Processing Pumpkin (Cucurbita moschata Duchesne) Breeding Lines with Resistance to Powdery Mildew and Their Canning Quality

Processing pumpkin (Cucurbita moschata Duch.) is an economically important crop in the United States, and commercial cultivars are susceptible to cucurbit powdery mildew (CPM). Ideally, CPM would be managed with fungicides and host resistance; however, this combination of tools is currently inaccessible to growers of processing pumpkin. The objectives of this study were to identify CPM-resistant processing pumpkin breeding lines and evaluate their canning quality. An industry standard and CPM-susceptible processing pumpkin cultivar Dickinson was crossed with Bugle, a butternut squash that is resistant to CPM and carries the common resistance gene Pm-0. Each line evaluated was homozygous for Pm-0 and was developed by selecting lines following three backcrosses to 'Dickinson'. Two lines with moderate and high levels of resistance were identified by a field trial in 2022 and assessed again in 2023. The same two lines were processed and canned along with 'Dickinson' and 'Bugle'. Their canning qualities were assessed and compared with a store-bought commercial standard. The dry matter (%), pH, moisture (%), soluble solids (degrees Brix), consistency, color, water activity, alcohol insoluble residue (AIR), and ratio of AIR to total solids were measured. The results indicated that the purees from both breeding lines more closely resembled 'Dickinson' and the commercial standard than 'Bugle'. We concluded that effective CPM resistance has been bred into a commercially promising processing pumpkin background.