2021 Volume 71 Issue 1 Pages 9-12
In this study, to evaluate the newly improved technique of the dichlorvos - ammonia (DV-AM) method, AF-producing fungi in an experimental field of Tsukuba were screened. The DV-AM method is the detection technique of the AF-producing fungi by judging from color of the reverse colony: the red (positive) or white (negative), and recently higher sensitivity is achieved by improvement of the nutrient medium composition. Soil samples were collected from 20 spots in an experimental field in July and screened for AF-producing fungi by the improved DV-AM method. As a result, four of positive isolates were isolated from three spot samples from 20 spots. TLC and HPLC assay revealed AF production of all four isolates. The sequence analysis of the calmodulin gene domain and microscopic observation were performed in two of four isolates, which revealed that both strains were Aspergillus flavus. While both were identified as A. flavus, the morphological and physiological characteristics such as production of sclerotia and AF production were different. Thus, the improved DV-AM method was evaluated to detect AF-producing fungi from field soil, and it was also shown that different types of A. flavus strains existed in the same field.
