Progress 10/01/19 to 09/30/20
Outputs
Target Audience:Target audiences: Growers; natural resource managers and park personnel, non-profits, and other managers of natural or semi-natural ecosystems that have edges adjacent to agricultural fields; virologists and plant pathologists in government or university research settings; chemical ecologists engaged in research on plant-insect interactions and plant defense responses; undergraduate students in entomology classes and research experience programs. Efforts: Communication of project activities and outputs to growers via commodity group meetings and in conjunction with the PD's funded work through the California Melon Research Board and the Specialty Crop Block Grant Program. Providing reports to natural reserve managers. Direct mentoring of undergraduate students through the UCR summer research programs and course credit-based research activities. Presentations on research opportunities to students participating in retention programs at UCR. Development and implementation of strategies for effective mentoring of underrepresented minority groups. Presentation of results via scientific conferences and through peer-reviewed publications. Where appropriate, discussion of project activities through social media and PD website. Changes/Problems:Pandemic restrictions have slowed progress on whitefly/virus resistance breeding efforts (Goal #4), but we are now on track to complete crosses in this project period. Goals regarding work with wild plant virus reservoirs (#2, 3, and 10) are modified slightly depending on the virus community present, but this does not change the overall goals and insights to be gained. For instance, another virus (CABYV) is dominant in reservoirs over CYSDV, so we have focused first on this virus for studying impacts on plant health and persistence. However, southernmost populations of reservoir hosts do have CYSDV present alongside CABYV.This will give opportunities for studying CABYV and CABYV-CYSDV co-infections, which are predicted to influence transmission of each pathogen. Additionally, we have expanded this work to include monitoring for psyllids and their microbiota (fastidious phloem-limited plant pathogens) which share ecological niches with the viruses we are studying. What opportunities for training and professional development has the project provided?Training activities Members of the laboratory received training in molecular techniques, statistical analysis, experimental design, and methods for quantifying behavior and performance of hemipteran vectors. Trainings were done on a one-on-one mentoring basis (remotely via Zoom) as well as through organized training sessions with small groups (via Zoom). Several undergraduates participated in remote hands-on experimental experiences curated by the PD and supported directly by Hatch funds. A writing group is ongoing to provide regular training in scientific communication and to ensure progress on writing and publishing results of ongoing projects. Professional Development The PD curated two special issues, one on microbe-plant-insect interactions in Journal of Chemical Ecology, and another on the 14th annual International Plant Virus Epidemiology symposium (Virus Research). Presentations were planned for the Pacific branch meeting of the Entomological Society of America and a symposium curated by the PD at the International Congress of Entomology, but both were cancelled due to the pandemic. The PD and graduate students presented research at the Entomological Society of America annual meeting. The PD also presented at the UC Davis Plant Pathology seminar series, and to the Specialty Crops Technical Council. Undergraduates presented at the 2020 RISE symposium and graduate researchers presented their work at the UC Riverside Entomology department student seminar day. Graduate students participate in professional development training through coursework within the UCR Entomology Department graduate program (grant writing, presentation skills, research ethics, and job application strategies). How have the results been disseminated to communities of interest?Many outreach activities to local schools and youth groups were cancelled due to the pandemic, so communication to these groups has suffered somewhat during 2020. However, we were able to present work through the "Skype a Scientist" program (graduate student). Prior to the pandemic, the PD presented research in the laboratory to freshman undergraduates participating in the PERSIST program, which is meant to attract and retain underrepresented minorities in STEM fields. Research has been presented at the UCR Entomology student seminar day, Entomological Society of America national meeting (PD, three graduate students), at departmental seminars (PD), the Specialty Crops Technical Council (PD), and to melon growers and agronomists at the California Melon Research Board annual meeting (PD). We have also published results as manuscripts (see products). What do you plan to do during the next reporting period to accomplish the goals?We will focus on completing goal #3 by finishing experiments to quantify effects of CYSDV and CABYV on the growth, reproduction, and stress tolerance of wild perennial plants. This will synergize with experiments for goal #10, which will incorporate vector interactions by studying the effects of virus infection in these hosts on vector feeding behavior and survival. We will continue to characterize viromes and genomic characteristics of identified viruses as a component of studying virus and vector movement across agroecological interfaces. In parallel, we will continue work on movement and distribution of psyllid vectors and phloem-limited bacterial pathogens, both of which share similarities with virus pathosystems we are already studying. We will complete breeding crosses of whitefly and virus-resistant melon germplasm and pursue resistance phenotyping to identify the genetic basis of resistance (goal #4) and continue analysis of data collected on whitefly endosymbiont influence on saliva (transcriptome/proteomes) (goal #6). Funding for these goals will be pursued with applications to commodity boards, USDA-NIFA grant programs, NSF, and the CA Depts. of Food and Agriculture and Pesticide Regulation. ?
