Population Genetic Structure of Apple Scab (Venturia inaequalis (Cooke) G. Winter) in Iran

Abstract

The population genetic structure of 278 Venturia inaequalis isolates, collected from different apple cultivars of eighteen different provinces in Iran, was investigated using 22 polymorphic microsatellite markers. Analysis of molecular variation, Bayesian clustering and Nei's genetic distance analyses based on 88 microsatellite alleles indicated substantial levels of gene flow among the collection sites. Ninety three percent of the variation was observed among the individuals within the populations and only 7% variation was observed among the populations. Structure analysis grouped the isolates into two populations. Maximum number of pathogen genotypes (44) was observed in the North of Iran that grows various different apple cultivars. Investigation on the variation of the pathogen on different cultivars in the North of Iran suggested a significant differentiation of the pathogen populations between wild apple and commercial cultivars. During sampling, varying ranges of scab infection were observed on various apple cultivars in forests, monoculture and mix orchards. Wild type apple (Malus orientalis) along the Caspian Sea Coast had the most infection in comparison with the Iranian endemic and commercial cultivars. Based on the genetic analysis and host tracking scenario of the pathogen, it was presumed that Iran could potentially be the center of origin of V. inaequalis, which requires further detailed studies with isolates collected from different parts of central Asia and world for confirmation.

High-Resolution Melting (HRM) Analysis Reveals Genotypic Differentiation of Venturia inaequalis Populations in Greece

“…The genetic analysis of apple scab populations originated from different regions in Greece revealed high genetic variation within the populations (96%) while only 4% of the total gene diversity was attributed to among-population differentiation. Those results are in accordance with previous studies in V. inaequalis populations conducted in Europe, Asia and Africa (Gladieux et al, 2010;Ebrahimi et al, 2016;Koopman et al, 2017). PCoA grouped the isolates into three populations.…”

“…The polycyclic nature of the disease (MacHardy, 1996), the evolution of races and their ability to overcome the resistance genes in the host (Bus et al, 2011) and also the development of resistance to fungicides (Köller and Wilcox, 2001) are the most important factors that lead to high variation in fungal genome and changes in population genetic structure. Because of the pathogen's ability to adapt to environmental changes in order to survive (McDonald, 1997), many studies have analyzed its genetic structure among populations all over the world (Gladieux et al, 2010;Ebrahimi et al, 2016;Koopman et al, 2017).…”

Population structure of Venturia inaequalis, a causal agent of apple scab, in response to heterogeneous apple tree cultivation

“…We wanted to explore the genetic relationship between the Rvi6- virulent populations and other virulent pathogen populations, particularly those affecting apple cultivars containing Rvi17 ( Va1 ), Rvi1 ( Vg ) or those without any known R genes by tracking the recombination possibilities between them. To reach this goal, we analysed 633 infected leaves, collected in 10 orchards across Poland and genotyped these samples at 11 microsatellite loci, since microsatellite markers were found as a good method used for V. inaequalis genotyping, suitable for inference about differentiation at fungal population level [ 2 , 10 , 11 , 15 , 16 ].…”

Population genome sequencing of the scab fungal speciesVenturia inaequalis,Venturia pirina,Venturia aucupariaeandVenturia asperata

“…In some cases, host specificity occurs; for instance strains from Pyracantha are not able to infect Malus and vice-versa, which is referred to as formae specialis f. sp pyracantha and f.sp pomi, respectively (Le Cam et al, 2002). Worldwide sampling of V. inaequalis strains has identified divergent populations, mostly reflecting their hosts: wild apple (Malus sieversii, M. orientalis, M sylvestris, M. floribunda) and domesticated apple (Malus x domestica) trees (Gladieux et al, 2008;Gladieux et al, 2010a;Gladieux et al, 2010b;Leroy et al, 2013;Ebrahimi et al, 2016;Leroy et al, 2016). Certain populations have experienced a secondary contact with subsequent gene flow, resulting in the introduction from a wild population into the agricultural compartment of strains that are virulent on resistant cultivars carrying the Rvi6 resistance gene (Guérin et al, 2007;Lemaire et al, 2016).…”