Toxigenic and Non-toxigenic Aspergillus Flavus Strains Isolated from Candlenut (Aleurites Moluccana) in North Sumatera

Abstract

: This study was conducted to investigate contamination of Aspergillus flavus strains in distribution chains of candlenut ( Aleuritaes moluccana ). Dried-stored unshelled candlenut were collected from farmers, collectors and distributors at 3 Ragencies in North Sumatra (Regency of Karo, Deli Serdang and Langkat) during harvest period (February to April 2019). One and half kilogram of candlenut was taken from each of the distribution chains. Kernel moisture content were determined by distillation. Population each of A. flavus strain was enumerated by a dilution method followed by a pour plate in dichloran 18% glycerol agar (DG18) medium. Culture method in agar medium containing 10% coconut milk was used to determine toxigenicity of A. flavus . Their toxigenicity also was determined molecularly using specific primers for amplifying regulatory ( aflR ) and structural genes ( nor-1, ver-1, omt-1 ) that determine aflatoxin biosynthesis. Results showed that moisture content of candlenut kernels at the level of farmers, collectors and distributors in Regency of Karo, Deli Serang and Langkat was above 5%. A total of 38 strains of A. flavus were isolated and 37 of the strains were toxigenic (aflatoxin producers). The average of A. flavus population (cfu/g) on candlenut at farmers was the lowest and the highest population was at distributor chain.