Impacts
What was accomplished under these goals?
Specific Objectives: 1. Quantify the effects of CYSDV infection on melon attractiveness to and resistance to whitefly vectors. This objective has been completed. We have a paper in review that details vector and non-vector responses to CYSDV manipulation of plant phenotypes (listed in products) and published a paper (Kenney et al. 2020) showing that commercial elicitor products can disrupt vector attraction to CYSDV-infected hosts. 2. Quantify the effects of CYSDV infection on reservoir host attractiveness to and resistance to whitefly vectors. We were unable to pursue work on this due to pandemic access restrictions to the laboratory. However, we did identify new reservoir hosts of CYSDV among wild cucurbit species using untargeted sequencing of viromes from populations throughout Southern CA. We also identified the distribution of CYSDV in these hosts and our data suggest it is more limited to southernmost populations, with northern populations dominated by CABYV, an aphid-borne cucurbit virus. 3. Quantify the effects of CYSDV infection on abiotic stress resistance, survival, and fecundity of wild perennial reservoir hosts. We discovered that while CYSDV is present in wild cucurbits, another virus, CABYV, is far more prevalent. We first pursued work with CABYV given its importance. We found that infection negatively affects establishment and growth of young plants of two wild cucurbit perennials that are keystone species in non-managed landscapes. Complementary field observations have been collected and are being entered and analyzed. 4. Characterize the mechanisms of whitefly and CYSDV resistance in melon accessions PI 122847, TGR 1551 (PI 482420), and PI 313970 Crosses were completed for F1, F2, and backcrosses to parents. F2:3 crosses are being completed presently. 5. Based on 1-4 above, develop management recommendations for reducing CYSDV incidence and impacts on melon production. Use of elicitors was discussed at the 2020 CA Melon Research Board meeting. We performed field trials to evaluate safety of elicitor products for melons under agronomic conditions. Our results suggest elicitors do not put undue stress on plants in central valley production areas and could be used for virus protection. Grower discussion occurred and several were recruited to run trials. 6. Evaluate the role of a facultative endosymbiont in modifying whitefly feeding behavior and whitefly responses to CYSDV-infected and healthy melon plants. We collected salivary glands for transcriptome analysis. Data from this experiment is being analyzed. We also tested use of single cell RNA-seq technology for single salivary gland transcriptomes. These data are also being analyzed. In complement to this, we collected saliva from whiteflies feeding on membranes and performed the first pilot proteomic analysis of symbiont-bearing and symbiont-free saliva. Based on these analyses, which showed promising results, we are collecting larger volumes for final analyses. 7. Use CMV as a model pathogen to study the relationship among virus evolutionary history, virulence, and induction of transmission-enhancing chemical phenotypes in host plants. We discovered that these efforts are being pursued by another group, so have shifted away from work on this system. We are using CMV as a model mosaic virus for testing effects of elicitor products on transmission, to implement such products as components of melon virus IPM. 8. Use functional genomics approaches to identify the genetic determinants of CMV effects on host chemical phenotypes. We discovered that these efforts are being pursued by another group, so have shifted away from work on this system. 9. Determine how beneficial rhizobacteria modify the behavioral responses of vectors to virus-induced changes in plant phenotypes. Work in this area was completed in 2019 and published. 