Identification of toxigenic fungal species associated with maize ear rot: Calmodulin as single informative gene

Abstract

Accurate identification of fungi occurring on agrofood products is the key aspect of any prevention and pest management program, offering valuable information in leading crop health and food safety. Fungal species misidentification can dramatically impact biodiversity assessment, ecological studies, management decisions, and, concerning toxigenic fungi, health risk assessment, since they can produce a wide range of toxic secondary metabolites, referred to as mycotoxins. Since each toxigenic fungal species can have its own mycotoxin profile, a correct species identification, hereby attempted with universal DNA barcoding approach, could have a key role in mycotoxins prevention strategies. Currently, identification of single marker for species resolution in fungi has not been achieved and the analysis of multiple genes is used, with the advantage of an accurate species identification and disadvantage of difficult setting up of PCR-based diagnostic assays. In the present paper, we describe our strategy to set up a DNA-based species identification of fungal species associated with maize ear rot, combining DNA barcoding approach and species-specific primers design for PCR based assays. We have (i) investigated the appropriate molecular marker for species identification, limited to mycobiota possibly occurring on maize, identifying calmodulin gene as single taxonomically informative entity; (ii) designed 17 sets of primers for rapid identification of 14 Fusarium, 10 Aspergillus, 2 Penicillium, and 2 Talaromyces species or species groups, and finally (iii) tested specificity of the 17 set of primers, in combination with 3 additional sets previously developed.

Keywords: Aspergillus; Calmodulin; Fungi; Fusarium; Penicillium; Species-specific primers; Talaromyces.