Deep mixing events in the ocean’s surface layer act as physical drivers of carbon export by detraining dissolved and particulate organic matter, including surface phytoplankton communities, to depth. Once removed from the sunlit surface ocean environment, phytoplankton accumulation rates are dependent on the relative contributions of loss processes, such as...
Grapevine Trunk Diseases (GTDs) are caused by a group of fungal pathogens that attack the xylem tissue of mature grapevines worldwide. In the past 30 years, their incidence has increased, both in emerging grape-producing regions, as well as those with an extended history of viticulture. In the same time span,...
Rhizopus microsporus is a globally ubiquitous opportunistic human and plant pathogen that is known to harbor endosymbiotic bacteria. Differences between populations of clinical and environmental R. microsporus isolates have yet to be assessed on a global scale. Whole-genome sequence data were used to explore fungal biology and to assess potential...
Anthropogenic induced climate change is predicted to alter distribution of existing plant populations. As plants migrate over space and time, populations often fragment and contract, affecting basic elements of population dynamics (e.g., population size, gene flow, genetic diversity, etc.). Little is known, however, how these impacts on plant species will...
Oomycete and fungal pathogens threaten food, fiber, and forests around the world. With climate change, these pathogens are expected to emerge more frequently. Evolution can facilitate their emergence through mechanisms such as mutations that change or expand host range. Characterizing evolutionary mechanisms in plant pathogens will contribute to our ability...
Diseases can be a substantial threat to woody plant production, a major industry in Oregon. Boxwood (Buxus spp.) and rhododendron (Rhododendron subgenus Rhododendron and Hymenanthes) represent the top two broadleaf evergreen woody plants by farmgate value in Oregon. Historically, Phytophthora root rot has been considered the most destructive disease of...
Null networks are a type of random graph that is favored for the analysis of a wide variety of real-world networks, including gene-regulatory networks, food webs, and species co-occurrence matrices. As a hypothesis-generating tool, null networks are invaluable because they can reveal network motifs and unusual large-scale properties of networks...
Xanthomonas hortorum pv. carotae (Xhc) is an epiphytic, plant pathogenic bacterium that causes the disease bacterial blight of carrot (Daucus carota subsp. sativus). Infection with Xhc can result in blighting of leaves and umbels and reduce quality and yield of carrot seed crops. Carrot production in the United States approaches...
We give references for illustrations in the third edition of Macrolichens of the Pacific Northwest. For each illustration, we list the photographer or illustrator, the specimen photographed, where the specimen was from, collector, collection number, and herbarium.
Within the Pacific Northwest, USA, root diseases of conifers are a major forest health concern. These diseases are primarily caused by basidiomycete fungi. These fungal associates play a vital role in carbon sequestration but also have a significant negative economic impact within the timber industry. As a result, research on...
Sudden Oak Death (SOD) is a forest disease caused by the oomycete pathogen Phytophthora ramorum, and infects trees in the Western United States and Europe. This generalist pathogen can infect over 130 species of plants, and causes rapid mortality in tree species in the Fagaceae. Sexual reproduction is thought to...
The scale of pest and disease dispersal is often larger than the scale of individual farms. Therefore, an individual grower’s response to pests and diseases can affect and is affected by their surrounding growing region. Individual growers are also not isolated, and engage in various forms of information gathering, sharing,...
Mosses (Phylum Bryophyta) are widely considered to be among the most ancient groups of land plants (embryophytes) and they are the second most speciose embryophyte phylum with ~13,000 extant species. Despite their diversity and antiquity, mosses have a limited fossil record, which primarily consists of gametophytes entombed in Cenozoic amber....
Managers of forest and plantation ecosystems are encountering growing problems involving plant pathogens and the expanding geographic ranges of these pathogens. Historically unexposed stands are exceptionally vulnerable when a non-native pathogen is introduced because these pathogens can cause devastating disease in a host population that lacks co-evolved resistance mechanisms. One...
In the Pacific Northwest (PNW), the two most common root-knot nematodes are Meloidogyne hapla and Meloidogyne chitwoodi. These nematodes can infect a wide variety of crops and can cause significant losses. Currently, it is common for the field of nematology to use labor-intensive microscopy to identify plant-parasitic nematodes based on...
The cultivated potato (Solanum tuberosum) is one of the most important food crops in the United States, as well as globally. As demand rises, growers in the Pacific Northwest are revisiting their crop management strategies to determine whether there are additional ways to enhance crop productivity while managing plant and...
Plant-pollinator mutualisms are one of the most prevalent and economically important mutualisms in nature. Like many other ecological systems, plant-pollinator communities are threatened by anthropogenic activity, both directly (e.g., habitat conversion and fragmentation) and indirectly (e.g., climate change). While we are aware of many of the activities that adversely impact...
