S01 - Session O7 - Direct-injection spectrometry and whole-genome genotyping unravel the genetic regulation of fresh and roasted kernels of almond

Authors: Gaetano Distefano *, Mario Di Guardo, Brian Farneti, Khomenko Iuliia, Leonardo Luca, Modica Giulia, Luca Bianco, Michela Troggio, Francesco Sottile, La Malfa Stefano, Franco Biasioli, Alessandra Gentile

Almond ( Prunus dulcis Mill.) is particularly appreciated for its nutraceutical value and aromatic profile of the kernels. To decipher the genetic mechanism of aroma production, a collection of 106 almond genotypes, including Sicilian accessions and Italian and foreign varieties, was genotyped using both the Illumina Infinium ® 18K Peach SNP array and the Axiom TM 70K almond SNP array. The same individuals were phenotyped for two consecutive years for the production of volatile organic compounds (VOCs) using a proton-transfer time-of-flight mass spectrometer (PTR-TOF-MS). Profiling of the almond aroma was carried out on fresh and roasted kernels, enabling the detection of 150 mass peaks. Some, such as those related to sulphur compounds, furan containing compounds, and aldehydes formed by Strecker degradation, significantly increased during roasting, while VOCs belonging mostly to alcohols and terpenes, significantly decreased. A total of 938 robust SNPs were selected from the Illumina Infinium18K Peach SNP array and employed for population genetic studies. Structure analysis detected significant genetic stratifications for K= 2, while linkage disequilibrium decay across the genome was equal to r 2 = 0.048. The Axiom 70K almond SNP array will be employed instead for genome-wide association analysis. Preliminary results obtained with the Illumina 18K detected 38 mass peaks in fresh, and 42 ones in roasted almond s associated with at least one SNP marker. I n silico annotation enabled the identification of several candidate genes as three mass peaks, in particular, were characterized by SNPs in linkage with an alcohol dehydrogenase gene catalysing the oxidation and reduction of a wide variety of alcohols, aldehydes or ketones, and/or regulating the synthesis of esters through the reduction of the aldehydes. A precise elucidation of the genetic regions involved in the production of different VOCs is a fundamental step toward the understanding of the physiology and regulation of almond aroma. The detection of molecular markers linked to different VOCs will help both the understanding of their regulation and the selection of novel varieties with enhanced aromatic profiles through marker-assisted selection.