Genetic dissection of early blight resistance in tetraploid potato

Authors: XUE, WEIYA - Pennsylvania State University; HAYNES, KATHLEEN - Retired ARS Employee; Clarke, Christopher; QU, XINSHUN - Pennsylvania State University

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/2/2022
Publication Date: 3/25/2022
Citation: Xue, W., Haynes, K.G., Clarke, C.R., Qu, X. 2022. Genetic dissection of early blight resistance in tetraploid potato. Frontiers in Plant Science. https://doi.org/10.3389/fpls.2022.851538.
DOI: https://doi.org/10.3389/fpls.2022.851538

Interpretive Summary: Early blight is one of the most costly fungal diseases of potato. Few cultivars of potato are resistant to early blight and disease management tools are limited. Identifying genes that confer resistance to early blight is a critical step toward developing new potato cultivars highly resistant to early blight. In a previous study, we identified a potato clone that is highly resistant to early blight. To generate a biological resource to aid in the identification of genes that underpin early blight resistance, we crossed this resistant clone and a standard potato cultivar susceptible to early blight. Progeny from this cross were screened for resistance to early blight and unique differences in the genomes between these progeny were identified. These genotypic and phenotypic data were used to map genetic markers linked with early blight resistance genes. Multiple early blight resistance-associated genes were identified including several that are also associated with plant maturity. Markers for these genes can be integrated into potato breeding programs to accelerate the development of early blight-resistant cultivars of potato.

Technical Abstract: Early blight, caused by the fungus Alternaria solani, is one of the most economically important diseases of potatoes worldwide. We previously identified a tetraploid potato clone, B0692-4, which is resistant to early blight. To dissect the genetic basis of early blight resistance in this clone, a full-sib tetraploid potato population including 241 progenies was derived from a cross between B0692-4 and a susceptible cultivar Harley Blackwell in this study. The population was evaluated for foliage resistance against early blight in field trials in Pennsylvania in 2018 and 2019 and relative area under the disease progress curve (rAUDPC) was determined. The distribution of rAUDPC ranged from 0.016 to 0.679 in 2018, and from 0.017 to 0.554 in 2019. Broad sense heritability for resistance, as measured as rAUDPC, was estimated as 0.66-0.80. The population was also evaluated for foliar maturity in field trials in Maine in 2018 and 2020. A moderate negative correlation between rAUDPC and foliar maturity was detected in both years. A genetic linkage map covering a length of 1486.86 cM with 9126 SNP markers was used for mapping QTL for rAUDPC and foliar maturity. In 2018, three QTLs for early blight were detected; two of them on chromosome 5 overlapped with QTLs for maturity, one of them on chromosome 7 was independent of maturity QTL. In 2019, eight QTLs for early blight were detected, two QTLs on chromosome 5 overlapped with QTLs for maturity; the other six QTLs did not overlap with QTLs for maturity. The identification of these QTLs provides new insight into the genetic basis of early blight resistance and may serve as sources for marker-assisted selection for early blight resistance breeding.