Morphological and molecular characterization of Aspergillus niger causing postharvest rot of white yam (Dioscorea rotundata Poir)

Abstract

Aspergillus niger is an important plant pathogen producing fumonisin B₂ mycotoxin in white yam. The use of morphological characteristics is not complete in identification of plant pathogens, hence both morphological and molecular approaches were used to investigate Aspergillus niger in this study. Morphological identification was based on nature of fruiting body production. DNA sequence BLAST was conducted using BioEdit sequence alignment MEGA 6. Fragments of the ITS region were amplified with the primers TS1-5.8S-ITS2 and phylogeny inferred using maximum-likelihood method. Replicate trees in taxa cluster were obtained using bootstrap test with 1000 replications. Morphological analysis identified 12 isolates as Aspergillus niger and three others as A. brasiliensis, A. tubingensis and Aspergillus sp. Molecular identification validated 12 of the isolates identified in morphological assay, while phylogenetic analysis clustered the isolates into three. Information from this study would provide useful guide in breeding for resistance to A. niger.

Keywords:

• Bootstrap
• ITS region
• mycotoxin
• phylogenetic analysis
• white yam

Acknowledgements

Authors are grateful to Mr Esimehhuai Donatus and Mrs Olufunmilola K. Odeh, Principal Laboratory Technologists in the Departments of Botany and Crop Protection and Environmental Biology, respectively at the University of Ibadan, Nigeria who assisted in the production of micrograph of isolates used in this study.

Disclosure statement

No potential conflict of interest was reported by the author(s).