DIRECT AND INDIRECT EFFECTS OF CONSERVED AND LINEAGE-SPECIFIC VOLATILE ORGANIC COMPOUNDS AMONG EUDICOTS FOR CONTROL OF BOTRYTIS CINEREA

In light of expected increases in pest and pathogen pressure and decreases in pollinator availability under climate change, we must harness plants' natural abilities to manipulate biotic interactions to increase sustainability and maintain high yields in our crop systems.Through this work our goals are to exploit plants' use of volatile organic compounds (VOCs), specialized multifunctional metabolites capable of relaying dynamic and complex information across trophic levels, to manipulate biotic interactions. Plant VOCs serve as direct signals of infection and damage, relaying complex cues across species boundaries, providing information to neighboring plants concerning pest and pathogen outbreaks. From these chemical cues, neighboring plants enter a 'primed' state in which they can elicit a faster and more potent response when inevitably challenged with a biotic stressor (e.g., systemic acquired resistance(SAR)). In addition to volatile signals, VOCs can act directly by inhibiting pathogen growth or indirectly by altering the pathogen's transmission and infection success on new tissues.Currently, few studies have assessed variation in VOC efficacy as a biocide against genetically diverse pathogen isolates on various host crops. As with any chemical defense or biocide, standing genetic variation in a pathogen combined with variation among hosts may create a traditional evolutionary chemical arms race. In addition, current research often focuses on specialist pathogens with the common assumption of simple co-evolutionary models explaining the evolution of host-pathogen interactions. However, simple co-evolution is not comparable with generalist pathogens such as B. cinerea, which can infect over 1000 different plant species and has near-zero genetic indicators of host specialization. Based on the ubiquity of VOC use across plants in pathogen resistance and defense signaling, we extend our goals to explore the potential of VOCs as an integral role in generalist pathogen resistance across 16 species of domesticated crops.In addition to VOCs, plant resistance consists of multiple layers of defense mechanisms, ranging from innate immune responses activated by classes or species of pathogens to defense strategies effective against single pathogen isolates. Resistance mechanisms can be present across multiple plant species or be lineage-specific even for conserved defenses such as non-host resistance. Traditionally, the production of specialized metabolites and other resistance mechanisms are viewed as inherently metabolically costly, diverting resources from yield towards their production. Current efforts concerning SAR and induced defenses have inherent metabolic costs that are high in the short term and low over the plant's lifespan, as they include multiple defense mechanisms(metabolites, proteins, structural defenses).VOC production may bypass these limitations as several studies indicate no significant reduction in yield from high VOC production.Thus, VOCs may be harnessed as attractant or deterrent mechanisms at a low metabolic cost, with further potential to be exploited reactively via inducible SAR, providing a holistic plant-derived biocide. Further establishing short-term and long-term goals for implementation of new knowledge produced during this work will support initiatives based on VOC use in agricultural practices as a promising avenue for sustainable agricultural research to reduce yield loss due to plant pathogensTo accomplish our general goals of exploring the direct and indirect effects of plant VOCs during generalist pathogen infections, establishing short-term and long-term goals for VOC use in agricultural practices, and providing training opportunities for postdoctoral and undergraduate researchers we have established the following objectives:Objective 1: Assess variation in conserved and lineage-specific expression of VOC biosynthetic enzymes across a diverse set of eudicots infected with diverse B. cinerea strains.Objective 2: Identify the genetic architecture of B. cinerea variation in susceptibility to general and lineage-specific VOCs.To examine the range of VOC effects, we will compare the effects of plant VOCs on the direct growth, spore number, and viability of B. cinerea in a toxicology-based genome-wide association study (GWAS).Objective 3: Validate the fumigation effects of select plant VOCs on reducing B. cinerea pathogenicity across eudicots.Objective 4: Postdoctoral training in techniques and knowledge needed to develop an independent research program studying the direct and indirect effects of plant volatile metabolites on plant-biotic interactionsObjective 5: Train several undergraduates in the laboratory and statistical techniques, preparing them for careers in researchObjectives 1-3 will be conducted full time by the postdoc (Dr. Dowel) over two years (FTE2.0). Three undergraduate researchers (FTE 1.3) will further assist Dr. Dowell during the project's duration. During this time, the Postdoc will provide several opportunities to learn bioinformatic and microbiological skills while providing further opportunities for undergraduate researchers to present and publish aspects of their contributions to the overall project while fostering their ability to create and pursue novel research ideas, contributing to objective 4. For postdoctoral training, Dr. Dowel will present the products of this work at several national and international conferences. As the postdoctoral mentor, Dr. Kliebnestein will also guide the PD's progress on mentoring undergraduate researchers, navigating administration, and career development. Further during this project, Dr. Kliebenstein will receive regular feedback on preliminary analyses, draft manuscripts, and presentations.