Morphological and molecular identification of black Aspergillus spp. causing mould disease of Onion

Onion black mold disease mostly occurs post-harvest, affecting bulbs during storage. The main objective of the study is
to identify the black Aspergillus species causing onion black mold disease and determine their mycotoxin production
potential. A fungus infection was realized as a black spore mass on the outer scale leaves. Fifty samples of onions with
black masses were collected to isolate the pathogenic fungi. Eighty-three isolates of black aspergilli species were
identified using morphological and molecular characteristics. Five isolates were recorded according to microscopy of the
conidial structure, comprising A. ellipticus, A. carbonarius, A. japonicus, A. niger, and A. vadensis. Sequence data of the
nuclear Internal Transcribed Spacer (ITS) rDNA was used to build a phylogenetic tree from the 25 sequences comprising
our isolates. The neighbor-joining phylogenetic tree revealed the monophylogenetic relationship between species within
the same section but the polyphylogenetic relationship among species from different sections. The chloroform extracts of
different samples were tested for the presence of mycotoxin using thin layer chromatographic analysis, which includes
the determination of the following mycotoxins: aflatoxin B1, aflatoxin B2, aflatoxin G1, and aflatoxin G2. The results
indicated that aflatoxin was present in all collected samples.