Diversity and management of aflatoxin producing Aspergillus spp. in groundnut
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Date
2019
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Punjab Agricultural University, Ludhiana
Abstract
Survey was conducted in the major groundnut growing states of India to collect the groundnut samples to detect the aflatoxin contamination. Out of 53 samples collected, 32 isolates were isolated, among them six were of Aspergillus niger, which were proved to be nontoxic by ammonia vapour test. Other 26 isolates were carried for further identifications. Through this study, all 26 isolates were proved to be of A. flavus. Based on the morphological quantitative characters like growth rate, size of the conidia and conidiophores, all the isolates were classified into five clusters by multivariate cluster analysis at 93.13 per cent similarity level. Further, all the isolates were assessed with the qualitative tests to detect the toxigenic strains. In bioassay eight isolates were proved toxigenic and isolate afl 26 from Telangana was the most toxigenic. From ammonia vapour test, it was proved that 14 isolates were toxigenic, among these afl 26 isolate from Telangana was again proved highly toxic. All the isolates which proved toxic were further carried to quantify the aflatoxin production through HPLC. According to this, nine out of 17 isolates were proved to produce aflatoxin B2 above detectable levels, which were above the safe limits of Indian and USFDA standards. The field experiments were conducted to evaluate the effects of cultural practices viz., date of sowing, soil amendments like FYM & lime and bioagents like Trichoderma harzianum & Pseudomonas fluorescens on aflatoxin production. It showed that early sowing of crop in April month reduces the collar rot infection, but it aggravates the aflatoxin producing fungi. Application of FYM and lime reduces the aflatoxin contamination and meanwhile increased the pod yield of the groundnut. Whereas bioagents also reduced the aflatoxin contamination. In another experiment to evaluate the effect of storage conditions on aflatoxin production, higher aflatoxin contamination was found in the pods (inoculated with toxigenic strain afl 26) stored at 35°C with >20 per cent moisture content, hence it is recommended to store the pods at 15°C with 12-15 per cent moisture content.
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