Potato Early Dying (PED) in Alberta, Canada: Insights into Causal Agents and Implications for Yield Loss.

Potato early dying (PED) is a significant concern for potato growers globally. PED is believed to be caused by a combination of soil-borne fungi Verticillium dahliae, V. albo-atrum, Colletotrichum coccodes, Fusarium spp., and the root-lesion nematode Pratylenchus penetrans. However, the causal agents of PED in Alberta have not been thoroughly characterized. We investigated the incidence and abundance of V. dahliae and V. albo-atrum and assessed their relationship with PED severity and yield loss in southern Alberta. Soil samples were collected from 62 potato fields during the falls of 2020 and 2021 and analyzed using quantitative polymerase chain reaction (qPCR) to detect and quantify V. dahliae and V. albo-atrum. For both years, V. dahliae was found in 71% and 45% of the fields, respectively. In contrast, traces of V. albo-atrum were detected in only one field in 2020. Selected fields were surveyed to assess PED severity and yield loss in the summers of 2021 and 2022. The potato fields with high levels of V. dahliae in the soil typically showed more PED symptoms and, in some cases, lower yields. However, some fields with low levels of V. dahliae in soil also showed PED symptoms, indicating that factors in addition to V. dahliae levels in soils are involved in determining PED severity. Colletotrichum coccodes was present in 59% of plant samples collected in 2021 and 41% in 2022. Notably, in 2022, PCR- detectable levels of C. coccodes were apparent earlier than V. dahliae in the growing season.