Proton transfer reaction-mass spectrometry analysis is a valuable tool for the identification of genomic regions related to volatile organic compounds

Proton Transfer Reaction-Mass Spectrometry (PTR-MS) is a novel mass spectrometric technique that allows the detection of Volatile Organic Compounds (VOCs). In a previous study, we have shown that chemical information is available and allows the identification of relevant metabolites in ripe apples; moreover, PTR-MS analysis have permitted the detection of related QTLs in apple genetic linkage maps based on a segregating population of the cross ‘Fiesta’ × ‘Discovery’. In this study, PTR-MS has been applied to measure the VOCs emitted by apple fruit of the same progeny grown in three different sites in Switzerland (Conthey, Cadenazzo, Wädenswil). QTL analysis for all PTR-MS peaks was carried out and genomic regions associated with peaks at m/z=28, 43, 57, and 61 were identified (LOD >2.5) in linkage group 2 and 15. QTLs were confirmed consistently for all three different environments and they were the same QTLs detected in one location in the previous work. The remaining QTLs, which were present in the prior analysis based on Cadenazzo’s progeny, were confirmed for the same environment but they were not significant for the other two locations. Phenotypic variability ranged from 24 to 67% representing a starting point for quality breeding. Fruit quality parameters were evaluated in a set of the ‘Fiesta’ × ‘Discovery’ population (Wädenswil) through expert panel test and using a Pimprenelle Robotic machine. Thus, it was possible to identify putative QTLs for sweetness, sour taste, and malic acid in LG8.