Selectivity of chemical and biological foliar treatments on the phyllosphere communities of bacteria and fungi antagonistic to Fusarium verticillioides in maize

Abstract

Maize grain production in the tropics is affected by Fusarium verticillioides, leading to significant losses in yield and quality. Fungicides are commonly used to control foliar diseases and increase grain yield, but have limited efficacy against F. verticillioides and may even stimulate the fungus to produce mycotoxins. Biocontrol can reduce F. verticillioides populations and fumonisin, but little is known about the resulting microbial interactions on the phylloplane and their relationship with F. verticillioides. This study aimed at evaluating the impact of different foliar treatments on the cultivable phylloplane community of fungi and bacteria and their potential in controlling F. verticillioides in maize. Results showed that two sprays of Bacillus subtilis BIOUFLA2 increased the percentage of native phylloplane antagonist bacteria and fungi against F. verticillioides by 25.0% and 27.3%, respectively, compared with the water control. However, two sprays with a triazole + strobilurin fungicide at different phenological stages in maize reduced such antagonistic communities. From field trials, 34 bacteria and 13 fungi from the phylloplane were selected for their inhibitory activity against F. verticillioides, with most coming from the exclusive treatment with BIOUFLA2. The study also revealed that the biocontrol agent‐recruited phylloplane indigenous lineages act through antibiosis, competition, and parasitism. Therefore, the adoption of biocontrol to limit F. verticillioides population build‐up not only has a direct activity on the pathogen but also recruits fungal and bacterial antagonists that may act additively or synergistically with the applied biocontrol agent.