Using Genomic Tools to Explore Genetic Diversity and Enhance Watermelon Cultivars

There is a continuous need to enhance watermelon cultivars for disease and pest resistance.  U.S. Plant Introductions (PIs) representing the different groups of watermelon (Citrullus spp.) are considered a useful source for enhancing disease or pest resistance in watermelon cultivars.  In this study, high frequency oligonucleotides - targeting active gene (HFO-TAG) primers were used in polymerase chain reaction (PCR) experiments to produce over 560 polymorphic markers among the Citrullus genotypes. Also, genotyping by sequencing (GBS) produced over 4000 SNPs among the Citrullus genotypes. The HFO-TAG and SNP data were used in cluster and multidimensional scaling plot and population structure analyses to produce distinct groups of Citrullus PIs. The SNP and HFO-TAG marker results are consistent with our recent findings using fluorescence in situ hybridization (FISH) technology showing major differences in configuration of ribosomal DNA markers between the Citrullus groups. Overall, The HFO-TAG and SNP markers revealed a wide genetic diversity among the Citrullus groups and different sources of Citrullus spp. should be useful for enhancing disease or pest resistance in elite watermelon cultivars.