High phenotypic variability and low genetic similarity in Venturia pyrina : insights into pear scab dynamics in a semi-arid and cold-temperate region

Pear scab, caused by the fungus Venturia pyrina, reduces fruit quality and yield. In the High Valley of Río Negro, a vital fruit-growing region in northern Argentine Patagonia, outbreaks are sporadic, but also severe under favorable conditions. Yet, the biology of local strains is not well known. Thus, this study examined 20 local isolates by using genetic fingerprinting, morphology, and growth analyses. Isolates exhibited wide morphological diversity, significant differences in growth rate and thermal response, with optimal growth at 20 °C, and high genetic variability. Germination increased at 20 °C after 12 h of incubation. In contrast, conidial viability was highest at 4 °C and decreased with incubation time, indicating possible adaptation to the cool spring and arid climate of the region. Multivariate analysis further revealed continuous phenotypic variation and a significant association between the genetic family and phenological stage of the host. For the first time, an integrated approach was used for V. pyrina under the climatic conditions the High Valley of Río Negro. These findings are consistent with the biological regional adaptation of V. pyrina populations in this valley and suggest a potential role for conidia in this region.