Leaf scorch symptoms are not correlated with bacterial populations during Pierce's disease

Xylella fastidiosa (Xf) is a xylem-limited bacterium that lives as a harmless endophyte in most plant species but is pathogenic in several agriculturally important crops such as coffee, citrus, and grapevine (Vitis vinifera L.). In susceptible cultivars of grapevine, Xf infection results in leaf sco...

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Bibliographic Details
Published in:Journal of experimental botany 2007-12, Vol.58 (15-16), p.4037-4046
Main Authors: Gambetta, G.A, Fei, J, Rost, T.L, Matthews, M.A
Format: Article
Language:English
Subjects:
Bacteria
Bacterial diseases
Bacterial wilt
Biological and medical sciences
Citrus
disease resistance
Fundamental and applied biological sciences. Psychology
Generalities. Disease free stocks
Host-Pathogen Interactions - physiology
Inoculation
Leaves
Pathogenesis
Phytopathology
Phytopathology. Animal pests. Plant and forest protection
Plant Diseases
Plant Leaves - microbiology
Plants
Polymerase Chain Reaction
Research Papers
Symptom severity
Symptoms
Vitaceae
Vitis - microbiology
Vitis vinifera
water deficits
Xylella
Xylella - physiology
Xylella fastidiosa
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Summary:Xylella fastidiosa (Xf) is a xylem-limited bacterium that lives as a harmless endophyte in most plant species but is pathogenic in several agriculturally important crops such as coffee, citrus, and grapevine (Vitis vinifera L.). In susceptible cultivars of grapevine, Xf infection results in leaf scorch, premature leaf senescence, and eventually vine death; a suite of symptoms collectively referred to as Pierce's disease. A qPCR assay was developed to determine bacterial concentrations in planta and these concentrations were related to the development of leaf-scorch symptoms. The concentration of Xf in leaves of experimental grapevines grown in the greenhouse was similar to the concentration of Xf in leaves of naturally infected plants in the field. The distribution of Xf was patchy within and among leaves. Some whole leaves exhibited severe leaf-scorch symptoms in the absence of high concentrations of Xf. Despite a highly sensitive assay and a range of Xf concentrations from 102 to 109 cells g−1 fresh weight, no clear relationship between bacterial population and symptom development during Pierce's disease was revealed. Thus, high and localized concentrations of Xf are not necessary for the formation of leaf-scorch symptoms. The results are interpreted as being consistent with an atiology that involves a systemic plant response.
ISSN:0022-0957
1460-2431
DOI:10.1093/jxb/erm260