10. Use perennial grasses as models for understanding how plant traits and virus infection status interact to determine vector behavior and virus spread. As stated in prior reports, we have shifted to focus on perennial dicots that are keystone species in preserved natural habitats in CA. In the last project period we sampled plants from new populations and characterized viruses present. We determined that geography plays a large role in structuring virus populations, and that proximity to different types of agriculture and vector sources changes the virus community. We also found new host associations (e.g., cucurbit viruses infecting nightshade family plants) and performed both field and greenhouse experiments to characterize impacts of a key virus (CABYV) on perennial health. Two manuscripts are in preparation based on these activities.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2020
Citation:
Kenney JR, Grandmont M-E, Mauck KE (2020) Priming Melon Defenses with Acibenzolar-S-methyl Attenuates Infections by Phylogenetically Distinct Viruses and Diminishes Vector Preferences for Infected Hosts. Viruses 12:257. https://doi.org/10.3390/v12030257
- Type:
Journal Articles
Status:
Published
Year Published:
2020
Citation:
Mauck KE, Chesnais Q (2020) A synthesis of virus-vector associations reveals important deficiencies in studies on host and vector manipulation by plant viruses. Virus Res 285:197957. https://doi.org/10.1016/j.virusres.2020.197957
- Type:
Journal Articles
Status:
Under Review
Year Published:
2020
Citation:
Chesnais, Q., Sun, P., Mauck, K.M. Advanced infections by cucurbit yellow stunting disorder virus encourage whitefly vector colonization while discouraging non-vector aphid competitors. In review at Journal of Pest Science.
- Type:
Journal Articles
Status:
Published
Year Published:
2020
Citation:
Chesnais Q, Caballero Vidal G, Coquelle R, et al (2020) Post-acquisition effects of viruses on vector behavior are important components of manipulation strategies. Oecologia 194:429440. https://doi.org/10.1007/s00442-020-04763-0
- Type:
Other
Status:
Published
Year Published:
2020
Citation:
Ali JG, Casteel CL, Mauck KE, Trase O (2020) Chemical Ecology of Multitrophic Microbial Interactions: Plants, Insects, Microbes and the Metabolites that Connect Them. J Chem Ecol. https://doi.org/10.1007/s10886-020-01209-y
- Type:
Other
Status:
Published
Year Published:
2020
Citation:
Jeger M, Fereres A, Mauck K, Wintermantel WM (2020) Reducing the spread of plant viruses through communication and global cooperation. Virus Res 198139. https://doi.org/10.1016/j.virusres.2020.198139
|
Progress 10/01/18 to 09/30/19
Outputs
Target Audience:Target audiences: Growers (particularly of melons/cucurbits); natural resource managers and park personnel, non-profits, and other managers of natural or semi-natural ecosystems that have edges adjacent to agricultural fields; virologists and plant pathologists in government or university research settings; chemical ecologists engaged in research on plant-insect interactions and plant defense responses; undergraduate students in entomology classes and research experience programs. Efforts: Communication of project activities and outputs to growers via commodity group meetings, Cal Ag publications, newsletters, and in conjunction with the PD's funded work through the California Melon Research Board and the Specialty Crop Block Grant Program. Providing reports to natural reserve managers. Direct mentoring of undergraduate students through the UCR summer research programs and course credit-based research activities. Presentations on research opportunities to freshman participating in retention programs at UCR. Development and implementation of strategies for effective mentoring of underrepresented minority groups. Presentation of results via scientific conferences and through peer-reviewed publications. Where appropriate, use of social media. Changes/Problems:3. Quantify the effects of CYSDV infection on abiotic stress resistance, survival, and fecundity of wild perennial reservoir hosts. Work toward completion of this goal will be performed as a component of goal #10, which will include characterization of infections by crop-associated viruses in wild perennial dicots. CYSDV was not found in our sampling locations but will be included in future studies if found in wild plant sampling sites closer to the Imperial Valley. Proposals are pending by collaborators, and if resources become available we will use these to pursue the proposed work on CYSDV in non-cucurbit hosts. 