Occurrence of Blue Mold on Tomato Caused by Penicillium oxalicum in Korea

A blue mold on tomato fruit caused by Penicillium oxalicum occurred sporadically in a greenhouse at Gyeongsangnam-do Agricultural Research and Extension Services. Infection usually occurred through wounds or cracks on the fruits. Symptoms began with water soaking lesions, then became watery and softened eventually. Colony of the causal fungus was white at the early growing stage, turned green on Czapek yeast extract agar and malt extract agar. Conidia were ellipsoidal in shape and $2-6{\times}2-4{\mu}m$ in size. Stipes were septate, smooth, thin walled, and $90-280{\times}3-4{\mu}m$ in size. Penicilli were mostly biverticillate. Ramuli were 1-3 groups, smooth, and $10-16{\times}2-3{\mu}m$ in size. Rami were 1-2 groups and $6-30{\times}2-4{\mu}m$ in size. Metulae were 2-3(5) verticils, smooth, and $12-20{\times}3-4{\mu}m$ in size. Phialides were 5-7 verticilate, ampulliform to cylindroidal, smooth, and $8-12{\times}2-3{\mu}m$ in size. Optimum temperature for growth was about $25^{\circ}C$. Pathogenicity of the fungus was proved on tomato fruit according to Koch's postulation. On the basis of mycological and pathological characteristics, the fungus was identified as P. oxalicum Currie & Thom. This is the first report of the blue mold on tomato fruit caused by P. oxalicum in Korea.