Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2004
Publication Date: 1/20/2005
Citation: Haynes, K.G., Wanner, L.A., Thill, C.A., Miller, J., Novy, R.G., Corsini, D.L. 2005. National common scab trial of potato varieties and advanced selections in 2002. Am. J. Potato Res. 87:72-73 (Abstract). Interpretive Summary: Common scab is a serious soil-borne disease of potato tubers that causes raised, superficial, or pitted lesions. These lesions make the tubers unattractive for fresh market. In addition, these lesions result in peeling losses and generate excess waste for potato chip or french fry processors. Efforts to develop new scab resistant varieties have met with limited success because of the complex nature of host resistance, genetic variability in the causal organism, and environmental variability. The purposes of this study were to determine how much resistance to common scab exists in some of the more recently released varieties grown across a wide range of environments and to determine if the severity of scab infection is consistent from one growing environment to another. Seventeen potato varieties were evaluated in Idaho, Maine, and Minnesota in scab infested fields. We found that the severity of scab infection varies considerably across locations, making it difficult to predict how a variety grown in one location will react in a different location. In the future, breeding efforts to develop new resistant varieties should focus on identifying those varieties consistently having less severe reactions to scab across different locations. This information will be used by potato producers and extension agents to choose suitable potato varieties for production. Ultimately, the development and use of new scab resistant varieties will reduce economic losses to growers, processors, and consumers.
Technical Abstract: Common scab, caused by Streptomyces spp., is a soil-borne disease of potato tubers, seriously affecting marketability of the crop. The results of screening potato germplasm for severity of common scab can be variable. The purpose of this study was to evaluate the stability of common scab phenotypes in advanced germplasm from public potato breeding programs in different regions of the United States. Seventeen clones, consisting of four standard check varieties (Atlantic, Superior, Russet Burbank, Ranger Russet), six recently released varieties (Alturas, Bannock Russet, Gem Russet, Harley Blackwell, Ivory Crisp, Liberator), and seven numbered selections (A84118-3, A90586-11, AF1758-7, B0766-3, B1240-1, MSG227-2, SC8801-2) were evaluated at each of three locations (ID, ME, MN). After harvest, each tuber was scored for the percent of surface area covered with lesions and the type of lesion. These scores were converted to an area index (AI) and a lesion index (LI). There were significant differences among clones for LI, but not for AI. There were significant clone x location interactions for both AI and LI. Ten clones were unstable for AI before removal of environmental heterogeneity, and nine clones were stable after removal of environmental heterogeneity. Nine clones were unstable for LI before removal of environmental heterogeneity, and eight clones were unstable after removal of environmental heterogeneity. These results indicate that the responses of these clones vary considerably over environments and evaluation at multiple sites is important for identifying clones with stable disease phenotypes.