Evaluation of rose germplasm for resistance to rose rosette disease, and studies of disease transmission and vector management
Date
2017
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Publisher
University of Delaware
Abstract
Rose rosette disease (RRD) is a lethal disease of roses (Rosa spp.) caused by Rose rosette emaravirus (RRV) and vectored by the eriophyid mite Phyllocoptes fructiphilus. It is one of the most devastating diseases of landscape roses, producing aesthetically disfiguring symptoms within months and eventually killing the plant. Unfortunately, there is no known resistance among commercial rose cultivars and the few rose species that have demonstrated resistance are not ideal candidates for introgression of resistance genes into commercially viable cultivars. This thesis details three studies relating to the management of RRD. The first is a resistance trial intended to identify rose genotypes that merit consideration as candidates in a breeding scheme for resistance to RRD. A total of 216 genotypes are being screened in an ongoing field trial at the University of Delaware in Newark, DE. In addition to high natural disease pressure, the field has received multiple augmentations since its establishment in May 2015. Augmentation consisted of using twist ties to affix symptomatic shoots of RRD-infected Rosa multiflora to actively growing shoot tips of target roses. The vector preferentially feeds on symptomatic tissue, so augmentation artificially enhanced vector populations. Any roses that developed symptoms were subsequently tested by endpoint RT-PCR to confirm the presence of RRV. Thus far 94 genotypes have been verified as susceptible to RRD. The study will continue through 2018 and any roses remaining symptom-free will be assayed to confirm the absence of viral replication. The second and third studies in this thesis investigate (i) mechanical and graft transmission of RRV and (ii) the use of predatory mites as a biological control of the vector, P. fructiphilus.
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Keywords
Biological sciences, Emaravirus, Fructiphilus, RRD, RRV, Rose rosette disease