Vol. 10, Issue 10 (2021)

Author(s):
AG Meena and V Paranidharan

Abstract:
Grapes is the one of the most important fruit crop which is well adapted to the tropical and subtropical agro-climatic conditions. Ochratoxin A (OTA) is an effective carcinogenic mycotoxin produced by Aspergillus fungi contaminating on grapes and grapes by-products like fresh grapes, raisin and wine. In the present study, survey was conducted in local markets of various districts in Tamil Nadu to identify the presence of OTA producing fungi on fresh grapes, black raisin and raisin. The mycoflora assessment identified that 90 per cent of all the three samples were contaminated with Aspergillus niger, Aspergillus flavus, Rhizopus spp. and Penicillium spp. whereas the maximum A. niger colonies were produced in black raisin (25.66 ± 0.57) sample NgBRS2 collected from Nilgris district and grape (5.53 ± 0.44) sample TGM2 collected from Theni district. The morphological studies on confirmation of the maximum colony producing A. niger isolates (MRL1, NgBRS2, TGM2) revealed that the growth pattern of the colony, colour of mycelia was similar and the microscopic observations showed that the three isolates of A. niger have septate hyphae bearing dark conidiophore with globose vesicle producing acropetally dark brown coloured chain of conidia and whereas the metulae, phialides and vesicle were covered with mass of conidia. The maximum colony producing virulent strain NgBRS2 was subjected to molecular identification using the ITS 1 and ITS 4 transcribed region amplified 18S-28S rRNA gene fragment of A. niger at ~570 bp and the accession number for nucleotide sequence was obtained (OK284581). The HPLC analysis on OTA detection showed the potentiality of NgBRS2 A. niger strain in OTA production. The study provides the importance of potential carcinogenic fungal and OTA contaminations on grapes and its by-products in markets of Tamil Nadu which may oblige the future research on ochratoxigenic fungi and OTA detoxification.