Potential of microsatellites to distinguish four races of Fusarium oxysporum f. sp ciceri prevalent in India

Fusalium oxysporum f. sp. ciceri, the causal agent of chickpea wilt, is an important fungal pathogen in India. Thirteen oligonucleotide probes complem entary to microsatellite loci, in combination with 11 restriction enzymes, were used to assr:ss the potential of such markers to study genetic variabi lity in four Indian races of the pathogen. Hybridisation patterns, which we re dependent upon both the restriction enzyme and oligonucleotide probe use d, revealed the presence of different repeat motifs in the F. oxysporum f. sp. ciceri genome. Among the restriction enzymes used, hexa-cutting enzymes were more informative than tetra- and penta-cutting: enzymes, whereas tetr anucleotide and trinucleotide repeats yielded better hybridisation patterns than dinucleotide repeats. Dependent upon the levels of polymorphism detec ted, we have identified (AGT)(5), (ATC)(5) and (GATA)(4) as the best finger printing probes for the F: oxysporum sporum f. sp. ciceri races. The distri bution of microsatellite repeats in the genome revealed races 1 and 4 to be closely related at a similarity index value of 76.6%, as compared to race 2 at a similarity value of 67.3%; race 3 was very distinct at a similarity value of 26.7%. Our study demonstrates the potential of oligonucleotide pro bes for fingerprinting and studying variability in the F oxysporum f. sp. c iceri races and represents a step towards the identification of potential r ace diagnostic markers.