MYCOTOXIGENIC POTENTIAL OF ASPERGILLUS-FLAVUS STRAINS ISOLATED FROM GROUNDNUTS GROWING IN ISRAEL

Two hundred strains of the Aspergillus flavus group isolated from grou ndnuts (peanuts) growing in Israel were examined for their ability to produce mycotoxins in potato dextrose (PD) broth. Almost 77% of the is olates produced aflatoxin; aflatoxins B1 and B2 were formed by most of the isolates. Simultaneous production of aflatoxins of groups B and G was detected in only 0.5% of the isolates. Microscopic examination re vealed that 98% of the isolates were A. flavus and only 2% A. parasiti cus. Cyclopiazonic acid (CPA) was detected in 22.5% of the isolates, i ncluding 3.5% that produced only CPA. Sterigmatocystin was detected in only 2% of the isolates and only one isolate produced aflatoxin simul taneously with CPA and sterigmatocystin. The dry weight (DW) of myceli um, 7 days after inoculating the medium, was between 71-110 mg/30 ml m edium in more than 70% of the isolates. A general decrease in the pH w as observed and 75% of the isolates reduced the pH to 4.5 or below. Af ter 14 days, a small increase in DW and an increase in the pH toward n eutrality was observed. On PD agar, 30% of the isolates produced scler otia, including 5% that produced them profusely. No correlation betwee n mycelial growth, changes in pH of the medium, sclerotium formation, and aflatoxin accumulation could be observed. The mycotoxigenic potent ial of the A. flavus strains isolated from groundnuts seems to be rela tively high and may present a potential threat to human and animal hea lth.