Diversity and population genetic structure of Venturia inaequalis on different apple cultivars in the north of Iran

Apple scab disease caused by Venturia inaequalis is the most important economic disease worldwide where the apple is grown and causes annual epidemics. It reduces the quality and quantity of the yields in different regions of Iran. In this study, diversity and population genetic structure of V. inaequalis were surveyed on different apple cultivars using 18 microsatellite markers. 51 isolates were obtained from infected leaf and fruit specimens from wild apple, Iranian endemic and commercial apples from Northern provinces of Iran (Mazandaran, Golestan and Guilan). 28 SSR primers were used to investigate the genetic diversity of this pathogen. Among them, 18 primers showed polymorphism between isolates and populations. AMOVA analyses revealed that 97% of the variation was distributed among individuals within populations, and 3% was attributable to the differences among populations. Gene diversity indexes including Nei’s gene diversity, Shannon index and allele numbers in every population showed that diversity within the population on endemic cultivars is more than the diversity in the population of wild and commercial cultivars. Also, the population of commercial cultivars has more diversity in comparison with the wild population. High genetic diversity within the populations is caused by annual sexual reproduction, gene flow between populations and probably the existence of this fungus for a long time in this region.