Analysis of genetic and aflatoxin diversity among Aspergillus flavus isolates collected from sorghum seeds
S T Divakara1, M Aiyaz1, G G Moore2
1Department of Studies in Biotechnology, University of Mysore, Mysore, Karnataka, India.
Abstract:
Thirty-four Aspergillus flavus isolates were recovered from sorghum seeds sampled across five states in India. Our study included (1) species confirmation through PCR assay, (2) quantification of total aflatoxin concentrations by the indirect competitive-ELISA (ic-ELISA) method, and (3) analysis of molecular diversity among the A. flavus isolates using β-tubulin, ITS, and ISSR markers. Among the isolates studied, 28 were found to be positive for the production of aflatoxins. ITS and β-tubulin phylogenetic analysis segregated the A. flavus sample population into two major groups or clades with little to no subdivision based on geography. In contrast, ISSR analysis also separated the A. flavus isolates into two main clusters, showing a distance of 0.0-0.5, with one cluster exhibiting a high level of diversity though no geographic or chemotype subdivision could be observed. The majority of sampled A. flavus isolates were highly toxigenic, and also highly diversified in terms of toxin-producing potential in-vitro. Genetic diversity among the sorghum isolates of A. flavus further warrants the development of appropriate farming management practices as well as improved aflatoxin detection measures in India.
Insights
Most Indian Aspergillus flavus strains from sorghum seeds produce aflatoxins and show significant genetic diversity. This highlights the need for better management and detection strategies to control aflatoxin contamination.
Area of Science:
- Agricultural Science
- Mycology
- Food Safety
Background:
- Aspergillus flavus is a common fungal contaminant of crops like sorghum.
- Aflatoxins produced by A. flavus pose significant risks to food safety and human health.
- Understanding the diversity of A. flavus is crucial for developing effective control measures.
Purpose of the Study:
- To confirm Aspergillus flavus species from sorghum seeds using PCR.
- To quantify aflatoxin production in A. flavus isolates.
- To analyze the molecular diversity of A. flavus isolates using genetic markers.
Main Methods:
- Species confirmation via Polymerase Chain Reaction (PCR) assay.
- Aflatoxin quantification using indirect competitive-Enzyme-Linked Immunosorbent Assay (ic-ELISA).
- Molecular diversity analysis using beta-tubulin, Internal Transcribed Spacer (ITS), and Inter Simple Sequence Repeat (ISSR) markers.
Main Results:
- Twenty-eight out of thirty-four Aspergillus flavus isolates were positive for aflatoxin production.
- Phylogenetic analysis of ITS and beta-tubulin revealed two major clades without clear geographic subdivision.
- ISSR analysis also showed two main clusters, with one cluster exhibiting high diversity but no geographic or chemotype subdivision.
Conclusions:
- The majority of sorghum-associated Aspergillus flavus isolates are highly toxigenic and genetically diverse.
- Significant genetic diversity among A. flavus isolates necessitates improved agricultural management practices.
- Enhanced aflatoxin detection methods are crucial for food safety in India.
