Genetic diversity among Sphaerulina frondicola populations, the causal agent of poplar leaf spot disease in East Azarbaijan Province using RAPD and ISSR molecular markers

Poplar leaf spot disease, caused by Sphaerulinafrondicola (syn: Septoria populi), is one of the important and serious diseases of populus trees, which cause significant loss on this host. Considering the importance of this disease, in the present study, the genetic diversity of 138 isolates S. frondicola isolates obtained from populus trees different regions of East and West Azerbaijan provinces was analysed using RAPD and ISSR molecular markers. The results indicated considerable genetic variations amongst the studied populations. The mean genetic diversity for all of the populations using data from all primers was 0.199 at the probability level of 0.001. The lowest genetic differentiation was observed between Horand and Kaleyber populations (0.352) with the highest gene flow (54.956) and the highest genetic differentiation was observed between Khoy and Bostanabad populations (0.516) with the lowest gene flow (0.468) which is consistent with geographical distance.Based on Nei's genetic distance, the Bostanabad population showed the highest genetic distance from the other six populations. Haplotype analysis clustered the isolates from a single tree or even single spot in different groups, suggesting the existence of high genetic diversity in a small scale. Overall, the existence of different haplotypes and distribution of genetic diversity in a small scale observed in this study, suggests occurrence of regular sexual cycle in S. frondicola populations and highlights the role of airborne ascospores as primary inoculum source in disease cycle.