NMR Analysis Reveals a Wealth of Metabolites in Root-Knot Nematode Resistant Roots of Citrullus amarus Watermelon Plants

Abstract

Citrullus amarus (CA) (previously known as Citrullus lanatus var. citroides) accessions collected in southern Africa are known to have resistance to root-knot nematodes (RKN) and are suitable rootstocks for grafted watermelon. The objective of this study was to conduct a comparative metabolomics analysis and identify unique metabolites in roots of CA accessions versus roots of watermelon cultivars (Citrullus lanatus (Thunb.) Matsum. and Nakai var. lanatus; CL). Nuclear magnetic resonance (NMR) technology and principal component analysis (PCA) were used to analyze and compare metabolic profiles of seven CA accessions resistant to RKN along with two RKNsusceptible watermelon cultivars (Charleston Gray and Crimson Sweet). Calculation of the Mahalanobis distance revealed that the CA United States Plant Introduction (PI) 189225 (Line number 1832) and PI 482324 (1849) have the most distinct metabolic profiles compared with the watermelon cultivars Charleston Gray and Crimson Sweet, respectively. Several amino acids identified in the CA accessions were reported in previous studies to have a nematicidal effect. The results in this study indicate that roots of watermelon accessions collected in the wild are rich in metabolic compounds. These metabolic compounds may have been diminished in watermelon cultivars as a consequence of many years of cultivation and selection for desirable fruit qualities.

Twenty Years of 1H NMR Plant Metabolomics: A Way Forward toward Assessment of Plant Metabolites for Constitutive and Inducible Defenses to Biotic Stress

“…Higher amounts of glucose and raffinose have been reported in watermelon roots resistant to root-knot nematodes, along with increased levels of choline and malic acid. 118 Resistance to blight disease in potato plants has been associated with the accumulation of organic acids but, in contrast to the studies above, lower levels of carbohydrates. 53 Based on the reviewed literature, resistance is often associated with higher free carbohydrate concentrations in many plants.…”

Combining targeted metabolite analyses and transcriptomics to reveal the specific chemical composition and associated genes in the incompatible soybean variety PI437654 infected with soybean cyst nematode HG1.2.3.5.7

“…Therefore, plant metabolomics is considered as an indispensable tool in the study of plant-pathogen interactions [ 30 ]. Plants respond to pathogen infection by producing defense-related metabolites, especially the plant secondary metabolites, which play important roles in plant resistance [ 31 ]. Metabolomics can provide technical support for the identification of plant metabolites, which are potential sources of new compounds for nematode control [ 32 ].…”

“…In addition, they studied the levels of metabolites in tomato plants after root-knot nematode infection, and found that tomato roots showed changes in biochemical pathways in response to root-knot nematode infection [ 33 ]. Recently, Kantor et al investigated the metabolite profiles of both incompatible and compatible watermelon accessions with root-knot nematode infection and found that the roots of incompatible wild watermelon accessions were rich in metabolic compounds that had a nematicidal effect but these compounds showed decreased levels in commercial watermelon cultivars [ 31 ]. However, there have been a few studies on soybean-SCN interactions based on proteomic and metabolomic analyses [ 34 , 35 ].…”

Combining Targeted Metabolite Analyses and Transcriptomics to Reveal Specific Chemical Composition and Associated Genes in Resistant Soybean Infected with Soybean Cyst Nematode

“…Therefore, plant metabolomics is considered as an indispensable tool in the study of plant-pathogen interaction [12]. Plants respond to pathogen infection by producing the defense metabolites, especially, the plant secondary metabolites play important roles in plant host's resistance [33]. Metabolomics will provide technical support for the identi cation of plant metabolites which are potential sources of new compounds for nematode control [9].…”