Department of Plant Pathology

Megan Nickerson
2023-10-30 16:00 - 17:00 (America/Los_Angeles)
“Genome Evolution of Plant Pathogenic and Symbiotic Fungi”
Megan Nickerson, PhD Candidate, Department of Plant Pathology, Washington State University
Abstract
Kingdom Fungi represents a highly diverse lineage of Eukaryota, with an estimated 2 – 11 million fungal species (Blackwell 2011; Hawksworth and Lücking 2017). Land plant associations have been central to the diversification of fungi (Lutzoni et al. 2018), and the majority of fungal species associate with plants or green algae either as symbionts or saprotrophs (Aguileta et al. 2009; Blackwell 2011; Phukhamsakda et al. 2022). With the exception of a few specialized lineages, parasitic, mutualistic, and saprophytic fungal species are interspersed across the fungal tree of life, supporting the hypothesis that transitions between trophic modes have occurred repeatedly over evolutionary time (Aguileta et al. 2009; Rodriguez et al. 2009). Increased analysis of fungal genomes has led to the identification of various genes (effector genes, CAZyme genes, etc.) contributing to observed ecological roles (Gluck-Thaler and Slot 2018; Rokas et al. 2020). Additionally, fungal genomes are unique in the arrangement genes involved in the biosynthesis and catabolism of secondary metabolites (SMs). “Metabolic gene clusters” (MGCs) are physically clustered genes typically encoding enzymes or SMs, as well as transporters and transcription factors (Rokas et al. 2020). Fungal MGCs have been linked to the production of plant specific toxins, catabolism of plant defense compounds, and SM production of various functions (Slot et al. 2017). My presentation will address the following questions: what methods are used to detect MGCs in fungal genomes, what is the evolutionary history and function of fungal MGCs, what is the adaptative advantage of gene clustering for fungi, and how does the presence of MGCs impact the ecological niche they occupy?
For more information regarding Megan’s seminar, please see the seminar announcement.

Kristen Bullough
2023-10-23 16:00 - 17:00
“Mycoremediation: The Potential Effect of Fungi on Remediating Heavy Metal Pollution”
Kristen Bullough, PhD Candidate, Department of Plant Pathology, Washington State University
Abstract
Mycoremediation can be used as a bioremediation tool to remove heavy metals and other pollutants from contaminated sites, including soil and wastewater. Remediating heavy-metal pollution specifically is becoming critical to maintaining important ecosystems and human health around the world (Anyanwu et al. 2018; CDC 2016; Zhao et al. 2022). Fungi has many potential benefits as remediation tools, such as low-cost, biodegradation ability, and high accumulation of heavy metal (Akpasi et. al. 2023; Kulshreshtha et al. 2014; Kumar et al. 2021); but there are many factors, such as temperature and pH, that contribute to the success of mycoremediation. There are many mechanisms for mycoremediation, including biotransformation, biodegradation, and sequestration. In this talk, two case studies will be discussed. The first study was on the tolerance of Pleurotus spp. in the presence of copper, cobalt, and nickel (Mohamadhasani and Rahimi 2022). In the second study, the authors utilized fungal species isolated from sites contaminated with heavy metals (cadmium, lead, chromium, and nickel) to determine their tolerance and capabilities of heavy metal uptake. They also looked at the ability of the tolerant species when exposed to a single heavy metal versus a combination of heavy metals (Joshi et al. 2011). More studies are needed to verify the potential uses of mycoremediation for remediating polluted sites.

For more information about Kristen’s seminar please see the seminar announcement.

Scott Anderson, PhD Exit Seminar
2023-10-16 16:00 - 17:00
“Novel Molecular Approaches to Identify and Control Plant Parasitic Nematodes”
Scott Anderson, PhD Student, Exit Seminar, Department of Plant Pathology, Washington State University
Abstract
Plant parasitic nematodes (PPNs) are responsible for 10-15% crop loss worldwide amounting to hundreds of billions of dollars of crop loss annually11; and in the U.S. alone, the annual crop loss by PPNs is estimated as $13 billion4. Among the many types of PPNs, the root-knot nematodes (RKN), genus Meloidogyne, cause the largest amount of crop loss world-wide. These nematodes are obligate biotrophs, meaning that they rely solely on plants for their food, restricting the nutrients available to their hosts, and decreasing crop yield and production5,9.
Traditionally, PPNs have been dealt with by applying nematicides, but over the last few decades these chemicals have been phased out or banned due to their effects on humans and the environment4. To avoid overreliance on expensive and dangerous nematicides, and to find a long-term robust solution to RKNs, a new form of control is badly needed. Another problem in controlling RKNs is knowing which species are present in a field via objective and reliable methods to prescribe appropriate management strategies in a timely fashion3. Currently, nematology heavily relies on microscopy to identify and quantify nematodes based on morphology; this is a low throughput, labor intensive, and technical skill which takes years to master. Thus, plant pathologists have been developing molecular techniques for faster, easier nematode identification2,13.
In this research, we endeavored to 1) develop a time saving and reliable molecular assay for identifying three RKN species: M. chitwoodi, M. fallax, and M. minor; 2) investigate the potential for using ferroptosis, an evolutionarily conserved form of programmed cell death triggered by omega-6 polyunsaturated fatty acids (PUFAs) as an alternate form of RKN control; and 3) identify key fatty acid synthesis genes in order to evaluate their impact in the RKN lifecycle when silenced via host-induced gene silencing (HIGS).
First, a molecular beacon qPCR assay for M. chitwoodi, M. fallax, and M. minor was developed that could detect the three species in a single multiplexed reaction. This assay was shown to reliably distinguish between these three RKN species. It was also sensitive enough to determine the species of RKN from a single J2 and had no cross reaction with other economically destructive RKN species (M. incognita, M. javanica, M. arenaria, or M. hapla)1. In addition to nematode identification, developing nematode control tools was a major component of my research. To test the applicability of ferroptosis as a means of controlling RKNs, we created transgenic tomato plants that produced gamma-linolenic (GLA) and dihomo-gamma-linolenic acid (DGLA) in their roots and challenged them with M. incognita. Because no reproducible reduction in RKN hatching was observed, it was concluded that roots producing GLA/DGLA had no measurable effects on M. incognita reproduction. Finally, two putative acetyl-CoA carboxylase (ACC) orthologs were characterized in silico in M. incognita, MiACC1 and MiACC2. In Caenorhabditis elegans, these enzymes are necessary early on in fatty acid synthesis, and their absence causes disruptions in lipid biosynthesis and molting6,12,15. Additionally, previous research showed that knocking-down these genes in a closely related cyst nematode, Heterodera schachtii, led to a delayed molting phenotype8. We attempted to knock these genes down via HIGS by creating three independent Arabidopsis thaliana lines that produced dsRNA targeting both MiACCs. RKNs feeding on these transgenic roots showed a delayed molting phenotype. These results are similar to the observations in previous studies that used pesticides or exogenously supplied dsRNA to reduce ACC activity in PPNs and C. elegans7,8,10,14. Overall, my research has produced a high throughput, reliable, and technically simple assay for identifying different RKN species, furthered our understanding of the fatty acid pathways in RKNs, and probed the effectiveness of feeding RKNs omega-6 PUFAs as an alternative control method to pesticides.
For more information regarding Scott’s seminar, please see the seminar announcement.

