Antifungal Activity of Various Bacterial Species against Botrytis cinerea, Fusarium pallidoroseum, and Fusarium moniliforme

Introduction: Botrytis cinerea, Fusarium pallidoroseum and Fusarium moniliforme are fungal plant pathogens that can cause significant produce loss, both pre- and post-harvest.  Typical fungal control requires the application of chemical fungicides that may negatively impact the environment and human health.  Alternatively, the use of biological control agents has shown potential for fungal control; however, commercial use is limited.  Due to development of fungicide resistance in pathogen populations and the demand for more environmentally sustainable solutions, further research on the identification and development of biocontrol methods that could extend produce shelf life is merited.

Purpose: The purpose of this study was to screen 22 bacterial isolates for antifungal activity against Botrytis cinerea, Fusarium pallidoroseum, and Fusarium moniliforme.

Methods: Bacterial isolates were individually spot-inoculated onto Tryptic Soy Agar, Potato Dextrose Agar, or Lactobacillus MRS agar, depending on isolate growth requirements, and a 9 mm plug of fungal-colonized agar was placed onto the center of the isolate-inoculated plate.  Plates were incubated at 24°C for 10 days.  Fungal growth was evaluated daily, beginning on Day 3, by measuring the diameter of the fungal colony.

Results: Nine of the 22 isolates, including Bacillus megaterium, Bacillus coagulans, Bacillus amyloliquefaciens, and Serratia plymuthica, inhibited all three fungi; fungal inhibition ranged from 51 - 62% for B. cinerea, 60 - 68% for F. pallidoroseum, and 40 - 61% for F. moniliforme.  Three Lactic Acid Bacteria species – Lactobacillus plantarum, Pediococcus acidilactici, and Pediococcus pentosaceus – and three Bacillus species – Bacillus thiaminolyticus, Bacillus firmus, and Bacillus clausii – inhibited B. cinerea only by 30 - 56%.  Seven isolates showed no suppression of any of the three fungi.

Significance: This study identified nine bacterial isolates capable of suppressing the growth of B. cinerea, F. pallidoroseum, and F. moniliforme in vitro.  Evaluation of antifungal efficacy on produce (in planta) is required to determine an isolate’s potential use as a biocontrol agent.