In the mountains of central and southern California, high elevation wilderness areas lack epiphytic lichens that can be used to inform us about atmospheric deposition in multiple ways. Epiphytic lichens are capable of accumulating elements proportionally to the local atmospheric concentration, establishing them as commonly used biomonitor of key elements....
Wheat sharp eyespot (SES), caused by the soil-borne fungus Rhizoctonia cerealis is a common stem disease of wheat globally. The disease caused a severe and extensive epidemic throughout the Willamette Valley of Oregon in 2014 and has remained one of the most important wheat diseases in this region. However, litte...
Sudden oak death is caused by the clonally reproducing generalist oomycete Phytophthora ramorum. The pathogen can infect more than 130 different plant hosts including Quercus spp., Larix kaempferi, and Notholithocarpus densiflorus, as well as common nursery genera such as Rhododendron and Camelia, where it causes symptoms ranging from bleeding cankers...
Secondary metabolites (SMs) play an integral role in the life history of most fungal species. Fungal metabolomic studies provide insights into how fungi perform certain ecological functions, how they compete and interact with other organisms, and the breadth of fungal chemodiversity. Fungal SMs have also been utilized for a variety...
Pseudomonas syringae are plant pathogenic bacteria that cause disease by rapidly multiplying within the aboveground tissues of host plants. Growth of P. syringae within plant host tissues requires the disarmament of host immune defenses that limit microbial growth. To combat host defenses, P. syringae deploys a type III secretion system...
The climate of the Pacific Northwest is in flux, and existing forest ecosystems are stressed and poised to shift in fundamental ways, with or without human intervention. This dissertation probes the nature of forest responses to environmental change through investigations of morphology and genetics of three species of alder co-occurring...
Quinone outside Inhibitor (QOI) fungicides are one of the most widely used fungicide classes (FRAC 11) in the world. This popularity is the result of their ability to effectively manage a wide array of economically important pathogen species on a broad range of crops. While having mostly preventative activity, some...
Disease detection through traditional techniques such as scouting fields on foot, molecular assays, or morphological identification of plant pathogens is time consuming and costly. Disease diagnosis in the field can be extremely subjective, and largely depends on the experience and knowledge of pathogen identification and disease quantification. This thesis provides...
Plant-parasitic nematodes (PPN) pose a severe threat to crop production with the economic losses due to nematode parasitism in excessive of US$ 80 billion each year. Meloidogyne incognita, a globally distributed pest with a diverse host range, contributes significantly to this economic loss. The most reliable way to manage PPN...
For tuberizing crops like potato (Solanum tuberosum), the geocaulosphere, or the zone of soil in contact with and influenced by the tuber, is a distinct sphere of microbial life and represents an important interface between the potato crop and the soil environment. Upon potato harvest, specific geocaulosphere soil called tare...
Pseudotsuga menziesii var. menziesii (coast Douglas-fir) is a tree of ecological, economic, and cultural value in its native North American Pacific Northwest (PNW) distribution. P. menziesii is host to a variety of well-documented endophytic foliar microorganisms, including the fungus Nothophaeocryptopus gaeumannii, the causal agent of Swiss needle cast (SNC), and...
Photoacclimation is the process by which plants and phytoplankton adjust the concentration and composition of their photosynthetic machinery (i.e. their photoacclimation state) in response to changes in their light or nutrient environment. The purpose of photoacclimation is to balance the rate at which light energy is absorbed with the energetic...
Cultivated plants are often living artifacts that can aid in evaluation of historic or cultural landscapes. However, a working definition for “culturally significant plant” is currently lacking in the guidance literature for the cultural resource management practitioners. Based on a review of the literature on cultivated plants as indicators of...
There are over 35 known virus and virus-like diseases of sweet cherry (Prunus avium), some with potential to cause severe economic impact by reducing vegetative growth, vigor, and/or quality of fruit. Oregon is the second-ranked state for sweet cherry production in the United States with 13,000 acres and $70.8 million...
Recent research in the UK has found that the wheat cultivar grown in the first year can have a significant impact on the amount of take-all that develops in the second year, regardless of the cultivar planted in year two. ‘Einstein’ is one such cultivar that reduces take-all disease (reduced...
Plant sexual reproduction requires a broad array of molecular mechanisms to proceed successfully. Some of these mechanisms are well-studied, but our knowledge of them as a whole is fundamentally incomplete. Pollen tube growth is a key part of this process, facilitating the delivery of the sperm cells to the female...
Bacterial soft rot of potato (Solanum tuberosum), caused by Pectobacterium and Dickeya species, is among the most common and destructive potato diseases in the United States. These pathogens cause a variety of vascular wilts, and in potato cause a disease complex that includes tuber soft rot, blackleg, aerial stem rot,...
