A new species of Penicillium section Ramosa from Tunisian Apples

Abstract

One of the limiting factors that influence the fruits economic chain value is the relatively short shelf-life period caused by fungal infections. The symptoms of fungal infection may be observed at different times but many fungi may remain dormant for varying periods until post-harvest favorable conditions become available for their development. In a mycotoxin contamination survey of apples from markets in Tunisia, 54 Penicillium strains were isolated. However, two isolates could not be assigned to any described species based on morphological and molecular phylogenetic analyses. The aim of this study was the characterisation and description of this new putative species. For morphological analyses, MUM 17.62 and MUM 17.80 were inoculated in triplicate in CYA, YES, G25N, CSN and MEA media and incubated in the dark at 25 ºC for 7 days. CYA plates were also incubated at 30ºC and 37ºC. Colony size was measured and for microscopy analysis fungi grown in MEA was used. Multilocus sequence analysis (MLSA) was performed through comparison of partial β-tubulin (benA), calmodulin (cmd) and nuclear ribosomal internal transcribed spacer (ITS) region with sequences available in GenBank derived from type strains of Penicillium species. All the sequences were aligned and phylogenetic trees were assembled using MEGA. For MUM 17.62 and MUM 17.80 morphologically, the colonies growth was very restricted in the different media. No growth was observed on CYA at 30 ºC and 37 ºC. The strains show slight differences in green colour. Both present velutionous, sulcate and irregular colonies in MEA. Microscopically, the conidiophores are biverticillate and conidia ellipsoidal. MLSA revealed that the two strains belong to Penicillium section Ramosa. Fingerprinting using the M13 microsatellite showed that the two strains are not clones and analysis of the isoepoxydon dehydrogenase (idh) gene revealed that they lack the ability to produce patulin. In summary, in terms of multigene phylogeny the two strains are closely related to P. lenticrescens, P. chroogomphum and P. soppii of the section Ramosa however they well-circumscribe a sp. nov. coined as Penicillium tunisinus.