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item Costanzo, S
item Simko, I
item Christ, B
item Haynes, Kathleen

Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2005
Publication Date: 6/20/2005
Citation: Costanzo, S., Simko, I., Christ, B.J., Haynes, K.G. 2005. QTL analysis of late blight resistance in a diploid potato family of Solanum phureja x S. stenotomom. Theor. Appl. Genet. 111:609-617.

Interpretive Summary: Late blight is a devestating disease of potatoes that occurs worldwide. New sources of genetic resistance to this disease are necessary because the organism that causes late blight, Phytophthora infestans, can readily overcome major resistance genes. In this molecular genetic research a unique population of South American potatoes was found to have several genes for late blight resistance, one of which had not previously been reported. This population will be used to develop late blight resistant potato cultivars for North America. This information will benefit breeders and pathologists trying to improve the levels of late blight resistance in commercial potatoes in the United States.

Technical Abstract: Field resistance to Phytophthora infestans (Mont.) de Bary, the causal agent of late blight in potatoes, has been characterized in a potato segregating family of 230 full-sib progenies derived from a cross between two hybrid Solanum phureja S. stenotomum clones. The distribution of area under the disease progress curve (AUDPC) values, measured in different years and locations, was consistent with the inheritance of multigenic resistance. Relatively high levels of resistance and transgressive segregations were also observed within this family. A genetic linkage map of this population was constructed with the intent of mapping quantitative trait loci (QTLs) associated with this late blight field resistance. A total of 132 clones from this family were genotyped based on 162 restriction fragment length polymorphism (RFLP) markers. The genome coverage by the map (855.2 cM) is estimated to be at least 70% and includes 112 segregating RFLP markers and two phenotypic markers, with an average distance of 7.7 cM between two markers. Two methods were employed to determine trait-marker association: the non-parametric Kruskal-Wallis test and interval mapping analysis. Three major QTLs were detected on linkage group III, V and XI, explaining 23, 17 and 10%, respectively, of the total phenotypic variation. One possible additional QTL was detected on linkage group VII with less statistical support. The present study revealed the presence of potentially new genetic loci in this diploid potato family contributing to general resistance against late blight. The identification of these QTLs represent the first step towards their introgression into cultivated tetraploid potato cultivars through marker-assisted selection.