First report of Aspergillus awamori as a fungal pathogen of garlic (Allium sativum L.)

Abstract

Garlic (Allium sativum L.) is one of the oldest horticultural crops and an important element for cuisines worldwide, especially in Korea. After isolating several black aspergilli from brownish lesions with black spores on garlic bulbs, we identified a representative isolate GL-125 through molecular analysis of its internal transcribed spacer (ITS)1-5.8S rRNA-ITS2 region, β-tubulin gene, and calmodulin gene. Morphological features of GL-125 were also compared with those of the Aspergillus awamori type strain NRRL 4948T. As a result, GL-125 was identified as A. awamori by neighbor-joining and maximum-likelihood methods with the examined gene sequences. The macro-morphological (colony growth and color) and micro-morphological (stripes, vesicles, metulae, phialides, and conidia) features of GL-125 were also similar, compared with those of NRRL 4849T. Furthermore, we conducted pathogenicity tests for GL-125 and NRRL 4948T against garlic cloves, using pin-prick inoculation with spore suspensions. Both GL-125 and NRRL 4948T were pathogenic on garlic cloves producing brown to pinkish sunken, water-soaking lesions with white mycelia and black spores in the center. These isolates were successfully re-isolated from the lesions, thereby fulfilling Koch's postulates, whereas no fungal mycelia were isolated from water-inoculated cloves (control). The identities of the re-isolated mycelia were re-confirmed by sequence analyses of the previously examined genes. To the best of our knowledge, this is the first report of A. awamori as a fungal pathogen of garlic.