Penicillium brasilianum as a novel pathogen of onion (Allium cepa L.) and other fungi predominant on market onion in Korea

• The occurrence of fungi on market onion bulbs was investigated.
• Aspergillus, Penicillium, Fusarium, and Rhizopus were predominant.
• Aspergillus awamori, Fusarium oxysporum, Penicillium brasilianum, and Rhizopus oryzae were the predominant species.
• The fungal species were pathogenic on onion bulbs.
• This is the first report that P. brasilianum is a fungal pathogen of onion crop.

Onion (Allium cepa L.) is an important vegetable crop in Korea, but its production is severely affected by fungal pathogens during plant growth and bulb storage. We investigated the occurrence of fungi on market onion bulbs; identified the predominant fungal species based on the internal transcribed spacer region, β-tubulin region, and elongation factor 1-α gene sequences; and tested the pathogenicity of each predominant fungal species in onion bulbs. The genera Aspergillus (63.9%), Penicillium (15.5%), Fusarium (6.4%), Rhizopus (5.2%), and others (9.0%) were detected in the samples. Among these genera, Aspergillus awamori, Fusarium oxysporum, Penicillium brasilianum, and Rhizopus oryzae were identified as the predominant species. All of the fungi tested could infect both the inner layers and outer surfaces of onion bulbs and be re-isolated from the infected tissues. To our knowledge, this is the first report that P. brasilianum is a fungal pathogen of onion bulbs.