Cross-species transferability of microsatellite markers from Fusarium oxysporum for the assessment of genetic diversity in Fusarium udum

Expressed sequence tags (ESTs) are the source of simple sequence repeats (SSRs) that can be used to develop molecular markers for the study of polymorphism and genetic diversity. In the present investigation, 30 EST simple sequence repeats (SSR) primer sets derived from three formae speciales of Fusarium oxysporum: melonis (Fom), cucumerium (Foc), and lycopersici (Fol) - were tested for transferability to Fusarium udum. The majority of SSR loci contain trinucleotide (63.70%) while fewer contain di- (27.41%), tetra- (5.64%) and penta-nucleotide (3.22%) repeats. The number of alleles at these SSR loci ranged from one to three, with an average of 1.4 alleles per locus. CAG (24.19%) and AC (16.93%) were the most abundant motifs identified. Three markers (FomSSR-8, FolSSR-2 and FolSSR-4) were found highly informative for genetic characterization of F. udum and very useful in distinguishing the polymorphism rate of the markers at specific locus; however, polymorphic information content (PIC) was maximum (0.597) in FocSSR-7. In terms of cross species transferability, 70% of the primer sets of Fom-SSR and Fol-SSR and 30% of the Foc-SSR produced an amplicon in F. udum isolates. To the best of our knowledge, this is the first set of EST SSR markers developed and assessed for the variability, genetic analysis and evolutionary relationships of the F. udum population.