The occurrence of the aflatoxin (AF)-producing strains of Aspergillus flavus was surveyed on 11 retail samples of five kinds of other type edible nuts (mostly tree nuts) and, for the comparing purpose, on 10 samples of peanuts. All samples were imported from various countries in 1981 and 1983. A. flavus was present in 128 kernels (46.5%) out of the tested 275 kernels of the other type edible nuts, in contrast to 49.6% infection of peanuts. A total of 91 isolates of A. flavus were selected and examined on their AF producibility; of 44 isolates of A. flavus from the other type edible nuts, 37 (84.1%) were shown to produce AF on defatted peanut meal medium, while 43 (91.5%) of 47 isolates of A. flavus from peanuts were positive. Most aflatoxigenic isolates from the other type edible nuts were identified as A. flavus subsp. flavus var. flavus, and 4 isolates of these, which were isolated from Hawaiian macadamia nut, produced high levels of AF G1 and G2 than those of AF B
1 and B
2. On the contrary, most isolates in the peanuts imported from U.S.A. produced AF B and G, and were identified as A. flavus subsp. parasiticus var. parasiticus. This survey revealed that the imported edible nuts including almond, chick-pea, hazelnut, macadamia nut and pistachio were significantly infected with aflatoxigenic A. flavus.
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