Jessica Schallon
2023-10-09 16:00 - 17:00
“Phytochemical Production and Applications to Plant Pathology”
Jessica Schallon, M.S. Student, Department of Plant Pathology, Washington State University
Abstract
Plants have an incredible capacity to manufacture even very complex chemicals. For a long time, plants have served as organic chemistry factories, producing compounds that have been found to be helpful as human medicine (Houghton 2001). More recently, plants have also been harnessed for molecular farming, producing products of interest to people via genetic modification (Tschofen et al. 2016). In the future, genetic modification may in turn be used to help plants produce their own medicines and products of interest to the plant itself (Makeshkumar et al. 2021). While the use of genetic modification can be met with public pushback, many of these techniques have shown great promise in combatting plant diseases (Makeshkumar et al. 2021). Of particularly promising phytochemical products are single-chain variable fragment (scFv) antibodies, or more colloquially, “plantibodies.” These fragments are smaller but functionally analogous to the antibodies of animals, resulting in resistance to a specific pathogen with only minimal modification of the plant genome (Boonrod et al. 2004; Gargouri-Bouzid et al. 2006; Gil et al. 2011; Nickel et al. 2008; Tavladoraki et al. 1993). This unique transgenic approach could be particularly impactful in managing emerging plant diseases and recalcitrant diseases to which cisgenic approaches and cultural practices fail to provide time- and cost-effective control measures.
For more information regarding Jessica’s seminar, please see the seminar announcement.

Roshani Baral
2023-10-02 16:00 - 17:00
“Disease-Suppressive Soils as a Tool for Disease Management”
Roshani Baral, M.S. Student, Department of Plant Pathology, Washington State University
Abstract
As soilborne diseases continue to challenge crop production, suppressive soils offer a way to manage the disease condition even in the presence of a susceptible host and a virulent pathogen. To date, several microbial species have been identified as contributors to disease suppression. Introducing such strains to problematic soils can offer long-term disease control (Liu et al. 1995) and may promote plant growth (Meng et al. 2012). In this talk, I will present the role of suppressive soils to manage pathogens such as Streptomyces scabies (causing common scab of potato) (Liu et al. 1995; Meng et al. 2012), Fusarium oxysporum (causing Fusarium wilt) (Cha et al. 2016), and Gaeumannomyces graminis var. tritici (causing take-all of wheat) (Raaijmakers and Weller 1998). I will also discuss the attributes of disease-suppressive soils, mechanisms involved in disease suppression, and understand the importance of soil microbiomes in disease management (Jayaraman et al. 2021).
For more information regarding Roshani’s seminar please see the seminar announcement.

Purnima Puri
2023-09-25 16:00 - 17:00
“Bacterial Ice Nucleation”
Purnima Puri, M.S. Student, Department of Plant Pathology, Washington State University
Abstract
Did you know plant pathogens can facilitate ice formation? Pure water freezes at about -38°C, but in the presence of agents like dust particles or microorganisms, this process occurs at temperatures as high as -2°C (Lukas et al. 2022). Certain bacteria, like Pseudomonas syringae, possess specialized Ice Nucleation Proteins (INPs) facilitating ice crystal formation at temperatures above freezing point (Lindow et al. 1982). Interestingly, when these bacteria colonize plant surfaces, they can initiate ice formation in the plant tissues resulting in frost injury. This frost-induced stress can lead to significant damage and a subsequent reduction in crop yields (Anderson et al. 1982). Understanding this mechanism is thus crucial for enhancing agricultural productivity. The aim of this seminar is to provide insights into the process of bacterial ice nucleation, mechanics behind ice nucleation, and its impact as well as applications across various domains.
For more information regarding Purnima’s seminar, please see the seminar announcement .

Kayla Spawton, PhD Candidate Defense Seminar
2023-09-18 16:00 - 17:00
“Ecology and Management of Stemphylium Leaf Spot of Spinach”
Kayla A. Spawton, PhD Candidate Defense Seminar
Abstract
Stemphylium leaf spot of spinach has re-emerged as a disease of economic concern for fresh market, processing, and seed production. The disease was first described in 2001 as being caused by Stemphylium botryosum, based on fungal morphology1. After recent revisions to the nomenclature of Stemphylium based on DNA sequences2, two main species pathogenic to spinach have been identified, S. beticola (previously identified as S. botryosum) and S. vesicarium3,4. These fungi are seedborne and seed transmitted5,6. The objectives of this study were to elucidate the biology and epidemiology of these pathogens, and to refine options for disease management. Experiments were conducted to: i) identify Stemphylium species and development of the teleomorphs associated with Stemphylium leaf spot in spinach seed crops, and the species colonizing seed grown in key countries of seed production; ii) screen spinach cultivars for resistance to S. vesicarium; iii) determine the prevalence of resistance to the fungicides azoxystrobin and pyraclostrobin that have been used widely to control this disease; iv) evaluate genetic differences of pathogenic vs. non-pathogenic seedborne isolates of S. vesicarium; and v) sequence the genome of S. beticola isolates to complement genomes available for S. vesicarium. Of the 11 Stemphylium species identified from 244 isolates obtained from spinach seed, leaves, and residues, only isolates of S. beticola, S. vesicarium, and S. drummondii were pathogenic to spinach. The incidence of spinach seed infested by Stemphylium ranged from 2.5 to 73.5% per seed lot, with most isolates identified as S. vesicarium or S. beticola. However, only 60.7 and 62.3% of the isolates of these two species from all spinach samples were pathogenic to spinach, respectively. Ascospores of the two species were released from spinach seed crop residues on the soil surface from mid-winter to late spring or early fall, overlapping with spinach seed crops the next season. Cultivars with resistance to S. vesicarium were identified for fresh market and processing spinach production7. In vitro and in vivo assays confirmed resistance to azoxystrobin and pyraclostrobin in all spinach leaf and seed isolates of S. vesicarium tested, but not in any isolates of S. beticola4the G143A mutation in cytochrome b that confers resistance. The oldest isolate in which this mutation was detected was from a spinach seed lot grown in the Netherlands in 2003. The resistance mutation also was detected in isolates from a crop in Arizona in 2013, and 82.9% of isolates from spinach seed lots harvested from crops grown after 2017 in Europe, New Zealand, and the US, demonstrating widespread fungicide resistance in spinach seed isolates of S. vesicarium. The number of seedborne S. vesicarium isolates pathogenic to spinach varied among seed lots and was negatively correlated with genetic diversity of the isolates from seed lots. Seed populations of S. vesicarium were structured genetically based on pathogenicity to spinach, not based on seed lot or country of seed production. Genotypes of pathogenic S. vesicarium isolates obtained from symptomatic leaves were also detected on the seed lots used to plant the crops, but seed populations were far more diverse genetically than foliar populations. The genomes of two S. beticola isolates from spinach were sequenced8 to facilitate genetic comparison of species that cause the disease, and future development of molecular detection tools. This research provides new insights into Stemphylium leaf spot of spinach with implications for enhanced management of this disease.
For more information about Kayla’s seminar, please see the seminar announcement.

