Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/2001
Publication Date: 1/20/2002
Citation: LEVI, A., THOMAS, C.E., JOOBEUR, T., ZHANG, X., DAVIS, A.R. 2002. A GENETIC LINKAGE MAP FOR WATERMELON DERIVED FROM A TESTCROSS POPULATION: (CITRULLUS LANATUS VAR. CITROIDES X C. LANATUS VAR. LANATUS) X C. COLOCYNTHIS. Thoretical and Applied Genetics. v.105.p.555-563. Interpretive Summary: Watermelon production in the U.S. has increased from 1.2 M tons in 1980 to 2.2 M tons in 1999, with an at the farm value of $289 million. However, watermelon is susceptible to a large number of diseases and pests that cause significant damage. Therefore, there is an immediate need to find genes that make watermelon resistant to diseases and pests. The cultivated watermelon belongs to a mostly wild species Citrullus lanatus, which is found in Africa and is an essential source of genes that can give the cultivated watermelon more resistance to diseases and pests. In order to locate these genes DNA maps for watermelon were constructed using special molecular (DNA) procedures. This map will be used in genetic studies of watermelon, enabling plant breeders and other scientists to find and exploit important genes needed to improve the resistance of watermelon to diseases and pests.
Technical Abstract: A genetic linkage map was constructed for watermelon using a testcross population [Plant Accession Griffin 14113 (C. lanatus var. citroides) x New Hampshire Midget (NHM; Citrullus lanatus var. lanatus)] x U.S. Plant Introduction 386015 (C. colocynthis). The map contains 142 randomly amplified polymorphic DNA (RAPD) markers produced by 78 primers, 27 simple sequence repeat- (SSR-) anchored markers produced by 17 primers, and a SCAR marker that was previously reported as linked (1.6 cM) to race 1 Fusarium wilt (incited by Fusarium oxysporum Schlechtend.:Fr. f. sp. niveum [E.F.Sm.] W.C. Synder & H.N. Hans) resistance in watermelon. The map consists of 25 linkage groups. Among them, are a large linkage group that contains 22 markers covering a mapping distance of 237.6 cM, and six large groups each with 10 to 20 markers covering a mapping distance of 68.8 to 110.8 cM. There are five additional linkage groups consisting of 3 to 7 markers per group, each covering a mapping distance of 36.5 to 57.2 cM. The thirteen remaining linkage groups are small, each consisting of 2 to 11 markers covering a mapping distance of 3.5- 29.9 cM. The entire map covers a total distance of 1178.8 cM with an average distance of 8.1 cM between each two adjunct markers. This map is useful to the development of markers linked to disease resistance and watermelon fruit qualities.