Abstract
BACKGROUND: Litchi, an economically important fruit crop in Southeast Asia, is renowned for its distinctive flavor and nutrient value, but its genetic diversity and genetic basis underlying fruit quality regulation remain largely unexplored. RESULTS: We re-sequence 276 litchi accessions collected globally and identify 54 million high-quality biallelic SNPs. We then analyze the population structure and reveal four main subgroups within the population. By phenotypic profiling of 21 fruit-quality-related traits, followed with genome-wide association study, we identify a plethora of candidate genes and genomic loci that are responsible for regulating seed and fruit quality traits. In particular, we characterize and experimentally validate an invertase gene, LcSAI, encoding an enzyme catalyzing the conversion of sucrose into reducing sugars, as a key regulator of sugar composition in litchi fruit, affecting the sweetness of litchi fruits. CONCLUSIONS: Our study demonstrates the genetic diversity and population structure of litchi. We delineate the genetic basis of fruit quality through comprehensive genomic analyses and phenotypic profiling. These findings provide valuable resources and knowledge for understanding the genetic basis of fruit quality in litchi, which contribute to the theoretical basis for further genetic improvement.