Targeted Metabolic Profiles of the Leaves and Xylem Sap of Two Sugarcane Genotypes Infected with the Vascular Bacterial Pathogen Leifsonia xyli subsp. xyli

Abstract

Ratoon stunt (RS) is a worldwide disease that reduces biomass up to 80% and is caused by the xylem-dwelling bacterium Leifsonia xyli subsp. xyli. This study identified discriminant metabolites between a resistant (R) and a susceptible (S) sugarcane variety at the early stages of pathogen colonization (30 and 120 days after inoculation—DAI) by untargeted and targeted metabolomics of leaves and xylem sap using gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS), respectively. Bacterial titers were quantified in sugarcane extracts at 180 DAI through real-time polymerase chain reaction. Bacterial titers were at least four times higher on the S variety than in the R one. Global profiling detected 514 features in the leaves and 68 in the sap, while 119 metabolites were quantified in the leaves and 28 in the sap by targeted metabolomics. Comparisons between mock-inoculated treatments indicated a greater abundance of amino acids in the leaves of the S variety and of phenolics, flavonoids, and salicylic acid in the R one. In the xylem sap, fewer differences were detected among phenolics and flavonoids, but also included higher abundances of the signaling molecule sorbitol and glycerol in R. Metabolic changes in the leaves following pathogen inoculation were detected earlier in R than in S and were mostly related to amino acids in R and to phosphorylated compounds in S. Differentially represented metabolites in the xylem sap included abscisic acid. The data represent a valuable resource of potential biomarkers for metabolite-assisted selection of resistant varieties to RS.

Flavonoids and phenolic acids from sugarcane: Distribution in the plant, changes during processing, and potential benefits to industry and health

“…Compounds identified without hydrolysis with a high level of certainty by LC/MS include various chlorogenic acids, including caffeoyl‐ and feruloyl‐quinic acid isomers with a lower level of free phenolic acids. Orientin and iso‐orientin, C‐ glycosides of luteolin, and vitexin, a C‐ glycoside of apigenin, are predominant flavonoids in sugarcane leaves (Castro‐Moretti et al., 2021). The other publications shown in Table 2 identified (poly)phenols only by absorption spectra against standards and so have a lower degree of confidence in identification.…”

“…(2005, 2006, 2008) (4) Castro‐Moretti et al. (2021); (5) Sun et al. (2014); (6) Duarte‐Almeida et al.…”

Dare to be resilient: the key to future pesticide-free orchards?

“…Chlorophyll content has also been studied as a possible index of tree health ( Talebzadeh and Valeo, 2022 ). Therefore, many biomarkers of resilience can be considered, such as fruit productivity; vegetative growth through measurements of above-ground or root biomass based on height, leaf or canopy volume, basal area, and branch or trunk diameters ( Dobbertin, 2005 ); ecophysiological parameters such as photosynthetic activity, evapotranspiration, water use efficiency, or canopy temperature ( Méthy, 2000 ; Oerke et al , 2011 ; Klein et al , 2013 ); and metabolomic profiles of leaves and sap throughout the entire time of infestation ( Castro-Moretti et al , 2021 ) ( Fig. 3 ).…”

A metabolomic platform to identify and quantify polyphenols in coffee and related species using liquid chromatography mass spectrometry

“…Synapaldehyde increases reactive oxygen species in plants and has anti-fungal activity (Millan et al, 2022). Also, this metabolite was more abundant in sugarcane resistant to the causal agent of ratoon stunting (Castro-Moretti et al, 2021), associating its role to plant defense. Overall, WR leaves had a higher diversity of phytochemicals in comparison to the CC.…”