ARS | Publication request: EFFECT OF SPACING AND TIMING ON THE BIOCOMPETITIVENESS OF ATOXIGENIC ASPERGILLUS FLAVUS AGAINST TOXIGENIC STRAINS

Submitted to: Aflatoxin Workshop
Publication Type: Abstract Only
Publication Acceptance Date: October 25, 2004
Publication Date: N/A

Technical Abstract: AF 827 is an excellent strain for monitoring the interactions with either atoxigenic strain or aflotoxigenic strain because the red orange color can be used as a visual score for aflatoxin production and fungal colony growth of the two interacting A. flavus strains can be visually traced by the color of the spores. AFP8, CA 26 and CA35 are atoxigenic isolates, CA 28 is a S type aflatoxigenic isloate. The results indicate that the competing atoxigenic strains do not inhibit either the growth or aflatoxin production of AF827 when the spores are as close as 0.1mm apart (spiral plating) or spotted at least 1 mm apart. It seems that two competing strains in the spore mixtures grow independently and do not interfere the growth or red orange color formation of AF827. AFP8 and CA28 appear to stimulate aflatoxin production of AF827, which can be visualized by the intensity of red-orange color of the fungal colony. When the paired spore mixtures were spotted in the center of PDA plates, sector growth of AF827, AFP8, CA26, CA28 and CA 35 were observed. The inhibitory effect of AFP8 on afatoxin production of CA28 was significantly reduced once the toxigenic strain has started to grow on PDA plates.