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Plant Health 2019 Abstracts of Presentations

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Plant Health 2019 Abstracts of Presentations Plant Health 2019 Abstracts of Presentations Abstracts submitted for presentation at the APS Plant Health 2019 Annual Meeting in Cleveland, Ohio, U.S.A., August 3–7, 2019 (including abstracts submitted for presentation at the 2019 APS North Central Division meeting). The recommended format for citing annual meeting abstracts, using the first abstract below as an example, is as follows: Chen, Y., Badillo-Vargas, I. E., Martin, K., Rotenberg, D., and Whitfield, A. E. 2019. Characterization of novel thrips vector proteins that bind to tomato spotted wilt virus. (Abstr.) Phytopathology 109:S2.1. https://doi.org/10.1094/PHYTO-109-10-S2.1 The abstracts are published as a supplement to Phytopathology for citation purposes. They were not reviewed by the Phytopathology Editorial Board and were not edited by the APS editorial staff. https://doi.org/10.1094/PHYTO-109-10-S2.1 © 2019 The American Phytopathological Society Characterization of novel thrips vector proteins that bind to tomato spotted wilt virus Y. CHEN (1), I. E. Badillo-Vargas (2), K. Martin (1), D. Rotenberg (1), A. E. Whitfield (1), (1) North Carolina State University, Raleigh, NC, USA; (2) Texas A&M AgriLife Research, Weslaco, TX, USA Tomato spotted wilt virus (TSWV) is transmitted by thrips species in a persistent, propagative manner. Frankliniella occidentalis is the most efficient vector, but at least six other thrips species are competent vectors. The TSWV structural glycoprotein (GN) plays an important role in viral attachment and possibly entry into insect host cells. However, the insect molecules that interact with GN during infection and dissemination in thrips vector are still largely unknown. The goals of this study were to characterize TSWV-interacting proteins (TIPs) that interact directly with TSWV GN and to localize expression of these proteins in thrips tissues of importance along the route of virus dissemination. We identified six novel TIPs from first instar larvae (L1) that share homology to proteins associated with the infection cycle of other vector-borne viruses. Two of the thrips proteins, endocuticular structural glycoprotein (endoCP-GN) and cyclophilin, were validated to be consistent interactors with GN in membrane-bound yeast two-hybrid and insect cell co-localization assays. Immunolocalization of these TIPs in L1s revealed robust expression in the midgut and salivary glands of F. occidentalis, the key tissues during viral infection, replication and plant-inoculation. In addition, the homologous endoCP-GN from another thrips vector F. fusca was cloned and validated to interact with TSWV GN. Our findings suggest that the TIPs-GN interaction occurs in vivo and the TSWV GN-endoCP-GN interaction may be conserved among Frankliniella vector species of TSWV. Investigations on the quiescent behavior of Diaporthe ilicicola in deciduous holly fruit I. EMANUEL (1), F. Peduto Hand PhD (2), (1) Ohio State University, Columbus, OH, USA; (2) The Ohio State University, Columbus, OH, USA Cut branches of deciduous holly (Ilex spp.) carrying brightly colored fruit are commonly used for winter holiday decorations, providing nurseries with a source of revenue in low-income periods of the year. In 2012, a fruit rot disease arose in the US, often leading to significant loss of marketable branches. One of the pathogens, the fungus Diaporthe ilicicola, was found to infect flowers during bloom and cause fruit rot symptoms later in the season. The delayed symptom onset suggests that the fungus undergoes a quiescence period until conditions change to favor tissue colonization. We inoculated with D. ilicicola during bloom and monitored physiological changes throughout the growing season in the resulting fruit. A strong positive correlation was found between disease incidence and soluble sugar concentrations, and a negative correlation was seen between disease incidence and phenolic compound concentrations. We hypothesize that the observed increase in susceptibility may be facilitated by greater concentrations of available sugars serving as a carbon source for the pathogen, and/or by a decrease in phenolic-based antifungal compounds within the fruit tissue. These results will direct future research aimed to determine the roles of available sugar concentrations within Ilex fruits in initiating D. ilicicola infection and to identify phenolic antifungal compounds which may inhibit D. ilicicola spore germination or infection. S2.1 Linking sources and sinks in the long distance aerial dissemination of ubiquitous pathogens C. MORRIS (1), O. Berge (2), C. Chandeysson (1), C. Guilbaud (1), C. Monteil (1), P. Darwin (3), A. Sigurbjörnsdóttir (4), O. Vilhelmsson (4), (1) INRA, Plant