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Research Project: Genetic Enhancement of Watermelon, Broccoli, and Leafy Brassicas for Economically Important Traits

Location: Vegetable Research

Title: NMR analysis reveals a wealth of metabolites in root-knot nematode resistant roots of Citrullus amarus watermelon plants

item KANTOR, MIHAIL - Claflin University
item Levi, Amnon
item Thies, Judy
item GUNER, NIHAT - Sakata Seed America, Inc
item KANTOR, CAMELIA - Claflin University
item PARNHAM, STUART - National Institute Of Standards & Technology (NIST)
item BOROUJERDI, AREZUE - Claflin University

Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/24/2018
Publication Date: 9/5/2018
Citation: Kantor, M., Levi, A., Thies, J.A., Guner, N., Kantor, C., Parnham, S., Boroujerdi, A. 2018. NMR analysis reveals a wealth of metabolites in root-knot nematode resistant roots of Citrullus amarus watermelon plants. Journal of Nematology. 50(3)303-316.

Interpretive Summary: Watermelon is an important vegetable crop in the United States and throughout the world. As a result of many years of domestication watermelon cultivars are highly susceptible to soil-borne diseases, like Fusarium wilt, and pests, like root-knot nematodes. There is a continuous need to improve watermelon varieties for resistance to these diseases and pests. Watermelon accessions collected in the wild in southern Africa have shown to have high tolerance to root-knot nematodes compared with watermelon cultivars. In this study, ARS scientists at the U.S. Vegetable Laboratory, Charleston, S.C. collaborated with scientists from Claflin University (South Carolina) on using nuclear magnetic resonance (NMR) technology to identify metabolic compounds unique to roots of the African watermelon accessions that show resistance to root-knot nematodes. The scientists were able to identify a plethora of unique compounds in the wild African watermelon that do not exist in watermelon cultivars. The data in this study elucidate the metabolic differences in roots of wild versus cultivated watermelon and should be useful for researchers interested in identifying unique compounds that may repeal or inhibit root-knot nematode infection in watermelon and other cucurbit crops.

Technical 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. A comparative metabolomics study was performed to identify unique metabolites in roots of CA accessions versus roots of watermelon cultivars (Citrullus lanatus (Thunb.) Matsum. & 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 RKN-susceptible 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 profile compared to 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 compound may have been diminished in watermelon cultivars as a consequence of many years of cultivation and selection for desirable fruit qualities.