Molecular Diversity of <i>Fusarium oxysporum</i> and <i>Geotrichum candidum</i> Isolated from Two Tomato Varieties Commonly Consumed in Some Southwestern Town in Nigeria

Abstract

Fusarium oxysporum and Geotrichum candidum , which are among important pathogens of Solanum lycopersicum L. (Tomato), are sometimes misidentified during morphological misidentification. The study was carried out to evaluate molecular diversity of F . oxysporum and G . candidum isolated from two tomato varieties obtained from Akure, Ilorin and Ibadan, Nigeria. The tomato samples were collected and brought back to the laboratory for fungal isolation. Isolation of the pathogens were done following standard procedures. DNA extraction from pure cultures of the pathogens was done at the Centre Laboratory of University of Ibadan. Genetic relationships among the organisms were also estimated by constructing a Dendrogram through UPGMA using the Mega6 Software and genetic distance was computed also using the Mega6 Software. Five strains of F . oxysporum and seven strains of G . candidum were identified. Percentage similarity of the pathogens with those in GenBank was 99.17 % - 100.00% for F . oxysporum and 98.48 % - 100.00% for G . candidum . The T-01 marker showed the lowest major allele frequency of 0.0833, while T-10 marker has the highest value for major allele frequency of 0.6667 and an average value of 0.3958. Evolutionary relationship showed that the two strains of G . candidum (MN650247 and MN650250) were similar. The three strains of F . oxysporum (MN650246 and MN650248, MN650245 and MN650253) were also similar. Genetic distances among pairs of the fungal strains ranged from 0.12 to 6.30 in pairwise fashion, with an average of 1.32. Evolutionary relationship or closeness among strains of a fungal species can thus be said not to depend on location.