Dr. Steve Klosterman
2023-09-11 16:00 - 17:00
“Retrospective and Prospective Look at Discoveries from Verticillium Comparative Genomics”
Dr. Steve Klosterman, Research Molecular Biologist United States Department of Agriculture Agricultural Research Service, Salinas, California
Fungal pathogens in the genus Verticillium cause Verticillium wilt of high value crops, ornamentals, and trees worldwide. Today we recognize 10 species of Verticillium; the most notorious among these species is V. dahliae. Early comparative genomics focused on the comparisons of two species, V. dahliae and V. alfalfae, giving rise to valuable insights into their genome structures, predicted secretomes, and horizontal gene transfer. Next generation sequencing technologies and the increased availability of high‐quality genome assemblies have rapidly yielded discoveries of avirulence genes, the genetic basis of the defoliating and nondefoliating phenotypes of V. dahliae and paved the way for additional comparative studies. In this talk, I will provide insights on the discoveries of early and two recent Verticillium comparative genomics projects and provide insights on Verticillium comparative genomics of the future.
For more information about Dr. Klosterman’s seminar please see the seminar announcement.

No Seminar
2023-09-04 16:00 - 17:00
Labor Day

Dr. Robert Brueggeman
2023-08-28 16:00 - 17:00
“Rpt5, Rpg1, and rpg4/5: Characterizing Broad Resistance against Important Necrotrophic and Biotrophic Fungal Pathogens of Barley”
Dr. Robert Brueggeman Associate Professor, Barley Breeding/Molecular Genetics
Robert A. Nilan Endowed Chair in Barley Research and Education Dept. of Crop and Soil Sciences, WSU
Abstract
Two pathogens that threaten barley production worldwide are the necrotrophic fungal pathogen Pyrenophora teres f. teres (the causal agent of net form net blotch) and the biotrophic fungal pathogen Puccinia graminis f. sp. tritici (the cause agent of wheat stem rust). Net form net blotch resistance/susceptibility is complex, but the broadest and most effective resistance is provided by the Rpt5 gene which has been deployed in important barley producing regions worldwide. Rpt5 was effective against all known isolates of P. teres f. teres until the recent emergence of Moroccan and Canadian isolates with virulence on Rpt5. Stem rust resistance in North American barley has primarily relied on a single source of resistance, but rpg4/5 has recently been deployed to address North American isolates with virulence on Rpg1. Alarmingly, the recent characterization of stem rust populations from Washington determined that 99% of the isolates were virulent on Rpg1, 16% were virulent on rpg4/5, and 10% were virulent on both genes when stacked together. This was the first report of P. graminis f. sp. tritici races or isolates that were virulent on both R‐genes when stacked together, representing the most virulent Pgt population on barley from across the globe. In this talk I will present our research to identify and characterize these important barley resistance genes and the pathogen effectors that interact with them. An interesting point of discussion is how and why these virulent pathogen populations arose. It is understandable for Rpt5 virulence as the gene was deployed over large acreage under heavy disease pressure. However, for the PNW Rpg1‐rpg4/5 virulence it is a mystery as neither gene was deployed in PNW barley varieties.
For more information regarding Dr. Brueggeman’s seminar, please see the seminar announcement.

Dr. Arild Arifin
2023-05-01 16:00 - 17:00
“Early detection of major quarantine postharvest pathogens of apple and pear in the U.S. Pacific Northwest”
Dr. Arild R. Arifin, Department of Plant Pathology, Tree Fruit Research and Extension Center Washington State University
Abstract:
The postharvest pathogens Phacidiopycnis washingtonensis, Phacidiopycnis pyri, Sphaeropsis pyriputrescens, and Neofabraea spp. are important quarantine pathogens of apple and pear from the U.S Pacific Northwest. These pathogens can threaten the pome fruit export from the region and because their morphology is similar, a molecular diagnostic assay based on loop-mediated isothermal amplification (LAMP) is being developed for each pathogen. LAMP method is highly specific, sensitive, rapid, and can be used for point-of-care detection. The aims of this study are to develop and optimize the LAMP primers of four mentioned pathogens, and validate their specificity and sensitivity on fruit from commercial orchards and warehouses. The designed LAMP primers targeting the β-tubulin gene are specific to detect genomic DNA of Phacidiopycnis washingtonensis, P. pyri, Sphaeropsis pyriputrescens, and Neofabraea alba in 15 minutes by measuring the fluorescence. To confirm the specificity, all respective primer sets are also tested against several common pome fruit fungal pathogens, i.e., Neonectria, Botrytis, and Alternaria. Once developed, we hope that the LAMP assays will enable faster and efficient detection to prevent significant economic loses and ease exports.
References:
Enicks, D. A., et al. (2020). “Development of a Portable LAMP Assay for Detection of Neofabraea perennans in Commercial Apple Fruit.” Plant Disease 104: 2346-2353.
Notomi, T., et al. (2000). “Loop-mediated isothermal amplification of DNA.” Nucleic Acids Research 28: e63.
Tomita, N., et al. (2008). “Loop-mediated isothermal amplification (LAMP) of gene sequences and simple visual detection of products.” Nature Protocol 3: 877-882.
For more information regarding Dr. Arifin’s seminar, please see the seminar announcement.

Dr. Jenny Broome
2023-04-24 16:00 - 17:00
“New Tools for Safe-Guarding Berry Plant Health” From the Nursery to the Consumer”
Dr. Janet C. “Jenny” Broome, Senior Research Manager, Global Plant Health Department, and Scientist, Driscoll’s Inc., Watsonville, CA.

For more information regarding Dr. Broome and her seminar, please see the seminar announcement.

Dr. Joey Hulbert and Dr. Kylie Swisher-Grimm
2023-04-17 16:00 - 17:00
“Citizen science can enhance biosecurity surveillance: opportunities for plant disease monitoring and research at WSU”
Dr. Joey Hulbert, post-doctorial researcher with Dr. Gary Chastagner.
Abstract
Citizen science is an approach to research that benefits society through both research and participation outcomes. While limited in its application, there is enormous potential to engage the public more directly in plant disease research. In addition to the value of citizen science initiatives for early detection and monitoring, they also contribute widely to raising awareness, informing decisions to reduce pathogen spread, and finding resistant plant material for restoration of landscapes degraded by disease. The aim of this seminar is to provide an overview of the merit of citizen science for biosecurity surveillance, highlight ongoing and upcoming projects and findings within the WSU Department of Plant Pathology, and discuss possible applications for engaging the public in more collaborative plant disease research projects at WSU.
Reference
Hulbert, J. M., Hallett, R. A., Roy, H. E., and Cleary, M. (2023). Citizen science can enhance strategies to detect and manage invasive forest pests and pathogens. Frontiers in Ecology and Evolution 11. https://www.frontiersin.org/articles/10.3389/fevo.2023.1113978
For more information regarding Dr. Hulbert’s seminar, please see the seminar announcement.

“Potato mop-top virus: Impact of seedborne virus infection and the search for resistant germplasm”
Dr. Kylie Swisher-Grimm, USDA-ARS
Abstract
Potato mop-top virus (PMTV) is a tuber necrotic virus transmitted by the Spongospora subterranea pathogen that causes powdery scab blemishes on tuber surfaces. Tuber defects caused by both pathogens can lead to severe economic losses for growers; the asymptomatic detection of PMTV has even negatively impacted foreign trade from the United States. For the past seven years, we have assessed the presence of PMTV entering Washington State commercial potato fields by testing seed lots submitted to the WSU Seed Lot Trial. We detected PMTV in the seed lots each year, ranging from 1.73 – 5.50%. Infected lots originated from across the U.S. and from Canada, and consisted of 23 different cultivars, indicating that virus infection is not limited to specific regions or seed producers. To assess the risk of planting this PMTV-infected seed in vector-free soil, we conducted transmission assays that determined the effect of PMTV on daughter tuber yield, symptom development and virus expression. The presence of PMTV (and not the presence of symptoms) in the seed piece led to increased PMTV detection in daughter tubers but did not have a significant effect on daughter tuber symptom development. Unfortunately, reliable tools to manage PMTV and S. subterranea are not readily available to growers, and as a result, the best management solution for these pathogens is the generation of resistant cultivars. We have designed and validated a greenhouse screen to identify PMTV- and/or S. subterranea-resistant plants, identifying potential sources of resistance in wild potato accessions originating from three different taxon. Validation of these results is underway and will not only aid potato breeders in generating PMTV/S. subterranea-resistant cultivars but will also help with the identification of resistance markers to assist in the selection of resistant material. These efforts will ultimately benefit the commercial potato grower by providing them with improved management options for PMTV and S. subterranea.

