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Fusarium verticillioides is pathogenic to maize and mycotoxin-producer, causing yield losses, feed and food contamination, and risks to human and animal health. Endophytic (ISD04 and IPR45) and epiphytic (CT02 and IM14) bacteria from maize silks were tested in vitro and greenhouse against F. verticillioides and for hydrolytic enzyme production (cellulase, pectinase, protease, lipase, and chitinase). The strains were assigned as Achromobacter xylosoxidans (ISD04), Pseudomonas aeruginosa (IPR45), and Bacillus velezensis (CT02 and IM14) by 16S gene sequencing. All strains showed antifungal activity in vitro with inhibition values from 58.5–100%; they changed hyphae morphology and inhibited the conidial germination by up to 100% (IPR45). The four strains produced at least one enzyme with antifungal activity. The microbiolized seeds reduced the fungal development in stored grains and stalk rot severity in the greenhouse by 72.6% (ISD04). These results highlight the potential of these strains as biocontrol agents against F. verticillioides

The mycotoxigenic fungus Fusarium verticillioides is the primary maize pathogen and causes the maize stalk and ear rot diseases with significant economic losses. Furthermore, the excessive use of fungicides to control F. verticillioides constitutes threats to the environment and human health. Thus, sustainable alternatives such as biological control are needed to minimize the hazards associated with the current method. Although much is known about the vulnerability of the maize silks as a gateway for several fungal pathogens invading the developing grains, studies on the chemical properties of silk extracts and their resident microbiota are scarce. This study isolated and characterized bacteria and fungi that colonize the maize stigma to assess new potential biocontrol agents. The samples were collected from maize fields in the Brazilian localities of Sete Lagoas-MG, Sidrolândia-MS, Sertaneja-PR, and Goiânia-GO. One hundred sixty-seven microorganisms were isolated, 46% endophytic and 54% epiphytic. First, the antagonist activity was evaluated by the agar disc diffusion method performed in triplicate, and 83% of the isolates showed antagonist activity against F. verticillioides. Then, the 42 most efficient isolates were identified based on the partial sequencing of the bacterial 16S rRNA gene and fungi ITS region. The bacteria belong to the genera Bacillus (57.1%), Burkholderia (23.8%), Achromobacter (7.1%), Pseudomonas (2.4%), and Serratia (2.4%), while the fungi are Penicillium (2.4%), Candida (2.4), and Aspergillus (2.4%). The results showed that microorganisms from maize stigma might represent new promising agents for F. verticillioides control.