Streptomyces Inhibition of Potato Tuber Pathogens Helminthosporium, Colletotrichum, and Pythium
Date & Time
Tuesday, July 19, 2022, 3:15 PM - 5:15 PM

Fungal diseases, Pythium and Helminthosporium have detrimental effects on potato tuber quality and yield. Streptomyces bacteria are known for producing a wide variety of secondary metabolites with antifungal properties. Isolates of Streptomyces collected from tubers surfaces all over North America have recently shown inhibitory effects towards P. ultimum and H. solani in Petri dish assays. We tested talc-based powder formulas for their ability to maintain viable Streptomyces spores in storage. The formula that maintained spores the longest was then used to coat varying Streptomyces isolates onto a seed tuber surface. Tests were conducted in a lab, greenhouse, and field setting. We found a powder formula that kept 50% of the added Streptomyces spores viable for a period of three to six months. Isolates with inhibitory effects towards H. solani were applied as a powder on seed tubers infected with H. solani and grown in a greenhouse. Helminthosporium was not identified on the progeny tubers, but some isolates significantly limited C. coccodes compared to the control. This experiment was repeated in a field setting where C. coccodes was again the primary disease on progeny tubers. In the field, isolates showed no inhibitory effect towards C. coccodes, but fungicide seed treatment Maxim MZ did. Isolates with inhibitory effects towards P. ultimum were applied as a powder onto wounded tubers in a storage study. One hour later the tubers were exposed to P. ultimum. Isolates did not limit P. ultimum compared to the control. A follow up experiment revealed the Streptomyces isolate used needed at least 24 hours of growth to produce antifungal secondary metabolites. Our data suggests that Streptomyces bacteria can easily be stored in a powder and that there are beneficial effects as a biocontrol against C. coccodes under certain conditions.

Session Type
Parent Session