Xylella Fastidiosa: Its Biology, Diagnosis, Control And Risks

Journal of Plant Pathology (2010), 92 (1, Supplement), S1.35-S1.48

Edizioni ETS Pisa, 2010

S1.35

MINIREVIEW

XYLELLA FASTIDIOSA: ITS BIOLOGY, DIAGNOSIS, CONTROL AND RISKS
J.D. Janse1 and A. Obradovic2
1 Department

of Laboratory Methods and Diagnostics, Dutch General Inspection Service, PO Box 1115, 8300 BC Emmeloord, The Netherlands 2 Plant Pathology Department, University ofBelgrade, Serbia

SUMMARY

The bacterium Xylella fastidiosa, a xylem-inhabiting, vector-transmitted, Gram-negative, very slow growing bacterium, was cultured and properly described for the first time in 1987 in the USA as the cause of Pierce’s disease (PD) of grapevine, Vitis vinifera (disease observed already in 1884) and as the cause of phony peach disease (PPD) in peach, Prunus persica (diseaseobserved in 1890 in the USA) and in 1993 in Brazil as the cause of citrus variegated chlorosis (CVC) or citrus X disease. Moreover, it was found that the bacterium also causes a number of so-called leaf scorch diseases in Prunus spp. (including almond leaf scorch or ALS in Prunus amygdalus and plum leaf scald or PLS in Prunus domestica), Acer spp., Carya illinoinensis (pecan), Coffea arabica(CLC, in Brazil isolated in 1995 and also pathogenic to Citrus), Hedera helix, Morus rubra, Nerium oleander (OLS), Platanus occidentalis, Quercus spp., and Ulmus americana. It infects also Medicago sativa (alfalfa dwarf) and Vinca major (wilting symptoms). Many wild plants may carry the pathogen with, but more often without showing symptoms, such as grasses, sedges and trees. A list of main hosts ispresented. All these diseases are not seed-borne and occur mainly in tropical/subtropical areas, although leaf scorch diseases also occur in much colder climate, e.g. oak leaf scorch in eastern North America up to Canada. Several pathogenic varieties of the bacterium have been described, that are often hostspecific (e.g., the PD strain will not cause disease if introduced to peach or plum). Thefollowing subspecies have been described: (i) Xylella fastidiosa subsp. fastidiosa (erroneously named X. f. subsp. piercei), PD and LSA, strains from cultivated grape, alfalfa, almond, and maple; (ii) X. fastidiosa subsp. multiplex, PPD, PLS, strains from peach, elm, plum, pigeon grape, sycamore and almond; (iii) X. fastidiosa subsp. pauca, CVC, strains from citrus and probably those from coffee(CLC); (iv) X. fastidiosa subsp. sandyi, strains from Nerium oleander (OLS); (v) X. fastidiosa subsp. tashke,
Corresponding author: J.D. Janse Fax: +31.527.635411 E-mail: jjanse@nak.nl

strains from the ornamental tree Chitalpa tashkentensis. Vectors are mainly sharpshooters and froghoppers or spittlebugs (Cicadellidae) that lack a latent period, and have no transstadial or transovarialtransmission of the bacterium. The pathogen shows persistence in the vector adults, and ability to multiply in the foregut. In North America main vectors (for PD unless indicated) are Cuerna costalis (PPD), Draculacephala minerva (green sharpshooter) important also in ALS in California; Graphocephala atropunctata (blue-green sharpshooter), most important before the introduction of the glassy wingedsharpshooter; G. versuta (PPD); Hordnia circellata, most efficient; Homalodisca vitripennis [formerly H. coagulata (glassy-winged sharpshooter or GWSS)]; H. insolita (PPD), Oncometopia nigricans, O. orbona (PPD), Xyphon fulgida [formerly Carneocephala fulgida (red-headed sharpshooter)]. CVC vectors in Brazil are Acrogonia terminalis, that lays eggs externally on leaves, Dilobopterus costalimai andOncometopia fascialis. Local possible vectors for Europe are Cicadella viridis and Philaenus spumarius (meadow spittle bug). X. fastidiosa is an emerging threat in the south-west USA, mainly due to recent establishment of H. vitripennis, providing much more efficient transmission than local vectors, and leading to very serious outbreaks of PD in grapevine, ALS and OLS. GWSS probably first entered...