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ARS Home » Northeast Area » Washington, D.C. » National Arboretum » Floral and Nursery Plants Research » Research » Publications at this Location » Publication #314685
Title: Specific detection and identification of mulberry-infecting strains of Xylella fastidiosa by polymerase chain reaction

Author
item GUAN, WEI - Chinese Academy Of Agricultural Sciences
item Shao, Jonathan
item Davis, Robert
item ZHAO, TINGCHANG - Chinese Academy Of Agricultural Sciences
item Huang, Qi

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2015
Publication Date: 6/10/2015
Citation: Guan, W., Shao, J.Y., Davis, R.E., Zhao, T., Huang, Q. 2015. Specific detection and identification of mulberry-infecting strains of Xylella fastidiosa by polymerase chain reaction. PLoS One. DOI: 10.1371/journal.pone.0129330.

Interpretive Summary: Xylella fastidiosa is a slow growing, xylem inhabiting, nutritionally fastidious and insect-transmitted bacterium. The bacterium is associated with bacterial leaf scorch and decline in many economically important landscape trees including oak, elm, sycamore, maple and mulberry. Bacterial leaf scorch caused by X. fastidiosa in mulberry was first reported in 1986, and was found in NY, NJ, PA, DE, VA, MD, Washington DC, NE, KY and CA. So far, no detection method is available to specifically detect and identify a particular landscape tree strain of X. fastidiosa to facilitate epidemiological and etiological studies and control of X. fastidiosa in landscape trees. Based on the genome sequence we recently published, we developed two sets of PCR primers that are specific for mulberry strains of X. fastidiosa in the U. S. The PCR assay using such primers allowed specific detection and differentiation of mulberry strains from other North or South American strains of X. fastidiosa in cultured bacterium strains and infected plant samples. Unexpectedly, the specific DNA sequence we identified only in the mulberry-infecting strains in the U. S. was also found in the recently sequenced olive strain isolated from Italy, so the two primer sets might also be useful for specific detection and differentiation of the olive-infecting strains in Italy to aid better understanding of the evolution and biology of this new group of X. fastidiosa strains. Our work will be of value primarily to plant pathologists, entomologists and clinicians interested in diseases caused by X. fastidiosa.

Technical Abstract: X. fastidiosa causes bacterial leaf scorch in many landscape trees including elm, oak, sycamore and mulberry, but methods for specific identification of a particular tree host species-limited strain or differentiation of tree-specific strains are lacking. It is also unknown whether a particular landscape tree-infecting X. fastidiosa strain is capable of infecting multiple landscape tree species in an urban environment. We developed two sets of PCR primers specific for mulberry-infecting strains of X. fastidiosa based on the nucleotide sequence of a unique open reading frame identified only in mulberry-infecting strains among all the North and South American strains of X. fastidiosa sequenced to date. PCR using either set of primers allowed specific detection and identification of mulberry-infecting X. fastidiosa strains in cultures and in samples collected from naturally infected mulberry trees. In addition, no mixed infections with or unspecific detections of the mulberry-infecting strains of X. fastidiosa were found in naturally X. fastidiosa-infected oak, elm and sycamore trees growing in the same region where naturally infected mulberry trees were grown. This genotype-specific PCR assay will be valuable for disease diagnosis, studies of strain-specific infections in insects and plant hosts, and management of diseases caused by X. fastidiosa. Unexpectedly, the unique open reading frame conserved only in the mulberry-infecting strains in the U. S. was also identified in the recently sequenced olive strain CoDiRO isolated from Italy, so the two primer sets might also be useful for specific detection and differentiation of the olive-infecting strains in Italy to aid better understanding of the evolution and biology of this new group of X. fastidiosa strains.