Evaluation of Venturia pyrina virulence on European pear ( Pyrus communis ) cultivars by an in vitro methodology

Abstract European pear scab caused by Venturia pyrina is a primary disease in pear‐growing areas worldwide. Growing of resistant cultivars is crucial for the long‐term control of the disease. Studies on pear resistance and virulence of the pathogen are still limited. The majority of available knowledge is based on the cultivar performance in the field. Inconsistency of cultivar resistance to V . pyrina in different regions indicates the possible presence of various biotypes of the pathogen. In this study, we assessed the virulence of seven monoconidial strains of V . pyrina originated from different regions and cultivars in Latvia and evaluated host reactions of 18 pear cultivars using artificial inoculations on detached leaves and immature fruits. All previously described interaction phenotypes ranging from immune to susceptible were recorded indicating divergent virulence of V . pyrina and different levels of resistance of the tested cultivars. Most of the pear cultivars were scored as partially resistant or susceptible. The fully compatible interactions without host tissue reactions were rare. Only cultivars ‘Conference’ and ‘Belorusskaya Pozdnaya’ were compatible with most of the strains and field populations. We used strains purposely selected from different regions, habitats and cultivars to get insight into the potential diversity of the local populations. Considerable differences in virulence among the strains and cultivar responses were detected, and each of the isolates was virulent on a different set of the cultivars, confirming the expected diversity.