A review of powdery mildew in strawberries: the resistance of species, hybrids and cultivars to the pathogen is highly variable within and across studies with no standard method for assessing the disease

Genetic loci associated with tissue-specific resistance to powdery mildew in octoploid strawberry (Fragaria × ananassa)

“…P. aphanis undergoes rapid asexual reproduction during the summer and autumn months with optimum temperatures for infection ranging between 15-25°C, where humidity levels are above 75%RH ( Amsalem et al., 2006 ). In infected strawberry leaves, fungal mycelia typically develop first on the underside (abaxial) of the leaf, before spreading to the upper side (adaxial) causing the leaves to curl inwards ( Menzel, 2022 ). Powdery mildew foliage infections lead to a reduction in photosynthesis and thus lower CO 2 assimilation, and, under severe infections, this can have an indirect impact on yield ( Hibberd et al., 1996 ; Nam et al., 2012 ; Menzel, 2022 ).…”

“…In infected strawberry leaves, fungal mycelia typically develop first on the underside (abaxial) of the leaf, before spreading to the upper side (adaxial) causing the leaves to curl inwards ( Menzel, 2022 ). Powdery mildew foliage infections lead to a reduction in photosynthesis and thus lower CO 2 assimilation, and, under severe infections, this can have an indirect impact on yield ( Hibberd et al., 1996 ; Nam et al., 2012 ; Menzel, 2022 ). The pathogen also impacts yield directly through infection of strawberry reproductive tissue, causing fruit to become misshapen and restricting or even terminating fruit growth ( Menzel, 2022 ).…”

“…Powdery mildew foliage infections lead to a reduction in photosynthesis and thus lower CO 2 assimilation, and, under severe infections, this can have an indirect impact on yield ( Hibberd et al., 1996 ; Nam et al., 2012 ; Menzel, 2022 ). The pathogen also impacts yield directly through infection of strawberry reproductive tissue, causing fruit to become misshapen and restricting or even terminating fruit growth ( Menzel, 2022 ). As a result, powdery mildew outbreaks can lead to 20% to 70% strawberry yield loss annually ( Jin and Hall, 2017 ).…”

“…However, no major gene or single locus has been demonstrated to endow complete resistance against P. aphanis . In fact, most commercial strawberry cultivars are susceptible to powdery mildew, with only a few strawberry varieties that are deemed to be moderately resistant ( Menzel, 2022 ). Indeed, strawberry powdery mildew resistance characterised to date is highly polygenic ( Cockerton et al., 2018 ; Palmer and Holmes, 2022 ).…”

A Genomic Resource for the Strawberry Powdery Mildew Pathogen Podosphaera aphanis

“…commercial strawberry varieties are considered highly susceptible and where resistant cultivars have been identified, this resistance frequently varies across environmental conditions (Nelson et al 1996;Masny et al, 2016;Cockerton et al, 2018;Sargent et al, 2019;Menzel, 2021).…”