6. Evaluate the role of a facultative endosymbiont in modifying whitefly feeding behavior and whitefly responses to CYSDV-infected and healthy melon plants. This work has expanded to include study of interactions between bacterial symbionts in the genus Candidatus Liberibacter and psyllid hosts/vectors. We are studying whiteflies and psyllids in tandem and using other hosts in addition to melon. 7. Use CMV as a model pathogen to study the relationship among virus evolutionary history, virulence, and induction of transmission-enhancing chemical phenotypes in host plants. and 8. Use functional genomics approaches to identify the genetic determinants of CMV effects on host chemical phenotypes. These linked objectives require significant resources to pursue and will be completed if extramural funding can be obtained. Two other groups (one at UC Riverside and another the United Kingdom) are pursuing similar research goals using the CMV system. Therefore, it may be unwise to continue pursuit of these objectives without a collaboration in place to ensure that efforts are not duplicated. We will continue to monitor this situation to make a decision about pursuing this work. What opportunities for training and professional development has the project provided?Training activities Members of the laboratory received training in molecular techniques and electrophysiological techniques for quantifying the feeding behavior of hemipteran vectors. Trainings were done on a one-on-one mentoring basis as well as through organized training sessions. General training in insect behavioral assay techniques, safety training, and research ethics discussions took place. A writing group is ongoing to provide regular training in scientific communication and to ensure progress on writing and publishing results of ongoing projects. Professional Development Two graduate students presented their work at the Entomological Society of America Pacific Branch Meeting (San Diego, CA) and three graduate students presented their work at the national meeting of the Entomological Society of America. One of these presentations was an invited speaker role, and the other won second place in the student competition. Undergraduate and graduate researchers presented their work at the UC Riverside Entomology department student seminar day. Graduate students participate in professional development training through coursework within the UCR Entomology Department graduate program (grant writing, presentation skills, research ethics, and job application strategies). Graduate students have also successfully applied for and obtained various small grants due to their training in these areas. How have the results been disseminated to communities of interest?Graduate student trainees regularly perform outreach to local schools and youth groups. Graduate students and the PD also presented research in the laboratory to freshman and sophomore undergraduates participating in the PERSIST program, which is meant to attract and retain underrepresented minorities in STEM fields. Research has been presented at the UCR Entomology student seminar day, Entomological Society of America national and Pacific branch meetings (PD and graduate students), the Gordon Research Conference on Plant-herbivore interactions (PD), International Society of Chemical Ecology, American Chemical Society, 14th International Plant Virus Epidemiology Symposium, and to melon growers and agronomists at the California Melon Research Board annual meeting (PD). What do you plan to do during the next reporting period to accomplish the goals?Efforts described above will continue.Outreach and student trainingefforts will increase in the future due to a recently funded USDA-NIFA Hispanic Serving Institution Educational Grant, with the PD of this HATCH project as a co-PD on the grant. The PD will also present research at several departmental seminars throughout the U.S.
Impacts
What was accomplished under these goals?
