Isolation and Identification of Pathogens Causing Mycotoxins in Peanuts (Arachis hypogaea L.)

In Nicaragua, a large volume of peanut (groundnut) grains is produced for export, and the deterioration of peanut grains by fungi is a highly recurrent issue. Fungi belonging to the genera Penicillium, Aspergillus, and Fusarium are very common and pose a great threat because of their saprophytic tendency, as well as their capacity to produce mycotoxins. The objective of this study was to identify the main fungi associated with peanut crops (Arachis hypogaea L.) during the pre-harvest stage. Samples were collected from peanut fields in the León Department, Nicaragua, using sterilized rice traps, which were then taken to the laboratory to isolate and purify mycotoxigenic pathogens. The isolates were identified and characterized morphologically and morphometrically, and peanut grain samples were obtained from the study farms and subjected to aflatoxin analysis for identification and quantification using High-Performance Liquid Chromatography (HPLC). Four mycotoxigenic pathogens were isolated, purified, and identified based on their micro-and macroscopic characteristics: Aspergillus flavus, Aspergillus niger, Penicillium spp, and Fusarium solani; morphometrically, Fusarium solani presented the largest colony diameter. The aflatoxin analysis indicates that only aflatoxin B1 and B2 were found, with the San Antonio farm recording the highest number of total aflatoxins 35.23 μg/kg ± 4.39 μg/kg. All farms where aflatoxins were identified and quantified also presented Aspergillus flavus as a common pathogen. The confirmed presence of these mycotoxigenic pathogens, especially Aspergillus and Fusarium species, underscores the high risk of peanut contamination during the pre-harvest stage in the León region, which represents a serious threat to the quality of grains destined for export.