Indirect evaluation of the volatile profile of watermelons using e-nose systems: application to rootstock phenotyping

The data presented here includes cromatografic and e-nose data obtained for the following study:

The evaluation of aroma in breeding programs of fruity species has been widely overlooked, resulting in drastic flavour deterioration. The high costs of sensory evaluations and the low number of samples that can be assessed per session limit its use for selecting finalist lines. Gas chromatography-mass spectrometry (GC-MS) avoids some of the limitations of sensory panels, but still, it requires complex volatile extraction procedures and compound separation, it is expensive, and it cannot be applied to contexts where a high number of samples is to be analyzed. In this work, we have assessed the volatile profile of different scion-rootstock combinations in watermelon using GC-MS and an e-nose system to evaluate the feasibility of incorporating the last system for a fast and reliable evaluation of the volatile profile of watermelon. PLS-DA models for group classification using GC-MS and e-nose data offered moderate performances, mainly due to the subtle differences present between groups, as the same F1 hybrid cultivar was used as scion. Nonetheless, PLS-DA biplot provided a clear correlation between GC-MS and e-nose data. Using this methodology, the e-nose system was capable of detecting the effects of specific root-scion combinations in comparison with the non-grafted control. It also detected which combinations offered more variable volatile profiles. It could even detect samples within each combination that offered an anomalous volatile profile precisely in the same way as the CG-MS data did. Furthermore, PLS models were developed, allowing reasonably accurate predictions of the contents in key compounds such as geranylacetone, (Z)-6-nonen-1-ol or (Z)-6-nonenal, which can have positive or negative impacts on flavour and taste perception of watermelon. The low cost and analysis time of the electronic olfactometer, as well as its similarity to the information provided by GC-MS, will enable the incorporation of high-throughput volatile profile phenotyping in breeding programs of new cultivars and rootstocks and for the evaluation of crop management techniques.