Impact statement: Understanding the effects of plant pathogens requires knowledge of both plant responses to infection and vector behavior in relation to infected and healthy hosts. During this reporting period we demonstrated that a plant virus enhances its own chances of transmission by changing the appearance and quality of host plants for whitefly vectors. The virus, CYSDV, causes millions of dollars in lost revenue due to effects on melon crops in California, and our findings have led to new proposal submissions to federal, state, and commodity groups to develop tools for disrupting CYSDV effects on plants and vectors using environmentally safe compounds that enhance plant defenses. We have also made progress on a funded project to breed melon cultivars with resistance to both CYSDV and whitefly vectors. These efforts will lead to reduced insecticide inputs and recovery of lost production. Alongside this virus-focused work, we also made progress in understanding how the bacteria living inside whitefly vectors assist their host organisms in feeding on host plants. This work was partially completed by undergraduates participating in UC Riverside programs that help enhance inclusion and retention of underrepresented groups in science fields. A NIFA grant on this project began in March 2019 and we are already gaining new insights into how a globally devastating insect vector can feed on a wide variety of host plants. We also made great progress in understanding how viruses and vectors move from agricultural environments into preserved natural areas housing native vegetation. Building on our 2018 publication describing diverse virus communities in drought-tolerant native plants that are key players in arid habitats, we discovered that crop-associated viruses and their vectors are highly prevalent in these species. The costs or benefits of these viruses for native vegetation are unknown and we are currently performing manipulative experiments with isolated viruses and wild plant germplasm to understand how viruses from crops are changing the essential natural landscapes that provide habitat for native species. 1. Quantify the effects of CYSDV infection on melon attractiveness to and resistance to whitefly vectors. We completed work on this aim. In follow-up studies, we identified changes in volatiles and primary metabolites anddetermined that preferential attraction to infected hosts is driven by visual rather than odor-based cues. By knowing what symptoms are driving whitefly preferences, we can more effectively target disruption of these symptoms through breeding and immunity priming. This project involved training of one graduate student, one post-doctoral researcher, and one high-school student. 2. Quantify the effects of CYSDV infection on reservoir host attractiveness to and resistance to whitefly vectors. We have not completed additional work. Collaborators have proposals pending to fund this work. 3. Quantify the effects of CYSDV infection on abiotic stress resistance, survival, and fecundity of wild perennial reservoir hosts. We have not completed additional work. Collaborators have proposals pending to fund this work. 4. Characterize the mechanisms of whitefly and CYSDV resistance in melon accessions PI 122847, TGR 1551 (PI 482420), and PI 313970. We developed and validated phenotyping assays to quantify whitefly antixenosis (repellency), antibiosis (toxicity), and CYSDV resistance. Crosses of germplasm with cultivated backgrounds are partially completed. When done, the offspring from these crosses will be screened using the phenotyping methods we developed. Alongside this work, we screened immunity priming products for the capacity to reduce infection success and severity in non-resistant melon cultivars. We identified one effective product (Actigard) thatreduces infection severity by CYSDV and Cucumber mosaic virus (CMV). This project involved training of one graduate student. 5. Based on 1-4 above, develop management recommendations for reducing CYSDV incidence and impacts on melon production. We have presented results on Actigard experiments to students, researchers, industry personnel, and growers at several venues. Recommendations for use of Actigard are in development. Growers are trying out some dose regimes this year. 6. Evaluate the role of a facultative endosymbiont in modifying whitefly feeding behavior and whitefly responses to CYSDV-infected and healthy melon plants. Previously, we showed that feeding by whiteflies with a facultative symbiont enhances the performance of symbiont-free whiteflies on systemic leaves. Last year we began work on a NIFA-funded project to characterize the salivary components responsible for plant defense suppression. We have performed salivary collections and preliminary proteomics evaluations, developed new methods for increasing efficiency of salivary collections, and performed sequencing of expressed RNA in single salivary glands. Data analysis for these activities is ongoing. This work involved training of one undergraduate student. Complementary studies are underway for other related vector organisms (psyllids) and this work also involves training of one undergraduate student. 