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 <i>Verticillium dahliae</i>, <i>V. albo-atrum</i>, <i>Colletotrichum coccodes</i>, <i>Fusarium</i> spp., and the root-lesion nematode <i>Pratylenchus penetrans</i>. However, the causal agents of PED in Alberta have not been thoroughly characterized. We investigated the incidence and abundance of <i>V. dahliae</i> and <i>V. albo-atrum</i> 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 <i>V. dahliae</i> and <i>V. albo-atrum</i>. For both years, <i>V. dahliae</i> was found in 71% and 45% of the fields, respectively. In contrast, traces of <i>V. albo-atrum</i> 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 <i>V. dahliae</i> in the soil typically showed more PED symptoms and, in some cases, lower yields. However, some fields with low levels of <i>V. dahliae</i> in soil also showed PED symptoms, indicating that factors in addition to <i>V. dahliae</i> levels in soils are involved in determining PED severity. <i>Colletotrichum coccodes</i> was present in 59% of plant samples collected in 2021 and 41% in 2022. Notably, in 2022, PCR- detectable levels of <i>C. coccodes</i> were apparent earlier than <i>V. dahliae</i> in the growing season.