Genomic insights into apple aroma diversity

An apple's aroma is a major determinant of its desirability by consumers. To better understand the aroma of apples, 2-dimensional gas-chromatography mass-spectrometry (2D-GCMS) was used to quantify 106 volatile organic compounds (VOCs) from 515 apple varieties. We identified esters and aldehydes as the most abundant classes of VOCs, with butyl acetate and hexyl acetate being present in nearly every variety. Principal component analysis (PCA) revealed that the primary axis of variation in the apple volatilome is correlated with harvest date, with early-harvested apples expressing a greater number and higher concentration of VOCs compared to late-harvested apples. Genome-wide association studies (GWAS) using 250,579 single nucleotide polymorphisms (SNPs) identified a significant association between SNPs near the alcohol acyltransferase (AAT1) locus and the abundance of several esters. Additionally, strong associations were observed between SNPs at the NAC18.1 transcription factor locus and the abundances of 1-hexanol and 1-butanol, which serve as precursors for hexyl acetate and butyl acetate, respectively. These findings provide a foundation for understanding the genetic basis of apple aroma production and pave the way for the genomics-assisted enhancement of the aroma profiles of apple varieties to meet consumer preferences.