Litchi40K v1.0: a cost-effective, flexible, and versatile liquid SNP chip for genetic analysis and digitalization of germplasm resources in litchi

Genetic breeding and molecular identification in varieties depend on high-performance genotyping tools. The high heterozygosity of the litchi genome contributes to increased resequencing costs and elevated error rates in hybridization-based genotyping methods. In this study, a liquid chip named Litchi40K v1.0 was developed with high-depth resequencing data from 875 litchi samples, and its efficacy was validated across three different populations. In the <i>L. chinensis</i> var. <i>fulvosus</i> population, three subpopulations characterized by spatial distribution, and a total of 1110 genes were identified in the genomic regions with subpopulation differentiation. Additionally, a total of 30 significant signals associated with diverse agronomic traits were identified. The H002 haplotype of <i>LITCHI02696</i>, dominant in the Sub2 subgroup, significantly increased the soluble solid content in the <i>L. chinensis</i> var. <i>fulvosus</i> population. In a hybrid F₁ population, a high-density genetic map was constructed and 79 dwarfing-related QTLs were identified with the liquid chip. An NAC transcription factor was identified as a candidate gene with a heterozygous frameshift variant in the male parent. To facilitate the digitization of germplasm resources, 384 SNPs were selected, and the DNA fingerprint map revealed clear genetic relationships and a total of 10 potential synonym groups or instances of bud mutations were identified in 164 main cultivated litchi varieties. This study provides cost-effective, flexible, and versatile liquid chip for genetic analysis and digitalization of germplasm resources in litchi.