Phenolics, flavonoids and antioxidant capacities in Citrus species with different degree of tolerance to Huanglongbing
Date
2020-04-14
Authors
Hijaz, Faraj
Al-Rimawi, Fuad
Manthey, John A.
Killiny, Nabil
Journal Title
Journal ISSN
Volume Title
Publisher
Taylor & Francis
Abstract
Huanglongbing (HLB) is a highly destructive disease to the citrus industry in Florida caused by the
bacterium, Candidatus Liberibacter asiaticus(CLas) and is transmitted by Diaphorina citri. It is hypothesized
that plants with high phenolic contents show higher tolerance to certain plant pathogens. In this
regard, different citrus varieties and plants of genera related to Citrus were analyzed for their total
phenolic and flavonoids contents, and their antioxidant capacities. In addition, the secondary metabolites
in the leaves of seven citrus species were analyzed using high performance liquid chromatographymass
spectrometry (HPLC-MS). Colorimetric assays showed that curry leaf contained the highest total
phenolic content and free radical scavenging activity (DPPH). Curry leaf also contained high concentrations
of an unusual class of carbazole alkaloids. Tolerant Citrus species contained high levels of phenolics
and flavonoids and showed high antioxidant capacities. Our results suggest that high phenolic and
flavonoid leaf contents correlate with increased citrus tolerance to CLas bacterium. The results also
suggest that the high level of carbazole alkaloids, known for their strong antimicrobial properties in
curry leaf, could make it immune to the CLas bacteria. Understanding the mechanisms underpinning
citrus tolerance to HLB will contribute to the development of commercially tolerant citrus cultivars.
Description
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Citation
Faraj Hijaz, Fuad Al-Rimawi, John A. Manthey & Nabil Killiny (2020): Phenolics, flavonoids and antioxidant capacities in Citrus species with different degree of tolerance to Huanglongbing, Plant Signaling & Behavior, DOI: 10.1080/15592324.2020.1752447