Characterization of Early Blight Resistance in Potato Cultivars

Authors: XUE, WEIYA - Pennsylvania State University; Haynes, Kathleen; QU, XINSHUN - Pennsylvania State University

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/22/2018
Publication Date: 2/11/2019
Citation: Xue, W., Haynes, K.G., Qu, X. 2019. Characterization of Early Blight Resistance in Potato Cultivars. Plant Disease. https://doi.org/10.1094/PDIS-05-18-0794-RE.
DOI: https://doi.org/10.1094/PDIS-05-18-0794-RE

Interpretive Summary: Early blight disease is an important disease of potatoes worldwide. The disease is increasing in importance because of resistance to fungicides and climate change. In this study, 217 potato cultivars were evaluated for both early blight disease and foliar maturity. The strong negative correlation between resistance and maturity was confirmed: resistant cultivars are late maturing and susceptible cultivars are early maturing. However, a few notable exceptions were uncovered. Of particular interest for breeding are those resistant cultivars with early to moderate maturity. This information will be of interest to potato breeders searching for resistant materials to initiate a breeding program for developing early maturing, early blight resistant cultivars. It will also be of interest to organic potato growers looking for cultivars they can grow without applying fungicides.

Technical Abstract: Early blight, caused by the fungus Alternaria solani, is one of the most economically important foliar diseases of potatoes worldwide. In recent years, the incidence and severity of the disease has been increasing due to climate changes and fungicide resistance in the pathogen population. Although the disease can be controlled by extensive use of fungicides, genetic disease resistance is the best long term solution for sustainable management. In this study, 217 tetraploid old and modern potato cultivars were evaluated for foliar resistance to early blight in field experiments in Pennsylvania in 2016 and 2017. The experimental design was a randomized complete block design with two replications each year. A mixture of A. solani isolates was used in inoculations each year. Area under the disease progress curve (AUDPC) was calculated based on visual assessment of foliar disease during the growing season each year. AUDPC ranged from 24 to 2285 in 2016 and from 58 to 2130 in 2017, respectively. Significant differences in resistance to A. solani among cultivars were found (p<0.0001). Significant interaction was found between cultivar and environment (p<0.0001). Cluster analysis classified the cultivars into 5 groups: resistant, moderately resistant, intermediate, moderately susceptible, and susceptible. Broad sense heritability for early blight resistance was estimated as 0.89 with a 95% confidence interval of 0.86 to 0.91. All cultivars were also evaluated for foliage maturity in separate replicated field trials in 2016 and 2017, and a strong negative correlation between early blight resistance and maturity was found. Although most resistant and moderately resistant cultivars showed late maturity and most susceptible cultivars showed early maturity, a few exceptions were found.