9.5.13 lecture 4 pp.docx

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Plant Biology
PBIO 117
Terrence P.Delaney

9/5/13 Gram negative, Bacterial Pathogens Mollicutes & and Controls for Bacterial Disease  Xylella o Rod shaped, non-motile (aflagellate) o Walled, xylem limited o Nutritionally fastidious (picky), host dependent  Need specialized medium to culture (adapted to specialized environment)  100+ hosts (grapes, citrus, coffee)  Considered emerging pathogen due to upsurge & damage to valuable crops  Pierce’s disease of grape  Identified 1880’s in southern California  doesn’t affect north, not enough insect vectors that can live in the environment  sever outbreaks began when insect vectors appeared in grape producing areas  major threat to west & south  causes scorching & fruit loss  insect vectors o typically pierce into xylem to feed on sap o bacteria take up residence on insect vectors o glassy winged sharp shooter  invasive  breeds in more habitats/ moves frequently & further  feeds on wood in winter o disease spread favored by riparian habitats (b/c of sharpshooters) o difficult to prove as a pathogen w/ Koch’s Postulates o control measures  resistant varieties  keep away from riparian habitats  control sharpshooters  remove diseased vines  Mollicute o Wall-less prokaryotes  Negative b/c no wall to hold stain, soft-skinned bacteria o Two pathogen groups  Spiroplasms, phytoplasms o Insect vectored disease o Very small size & genome o Spiroplasms (genus)  Cultureable, helical  Phloem limited  Leaf hopper/ graft transmitted
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