Genetic diversity and fumonisin analyses of Fusarium verticillioides (Sacc.) Nirenburg and F. fujikuroi Nirenburg isolates

Genetic diversity and fumonisin production of 53 Fusarium verticillioides isolates from Isabela and Laguna [Philippines] and 21 F. fujikuroi isolates from Laguna and Nueva Ecija [Philippines] were analyzed using molecular techniques. The effect of crude toxins of F. verticillioides and F. fujikuroi on germination and root length of corn and rice seeds/seedlings was also investigated. Using Polymerase Chain Reaction (PCR)-based technique, 49 of the 53 isolates were identified as F. verticillioides with an amplified product of 800 bp in size using VERT-1 and VERT-2 primers. Of these, 39 isolates were fumonisin-producers as exhibited by single fragment of 400 bp using VERTF-1/VERTF-2 primers. This assay which utilizes primers derived from the intergenic spacer (IGS) sequence of F. verticillioides isolate A0999, showed considerable specificity since F. verticillioides tester strains were amplified in VERT-1/VERT-2 and VERTF-1/VERTF-2, but not F. proliferatum and F. subglutinans tester-trains. Using Universally Primed-PCR (UP-PCR) markers, F. verticillioides and F. fujikuroi populations were grouped based on geographical origin and species as supported by intermediate to high bootstrap values. Unweighted Pair Group Method with Arithmetic Mean (UPGMA) cluster analysis with Jaccard's coefficient showed that similarities among isolates within F. verticillioides were intermediate to high ranging from 57.9 to 97.5% and resolved five major groups at 71% similarity level. Some F. verticillioides and F. fujikuroi isolates were associated with each other in the phylogenetic tree which could probably be attributed to the high nucleotide similarities of both species. The effect of crude toxins of selected high and low fumonisin-producing isolates of F. verticillioides and F. fujikuroi on the germination and root length of rice and corn seeds/seedlings was analyzed. The extent of inhibition of germination and root length of both crops was not associated with fumonisin-producing ability of F. verticillioides and F. fujikuroi. This experiment suggested that the inherent capacity of each isolate to produce toxins is independent on their relative ability to cause substantial effects on a particular crops.