For more information on Dr. Swisher-Grimm’s seminar please see the seminar announcement.

Student Invited Speaker- Dr. Adam Steinbrunner
2023-04-10 16:00 - 17:00
“Within Spitting Distance: A Plant Immune Receptor for Caterpillar Oral Secretions”
Assistant Professor at University of Washington. Dr. Steinbrunner is one of the world leading scientist researching pattern recognition receptors (PRR) and discovered the first receptor of HAMP (herbivore-associated molecular patterns) from chewing insects.
The plant innate immune system detects molecular patterns associated with diverse pests and pathogens. While plant mechanisms for recognition of microbial pathogens are well characterized, recognition of insect herbivores is less well understood. To address this gap, we have studied recognition of inceptin peptides found in oral secretions of Lepidopteran larval herbivores (caterpillars). Inceptins are only bioactive on specific legume species. We leveraged germplasm resources in cowpea (Vigna unguiculata) to identify an Inceptin Receptor (INR) able to bind inceptin peptide and activate signaling and defense responses against chewing herbivores. I will discuss functional aspects of INR as an means to both amplify and tune the plant wound responses. I will also describe a recent investigation of the evolutionary origin of INR in Phaseoloid legumes. Finally, I will describe ongoing efforts to restore INR to soybean to provide a novel pest resistance trait. I will argue that phylogenomic and functional characterization of key immune receptors provides a roadmap for durable pest resistance.
Click here to discover more about his work. For more information about Dr. Steinbrunner’s seminar, please see the seminar announcement.

Richard Manasseh-PhD Candidate Defense Seminar
2023-04-03 16:00 - 17:00
“Molecular Features of the (In-) compatibility between Potato and Potato virus Y”
Richard Manasseh, PhD candidate defense seminar, Dr. Hanu Papu Laboratory, Department of Plant Pathology
Abstract:
Viral phytopathogens attack a wide range of crops worldwide, resulting in economic losses of nearly US$60 billion annually. In potato (Solanum tuberosum L.), the most devastating crop losses are caused by potato virus Y (PVY). Until recently, resistant cultivars have been used as the most cost-effective and reliable option for managing PVY in potato. However, the current arsenal of genetic resistance appears inadequate for combating the recent emergence of more aggressive strains such as PVYNTN and PVYN-Wi. Developing effective genetic resistance to these strains would greatly benefit from an in-depth picture of the strategies they use that result in host susceptibility. Thus, the goal of this dissertation was to gain a system-wide view of the changes occurring in potato after infection with these necrotic strains. For this, gas chromatography coupled with mass spectroscopy (GC–MS) was first used for an untargeted investigation of the changes in leaf metabolomes of PVY-resistant cultivar Premier Russet, and a susceptible cultivar, Russet Burbank, following inoculation with PVYNTN, PVYN-Wi, and their common progenitor PVYO. Subsequently, the transcriptional responses of these inoculated plants were then examined using RNA-seq. At the metabolome level, the analysis showed PVY infections in potato elicit detectable changes in several primary metabolic pathways related to amino acid, energy, and fatty acid metabolism. In the resistant cv. Premier Russet, a major overlap in differential accumulation was found between PVYN-Wi and PVYO. In contrast, the main overlap in differential metabolite profiles and pathways in the susceptible cv. Russet Burbank was between PVYNTN and PVYO. Overall, limited overlap was observed between PVYNTN and PVYN-Wi, suggesting that PVYN-Wi-induced necrosis may be mechanistically distinguishable from that of PVYNTN. At the transcriptome level, primary metabolism was also shown to be affected by all three PVY inoculations. In addition, the analysis also recovered a core set of 9 pathways of secondary metabolism that may confer the PVY susceptibility in Russet Burbank. As a whole, these pathways can potentially be targeted for developing genetic resistance in potato and other economically important Solanaceous PVY host.
References:
Song, B., Yang, S., Jin, L.-H. and Bhadury, P.S. (2010). Environment-friendly antiviral agents for plants. Springer-Verlag, Berlin Heidelberg.
Li G, Shao J, Wang Y, Liu T, Tong Y, Jansky S., et al. (2022). Rychc Confers Extreme Resistance to Potato virus Y in Potato. Cells.;11(16):2577. doi: 10.3390/cells11162577. PMID: 36010654; PMCID: PMC9406545.
Dupuis, B., Bragard, C. and Schumpp, O. (2019). Resistance of potato cultivars as a determinant factor of potato virus Y (PVY) epidemiology. Potato Res. 2019;62: 123–138. doi: 10.1007/s11540-018-9401-4.
Kogovšek, P., Pompe-Novak, M., Petek, M., Fragner, L., Weckwerth, W. and Gruden, K. (2016). Primary metabolism, phenylpropanoids and antioxidant pathways are regulated in potato as a response to potato virus Y Infection. PloS ONE. 11(1): e0146135. doi: 10.1371/journal.pone.0146135
Goyer, A., Hamlin, L., Crosslin, J. M., Buchanan, A. and Chang, J. H. (2015). RNA-Seq analysis of resistant and susceptible potato varieties during the early stages of potato virus Y infection. BMC genomics. 16(1), 472. doi: https://doi.org/10.1186/s12864-015-1666-2

For more information regarding Richard’s seminar, please see the seminar announcement.

Hannah Merrill and Jonathan Puglisi
2023-03-27 16:00 - 17:00
“Developing KASP markers associated to avirulence genes in Puccinia striiformiss f. sp. triciti, the wheat stripe rust pathogen”
Hannah Merrill, Masters of Science candidate, Department of Plant Pathology, Dr. Xianming Chen’s Laboratory
Wheat is one of the most important crops produced in the United States. Stripe rust, caused by fungal pathogen Puccinia striiformis f. sp. triciti (Pst), can cause severe losses in yield and quality or cost multimillion dollars spent on control with fungicides (Chen 2014, 2020). Because of the economic impact that stripe rust has on the production of wheat, it is important to develop techniques for monitoring the pathogen populations. In our lab, Pst populations have been characterized by virulence testing on 18 Yr single-gene differentials every year (Liu et al. 2017; Wan and Chen 2014, Wan et al. 2016; Wang et al. 2022), and by simple sequence repeat (SSR) and secreted protein gene based single-nucleotide repeat (SP-SNP) markers (Bai et al. 2021, 2022; Li et al. 2019, 2020; Liu et al. 2021; Xia et al. 2016a, 2016b, 2017, 2018, 2020). However, a more efficient technique is needed to monitor virulence changes in the pathogen.
This goal of my study is to develop Kompetitive Allele Specific PCR (KASP) markers associated to avirulence genes of Pst to be used in monitoring virulence changes of the pathogen populations. The specific objectives are (1) design KASP markers based on SP-SNP markers associated to avirulence genes identified in our lab and test the KASP markers with a selected panel of Pst isolates; and (2) validate markers selected from Objective 1 with Pst collections of the recent years. Currently, progress has been made on selecting isolates, increasing urediniospores for DNA extraction, and learning the techniques in designing primers and testing KASP markers.
References:
Bai, Q., Wan, A. M., Wang, M. N., See, D. R., and Chen, X. M. 2021. Population diversity, dynamics, and differentiation of wheat stripe rust pathogen Puccinia striiformis f. sp. tritici from 2010 to 2017 and comparison with 1968 to 2009 in the United State. Front. Microbiol. 12:696835.
Bai, Q., Wang, M. N., Xia, C. J., See, D. R., and Chen, X. M. 2022. Identification of secreted protein gene-based SNP markers associated to virulence phenotypes of Puccinia striiformis f. sp. tritici, the wheat stripe rust pathogen. Int. J. Mol. Sci. 23:4114.
For more information on Hannah’s seminar please see the seminar announcement.

