Preharvest applications of monopotassium phosphate to improve fruit quality and volatilome composition in cold-stored cherry tomato

The experiment addressed the effects of preharvest KH₂PO₄ foliar spraying (20 mmol · L⁻¹) on fruit quality and composition (including volatile organic compounds, VOCs) of cherry tomatoes ('Caravaggio', 'Sugarland' and 'Top Stellina') after 0 (S₀ ), 7 (S₇) and 14 days (S₁₄) of storage at 8.0 °C. On the average of the 3 genotypes, the KH₂PO₄ treatment improved fruit pressure firmness, total soluble solids (TSS), titratable acidity (TA), total phenols and carotenoids concentrations, along with the fruits' antioxidant capacity (by up to 17% for FRAP assay). Within the S₇-S₁₄ period, control fruits showed the highest reductions in TSS, TSS/TA ratio and total carotenoids (-17,-12 and-45, respectively), whereas treated fruits proved the strongest increase in DPPH (+12%). Sixteen out of 32 VOCs were promoted following KH₂PO₄ application, including the aldehydes hexanal, (E)-2-hexenal and (Z)-3-hexenal and the apocarotenoids (E)-citral, (E)-β-ionone, geranylacetone and 6-methyl-5-hepten-2-one. Proceeding from S₀ to S₁₄, several VOCs decreased more strongly in control fruits, as for hexanal (-48%\) and total aldehydes (-42%\, whereas at S₁₄ treated fruits had higher concentrations of linalool, geranylacetone and 6-methyl-5-hepten-2-one (1.06, 52.50 and 79.27 µg · kg⁻¹, respectively). 'Caravaggio' demonstrated the strongest apocarotenoid reduction at S₁₄, whereas 'Top Stellina' was more responsive to KH₂PO₄ (mainly for b-cyclocitral, geranylacetone and total terpenes/terpenoids), thus highlighting the central role of the genotype in responding to other experimental factors. Nonetheless, these results suggest that proper preharvest KH₂PO₄ applications can preserve specific commercial, nutritional and quality traits of cold-stored cherry tomatoes.