagonistic properties and competitiveness in the rhizosphere (including through sporulation). The aim of this study was the “in vitro” evaluation of biocontrol capacity of different Bacillus spp. strains isolated from soil and compost against strains of Fusarium graminearum and F. culmorum. The ability of four strains of bacilli (B1, B3, B5 and BIR) to inhibit fungal growth was established. For their identification BIOLOG system was used, coupled with molecular techniques (ARDRA). It was proved that the strains of interest belong to Bacillus amyloliquefaciens (BIR and B3) and Bacillus spp. (B1 and B5). The Bacillus amyloliquefaciens strains, BIR and B3, were also evaluated in pot experiments, in climatic chamber conditions, for their ability to stimulate wheat seeds germination and/or plantlet growth and reduce Fusarium infections in first stages of wheat vegetation. After 21 days of incubation significant differences were registered between variants infected with Fusarium and supplemented with Bacillus and control variants, not only in germination rate but also in wheat plantlets development. Further differences were observed in the number of Fusarium CFU/g of soil from the soils treated with bacteria in contrast with control variants.