Characterization of Aspergillus species associated with commercially stored triphala powder

Abstract

About 82 triphala powder samples were analyzed for the association of different fungi. Results reveal the predominance of Aspergillus as the major genera with six predominant species namely, A. niger, A. flavus, A. fumigatus, A. terreus, A. nidulans and A. amstelodami. Therefore, these six isolated Aspergillus species were characterized morphologically, microscopically and molecularly. In addition, an attempt was made to characterize the frequently occurring aflatoxigenic and non toxic Aspergillus species at molecular level along with their identification. Morphological variability was detected among isolates in regard to colony morphology, conidia colouration, exudates and reverse, colony texture and growth rate. Microscopic characteristics for the identification were conidial heads, stipe, colour and length of vesicles, shape and seriation, metulae covering, conidia size and shape. For molecular characterization, internal transcribed spacer (ITS)-4, a universal fungal primer was utilized. Differences in band patterns and number of bands obtained after polymerase chain reaction (PCR) amplification clearly differentiates between the Aspergillus species. Results also reveal that only A. flavus showed amplification with all the three aflatoxigenic primers apa-2, ver-1 and omt-1, which means that only A. flavus was identified as aflatoxigenic and other Aspergillus species as non-toxigenic after PCR analysis. Hence, morphological, microscopic and molecular methods are important for the complete identification of important Aspergillus species and other fungi isolated from stored commodities.

Key words: Aspergillus, triphala, identification, macroscopic and microscopic characteristics, molecular methods.