Features of the fruit epicuticular waxes of Prunus persica cultivars and hybrids concerning pathogens susceptibility

Abstract

The high susceptibility of peach (Prunus persica L. Batsch) fruits to fungal diseases, which cause significant crop losses and a decrease in crop quality and the unsatisfactory effectiveness of chemical pathogen control agents, force us to look for unrealized reserves of plant resistance. In this regard, we hypothesized that the identification of differences in the hydrocarbon composition of fruit epicuticular waxes of peaches hybrids, which differ in resistance to pathogens, may contribute to a better understanding of the possible role of wax components in pathogenesis. The study was carried based on the Botanical Garden of Oles Honchar Dnipro National University (Dnipro city, Ukraine) using the ripening peach fruits of the "Red Heaven" cultivar and two hybrids with differences in the crossing schemes, fruit ripening rates, and fruit susceptibility to fungal diseases. The chloroform extracts of fruit epicuticular waxes were analyzed by gas chromatography connected to mass-spectrometry. GC/MS assay was performed using Shimadzu GCMS-QP 2020 El equipped with a capillary column (5% diphenyl/95% dimethyl polysiloxane) and helium carrier gas. Mass Spectrum Library 2014 for GCMS was used to identify the separated compounds of the wax extracts. The dominant components of all peach fruits' epicuticular waxes were n-alkanes with an even and odd carbons number from C27 to C60. Of these, some alkanes with an even number of carbons were represented by several isomers. The epicuticular wax of the most stable hybrid 1 contained a significant portion of odd alkanes, including hexacosane, which can be regarded as a factor contributing to cuticle integrity and, thus, counteracting the pathogenic infection development. The epicuticular fruit wax of the "Red Heaven" cultivar contains the highest total amount of alkanes, responsible for fruit sensitivity to pathogenic fungi attacks. In the epicuticular waxes of the most vulnerable hybrid 2, the highest amount of very-long-chain alkanes, the hexadecanoic fatty acid, and fatty aldehyde eicosanal were detected, which together could cause cuticle damage and high susceptibility of fruits to fungal diseases.