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Xanthomonas
Xanthomonas leaf blight of onion
Onion Xanthomonas leaf blight of onion Xanthomonas axonopodis pv. allii
Scientific Classification
Kingdom: Bacteria
Phylum: Proteobacteria
Class: Gamma Proteobacteria
Order: Xanthomonadales
Family: Xanthomonadaceae
Genus: Xanthomonas
Species: Xanthomonas axonopodis pv. allii
Xanthomonas leaf blight of onion geographical distribution
Countries were xanthomonas leaf blight of onion is present[1]
Synonyms
Onion bacterial blight

Xanthomonas leaf blight of onion

Xanthomonas campestris pv. allii Kadota et al.

Xanthomonas leaf blight of onion (Xanthomonas axonopodis pv. allii) is a bacterium causing damage to Allium crops has been reported from several parts of the world as an emerging disease. It was first observed in Barbados in 1971, and then spread to other continents (America, Africa and Asia).[1]

SymptomsEdit

Leaf lesions initially appear as white flecks, pale spots, or lenticular lesions with water-soaked margins. Lesions quickly enlarged, becoming brownish, with extensive water-soaking. As the disease progresses, lesions coalesce causing tip dieback and extensive blighting of older leaves. Reduction of foliage leads to stunting of the plants and smaller bulbs. In case of severe outbreaks, premature plant death is observed. The disease is favoured by temperatures higher than 27°C (80°F) and severe outbreaks usually occur 7-10 days after a period of humid, rainy weather. In USA, yield reductions of 20 % or greater are commonly observed in affected fields.[1]

TreatmentEdit

Control in the US is most often partially achieved through a massive use of copper bactericides sometimes amended with ethylenebisdithiocarbamate fungicides, but this strategy is economically and environmentally not satisfactory.[2]

PreventionEdit

Crop rotation should be practiced, however, the longevity of the pathogen’s survival in the field in association with crop debris or in the absence of Allium spp. and weeds is not precisely known. Overhead irrigation should be avoided [3] and furrow or drip irrigation should be considered as alternative irrigation modes. No Allium cultivar has been consistently characterized as resistant to X. axonopodis pv. allii and no source of resistance has been identified to date.[4]

ExamplesEdit

ReferencesEdit

  1. a b c (2009). Xanthomonas axonopodis pv. allii (an emerging disease of onion and garlic crops). European and Mediterranean Plant Protection Organization. Retrieved: 2010-10-21.
  2. Gent, D.H. & Schwartz, H.F. (2005). Management of Xanthomonas leaf blight of onion with a plant activator, biological control agents, and copper bactericides. Plant Dis 89: 631-639.
  3. Roumagnac, P. Pruvost, O. Chiroleu, F. & Hughes, G. (2004). Spatial and temporal analyses of bacterial blight of onion caused by Xanthomonas axonopodis pv. allii. Phytopathology 94: 138-146.
  4. Xanthomonas axonopodis pv. allii. European and Mediterranean Plant Protection Organization. Retrieved: 2010-10-21.

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