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Title: Disrupting insect-mediated transmission of plant viruses
Author: Bravo Cazar, Ana Lucía
ISNI:       0000 0004 7968 3544
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2018
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Many plant viruses are vectored by aphids in the non-persistent mode, in which virus particles are transported on these insects' specialised piercing mouthparts (stylets). Virus infection can change plant-vector interactions and it is thought that this may accelerate virus transmission. To better understand how to inhibit virus transmission, I studied vectoring of cucumber mosaic virus (CMV) and turnip mosaic virus (TuMV) between Arabidopsis thaliana plants by the aphid Myzus persicae. Among other things, I investigated if there were differences in the extent to which the viruses modified aphid-plant interactions in different Arabidopsis accessions, as well as the intrinsic susceptibility of these accessions to aphid infestation. A range of Arabidopsis accessions showed differences in attractiveness and susceptibility to aphids and variations in virus-induced changes in plant-aphid interactions. I found that aphids were attracted to plant volatiles emitted by CMV-infected Col-0 and CMV-infected Ei-2 plants. Interestingly, aphids settle more readily on CMV-infected Ei-2 plants than CMV-infected Col-0 plants. However, aphids did not prefer to settle on CMV-infected plants of either accession. Thus, I used these accessions to determine how to manipulate aphid behaviour to inhibit virus transmission using two types of microcosm: simple lines of plants (with various mixtures of the two accessions) and two-dimensional arrays ('fields') of plants. The simple line experiments showed that aphid-mediated transmission could be disrupted using mixtures of accessions with differences in intrinsic aphid attractiveness and susceptibility to aphid infestation. In the two-dimensional 'field' experiments, two approaches, which included CMV- and TuMV-resistant plants were most effective in inhibiting virus transmission. Resistant plants in both Arabidopsis backgrounds were either mixed in various proportions (resistant v. susceptible and Col-0 v. Ei-2) in randomised planting layouts or with plants arranged as barriers. A 33% proportion of virus-resistant plants randomly distributed was sufficient to inhibit virus transmission. A barrier of Ei-2 CMV-resistant plants or TuMV-resistant plants in a population of Col-0 plants reduced virus transmission of CMV and TuMV. The latter approach retained more aphids than populations of solely Col-0 plants. Thus, Ei-2 plants can be used as trap plants to attract and 'sanitise' viruliferous aphids by inducing them to deposit virus particles in resistant plants, thus inhibiting onward transmission. The results show that there is potential for using intraspecific variation in host plants to inhibit aphid-mediated transmission.
Supervisor: Carr, John Peter Sponsor: SENESCYT (Secretaria de Educación Superior ; Ciencia y Tecnología e Innovación)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: plant ; virus ; transmission ; vector ; arabidopsis ; resistance ; aphid ; myzus ; CMV ; TuMV