“Venturia inaequalis: The Importance, Epidemiology, and Management of a Destructive Apple Pathogen”
Jonathan Puglisi, Master of Science candidate, Department of Plant Pathology, Dr. Achour Amiri Laboratory
Apple scab, caused by the ascomycete fungus Venturia inaequalis, is one of the most common and devastating diseases of apple in temperate regions worldwide. The earliest depictions of apples with scab-like symptoms are found in paintings from the 15th and 16th centuries, but Spilocaea pomi, the anamorph of V. inaequalis was first documented by Swedish scientist Elias Fries in 1819. Apple scab infection produces lesions on leaves, blossoms and fruit, and can cause fruit drop and defoliation under high disease pressure conditions. Repeated defoliation events due to apple scab infection will increase the host tree’s susceptibility to environmental and insect stressors. Trees infected in the previous seasons may also show reduced and late-returning bloom. V. inaequalis infection occurs in the early spring when windborne sexual spores (ascospores) are released after rainfall. Lesions resulting from infection by ascospores produce secondary inoculum (conidia), which are transmitted to apple blossoms, fruit, and leaves by wind or rain. Disease management relies primarily on planting of scab-resistant apple and crab apple varieties, and fungicide application. The extensive usage of fungicides to control apple scab has resulted in the evolution of multi-fungicide resistance in V. inaequalis populations. The disease symptoms of apple scab, which result in unmarketable fruit and systemic tree damage, in combination with its global distribution and multi-fungicide resistance, solidify it as one of the most economically important diseases of apple.
References:
Belete, T. and Boyraz, N. 2017. Critical Review on Apple Scab (Venturia inaequalis) Biology, Epidemiology, Economic Importance, Management and Defense Mechanisms to the Causal Agent. J Plant Physiol Pathol, 5:2. doi: 10.4172/2329-955X.1000166.
Chapman, K.S., Sundin, G.W., Beckerman, J.L. 2011. Identification of Resistance to Multiple Fungicides in Field populations of Venturia inaequalis.
Gauthier, N. 2018. Apple scab. The Plant Health Instructor. doi: 10.1094/PHI-I-2000-1005-01.
Jha, G., Thakur, K., and Thakur, P. 2009. The Venturia Apple Pathosystem: Pathogenicity Mechanisms and Plant Defense Responses. J Biomed Biotechnol. 680160. doi: 10.1155/2009/680160.
For more information on Jonathan’s seminar please see the seminar announcement.

Prabu Gnanasekran and Madan Panday
2023-03-20 16:00 - 17:00
Dr. Prabu Gnanasekran is a post-doctorial researcher in Dr. Hanu Pappu’s Laboratory and Pandey Madan is a graduate student with Dr. Achour Amiri.
“Phenotypic and molecular Characterization of fungicide sensitivity in various Penicillium species causing blue mold of pome fruit in Pacific Northwest”
Madan Pandey, Masters student, Department of Plant Pathology
Abstract:
Blue mold disease poses a significant threat to apples and pears in storage, causing economic losses estimated to make up to 50% of total decays. Penicillium expansum is believed to be the primary causal species of blue mold, however several other Penicillium species have been identified and reported to make up to 25% of PNW Penicillium population. Postharvest fungicides, i.e., thiabendazole (TBZ), pyrimethanil (PYR), and fludioxonil (FDL) have been used to manage blue mold and other postharvest diseases for decades, whereas difenoconazole (DIF) has been registered in 2017. Frequent applications of these fungicides have selected for strains of P. expansum . that are resistant to TBZ, FDL and PYR. .However, Penicillium species that were phenotypically different from P. exapansum showed unusual higher levels of tolerance when tested in vitro on a single discriminatory dose of each of the 3 fungicides. The reasons behind the elevated in vitro tolerance of these “non-expansum” isolates are unknown. The ability of the label rates of the four postharvest fungicides to control these Penicillium spp. populations on fruits is also unknown. Therefore, a research study that combines both in vitro and in vivo fungicide sensitivity assays among various Penicillium isolates, along with molecular characterization of the Penicillium populations will help understand the resistance mechanisms and the development of effective control measures. Our preliminary findings indicate a high level of tolerance to FDL among various Penicillium species, whereas the test for sensitivity to PYR, TBZ and DIF is currently being done. The research goal is to determine if the level of in vitro tolerance translates into in vivo resistance, hence control failure. Furthermore, the research is also aimed towards identifying the possible molecular mechanism(s) that may be causing this high level of resistance in comparison with known mechanisms in P. expansum.
References:
Amiri A., and Pandit LK. 2019. Fungicide resistance in Penicillium expansum from pome fruit in the U.S. Pacific Northwest. Phytopathology 109-10: S2.75.
For more information about Madan’s seminar, please see the seminar announcement .
“Potato virus Y modulates the auxin-signaling pathway to promote disease development”
Dr. Prabu Gnanasebaran, post-doctorial researcher in Pappu Laboratory, Department of Plant Pathology
Abstract:
Potato virus Y (PVY) is one of the most economically important plant pathogens that affects staples such as potato and several other solanaceous plants and is considered as top five economically important viruses in the world. The PVY genome encodes a single polyprotein which is then post-translationally cleaved into P1-pro, HC-pro, P3, CI, VPg, NIa-pro, NIb, and coat protein (CP). In this study, we performed a yeast two-hybrid (Y2H) screen of Nicotiana benthamiana cDNA library using PVY-encoded NIa-pro as the bait. The N. benthamiana Indole-3-acetic acid-amido synthetase (IAAS) was identified as an interactor of NIa-pro protein. The interaction was confirmed via targeted Y2H and bimolecular fluorescence complementation (BiFC) assays. We have shown the subcellular localization of both NIa-pro and IAAS protein in the nucleus and cytosol. IAAS converts free (active) IAA to the inactive, conjugated form, which plays a crucial regulatory role in auxin signaling. Transient silencing of IAAS in N. benthamiana plants interfered with the PVY-mediated symptom induction and virus accumulation. Conversely, overexpression of IAAS enhanced the symptoms induction and virus accumulation in the infected plants. In addition, the expression of several auxin-responsive genes was found to be downregulated during PVY infection. Our findings demonstrate that PVY NIa-pro protein potentially promotes disease development via modulating auxin homeostasis.
References:
Gadhave, K. R., Gautam, S., Rasmussen, D. A. & Srinivasan, R. 2020. Aphid Transmission of Potyvirus: The Largest Plant-Infecting RNA Virus Genus. Viruses, 12, 773.
González-Lamothe, R., El Oirdi, M., Brisson, N. & Bouarab, K. 2012. The conjugated auxin indole-3-acetic acid-aspartic acid promotes plant disease development. The Plant cell, 24, 762-777.
For more information about Dr. Gnanasebaran seminar, please see the seminar announcement.

