Click any image to enlarge.
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| Figure 3-1. Bacterial colonies on a nutrient medium. Note that the bacteria have been diluted through streaking. The small, round colonies are made up of hundreds of cells and probably grew from a single bacterium. |
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Figure 3-2.
A bacilliform bacterium, typical of plant pathogens. Note that it has polar flagella.
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| Figure 3-3.
Phytoplasmas (arrows) in a phloem cell of an infected plant. Note that the phytoplasmas are pleomorphic (variably shaped). |
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Figure 3-4.
Spiroplasmas in phloem cells of an infected corn plant. Note the helical shape. |
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| Figure 3-5. Bacterial cell. Note the EPS (extracellular polysaccharide) and polar flagellum. |
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Figure 3-6. Thomas J. Burrill in a laboratory with students, 1882. |
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| Figure 3-7. Ooze, a diagnostic sign of a bacterial infection. In bacterial wilt of cucurbits, the sticky strands of bacterial ooze become evident as two portions of a cut stem are pulled apart. |
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Figure 3-8. A, To diagnose Stewart’s wilt, a section of symptomatic corn leaf tissue is placed in a drop of water on a microscope slide. B, Bacterial streaming, viewed with a compound microscope. |
| Figure 3-9. Angular leaf spots typical of those caused by Pseudomonas spp. and Xanthomonas spp. |
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Figure 3-10. Soft rot in a potato tuber. |
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| Figure 3-11.
Crown gall on euonymous caused by Agrobacterium tumefaciens. |
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Figure 3-12.
Bacterial wilt of tomatoes caused by Ralstonia solanacearum. |
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| Figure 3-13.
Brooming in lime infected by a phytoplasma. |
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Figure 3-14.
The glassy-winged sharpshooter, a leafhopper vector of Xylella fastidiosa. These insects subsist on xylem fluid and often feed upside down. |
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| Figure 3-15.
Various modes of penetration and invasion of a leaf by fungi (left) and bacteria (right). Water is required for bacteria to enter cells. |
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Figure 3-16.
Dilution plating to obtain pure colonies of a bacterium. The tissue is torn apart to release the bacteria. The sample is then diluted to reduce background contaminants. A sample of each dilution is spread on a plate of nutrient medium. |
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| Figure 3-17.
Commercial chipping machine used to chip citrus trees infected by or exposed to citrus canker in urban Miami, Florida. |
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Figure 3-18.
Typical air-blast sprayer for application of copper sprays or antibiotics. |
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| Figure 3-19.
Pepper plants susceptible (left) and resistant (right) to specific strains of the leaf spot bacterium, Xanthomonas axonopodis pv. vesicatoria. |
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