# Metabolomic Profiling of Citrus Grafts Challenged by Phytophthora citrophthora: Using the Same Samples Previously Analyzed for Epigenetic Responses

## TL;DR

This study uses metabolomics to analyze how citrus grafts respond to a pathogen, revealing chemical changes that could help in early disease detection.

## Contribution

The novel contribution is a metabolomic analysis of citrus grafts infected with Phytophthora citrophthora, using the same samples previously studied for epigenetic responses.

## Key findings

- Infection induced metabolic shifts, including increased levels of coumarins, flavonoids, and alkaloids.
- Sixty-six metabolites were annotated, with their distribution varying by graft combinations and inoculation regimes.
- Chemical profiles did not directly correlate with prior DNA methylation patterns but support metabolomics for early gummosis detection.

## Abstract

Phytophthora citrophthora infection
severely affects citrus crops, demanding improved diagnostic and control
strategies. In a previous study, epigenetic responses, including DNA
methylation patterns, were analyzed in grafted citrus plants exposed
to this pathogen. Here, we report a complementary metabolomic analysis
using the same biological material, stored under cryogenic conditions
to preserve chemical integrity. “Pera” sweet orange
and “Tahiti” acid lime scions grafted onto contrasting
rootstocks were inoculated and reinoculated with P.
citrophthora. Untargeted metabolomics via LC-MS/MS
and molecular networking revealed infection-induced metabolic shifts,
including increased levels of coumarins, flavonoids, and alkaloids
potentially involved in plant defense. Sixty-six metabolites were
annotated, and their distribution varied according to graft combinations
and inoculation regimes. While the chemical profiles provided insights
into differential metabolic responses, they did not directly correlate
with previously observed DNA methylation patterns. Nonetheless, the
results support the use of metabolomics for early detection of gummosis
and highlight the value of integrating molecular approaches to guide
citrus breeding for disease resistance.