No seminar
2023-03-13 16:00 - 17:00, 2023-03-06 16:10 - 17:00, 2023-02-20 16:00 - 17:00

Jonathan Puglisi and Pandey Madan
2023-02-27 16:10 - 17:10
Jonathan Puglisi and Pandey Mandan are graduate students with Dr. Achour Amiri.
“Nanoparticles and their use in plant disease management”
Madan Pandey , Masters Degree Candidate, Achour Lab, Department of Plant Pathology
Abstract:
The global increase in demand for food production with minimum ecological damage has been very challenging. Although it is possible to meet the global food demand through various approaches, the environmental cost that is incurred may be more than what can be achieved. However, the advent of nanotechnology may stand as a strong tool that can sustainably reduce the impact of many factors that hinder plant health. Nanoparticles are simply the particles of any matter that are in the size of 1-100 nanometers. With this small size, nanoparticles have larger surface area compared to materials of non-nano scale. Thus, one of the major advantages of using nanoparticles is the large reduction in the volume of active chemicals that enter the agroecosystem. A proportion of the chemicals we use conventionally to control a disease or pest does not reach the target, and rather contaminates the vulnerable ecosystem, which can be reduced using nanoparticles. Although many nanoparticles exist currently, most of them are yet to be studied for their agricultural use. Most nanoparticles that are currently in use in agricultural sector include nanoparticles of metalloids, metallic oxides, non-metals, carbon nanomaterials and nanotubes, graphene oxides and many more. Most of the research works have centered on the use of silver, copper, and zinc due to their peculiar properties such as antimicrobial activity and alteration of host defense. Silver was the first nanoparticle investigated for managing plant diseases. Lamsal et al. (2011) demonstrated at 100 μg/ml, silver nanoparticles suppressed powdery mildew comparable to conventional fungicide but also reported some curative responses. Although the research has been showing exciting results for their potential use at a larger scale in controlling plant diseases, there are some challenges for using nanoparticles. One of the challenges is that the nanoparticles behave differently in different plant and disease system, requiring individual research works for each disease. Moreover, the long-term impact of nanoparticles in the environment is yet to be researched at a broader level. However, considering the huge challenge faced by the agriculture sector, nanomaterial-based disease suppression may play a key role in achieving sustainable global food security.
References:
Lamsal K, Kim SW, Jung JH, Kim YS, Kim KS, Lee YS (2011). Inhibition Effects of Silver Nanoparticles against Powdery Mildews on Cucumber and Pumpkin, Mycobiology, 39:1, 26-32, DOI: 10.4489/MYCO.2011.39.1.026
More information about Madan’s seminar can be found in the seminar announcement.

“Assessing saprophytic and pathogenic fitness in fungicide-resistant isolates of Penicillium expansum”
Jonathan Puglisi, Masters degree candidate, Achour Lab, Department of Plant Pathology
Abstract:
Blue mold (BM), primarily caused by Penicillium expansum, is the most important postharvest disease of apple and pear worldwide and in the Pacific Northwest (PNW). Packinghouse surveys indicate that P. expansum has begun to exhibit resistance to thiabendazole (TBZ), pyrimethanil (PYR), and fludioxonil (FDL), the three most used postharvest fungicides in the PNW. To better understand if the evolution of fungicide resistance alters the ability of resistant populations to cause epidemics of BM, P. expansum isolates sensitive or resistant to TBZ, PYR, and FDL were evaluated using several fitness parameters. Spore germination, mycelial growth, sensitivity to reactive oxygen species, osmotic stress, and resistance stability were assessed in vitro, while virulence, sporulation, and resistance stability were assessed in vivo. In preliminary in vitro trials at 1.5°C, resistant isolates exhibited reduced conidial germination on nutrient restricted media and susceptibility to osmotic stress. Virulence of resistant isolates was similar to those of sensitive isolates on detached fruit after 3 months at 1.5°C. Our preliminary findings indicate that while some fungicide-resistant phenotypes of P. expansum may incur fitness costs, their ability to cause BM in cold storage may not be affected. The goal of this research is to help fruit packers effectively assess and mitigate the risk of fungicide resistant disease populations.
References:
Amiri, A., Ali, M.E., De Angelis, D.R., Mulvaney, K.A., Pandit, L.K. (2021). Prevalence and distribution of Penicillium expansum and Botrytis cinerea in apple packinghouses across Washington State and their sensitivity to the postharvest fungicide pyrimethanil. Acta Hortic, 1323. DOI 10.17660/ActaHortic.2021.1323.26
For more information regarding Jonathan’s seminar please see the seminar announcement.

Hannah Merrill and Elliot Marston
2023-02-13 16:10 - 17:10
Hannah Merrill is a graduate student with Dr. Xianming Chen and Elliot Marston is a graduate student with Dr. Deven See.
“A Light in the Darkness: History, Phylogeny, Physiology, and Applications of Bioluminescent Fungi”
Elliot Marston, PhD Candidate, See Lab, Department of Plant Pathology
Abstract:
Our record of bioluminescent fungi dates back nearly two millennia, but research into bioluminescent fungi has been sparse. More than 150,000 species of fungi that have been described, but only 71 species are known to bioluminescence. Of the 71 known species of bioluminescent fungi, all are white-rot basidiomycetes and saprotrophs (with the exception of some phytopathogens) that fall into four distinct lineages within the order of Agaricales. A luciferin (heat-stable substrate) and lucerifase (enzyme) mechanism of luminescence was hypothesized but not confirmed until Airth and Foerster used Dubois’ hot-cold extract method in 1959. Failure to replicate their results led researchers to suggest non-enzymatic mechanisms until Oliveira and Stevani verified the results of Airth and Foerster in 2009. Oliveira and Stevani went on in 2012 to confirm cross-reactivity of luciferin and luciferase extracts both within the Mycenoid lineage and between all four lineages of bioluminescent fungi. Originally hypothesized to be a two-enzyme process, the mechanism behind bioluminescence in fungi involves four enzymes and begins with caffeic acid, an organic compound frequently found in many plants and an intermediate of lignin biosynthesis. The genes of the four enzymes directly involved in fungal bioluminescence have been successfully sequenced, cloned, and expressed within several organisms including yeast, tobacco, Arabidopsis, tomato, dahlia, and other ornamental plants. Current applications of fungal bioluminescence include ecological toxicity assays, as well as molecular imaging techniques. With the recent breakthrough in developing a bioluminescence gene cassette specifically for expressing bioluminescence within eukaryotes, there are many opportunities to develop in vivo bioluminescence assays for research and medical applications.
References:
1. Ke, HM and Tsai, IJ. (2022). Understanding and using fungal bioluminescence – Recent progress and future perspectives. Current Opinion in Green and Sustainable Chemistry, 33: 100570.
2. Mihael, JD. (2013). Comparative bioluminescence dynamics among multiple Armillaria gallica, A., mellea, and A. tabescens genets. Fungal Biology, 117: 202 – 210.
3. Oliveira, AG, Desjardin, DE, Perry, BA, Stevani, CV. (2012). Evidence that a single bioluminescent system is shared by all known bioluminescent fungal lines. Photochemical and Photobiological Sciences, 11: 848 – 852.
4. Stevani, CV, Oliveira, AG, Mendes, LF, Ventura, FF, Waldenmaier, HE, Carvalho, RP, and Pereira, TA. (2013). Current Status of Research on Fungal Bioluminescence: Biochemistry and Prospects for Ecotoxicological Applications. Photochemistry and Photobiology, 89: 1318 – 1326.
5. Tsarkova, AS, Kaskova, ZM, and Yampolsky, IV. (2016). A Tale of Two Luciferins: Fungal and Earthworm New Bioluminescent Systems. Accounts of Chemical Research, 49: 2372 – 2380.
More information regarding Elliot’s seminar can be found in the seminar announcement.

