California Agricultural Research Priorities Pierce's Disease (2004) / Chapter Skim
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5 Vector-Pathogen Interaction
5 Vector-Pathogen Interaction
Pages 105-113
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From page 105... ...
. Data suggest that members of the sharpshooter tribe Cicadellini transmit more efficiently than do members of the Proconiini tribe (Almeida and Purcell, 2003; Krugner et al., 1998; Redak et al., 2003)
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From page 106... ...
PATHOGEN TRANSMISSION The characteristics of Xf transmission by GWSS are similar to those of other known leafhopper vectors of Xf, although GWSS is a less efficient vector than is BGSS, a primary vector in Northern California. Leafhopper vectors acquire Xf through feeding on the xylem of host plants, and the bacteria replicate in the mouthparts (Purcell et al., 1979)
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From page 107... ...
Despite the evidence that the number of bacteria acquired by the vector can dictate subsequent transmission, the relationship between number of bacteria in vector heads and transmission efficiency is not well understood. Efficient transmission of Xf requires less than 100 cultivable bacteria for the BGSS (Hill and Purcell, 1995)
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From page 108... ...
For instance, acquisition of the MAV strain of the barley yellow dwarf virus by aphid vectors markedly reduces the transmission of the PAV strain by those insects (Gildow and Rochow, 1980)
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From page 109... ...
The second transgenic approach focuses on genetic engineering of bacterial symbionts of vectors to express and release transgene products that damage the pathogen. That process has been called "paratransgenesis." In the Chagas disease system, researchers have engineered the bacterial symbiont Rhodococcus rhodnii to express and release transgene products into insect tissues that are damaging to the disease agent (Durvasula et al., 1997)
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From page 110... ...
However, no studies have isolated unambiguously the direct effects of a pathogen on vector fitness from the indirect effects mediated through the host. BOX 5-1 Pathogen Effects on Vector Survivorship and Reproduction There have been no studies of the effects of Xf on GWSS survivorship, but some work has demonstrated the effects of viruses on leafhopper survivorship on infected plants.
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From page 111... ...
reported that beet leafhoppers preferentially colonized, and performed better on, beet plants infected with beet curly top virus than they did on healthy beets. Similarly, aster leafhoppers prefer carrot plants infected with the aster yellows phytoplasma over
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From page 112... ...
indicate that volatile compounds from PLRV-infected potatoes are involved in the attraction and arrestment of aphid vectors of the virus, and that those compounds could similarly influence the behavioral responses of other vectors to infected hosts. healthy plants (Peterson, 1973)
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From page 113... ...
Epidemiologic models have predicted that vector preference behavior will have a significant influence on the rate of pathogen spread, and conventional wisdom postulated that vector preference for infected hosts over healthy ones would promote the spread of disease (e.g., Irwin and Thresh, 1990; Matthews, 1991)
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