Aflatoxins are carcinogenic, teratogenic and immunosuppressive secondary metabolites produced by Aspergillus flavus and Aspergillus parasiticus. Aflatoxin contamination of peanut is one of the most important constraints to peanut production worldwide. In order to develop an eco-friendly method of prevention of A. flavus infection and aflatoxin contamination in peanut, aqueous extracts obtained from leaves of 30 medicinal plants belonging to different families were evaluated for their ability to inhibit the growth of A. flavus in vitro. Among them the leaf extract of zimmu (Allium sativum L. · Allium cepa L.) was the only one that showed antifungal activity against A. flavus and recorded 73% inhibition of A. flavus growth. The antifungal activity of the zimmu extract was significantly decreased upon dialysis with a dialysis membrane having molecular cut off 12 kDa or autoclaving at 121°C for 20 min or boiling at 100°C for 10 min and recorded inhibition of 52, 16 and 21%, respectively. When A. flavus was grown in medium containing zimmu extract the production of aflatoxin B 1 (AFB 1 ) was completely inhibited even at a concentration of 0.5%. When AFB 1 was incubated with zimmu extract a complete degradation of AFB 1 was observed 5 days after incubation. When the roots of zimmu were incubated in water containing 70 ng of AFB 1 /ml, a reduction (by 58.5%) in AFB 1 concentration was observed 5 days after incubation. A significant reduction in the population of A. flavus in the soil, kernel infection by A. flavus and aflatoxin contamination in kernels was observed when peanut was intercropped with zimmu. The population of the fungal antagonist, Trichoderma viride in the zimmu-intercropped field increased approximately twofold.

A total of seventeen isolates of Aspergillus flavus from maize were collected from different agro-ecological zones of Tamil Nadu, India. The isolates were tested for their ability to produce aflatoxin B 1 (AFB 1 ) in vitro by indirect competitive enzyme-linked immunosorbent assay (ELISA). The amount of AFB 1 produced by the isolates of A. flavus ranged from 1.9 to 206.6 ng/ml. Among the various isolates of A. flavus, the isolate AFM46 produced the highest amount of AFB 1 . DNA was extracted from A. flavus isolates and their molecular variability was investigated by using restriction fragment length polymorphism (RFLP) analysis of the PCR-amplified internal transcribed spacer (ITS) regions of ribosomal DNA. PCR amplification with ITS1 and ITS4 primers resulted in the amplification of a product of approximately 600 bp. Digestion of the PCR products with the restriction enzymes EcoRI, HaeIII and TaqI produced fragments of different sizes. Analysis of the genetic coefficient matrix derived from the scores of RFLP profiles showed that minimum and maximum per cent similarities among the tested A. flavus strains ranged from 0 to 88%. Cluster analysis using the unweighted pair-group method with arithmetic average (UPGMA) clearly separated the isolates into five groups (group I-V) confirming the genetic diversity among the A. flavus isolates from maize.

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Aflatoxins, a group of mycotoxins mainly produced by Aspergillus flavus and A. parasiticus, have adverse health effects on humans and livestock that ingest aflatoxin-contaminated food products and feeds. To secure the safety of food and feed, regular monitoring of aflatoxin levels is necessary. In order to understand the magnitude of aflatoxin contamination, a survey was conducted in different agro-ecological zones of Tamil Nadu, India and 242 samples consisting of pre-and post-harvest maize kernels, food products, poultry and livestock feeds were collected from farmers' fields, poultry farms, retail shops and supermarkets and analyzed for aflatoxin B 1 (AFB 1 ) contamination by enzyme-linked immunosorbent assay (ELISA) using antiserum raised against aflatoxin B 1 -Bovine serum albumin (AFB 1 -BSA). The results indicated that 61.3% of the maize kernel samples were contaminated with AFB 1 and the levels of AFB 1 in 26% of the pre-and post-harvest maize kernels exceeded 20 µg/kg. The highest level of AFB 1 (245 µg/kg) was recorded in post-harvest maize kernel samples. In food products AFB 1 was detected only in two samples out of 30 samples tested.Furthermore, the levels ranged from 0.6 to 3.7 µg/kg. In poultry feeds, AFB 1 was detected in 30 out of 53 samples and the levels ranged from 0.7 to 31.6 µg/kg. Among the 40 livestock feed samples evaluated 29 samples were contaminated with AFB 1 at level ranging from 1.8 to 244.9 µg/kg.

The effect of triadimefon (TDM) a triazole compound on antioxidant potential and eugenol content was studied in Ocimum tenuiflorum L. The plant was subjected to 15 mg/l TDM by soil-drenching on 50th, 70th and 90th days after planting (DAP). Analyses were carried out on 60th, 80th and 100th DAP. Both enzymatic and nonenzymatic antioxidant potential estimation was carried out. The non-enzymatic antioxidant viz ascorbic acid, a-tocopherol and reduced glutathione were found to increase under triadimefon treatment. The antioxidant enzyme like superoxide dismutase, ascorbate peroxidase and catalase activities showed significant increase in TDM treatment. Triazole-treated plants yielded more eugenol (a major component of Ocimum-essential oil) in comparison to control. The study evidenced that TDM residues could be detected in the upper soil layer only and does not accumulate in the soil. These preliminary results suggest that TDM may be useful to increase the antioxidant content in medicinal plants and also to act as an elicitor to enhance the production of secondary metabolites of medicinal plants.