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Cuppels Biology 4218a
Disease Diagnosis and Identification of Phytopathogenic Bacteria
Bacterial streaming
• Internal/external symptoms• Culture bacteria and characterize:
Clostridium (Tuber rot, wetwood of elm and poplar)
DIVISION: FIRMICUTES** CLASS: THALLOBACTERIA (branched)Arthrobacter (Bacterial blight of holly)*Clavibacter (Bacterial wilts in potato, tomato, alfalfa; ring rot of potato)Leifsonia (Ratoon stunting of sugarcane)Rhodococcus (Fasciation of ornamentals and sweet pea)Streptomyces (Common scab of potato)
Family: Enterobacteriaceae (Gram -)*Erwinia species
Fire blight, soft rot (most common on fleshy vegetables and fruit)Pantoea species
Stewart’s wilt of corn…spread by corn flea beetles Serratia species (fastidious, phloem-inhabiting)
Yellow Vine Disease of Cucurbits…spread by squash bugSphingomonas melonis
Brown spot of yellow Spanish melon fruit
Erwinia, Oregon State Univ. Bacterial ooze from infected apple, Van der Zwet, USDA
Erwinia carotovora supsp. atroseptica Blackleg of potato,S. DeBoer, CFIA, PEI
Cuppels Biology 4218a
Fire blight of apple in Michigan
photo by M. Longstroth, Mich. State Univ.
This picture was taken in early June of 2000, 2 weeks after a hail storm and onset of widespread fire blight symptoms in the region. New shoots have been killed and the leaves have died giving the trees a brown appearance. Both 'Gala' and the M9 rootstock are very susceptible to fire blight.
Cuppels Biology 4218a
Bacteria overwinter on margins of old cankers
Young tree heavily infected with fire blight
Twig killed by fire blight
Bacteria in exudate carried by insects and rain
Bees carry bacteria to flowers
Formation of new cankers on branches and stems
Intercellular multiplication in bark
Infected flowers shrivel and die
Infected bark cells collapse
Bacteria penetrate flowers then multiply and spread rapidly
Example : Candidatus liberobacter asiaticus or africanusDisease: Citrus greening or Huanglongbing (yellow dragon)
Example : Serratia marcescensDisease: Yellow vine disease of cucurbits
Cuppels Biology 4218a
MOLLICUTESDIVISION: TENERICUTES CLASS: MOLLICUTESFamily: still unnamed
Phytoplasma (Yellows diseases, decline diseases in trees, proliferation disease)
Cannot be cultivatedSmall genome (500-1000 kb)Greater than 200 diseasesPleomorphicFound in phloem sap, insect organsLeafhopper-transmitted
Aster yellowswww.apsnet.org
Cuppels Biology 4218a
Can be cultivatedSmall genome (500-1000 kb)Relatively few diseasesHelical to branched filamentsMotile but no flagellaIn phloem sapLeafhopper-transmittedCan live saprophytically