Mating type genes and genetic markers to decipher intraspecific variability among Fusarium udum isolates from pigeonpea

To ascertain the variability in Fusarium udum (Fu) isolates associated with pigeonpea wilt is a difficult task, if based solely on morphological and cultural characters. In this respect, the robustness of five different genetic marker viz., random amplified polymorphic DNA (RAPD), enterobacterial repetitive intergenic consensus (ERIC), BOX elements, mating type locus, and microsatellite markers were employed to decipher intra-specific variability in Fu isolates. All techniques yielded intra-specific polymorphism, but different levels of discrimination were obtained. RAPD-PCR was more discriminatory, enabling the detection of thirteen variants among twenty Fu isolates. By microsatellite, ERIC- and BOX-PCR fingerprinting, the isolates were categorized in seven, five, and two clusters, respectively. Cluster analysis of the combined data also showed that the Fu isolates were grouped into ten clusters, sharing 50-100% similarity. The occurrence of both mating types in Fu isolates is reported for the first time in this study. All examined isolates harbored one of the two mating-type idiomorphs, but never both, which suggests a heterothallic mating system of sexual reproduction among them. Information obtained from comparing results of different molecular marker systems should be useful to organize the genetic variability and ideally, will improve disease management practices by identifying sources of inoculum and isolate characteristics.