“Grapevine Red Blotch”
Hannah Merrill, Master’s degree candidate, Chen Lab, Department of Plant Pathology
Abstract:
Grapevines are one of the most important and prolific crops grown commercially, with about 6.05 million tons of grapes grown annually in the United States with an average of 69 tons of grapes produced per acre, valued at 5.53 million dollars. Because grapes are such an important crop in the United States, it is important to consider all aspects of grapevine health. Recently, an emergent pathogen called Grapevine Red Blotch (GRBaV) has damaged grapevine and limited production of usable grapes on the west coast and primarily in California and Oregon. One of the primary symptoms of the virus is leafroll, which is indicative of many viruses affecting grapevines, although tests run on diseased grapevines did not yield positive results for any known virus. This led to the discovery of GRBaV and an emphasis has been placed on the study of the pathogen to limit its spread.
Research on GRBaV includes studying the genetic material and determining what causes the spread of the virus. Since being discovered, the genome of 15 isolates have been sequenced, and 2 distinct groups have been identified, although there does not appear to be a biological difference between the two groups. The virus is monopartite and contains a circular strand of ssDNA. Additionally, several studies have been done to determine the ways through which the virus is spread. It was determined through PCR techniques by multiple researchers that GRBaV is spread by an insect vector called the three-cornered alfalfa hopper, Spissistilus festinus. One group concluded that in addition to the insect vector, there is a possibility that there are host plants which do not exhibit symptoms, but rather host the virus until a vector is able to transmit the pathogen, but further research is needed to confirm this hypothesis. A $3 million USDA -NIFA grant has been issued to UC Davis, UC Berkeley, and Oregon State University to continue research on this virus, as the only known treatment for GRBaV is to remove the entire vine. The partnership between these universities will allow progress to be made quickly and ensure successful yield of healthy grapes.
References:
Bahder, B. W., Zalom, F. G., Jayanth, M., and Sudarshana, M. R. 2016. Phylogeny of Geminivirus Coat Protein Sequences and Digital PCR Aid in Identifying Spissistilus festinus as a Vector of Grapevine red blotch-associated virus. Phytopathology®. 106:1223–1230.
Flasco, M., Hoyle, V., Cieniewicz, E. J., Roy, B. G., McLane, H. L., Perry, K. L., et al. 2021. Grapevine Red Blotch Virus Is Transmitted by the Three-Cornered Alfalfa Hopper in a Circulative, Nonpropagative Mode with Unique Attributes. Phytopathology®. 111:1851–1861.
Iowa State University. 2023. Grapes. Agricultural Marketing Resource Center, Iowa State University.
Rumbaugh, A. C., Durbin-Johnson, B., Padhi, E., Lerno, L., Cauduro Girardello, R., Britton, M., et al. 2022. Investigating Grapevine Red Blotch Virus Infection in Vitis vinifera L. cv. Cabernet Sauvignon Grapes: A Multi-Omics Approach. IJMS. 23:13248.
Quinton, A. 2019. Grapevine Red Blotch Disease Threatens U.S. Grape Industry. UC Davis.
Sudarshana, M. R., Perry, K. L., and Fuchs, M. F. 2015. Grapevine Red Blotch-Associated Virus, an Emerging Threat to the Grapevine Industry. Phytopathology®. 105:1026–1032.
For more information regarding Hannah’s seminar please see the seminar announcement.

Dr. Kasi Viswanath Kotapati
2023-02-06 16:10 - 17:00
Dr. Kasi Viswanath is a post doctorial researcher with Dr. Hanu Pappu.
“Antiviral mechanism in Orchid plants under Cymbidium mosaic virus and Odontoglossum ringspot virus infection”
Abstract:
The orchid industry faces severe threats from diseases caused by viruses. Argonaute proteins (AGOs) have been shown to be the major components in the antiviral defense systems through RNA silencing in many model plants. However, the roles of AGOs in protecting orchids against viral infections have not been analyzed comprehensively. In our previous studies, Phalaenopsis aphrodite subsp. formosana was chosen as the representative to analyze the AGOs (PaAGOs) involved in the defense against two major orchid viruses, Cymbidium mosaic virus (CymMV) and Odontoglossum ringspot virus (ORSV). A total of 11 PaAGOs were identified from the expression profile analyses of these PaAGOs in P. aphrodite subsp. formosana, singly or doubly infected with CymMV and/or ORSV. PaAGO5b was found to be the only one that was highly induced. Overexpression of individual PaAGO5 family genes revealed that PaAGO5b plays critical roles in P. aphrodite subsp. formosana antiviral defense mechanism. To understand the underlying antiviral defense mechanism, we cloned PaAGO5s promoters (pPaAGO5s) and analyzed their activity in transgenic Nicotiana benthamiana using β-glucuronidase (GUS) as a reporter gene. GUS activity analyses revealed that during CymMV and ORSV infections, pPaAGO5b activity significantly increased compared to pPaAGO5a and pPaAGO5c. Analysis of pPaAGO5b 5′-deletion revealed that pPaAGO5b_941 has higher activity during virus infection. Further, yeast one-hybrid analysis showed that the transcription factor NbMYB30 physically interacted with pPaAGO5b_941 to enhance its activity. Overexpression and silencing of NbMYB30 resulted in up- and downregulation of GUS expression, respectively. Exogenous application and endogenous measurement of phytohormones have shown that methyl jasmonate and salicylic acid respond to viral infections. NbMYB30 overexpression and its closest related protein, PaMYB30, in P. aphrodite subsp. formosana reduced CymMV accumulation in P. aphrodite subsp. formosana. Based on these discoveries, this study provided insights into the underlying antiviral defense mechanism in orchids in response to virus infections. Findings may provide useful information for the breeding of traits for resistance or tolerance to CymMV or ORSV infections in Phalaenopsis orchids.
References:
Kuo, S.Y., Hu, C.C., Huang, Y.W., Lee, C.W., Luo, M.J., Tu, C.W., Lee, S.C., Lin, N.S. and Hsu, Y.H., 2021. Argonaute 5 family proteins play crucial roles in the defense against Cymbidium mosaic virus and Odontoglossum ringspot virus in Phalaenopsis aphrodite subsp. formosana. Molecular Plant Pathology, 22(6), pp.627-643.
Kasi Viswanath, K., Kuo, S.Y., Huang, Y.W., Tsao, N.W., Hu, C.C., Lin, N.S., Wang, S.Y. and Hsu, Y.H., 2022. Characterization of Virus-Inducible Orchid Argonaute 5b Promoter and Its Functional Characterization in Nicotiana benthamiana during Virus Infection. International Journal of Molecular Sciences, 23(17), p.9825.
More information regarding Dr. Kotapati’s seminar can be found in the seminar announcement

