Evaluation of potato clones for resistance to stem canker and tuber black scurf in field studies following artificial inoculation with Rhizoctonia solani AG-3 in Maine∗

∗Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture and University of Maine.

Abstract

Potato clones were evaluated for resistance to Rhizoctonia stem canker, stolon lesion and black scurf in field experiments during the 1997 and 1998 growing seasons. Seed pieces were inoculated with Rhizoctonia solani Anastomosis group 3 (AG-3) by dipping them in a slurry or suspension of inoculum. Uninoculated controls were also planted. Seed emergence was assessed beginning at two weeks after planting. After 60 days, incidence and severity (%) of stem and stolon cankers were assessed. The numbers of root and stolon lesions were also quantified. At harvest, the incidence of black scurf on tuber yield and numbers were also determined. Significant differences in emergence of potato seed pieces (%) were detected between inoculated and control treatments and the incidence of stem and root cankers differed among clones in both years. The incidence and severity of stem cankers and the numbers of stem and root lesions were not significantly correlated with the black scurf incidence on tubers. These studies suggest that various symptom types incited by Rhizoctonia can be important epidemiological factors in disease development.

Keywords:

• Solanum tuberosum
• black scurf
• Rhizoctonia solani
• stem canker
• stolon canker

Acknowledgements

This research was supported in part by the Maine Potato Board and the grants for the Potato Breeding Program (MATES Number 2918 and Project Number 5-5-38805) at the University of Maine. We thank the New England Plant, Soil and Water Laboratory for logistical assistance.

Notes

∗Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture and University of Maine.

Additional information

Notes on contributors

O. M. Olanya

This work was authored as part of O. M. Olanya's official duties as an employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105 no copyright protection is available for such works under U.S. law.

A. F. Reeves§

§Deceased.