Macro and micromorphological characterization of different Aspergillus isolates

Aflatoxin contamination of groundnut (Arachis hypogaea L.) is a serious problem through out the world which leads to significant economic losses every year. Invasion of groundnut seed by the aflatoxin-producing fungi Aspergillus flavus and Aspergillus parasiticus, and subsequent contamination with aflatoxins, may occur at any stage during the postharvest handling of its seeds, which necessitates development of suitable procedures for identification of the pathogen. An identification key for different fungal isolates was developed on the basis of macromorphological features viz. diameter, elevation, margins, texture of the colony as well as colour of the colony from the top and reverse of the plate, extent of sporulation (low, medium and heavy) and presence and absence of radial sulcation after seven days of culture. Microscopic features such as shape and size of conidia, vesicles and hyphae have also been included in the key. On the basis of this key different Aspergillus isolates viz.A. Niger, A. fumigatus, A flavus, A. terreus, A. parasiticus, A. oryzae could be differentiated thereby showing a potential for detection of aflatoxigenic fungi in the infected lot.