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Title: An integrated genetic linkage map of watermelon and genetic diversity based on single nucleotide polymorphism (SNP) and simple sequence repeat (SSR) markers

Author
item NIMMAKAYALA, P - West Virginia State University
item BHANDARY, A - West Virginia State University
item ABBURI, V - West Virginia State University
item ALMEIDA, A - West Virginia State University
item REDDY, R - West Virginia State University
item VAJJA, V - West Virginia State University
item MALKARAM, S - West Virginia State University
item VENKATRAMANA, P - West Virginia State University
item TOMASSON, Y - West Virginia State University
item WEHNER, T - West Virginia State University
item Levi, Amnon
item REDDY, U - West Virginia State University

Submitted to: Molecular Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/24/2014
Publication Date: N/A
Citation: N/A

Interpretive Summary: There is a need to evaluate watermelon varieties collected in different parts of the world and identify valuable gene sequences useful for enhancing nutritional fruit quality and disease resistance in this important specialty crop. In this study, a USDA, ARS scientist collaborated with a team of scientists from West Virginia State University and North Carolina State University, using advanced genomic sequencing technologies to evaluate the genomes of 130 watermelon varieties collected in different parts of the world. The results in this study show the American watermelon varieties share a narrow genetic base with varieties collected in Asia, the Mediterranean region, Europe, and South America. The results in this study confirm the need to broaden the genetic base of the sweet red watermelon using varieties collected in Africa, the center of origin of watermelon. The information in this study should be useful for seed company breeders and researchers interested in enhancing watermelon fruit quality and disease resistance.

Technical Abstract: Watermelon (Citrullus lanatus var. lanatus) is an important vegetable fruit throughout the world. A high number of single nucleotide polymorphism (SNP) and simple sequence repeat (SSR) markers should provide large coverage of the watermelon genome and high phylogenetic resolution of germplasm accessions and linkage mapping, useful for marker-assisted breeding and incorporating quantitative trait loci and single genes into elite watermelon cultivars. In this study, we aimed to construct a genetic map and evaluate genetic relationships among 130 watermelon accessions collected throughout the world based on SNPs and SSR markers. We incorporated 282 markers (232 SNPs and 50 SSRs) into the linkage map. The genetic map consisted of 11 linkage groups, spanning 924.72 cM with an average distance of 3.28 cM between markers. The SNP sequences were assembled using the watermelon genome sequence draft and a corresponding chromosome number, and could be readily assigned for each of the linkage groups. Of the 232 SNP markers, 134 were polymorphic among the 130 cultivated watermelon accessions, confirming the low genetic diversity exists among sweet red watermelon varieties. The current 384-plex SNP set is a powerful tool for characterizing genetic relatedness and for developing medium-resolution genetic maps.