Watermelon super-pangenome paves the way for precision breeding

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Watermelon is a quintessential summertime fruit, evoking images of warm, sunny afternoons and cookouts with friends and family. You can easily picture its striped, green rind and pink flesh, imagine the delicate crunch as you bite into a slice, and almost taste the sweet juice bursting onto your tongue. What you likely don't consider is the biological basis of traits like fruit color, texture, and sweetness—the genetics that have undergone millions of years of selection, both in nature and through intentional breeding, to give you that exact experience.

How modern watermelons took shape

The watermelons we see in grocery stores are, indeed, just a few of many varieties, each with a distinct set of physical features, or phenotypes, that arise from differences in their genetic makeup, or genotype. Throughout history, breeding for desirable traits has significantly reduced the genetic diversity of cultivated watermelon, impairing its ability to adapt to environmental and disease pressures and endangering its long-term sustainability. However, wild watermelons have retained many valuable traits and could therefore hold the key to improving modern cultivars.

Building a watermelon super-pangenome

To better understand how genotypic differences contribute to phenotypic variation in watermelon, an international team led by Dr. Zhangjun Fei of the Boyce Thompson Institute has established a comprehensive watermelon super-pangenome, now published in Nature Genetics. This groundbreaking resource integrates 138 genomes from both wild and cultivated watermelons to depict evolutionary relationships between individual genomes at an unprecedented depth.

Traditional reference genomes are typically derived from a single representative of a species, while pangenomes incorporate multiple accessions within a species, but neither fully captures the diversity across related species. Fei explains, "We call ours a super-pangenome because we have incorporated accessions not just from one species, but from all seven extant species in the watermelon genus. The wild relatives provide abundant information for marker development and genomic prediction." Super-pangenomes, therefore, are powerful tools for targeted breeding of crops that can better meet the needs of society.

Mapping structural variants and traits

Watermelon genomes contain hundreds of megabases of DNA, and differences between individual genomes range from minor single nucleotide polymorphisms (SNPs) to large structural variants (SVs) that can span hundreds of thousands of bases. The graph-based nature of this watermelon super-pangenome yields an enhanced capacity for detecting such SVs, which can have dramatic impacts on phenotype. Integrating all of this information, Fei's team essentially created a complex map of watermelon genetic diversity.

With this powerful resource in hand, the team aimed to link specific genomic regions to important agricultural traits. The integration of SV data into their analysis vastly expanded the potential to identify strong genotype-phenotype associations, leading to the discovery of several SVs strongly associated with sweetness and pathogen resistance.

Discoveries that reshape breeding potential

Notably, one SV was found to be significantly associated with flesh color intensity, an important commercial trait that correlates with nutritional value and influences consumer appeal. This SV impacted the expression of one particular gene, and as Fei stressed, "This gene could only have been identified using this super-pangenome because the SV was not linked to any nearby SNPs."

Beyond individual gene discoveries, this super-pangenome opens the door to broader applications. "These resources can directly impact breeding strategies," says Fei, "as we can use them to build platforms for genomics-assisted breeding." Demonstrating this potential, the team generated predictive models that can deduce phenotypic characteristics based on a compact set of high-impact SNP and SV markers.

From lab insights to future fields

Genomic resources like super-pangenomes provide a wealth of insight into the genetic basis of important traits, but their implications extend beyond the laboratory. With molecular-level knowledge of how traits are inherited, targeted breeding strategies can be devised to more efficiently develop crops with favorable combinations of traits.

For watermelon, a primary goal is to reintroduce disease resistance from wild relatives while maintaining the sensory traits that have cemented it as a consumer favorite. In the era of super-pangenomes, such customization is becoming increasingly attainable.

Publication details

Honghe Sun et al, Population-level super-pangenome reveals genome evolution and empowers precision breeding in watermelon, Nature Genetics (2026). DOI: 10.1038/s41588-026-02598-8

Journal information: Nature Genetics

Key concepts

evolutiongeneticsgenotypeBiological Variation, PopulationPhylogenyGenomes

Provided by Boyce Thompson Institute