Strategies for Selecting Stable Common Scab Resistant Clones in a Potato Breeding Program

Abstract

Common scab (CS) of potato, caused by Streptomyces scabies, is an important disease in the US. CS problems can be avoided using resistant varieties. However, evaluating breeding clones can be complicated by high location and season-based soil and environmental variation. In this study we evaluated the efficacy of screening for CS resistance within the Wisconsin breeding program across multiple environments from 2006 to 2013. In each trial, 60–160 clones were evaluated. We compared the ability to select for CS resistance in a set of 18 dedicated CS screening trials (DST) versus 18 similar parallel standard breeding trials (SBT). Heritability for CS rating across DST was 0.83 vs. 0.53 in SBT. Data analysis from DST was able to separate CS susceptible cultivars (Atlantic, Snowden) from resistant cultivars (Pike, Snowden). However, same data analysis from SBT was not able to separate susceptible from resistant cultivars. Using DST datasets, we estimated the genotypic stability of scab performance across years and locations. We also calculated the probability distributions for the better or worse performance of a given clone vs. a standard variety. Using results from six or more DST we identified five round white clones that outperformed or matched CS tolerant Pike, eleven russet clones that outperformed or matched CS tolerant Russet Burbank and five red or yellow skin clones that outperformed or matched CS resistance level of Dark Red Norland. The approaches utilized here offer useful additional information for breeding programs which aim to improve selection efficiency for scab resistance.