Genetic Diversity of Pyrenophera tritici-repentis Isolates, the Causal Agent of Wheat Tan Spot Disease from Northern Iran

The tan spot disease of wheat caused by Pyrenophera tritici-repentis has become a major disease in most wheat growing areas worldwide. Here we used ISSR and RAPD markers to study the genetic diversity of 34 P. tritici-repentis isolates collected from North of Iran. The leaves having the typical symptoms of tan spot disease were collected and after fungal isolation, purification and identification, DNAs were extracted. After PCR amplification using each primer, PCR products were run in agarose gels, and the resulting bands were scored. Cluster analysis was performed using Un-Wighted Nighbor Joining method. A total of 178 reproducible bands were scored. Out of which 115 (65%) were polymorphic corresponding to an average of 8 polymorphic bands per primer. The average PIC values for ISSR and RAPD markers were 0.38 and 0.43, respectively. A high degree of genetic variability among Iranian P. tritici-repentis isolates was identified. Cluster analysis based on un-weighted neighbor-joining method using the combined molecular data revealed five distinct clusters. The results from the cluster analysis indicated that the genetic similarity among the Iranian P. tritici-repentis isolates could be partly explained by geographic origins where the isolates were collected. Genetic variability of P. tritici-repentis along with relatively high level of geographic diversity observed in this study may suggest longer evolutionary period for the isolates from the Middle East, wheat center of origin, as opposed to other places.