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ARS Home » Southeast Area » Fort Pierce, Florida » U.S. Horticultural Research Laboratory » Subtropical Insects and Horticulture Research » Research » Publications at this Location » Publication #328804

Title: Metabolic variations in different citrus rootstock cultivars associated with different responses to Huanglongbing

Author
item ALBRECHT, UTE - University Of Florida
item FIEHN, OLIVER - University Of California
item Bowman, Kim

Submitted to: Plant Physiology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/18/2016
Publication Date: 5/20/2016
Citation: Albrecht, U., Fiehn, O., Bowman, K.D. 2016. Metabolic variations in different citrus rootstock cultivars associated with different responses to Huanglongbing. Plant Physiology and Biochemistry. 107:33-44.

Interpretive Summary: Huanglongbing (HLB) is a very destructive disease of citrus, and since being discovered in Florida in 2005, has been estimated to have resulted in an overall economic loss of $4.5 billion. Some citrus rootstock cultivars have been shown to exhibit tolerance to the disease. In this study, we have compared metabolic compounds found in six different rootstock cultivars that range from tolerant to highly sensitive in response to infection with the bacteria that causes huanglongbing. The most tolerant cultivars exhibited very little metabolic change in response to infection with the pathogen, while the most sensitive cultivar had many and large metabolic changes in response to infection. Many metabolites associated with stress resistance were found in higher concentrations in the tolerant cultivars, independent of infection by the pathogen. Some of the these metabolites are hypothesized to play important roles in conferring tolerance to HLB.

Technical Abstract: Huanglongbing (HLB) is one of the most destructive bacterial diseases of citrus. No resistant cultivars have been identified, although tolerance has been observed in the genus Poncirus and some of its hybrids with Citrus that are commonly used as rootstocks. In this study we exploited this tolerance by comparing five different tolerant hybrids with a cultivar that shows pronounced HLB sensitivity to discern potential contributing metabolic factors. Whole leaves of infected and non-infected greenhouse-grown seedlings were extracted and subjected to untargeted GC-TOF MS based metabolomics. After BinBase data filtering, 342 (experiment 1) and 650 (experiment 2) unique metabolites were quantified, of which 122 and 195, respectively, were assigned by chemical structures. The number of metabolites found to be differently regulated in the infected state compared with the non-infected state varied between the cultivars and was largest (166) in the susceptible cultivar Cleopatra mandarin (Citrus reticulata) and lowest (3) in the tolerant cultivars US-897 (C. reticulata ‘Cleopatra’ x Poncirus trifoliata) and US-942 (C. reticulata ‘Sunki’ x P. trifoliata) from experiment 2. Tolerance to HLB did not appear to be associated with accumulation of higher amounts of protective metabolites in response to infection. Many metabolites were found in higher concentrations in the tolerant cultivars compared with susceptible Cleopatra mandarin and may play important roles in conferring tolerance to HLB. Lower availability of specific sugars necessary for survival of the pathogen may also be a contributing factor in the decreased disease severity observed for these cultivars.