Potato Virus Y (PVY) is an enduring problem for potato production worldwide. Potato varieties that resist the “ordinary” strain PVYO were developed by breeders, but in recent years, recombinant strains of PVY have been able to circumvent this strain-specific resistance and evade growers and seed certification officials by causing fewer...
Raspberries are an important commodity worldwide, with the United States (U.S.) leading fourth in global production in 2017. An important factor when shipping propagated Rubus across the globe is the security of clean plant material verified through pathogen detection methods which is vital in preventing disease spread. A raspberry virus...
Plant pathogens in the genus Phytophthora are known to cause disease on field crops, nursery plants, and forest trees. The best known example probably is Phytophthora infestans, which triggered the infamous Irish potato famine. Other important Phytophthora species include: P. ramorum (sudden oak death pathogen), P. sojae (soybean root rot...
The Red Dog Mine transports concentrated zinc and lead ore in northwestern Alaska through Cape Krusenstern National monument along a haul road. High metal levels in the moss Hylocomium splendens along the haul road have been attributed to ore dust released during transport. The mine has implemented several pollution abatement...
Classic biological control can be a powerful option for those tasked with managing biological invasions; however, some biocontrol releases lead to non-target attack – feeding, damage or development on species other than the target species. The cinnabar moth, Tyria jacobaeae L. (Lepidoptera: Erebidae) was introduced to Western Oregon as a...
Winter squash (Cucurbita maxima) grown in Oregon’s Willamette Valley for edible seed, frozen foods, and fresh markets is susceptible to an undiagnosed soilborne disease. Diseased squash fields exhibit symptoms of stunting, root and crown rot, vascular discoloration, and late-season wilt, which in extreme cases can lead to total crop failure....
A multi-year field study was conducted in Oregon and Washington to evaluate the influence of nitrogen fertilization rate and timing on cone quality, nitrate accumulation in cones, severity of powdery mildew (caused by Podosphaera macularis), arthropod pests, and the stability of conservation biological control of the twospotted spider mite (Tetranychus...
In recent years, our ecological knowledge of tropical dry forests has increased dramatically. However, whole components of the ecosystem, like lichenized fungi, remain mostly unknown. Crustose lichens in these forests are so abundant, that they are responsible for the characteristic appearance of a “white bark forest” during the dry season....
Foliar fungi – pathogens, endophytes, epiphytes – form taxonomically diverse communities that affect plant health and productivity. The composition of foliar fungal communities is variable at spatial scales both small (e.g., individual plants) and large (e.g., continents). However, few studies have focused on how environmental factors and host plant traits...
Biodiversity loss is of global concern, and is due in part to deforestation and high consumer demand for wood and wood products. The neotropical tree species Cedrela odorata (“Spanish cedar” or “cedro”) is economically valuable for its wood and faces threats of overexploitation. Due to strong similarities in wood features...
Phytophthora root rot decreases availability and quality of rhododendrons produced in the USA. Symptoms of Phytophthora root rot include root necrosis, leaf chlorosis, stunting, and permanent wilt. The purpose of this thesis was to better understand the impact of root damage, soil moisture, nitrogen fertilizer application, and pathogen species on...
There is growing interest in using biocrusts (assemblages of cyanobacteria, lichens, mosses, and other taxa in various proportions covering the upper few millimeters of the soil surface) to assist in restoring ecosystem function and native plant communities in dryland ecosystems. Biocrusts can be transplanted and established using jute or thatch,...
An increased understanding of secondary metabolism in fungi is important for both biological and societal reasons. The ascomycete genus, Tolypocladium, is an ideal system to explore secondary metabolism characterization, ecology, evolution and regulation. The genus produces and has the genomic potential to produce a wide array of metabolites. Paired with...
Cyanolichens, lichens with a cyanobacterial photobiont, benefit our ecosystems by the fixation of atmospheric nitrogen into a usable form for other organisms. They are highly sensitive to air pollution and require liquid water for photosynthesis. Many cyanolichen species frequently occur on the ground in the Pacific Northwest, however, most macrolichen...
The fungus Nothophaeocryptopus gaeumannii is the causative agent of Swiss needle cast (SNC), a foliar disease of Douglas-fir. Disease is characterized by premature loss of foliage and reduced growth resulting from the inhibition of photosynthesis due to the occlusion of stomata by the ascocarps of N. gaeumannii. Although the disease...
Conservation conflicts may develop on restoration sites with multiple species recovery objectives. For example, on Pacific Northwest prairies, the co-planting of the diploid cytotype of the common native wildflower Castilleja hispida with the endangered wildflower C. levisecta has resulted in putative Castilleja hybrids on restoration sites, prompting fears that genetic...