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Title: QTL-seq and marker development for resistance to Fusarium oxysporum f. sp. niveum race 1 in cultivated watermelon

item Branham, Sandra
item Wechter, William - Pat
item LAMBEL, SHAUNESE - Hm-Clause
item Massey, Laura
item MA, MICHELLE - Hm-Clause
item FAUVE, JULIE - Hm-Clause
item Farnham, Mark
item Levi, Amnon

Submitted to: Molecular Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/7/2018
Publication Date: 11/10/2018
Citation: Branham, S., Wechter, W.P., Lambel, S., Massey, L.M., Ma, M., Fauve, J., Farnham, M.W., Levi, A. 2018. QTL-seq and marker development for resistance to Fusarium oxysporum f. sp. niveum race 1 in cultivated watermelon. Molecular Breeding. 38:139.

Interpretive Summary: Watermelon is among the most important fruit crops around the world, with a farm-gate value approaching $500 million annually in the United States. Fusarium wilt is a major soil borne disease causing severe losses to watermelon yields in all cultivation regions of the world. ARS scientists at Charleston, SC in collaboration with scientists at a commercial seed company compared the genomes of two closely related groups of watermelon, a group resistant to Fusarium wilt and a susceptible group, to identify specific DNA regions associated with resistance to Fusarium wilt. The identified sequences provide both public and private watermelon breeders with an efficient toolkit to accelerate the development of watermelon cultivars resistant to Fusarium wilt.

Technical Abstract: Fusarium wilt, caused by the fungus Fusarium oxysporum f. sp. niveum (Fon), is one of the predominant diseases of watermelon. Resistance to Fon race 1 is conferred by a single major quantitative trait locus (QTL), Fo-1.1, but resolution of this region has been poor due to low marker density. In this study, a combination of whole-genome resequencing of bulked segregants (QTL-seq analysis) followed by QTL mapping with Kompetitive Allele Specific PCR (KASP) markers developed across Fo-1.1 successfully increased the resolution from 2.03 Mb to 1.56 Mb and 315 kb, respectively. The linkage of the KASP markers to Fon race 1 resistance across a wide range of watermelon germplasm was validated in a set of elite watermelon cultivars. The linked markers described here provide a breeder-friendly toolkit immediately available for high-throughput genotyping in large-scale breeding programs for fine mapping and incorporation of Fon race 1 resistance in watermelon.