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The Influence of Drought on the Ecological and Evolutionary Genomics of Fungal Pathogenesis in an Annual Plant, Brassica rapa

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dc.contributor.advisor Rest, Joshua S en_US
dc.contributor.author O'Hara, Niamh Breda en_US
dc.contributor.other Department of Ecology and Evolution. en_US
dc.date.accessioned 2017-09-20T16:52:37Z
dc.date.available 2017-09-20T16:52:37Z
dc.date.issued 2014-12-01 en_US
dc.identifier.uri http://hdl.handle.net/11401/77398 en_US
dc.description 80 pg. en_US
dc.description.abstract There is growing evidence that populations are evolving rapidly in response to climate change. However, the potential cost associated with adapting, and the genetic basis of both rapid evolution and costs of adaptation remain largely unexplored. With climate change, drought is increasing in frequency and severity, widely affecting plant yield and fitness in agricultural and natural populations. For my dissertation, I integrated multiple approaches (field, greenhouse, lab and bioinformatic) to explore the ecological and evolutionary effects of drought on an agriculturally important plant-pathogen system: the annual herbaceous plant Brassica rapa (field mustard), and its fungal pathogen Alternaria brassicae. In a field study, including multiple sites on the west coast of the U.S., I found a positive association between soil moisture and disease severity. However, the relationship between soil moisture and disease varied among locations and over time, and the factors influencing disease susceptibility in the field are complex. In a greenhouse study with pre-drought ancestors and post-drought descendants, I found an evolutionary shift to earlier flowering, and an evolutionary increase in disease susceptibility, indicating a cost of the drought adaptation. I found that that earlier flowering plants had thinner leaves, which are more easily invaded by fungal pathogens, indicating a potential mechanism for the increase in susceptibility observed. I conducted whole genome shotgun sequencing on 205 ancestral and descendant B. rapa plants. I found considerable genetic differentiation across the genome, consistent with a rapid evolutionary response to drought at multiple loci. Many significantly differentiated genes are involved in pathogen response, indicating a genetic basis for the observed shift in disease susceptibility. Site frequency spectrum analysis indicated that selection appears to have acted on standing genetic variation (soft sweeps). The results of this study shed light on both a cost of adaptation and on the genetic basis of rapid evolutionary responses to a change in climatic conditions. en_US
dc.description.sponsorship This work is sponsored by the Stony Brook University Graduate School in compliance with the requirements for completion of degree. en_US
dc.format Monograph en_US
dc.format.medium Electronic Resource en_US
dc.language.iso en_US en_US
dc.publisher The Graduate School, Stony Brook University: Stony Brook, NY. en_US
dc.subject.lcsh Evolution & development en_US
dc.subject.other Alternaria brassicae, climate change, cost of adaptation, drought, rapid evolution, resurrection approach en_US
dc.title The Influence of Drought on the Ecological and Evolutionary Genomics of Fungal Pathogenesis in an Annual Plant, Brassica rapa en_US
dc.type Dissertation en_US
dc.mimetype Application/PDF en_US
dc.contributor.committeemember TRUE, John en_US
dc.contributor.committeemember Gurevitch, Jessica en_US
dc.contributor.committeemember Franks, Steven. en_US


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