Olabisi Onabanjo University, Nigeria
Title: Genetic Diversity of Ochratoxigenic Aspergillus Section Nigri, Using RAPD AND VCG Techniques
Benjamin Thoha THOMAS, a lecturer II in the Department of Microbiology,
Olabisi Onabanjo University, Ago Iwoye, Ogun State, Nigeria is an enthusiastic, self motivated and methodical researcher who major in molecular biology, microbial genetics and bioinformatics. His major trust is in post transcriptional gene silencing, bioinformatic analysis of putative transcriptional factors controlling gene expression, phylogeny construction and reconstruction as well as understanding the genetic diversity of ochratoxigenic fungi using different molecular markers. Thomas has received tremendous training in cytotaxonomy, current trends in genetics, molecular systematics, bioinformatics, microbial genomics and proteomics, RAPD, SDS-PAGE and interpretation of sequenced data to address public health problems. He has also conducted (with other researchers) researches pertaining to the understanding of the molecular mechanism of antibiotic resistance and plasmid mediated resistance. His latest work is on the metagenomic analysis of ochratoxigenic fungi isolated from processed Manihot esculenta (Cassava flakes). Thomas as he is fondly called had his first and second degree in Microbiology from the same institution where he is currently working and very recently defended his Ph.D. in Cell Biology and Genetics (Molecular) at the University of Lagos, Akoka, and Lagos.
This study evaluates the genetic diversity of ochratoxigenic Aspergillus section Nigri using RAPD and VCG techniques. Results obtained revealed OPX 07 as the most informative of the tested RAPD markers generating 12 polymorphic bands while the least bands were generated by OPR 19. Of the 40 Aspergillus section Nigri (20 each of Aspergillus niger and Aspergillus carbonarius), 22 VCGs and 27 RAPD haplotypes were delineated. The two techniques demonstrated similar resolution except in few cases where the RAPD technique further sub divided some VCGs into simpler haplotypes. The average percentage of variable VCG and RAPD reactions were 25 and 50% in that order of sequence while 75 and 50% of the isolates were resolved as same isolates by these techniques respectively. It was also found that the Simpson index of genetic diversity approached one for the isolates from the four geopolitical zones of Ogun State, Nigeria with the mean genetic diversity within isolates (GL) contributing significantly approximately 89% of the total diversity observed within the isolates (F=22.23, p<0.05). The remaining 11% of variation could only be allotted to diversity among isolates (GS). On the whole, the total genetic diversity (HT) was found to be approximately 48%. In conclusion, RAPD markers provided better resolution than the classical VCG typing technique.