Journal of Agronomy and Field Innovations

Background: Early blight is a common disease in solanaceous plants caused by the fungus Alternaria solani and is responsible for substantial financial losses in agriculture and decreased crop production. It is vital to understand the genetic diversity and population structure of the fungus in order to develop better management practices to control it.
Objective: To study the genetic diversity and population structure of Alternaria solani isolates using the molecular markers such as ISSR and RAPD.
Method: A total of 48 isolates collected from different geographical areas and host plants were studied. The effect of the fungus was established by performing morphological studies. The number of strains is tested by applying the resistance markers to study genetic diversity.
Result: The results of the study indicated substantial phenotypic diversity existing among isolates. The ISSR analysis resulted in 96 bands of which 84 (87.5%) were polymorphic while RAPD produced 78 bands with 68 (87.2%) polymorphic. The genetic similarity coefficients varied between 0.52 to 0.94 indicating high genetic variability. Cluster analysis showed that isolates were classified into four main clusters and partially related to their geographical location and host plants. The ISSR markers showed higher discriminatory potential (PIC value = 0.43 ± 0.08) in comparison to RAPD markers (PIC value = 0.38 ± 0.07). The molecular diversity assessments suggested panmictic population structure with moderate genetic differentiation.
Conclusion: it was stated that ISSR and RAPD markers are effective molecular tools for evaluation of genetic diversity and population structure of A. solani. The ISSR markers possess higher discriminatory ability than RAPD markers. The results are important from the viewpoint of pathogen epidemiology, virulence evolution, and development of early blight resistance breeding programs.