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| C13.1. Symptoms of tobacco mosaic disease. |
C13.2. A painting by Dutch artist Jacob Marrel (1614-1681) that includes "bizarre" tulips with color breaking due to virus infection. |
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| C13.3.Vectors of plant viruses. A, wingless aphid. B, winged aphid. C, whiteflies. D, leafhopper. E, thrips (larva). F, eriophyid mites. G, migratory ectoparasitic nematode (arrow) feeding at a root tip. |
C13.4. Aphid vector feeding on a plant host and the internal route of the viruses that cause barley yellow dwarf. These viruses are transmitted in a persistent manner.
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| C13.5. Common symptoms caused by viruses. A, stunting or dwarfing (a healthy plant is on the left). B, yellows. C, mosaic. D, ringspot. E, flower break. F, leafroll. G, fruit deformation. |
C13.6. Replication cycle of Tobacco mosaic virus (TMV).
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| C13.7. Symptoms of barley yellow dwarf on barley. |
C13.8. Bioassay for virus infection of a plant. Top, sap from a test plant is rubbed on a leaf of an "indicator" plant, which shows distinct symptoms if the virus is present. Leaves are usually dusted with a fine abrasive powder, so that small wounds are produced when the sap is applied. Bottom, about one week later, small necrotic local lesions indicate a positive test for the presence of the virus. |
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| C13.9. Microtiter plate used for enzyme-linked immunosorbent assay (ELISA). Wells containing virus develop color; wells without virus do not. |
C13.10. Protection from TMV infection in transgenic tomato plants. A tomato plant with the gene for TMV coat protein (left) is protected from the virus; a plant without the virus gene (right) shows severe disease symptoms. |
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| C13-11. Cadang-cadang ("dying-dying") disease of coconut palm, caused by a viroid. |
C13.12. Symptoms of spindle tuber viroid disease in potato. The tuber on the far right is healthy. |
