Penicillium polonicum: Causal agent of onion bulb decay in storage

Abstract

Penicillium polonicum is an economically important fungal species with a wide host range which includes cereals, peanuts, onions, dried meats, citrus, apple, and yam tubers. Onion bulbs cv. Meranto with blue mold symptoms have been collected, in a storage facility in Stara Pazova during 2013. Fungal isolates were obtained from decayed bulbs and their pathogenicity was proven after wound inoculation of healthy onion bulbs. On differential media the isolates formed velutinous, green blue colonies with a white margin and a characteristic odor. The isolates grew at 5 C while no growth was observed at 37 C. Isolates produced cyclopiazonic acid and other alkaloids. Conidiophores of isolates were terverticillate, stipes were septate with smooth to finely roughened walls, and phialides were ampulliform. Conidia were globose to subglobose, smooth-walled, and borne in columns. The nucleotide sequences of amplified products (~800 bp) for partial β-tubulin gene showed in MegaBLAST search analysis a 99% similarity with several sequences of P. polonicum. Based on morphological and molecular features isolates obtained from stored onion were identified as P. polonicum.