92). The similarity was expected because both isolates belong to same forma specialis and geographical region. The most diverse (similarity coefficient value 0.12) isolates were Fol-6 and Foi-2. The dendrogram constructed based on similarity index resulted in two major clusters (Fig. 2). High bootstrap values were recorded with internodes, which indicate the robustness of the clustering. The first major cluster has been exclusively composed of Fom isolates, which is further divided into two subclusters having three Proteases inhibitor Fom isolates each. The second cluster having different subclusters comprises a mix of all the formae speciales taken into this study except Fom. The knowledge of abundance

and distribution of genetic variability within and among formae speciales of F. oxysporum buy CYC202 is a prerequisite to study their genetic relationships (Bruns et al., 1991). In the present study, the relative density and relative abundance of SSRs in Fom was higher. So far, we do not have any strongly supported explanation for this. However, this discrepancy may be occurred because of transfer of lineage-specific (LS) genomic regions in F. oxysporum that include four entire chromosomes and account

for a quarter of the genome (Ma et al., 2010). It has been observed from genome-wide study that the distribution of microsatellites in the genome is not random. Coding regions are mostly dominated by tri and hexa-nucleotide Sinomenine repeats, whereas di, tetra, and penta nucleotide repeats are often found in abundance in noncoding region (Kim et al., 2008; Levdansky et al., 2008). Differential distribution in terms of abundance of SSRs has been reported in between intronic and intergenic regions, 5′ and 3′ UTRs, and in different chromosomes and lastly, different species have different frequencies of SSR types and repeat units (Li et al., 2004; Garnica et al., 2006; Lawson & Zhang, 2006). In our study, we observed similar pattern of distribution

of SSR in the coding region where tri and hexanucleotide SSRs were predominant. These tri and hexanucleotide SSRs in the coding region are translated into amino-acid repeats, which possibly contribute to the biological function of the protein (Kim et al., 2008). Dinucleotide SSRs are often found in the exonic region of F. oxysporum; however, (GT)n and (AC)n repeats were common in all the three formae speciales. Stallings et al. (1991) reported that (GT)n repeat is able to enhance the gene activity from a distance independent of its orientation. However, more effective transcription enhancement resulted from the GT repeat being closer to promoter region. Similarly, (CA)n repeat can act as a bridge to bring the promoter into close proximity with a putative repressor protein bound downstream of the (CA)n SSR (Young et al., 2000).