Water soaking in strawberry (Fragaria x ananassa) has a polygenic background and is strongly influenced by environmental factors

Water soaking (WS) is an economically important surface disorder in open-field production of strawberry ( Fragaria ⋅ ananassa ). The disorder, which impairs fruit quality and quantity, develops after exposure of maturing fruit to rain or high concentrations of water vapor. The susceptibility to WS differs among genotypes, suggesting a genetic component, with earlier studies establishing a close positive relationship between susceptibility to WS and the water permeance of the fruit skin. However, until now, no published studies on the underlying genetics of WS exist. Here, we aimed to identify genetic regions associated with WS and fruit skin permeability using a genetic mapping approach. A biparental F ₁ population was established by crossing two genotypes (201409 ⋅ 210706) exhibiting contrasting susceptibility to WS. The trueness-to-type of the progenies was confirmed by genetic fingerprint analysis with molecular markers. WS and permeance for water uptake were phenotyped over two seasons under two different growing conditions using laboratory-based incubation assays. Furthermore, the population was genotyped with the Axiom™ Strawberry FanaSNP 50k Genotyping Array to facilitate genetic mapping and QTL analyses. WS and skin permeance showed a clear segregation and were closely related. Multiple QTL regions were identified for WS and permeance, with one accounting for 16.7% to 28.6% of the phenotypic variation. The detection of several QTLs and the moderate broad-sense heritability of 0.49 suggest a polygenic background of WS. These findings provide the first steps towards understanding the genetic background of this trait, which will allow for developing tolerant cultivars for open-field production.