P-542 - Investigating the Genetic Diversity and Mycotoxin Production Potential of Aspergillus niger Isolates from Vidalia Onions in Georgia

Abstract Text: Postharvest rots are major concern for Vidalia onion production in Georgia. Fungal rots due to black mold (Aspergillus niger) are common postharvest due to logistical delays. This results in extended suboptimal storage conditions prior to curing and refrigeration. Although not yet reported on onions, A. niger is also capable of producing mycotoxins such as ochratoxins and fumonisins. This study focuses on investigating the genetic diversity and mycotoxin production potential of Vidalia onion-associated Aspergillus section Nigri isolates. A total of 156 isolates were collected over two years from four locations within the Vidalia onion production zone of Georgia. PCR analysis on the first year’s 55 isolates revealed 42% had the fumonisin biosynthesis gene fum10 and 5% had the ochratoxin A gene ota1. Of the isolates with the fum10 gene, 70% were isolated from culls and only 1 also had ochratoxin genes amplified. Initial whole genome sequencing (WGS) studies of the first 55 isolates generated 35,717 SNPs using the A. niger KJC3 genome as reference. Structure and DAPC analyses revealed that isolates separated based on sample location and onion source. WGS is in progress for all isolates. Continuing analyses of the complete collection will focus on species identification, genomic structural variation, mycotoxin biosynthetic cluster comparisons, quantification of mycotoxin production, and fungicide sensitivity assays. Findings from this investigation will help develop informed extension recommendations to growers on methods of preventing black mold issues in postharvest storage.