Dr. Mustafa Jibrin and Dr. Hira Kamal
2023-01-30 16:00 - 17:10
Dr. Mustafa Jibrin is a post-doctorial researcher in Dr. Achour Amiri’s lab and Dr. Hira Kamal is a post-doctorial researcher with Dr. Hanu Papu.
“Insights into Patulin Contamination and threat to Washington State Processing Apple Industry”
Mustafa O. Jibrin, PhD Department of Plant Pathology
Abstract:
Patulin contamination in apples, usually associated with the blue mold rot causing Penicillium expansum, is challenging for apple processors globally because of its potential toxicity in foods. In Washington state, about 18 to 25% of apples, equivalent of $70M of the farm gate value, are processed each year. In 2018 and 2019, fruit processors in the state reported unusual high levels of patulin in apples with no apparent decay symptoms. This study was, therefore, conducted to understand the diversity of patulin-causing fungi recovered from apples in the processing industry to understand sources and nature of the reported patulin contamination. In my talk, I hope to provide a general background to help understand patulin and genetics as well as progress made thus far in our studies here in Amiri Lab at WSU Tree Fruit Research and Extension Center.
References:
Li B, Zong Y, Du Z, Chen Y, Zhang Z, Qin G, Zhao W, Tian S. Genomic characterization reveals insights into patulin biosynthesis and pathogenicity in Penicillium species. Mol Plant-Microbe Interact. 2015;28(6):635–47.
Nielsen, J., Grijseels, S., Prigent, S. et al. Global analysis of biosynthetic gene clusters reveals vast potential of secondary metabolite production in Penicillium species. Nat Microbiol 2, 17044 (2017). https://doi.org/10.1038/nmicrobiol.2017.44
Snini, S.P., Tannous, J., Heuillard, P., Bailly, S., Lippi, Y., Zehraoui, E., Barreau, C., Oswald, I.P. and Puel, O. (2016), Patulin is a cultivar-dependent aggressiveness factor favouring the colonization of apples by Penicillium expansum. Molecular Plant Pathology, 17: 920-930. https://doi.org/10.1111/mpp.12338

More information regarding Dr. Jibrin’s seminar can be found in the seminar announcement.

“Antagonistic dialogues in tripartite interactions among potato-protist-virus”
Hira Kamal, PhD Department of Plant Pathology
Abstract:
Potato is the most important vegetable crop worldwide. Potato production in the US, including states of Idaho, Oregon and Washington is affected by powdery scab (PS) disease caused by the soil-borne protist, Spongospora subterranea f. sp. subterranea (Sss). Disease symptoms include cosmetic damage to tuber skin and the formation of root galls (Falloon et al., 2011). Not much is known about the molecular interaction between powdery scab and its host, potato. Root galls exhibit in different shades of color, from white to brown, depending on the stage of the disease. A microscopic examination of white and brown galls was carried out using scanning electron microscopy and light microscopy. SEM revealed that white gall samples possess starch granules to start initiation of the spore ball formation suggesting that Sss consumed plant starch for sporpsori formation. while the mature, brown galls had abundant spore balls without any starch granules. These results suggested that Sss manipulates the plant root system by inducing starch biosynthesis ectopically, which provide biochemical and molecular insights into the plant-protist interaction.
Sss also acts as a vector for another pathogen, potato mop top virus (PMTV) (Harrison et al., 1997; Johnson and Cummings, 2015). To investigate the antagonistic interaction between PMTV and potato, a mechanical inoculation assay is being optimized using in vitro produced infectious transcripts of PMTV. Preliminary results showed the successful infection and replication of PMTV in inoculated Nicotiana benthamiana leaves. This assay will be used in our future transcriptomics and Gene Co-expression Network analysis. Additionally, the role (s) of PMTV-encoded proteins are being studied using a potato virus X (PVX)-based expression system in model plant N. benthamiana. The coat protein (CP), and triple gene block (TGB)-3 of PMTV were expressed in plants and their effect on plant phenotype were monitored. Plants expressing the TGB3 and CP showed mild symptoms with leaf crumpling and downward curling and yellowing in newly emerging younger leaves. When CP and TGB-3 were expressed together, plants produced a hypersensitive response and had severe symptoms on local and systemic leaves. These results suggest that CP and TGB3 play a potentially important role in symptom development for PMTV infection. Insights into the tri-partite interactions among Sss, PMTV and their host, potato could lead to the development of management strategies of this economically important disease complex of potato.
References:
Falloon, R.E., Merz, U., Lister, R.A., Wallace, A.R., and Hayes, S.P. (2011). Morphological enumeration of resting spores in sporosori of the plant pathogen Spongospora subterranea. Acta Protozoologica 50(2), 121.
Harrison, J., Searle, R., and Williams, N. (1997). Powdery scab disease of potato-a review. Plant Pathology 46(1), 1-25.
Johnson, D.A., and Cummings, T.F. (2015). Effect of powdery scab root galls on yield of potato. Plant Disease 99(10), 1396-1403.

More information regarding Dr. Kamal’s seminar can be found in the seminar announcement.

Dr. Allen Sutton, WSU Office of Outreach and Education and Division of Student Affairs
2023-01-23 16:10 - 17:00
Please join us for our first seminar of the Spring semester featuring Guest Speaker Dr. Allen Sutton presented by the Plant Pathology DEI Committee , his talk will be on “Inclusion 101”, January 23rd, 2023, at 4:10PM. For more information please see the Seminar Announcement- Dr. Allen Sutton

Seminar: Dr. Marin Talbot Brewer
2022-12-05 16:10 - 17:25 | Plant Pathology 515, 515, Pullman, WA
Speaker: Dr. Marin Talbot Brewer, Professor of Mycology/Plant Pathology University of Georgia, Athens, GA
mtbrewer@uga.edu
Tentative Seminar Title: TBD

Seminar: Dr. Enrico Bonello
2022-11-28 16:10 - 17:25 | Plant Pathology 515, 515, Pullman, WA
Speaker: Dr. Enrico Bonello, Professor of Plant Pathology,
The Ohio State University, Columbus, OH
bonello.2@osu.edu
Tentative Seminar Title: Beech Leaf Disease: A Forest Epidemic of National and International Concern

Seminar: Dr. Peter Henry
2022-11-14 16:10 - 17:25 | Plant Pathology 515, 515, Pullman, WA
Student-Invited Speaker:
Dr. Peter Henry
Research Plant Pathologist, USDA ARS Crop Improvement and Protection Research. Salinas, CA
Peter.Henry@usda.gov
Tentative Seminar Title: The Origins and Evolution of Fusarium oxysporum f. sp. fragariae, Cause of Fusarium Wilt of Strawberry

Seminar: Alex Batson
2022-11-07 16:10 - 17:25 | Plant Pathology 515, 515, Pullman, WA
Speaker: Alex Batson, PhD exit seminar
alex.batson@wsu.edu
Tentative Seminar Title: Characterization, Detection, and Genetics of the Spinach Fusarium Wilt Pathogen

Seminar: Joseph Mellow
2022-10-31 16:10 - 17:25 | Plant Pathology 515, 515, Pullman, WA
Speaker: Joseph K Mellow, MS student
joseph.mellow@wsu.edu
Tentative Seminar Title: Understanding Botrytis Gray Mold on Strawberry and its Fungicide Resistance Mechanisms
