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Title: Identification and translocation of metabolites from powdery mildew resistant rootstocks to susceptible watermelon scions using nuclear magnetic resonance spectroscopy

item MAHMUD, I - Claflin University
item Kousik, Chandrasekar - Shaker
item HASSELL, RICHARD - Clemson University
item CHOWDHURY, K - Claflin University
item BOROUJERDI, A - Claflin University

Submitted to: Metabolomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/24/2015
Publication Date: 8/25/2015
Citation: Mahmud, I., Kousik, C.S., Hassell, R., Chowdhury, K., Boroujerdi, A. 2015. Identification and translocation of metabolites from powdery mildew resistant rootstocks to susceptible watermelon scions using nuclear magnetic resonance spectroscopy. Metabolomics. J. Agric. Food Chem., DOI: 10.1021/acs.jafc.5b02108.

Interpretive Summary: Watermelon is an important vegetable crop, grown in 44 states in the United States. Powdery mildew caused by a fungus is a serious disease that can limit watermelon production by reducing yields and plant vigor. We have developed several rootstocks that are highly resistant to this disease. Grafting commercial watermelon on these resistant rootstocks is being evaluated as an alternative strategy to manage powdery mildew. Using nuclear magnetic resonance (NMR) spectroscopy, we have identified several metabolites that can potentially move from these resistant rootstocks to susceptible watermelon grafted onto them and that may play a role in providing some level of resistance. The results from this study will be useful to other researchers interested in developing biochemical markers for rapidly identifying disease resistant lines.

Technical Abstract: Watermelon (Citrullus lanatus), an important commercial crop, and nutritious fruit, is high in antioxidants, vitamins, and lycopene. Powdery mildew (PM) is a serious disease caused by Podosphaera xanthii, which significantly reduces watermelon production in the U.S. and other parts of the world. Currently no commercial edible watermelon variety resistant to PM is available. As an alternative to lengthy conventional breeding to develop resistant commercial watermelon, grafting susceptible cultivar on non-commercial resistant rootstocks is being explored as a management strategy. Previous studies have shown translocation of limited PM resistance from a resistant rootstock to a susceptible scion. To identify potential metabolites responsible for PM resistance, NMR-based metabolic profiles of susceptible and resistant rootstocks of watermelon and their corresponding susceptible scions (Mickey Lee) were compared using principal component analysis (PCA). Mahalanobis distance analysis showed significant score plot differences between the susceptible and resistant groups. Significantly different spectral buckets and their corresponding metabolites (including choline, fumarate, 5-hydroxyindole-3-acetate, and melatonin) have been identified quantitatively using loading and volcano plot analyses. Our data suggests that these metabolites were being translocated from the powdery mildew resistant (PMR) rootstocks to their corresponding powdery mildew susceptible (PMS) scions.