Pathology Research Unit, Montfavet, FRANCE; (2) INRA, Montfavet, FRANCE; (3) University of Reading, Biological Sciences, Reading, UNITED KINGDOM; (4) University of Akureyri, Akureyri, ICELAND The few cases where long distance aerial trajectories of plant pathogens from source to sink have been confirmed have specific traits: i) there are a limited number of sources, ii) sinks emerge along paths of air movement, and iii) sink and source populations have low enough genetic diversity to facilitate statistical comparisons of their population structures. Whereas rust fungi have all these traits, ubiquitous, highly diverse pathogens with broad host ranges do not - and this impedes understanding the dimensions of their natural spread. Our objective is to link sources, sinks and the long distance aerial trajectories of dissemination of ubiquitous pathogens. Here we have focused on Pseudomonas syringae because of its association with atmospheric processes of the water cycle. Its capacity to incite freezing of cloud water droplets and precipitation fosters its fall-out from long distance travel in air masses. For a sink where we collected P. syringae in snowfall - the observatory at Jungfraujoch, CH (46.5475° N, 7.9792° E, 3500 m altitude) - we examined the air mass trajectories of these snowfalls to identify possible sources. From one potential source – ground cover in northern Iceland – we have collected hundreds of strains of P. syringae. We present the comparison of the genetic diversity of Icelandic strains with strains from Jungfraujoch and other sites to assess if atmospheric connectivity between sites assures long distance dissemination of P. syringae. Association mapping and transcriptomic analyses reveal genes associated with resistance of Populus trichocarpa to Septoria leaf spot S. KERIO (1), K. L. Sondreli (1), K. Mondron (1), R. Lenz (1), K. Feng (2), J. Chen (2), W. Muchero (2), J. LeBoldus (3,4), (1) Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, USA; (2) Oak Ridge National Laboratory, Oak Ridge, TN, USA; (3) Oregon State University, Corvallis, OR, USA; (4) Dept. of Forest Engineering, Resources and Management, Oregon State University, Corvallis, OR, USA The ascomycete Sphaerulina musiva causes Septoria leaf spot and stem canker of Populus and is the most serious pathogen of poplars in North America. Knowledge of genes associated with resistance to leaf spot can be used to select for resistant planting stock. We inoculated and phenotyped 540 distinct Populus trichocarpa genotypes in a randomized complete block design to identify loci associated with leaf spot resistance. The leaf spot phenotypes were recorded after two weeks and correlated in a genome-wide association analysis to 8,253,066 SNPs and insertion/deletions. Subsequently, RNAseq was applied to study gene expression in a subset of resistant and susceptible genotypes. We will report the heritability estimates for leaf spot resistance, genes associated with phenotypic variation, and patterns of gene expression in response to S. musiva inoculation. The significance of the results for resistance breeding and management of foliar diseases in poplar plantations will be discussed. In planta experimental evolution experiments shed new insights on the mechanism and kinetics of Xanthomonas TAL effector host adaptation D. TEPER (1), N. Wang (2), (1) University of Florida, Lake Alfred, FL, USA; (2) Citrus Research and Education Center, University of Florida, Lake Alfred, FL, USA Phytopathogenic bacteria inject transcription activator-like effectors (TALEs) into plant cells to induce the expression of specific host susceptibility genes. The DNA binding specificity of TALEs is dictated by their tandem repeat regions, which are highly variable between different TALEs. We hypothesize that the unique features of the repeat regions of TALEs allow quick adaptation of the pathogens to variations of host target genes. To test this hypothesis, we utilized experimental evolution approach to mimic host adaptation of Xanthomonas citri subsp. citri (Xcc) pthA4 mutant carrying “non-adapted” TALE variants on sweet orange. We manufactured three “non-adapted” TALEs that where initially unable to induce the transcription of CsLOB1, the canker susceptibility gene, due to the presence of miss-matching repeats compared to the native CsLOB1 targeting TALE, PthA4. The TALEs were introduced into Xcc∆pthA4 and bacteria were repeatedly infected and re-isolated from sweet orange plants for 32 cycles. While initially all strains failed to promote canker development, canker symptoms started to appear between 9-18 infection cycles. Sequence analysis of the adapted TALEs identified four adaptive variants, which displayed deletions and rearrangements within the tandem repeat regions of the TALEs. Reintroduction of these adapted variants into
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