Characterization of volatile organic compounds in grafted tomato plants upon potyvirus necrotic infection

A headspace solid-phase microextraction-gas chromatography-mass spectrometry(HS-SPME/GC-MS)method was used to study the volatile organic compounds(VOCs)associated with the differential immune response of tomato plants infected with the recombinant strain of potato virus Y(PVY^(C)-to),necrogenic to tomato.Analysis was carried out in UC82(UC),a virus susceptible tomato variety,comparing the same UC plants grafted or not onto a virus tolerant tomato ecotype,Manduria(Ma);the three types of samples used for the GC-MS analysis were mock-inoculated UC/Ma plants,UC/Ma+PVY^(C)-to and UC+PVY^(C)-to plants;the VOCs obtained were 111.Results from symptomatic PVY^(C)-to-infected UC plants showed a VOCs composition enriched in alcohols,fatty acid derivates,benzenoids,and salicylic acid derivatives,while in mock-inoculated UC/Ma plants VOCs were mainly characterized by methyl ester compounds.The VOC profile was in line with RNAseq data analyses,denoting that PVY^(C)-to viral RNA accumulation and disease symptoms induce the specific transcriptional activation of genes involved in VOCs biosynthesis.Furthermore,principal component analysis highlighted that VOCs of PVY^(C)-to-infected and mock-inoculated grafted plants were much closer each other than that of symptomatic PVY^(C)-to-infected non-grafted UC plants.These results suggest that VOCs profiles of tomato plants are related to the viral RNA accumulation,disease intensity and graft-derived tolerance to PVY^(C)-to infection.