LAUSR

The interactions among grain-colonizing species on wheat and their effects on incidence and severity of Fusarium head blight are usually neglected in studies. Although saprophytes can predominate over pathogenic species, studies related to the control of saprophytic mycoflora in wheat production are rare. Here we hypothesized that the infection level of Fusarium and contamination level of Alternaria spp. are significantly influenced by environmental factors and their interactions and investigated the relationship between Fusarium and Alternaria spp. under field conditions and estimate its effect on conventional wheat production, The most prevalent species associated with wheat grain were Alternaria spp. (80% in 2012 and 55% in 2013), and the second was F. graminearum (9% in 2012 and 38% in 2013). In general, varieties that are moderately resistant to Fusarium infection are less contaminated with Alternaria spp. compared to susceptible and moderately susceptible varieties. F. graminearum on Alternaria spp. had a strong antagonistic effect on moderately susceptible and susceptible varieties with P < 0.001 using Spearman’s coefficient of correlation. An infection level of F. graminearum over 25% showed antagonistic activity against Alternaria spp. under field conditions. Using prothioconazole + tebuconazole as a chemical measure to prevent F. graminearum infection on susceptible varieties can be related to an increase in the contamination level of Alternaria spp., jeopardizing the effectiveness of seed health control measures.