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United States Department of Agriculture

Agricultural Research Service

Research Project: Control of Powdery Scab and Black Dot Through Resistance Breeding and Pathogen Management Strategies (WSU-Johnson)
2012 Annual Report


1a.Objectives (from AD-416):
Screen potato germplasm resistance for resistance to major pests and pathogens. Test management strategies and their interaction with different levels of host resistance.


1b.Approach (from AD-416):
Plant various genotypes of potato in affected fields infested with major pests and pathogens. Score resistance reactions and when appropriate find linkages between resistance and molecular markers. Test management strategies and study interactions with different levels of resistance in potato breeding lines and cultivars.


3.Progress Report:

This is the final report for this project, a study of the relationship between symptoms produced by powdery scab and yield in the variety Umatilla Russet. The research was conducted over two seasons, and relates to objective 1.B. of the related in-house project, "Develop germplasm with resistance to pests and diseases, establishing effective and efficient screening protocols, determining range of expression, inheritance, heritability, and discover molecular markers, while mapping genetic factors where possible and useful". Powdery scab debilitates roots, produces galls on the roots and stolons, and produces lesions on the tuber skin. In different years the physical manifestation of the disease can be dominated by one of these symptoms. In the case of Umatilla the number of galls is correlated with tuber size. Total yield stays the same, meaning that galling is related to tuber size. One theory is that powdery scab may function like a stolon pruner, reducing tuber number and increasing size.

Field screening of newly released varieties and advanced germplasm with mixed infection of powdery scab was carried out and identified high performers. These include Yukon Gem, Palisade Russet, Chipeta, PA99N2-1, AC99375-1RU and Premier Russet. Resistant germplasm at an earlier state of selection was identified in replicated plots in field screening. These include PA09BDPSY3-2, PA09NCY3-3, PA08NC24-5, and PA09LNCY2-1. A new technique was used to classify germplasm in field trials for root robustness which seems to be correlated with high yield under intense. Plants are attached to dynamometer which measures the force needed to pull the plant out of the ground. Overall there was a significant correlation between marketable yield and root pulling force (r = 0.6). However, the pattern of results suggests that while this technique is effective at identifying the extremes of yield by the force parameter, it does not give consistent results on the intermediate yielders.


Last Modified: 10/20/2014
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