7. Use CMV as a model pathogen to study the relationship among virus evolutionary history, virulence, and induction of transmission-enhancing chemical phenotypes in host plants. We have studied the effects of various plant immunity priming agents on expression of CMV symptoms and aphid vector responses. Our studies indicate that even within cucurbits, CMV effects on plant attractiveness to aphid vectors is variable, with infection increasing attraction in squash and having no effect on attraction in melons. This work is included in a recent manuscript that is pending acceptance following submission of minor revisions. The work involved training of one graduate student and one high-school student. 8. Use functional genomics approaches to identify the genetic determinants of CMV effects on host chemical phenotypes. Another group is carrying out these experiments independent of my laboratory group, and therefore we have de-prioritized work in this area to avoid overlap in efforts. 9. Determine how beneficial rhizobacteria modify the behavioral responses of vectors to virus-induced changes in plant phenotypes. A project on soybeans as a model was published in 2019 in the journal Proceedings of the Royal Society B: Biological Sciences. The paper reports that dual rhizobacterial colonization disrupts negative effects of a plant virus on plant attractivenss to biological control organisms that attack the insect vector. Additional work in another system (the model legume, Medicago sativa) is being prepared for publication. 10. Use perennial grasses as models for understanding how plant traits and virus infection status interact to determine vector behavior and virus spread. We performed sampling across multiple populations of focal species in the genus Cucurbita (wild squash) and determined infection prevalence of Cucurbit aphid-borne yellows virus (CABYV), a crop-associated virus that infects our wild hosts.Through manipulative experiments, we will determine how CABYV impacts plant growth during the next HATCH funding period and also identify the population structure of the insect vector across the region. We also sampled squash in the most extreme parts of its range (true desert to arid grassland/sagescrub ecotones) and have performed next-generation sequencing to characterize the viromes of plants in these areas. This project involved training/mentoring of one graduate student and two undergraduate students.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2019
Citation:
*Mauck KE, Sun P, Meduri V, & Hansen AK (2019) New Ca. Liberibacter psyllaurous
haplotype resurrected from a 49-year-old specimen of Solanum umbelliferum: a native host of the psyllid vector. Scientific Reports, 9(1), 9530.
- Type:
Journal Articles
Status:
Published
Year Published:
2019
Citation:
Pulido H, Mauck KE, De Moraes CM, & Mescher MC (2019) Combined effects of mutualistic
rhizobacteria counteract virus-induced suppression of indirect plant defences in soya bean.
Proceedings of the Royal Society B, 286(1903), 20190211.
|
Progress 10/12/17 to 09/30/18
Outputs
Target Audience:Target audiences: Growers (particularly of Cucurbits and alfalfa); natural resource managers and park personnel, non-profits, and other managers of natural or semi-natural ecosystems that have edges adjacent to agricultural fields; virologists and plant pathologists in government or university research settings; chemical ecologists engaged in research on plant-insect interactions and plant defense responses; undergraduate students in entomology classes and research experience programs. Efforts: Communication of project activities and outputs to growers via commodity group meetings, Cal Ag publications, newsletters, and in conjunction with the PD's funded work through the California Melon Research Board and the Specialty Crop Block Grant Program. Providing reports to natural reserve managers. Direct mentoring of undergraduate students through the UCR summer research programs and course credit-based research activities. Presentations on research opportunities to freshman participating in retention programs at UCR. Development and implementation of strategies for effective mentoring of underrepresented minority groups. Presentation of results via scientific conferences and through peer-reviewed publications. Where appropriate, discussion of project activities through social media and PD website. Changes/Problems:Changes associated with specific goals are outlined below: 3. Quantify the effects of CYSDV infection on abiotic stress resistance, survival, and fecundity of wild perennial reservoir hosts. Work toward completion of this goal will be performed as a component of goal #10, which will include characterization of infections by crop-associated viruses in wild perennial dicots. CYSDV was not found in our sampling locations but will be included in future studies if found in wild plant sampling sites closer to the Imperial Valley. 7. Use CMV as a model pathogen to study the relationship among virus evolutionary history, virulence, and induction of transmission-enhancing chemical phenotypes in host plants. and 8. Use functional genomics approaches to identify the genetic determinants of CMV effects on host chemical phenotypes. These linked objectives require significant resources to pursue and will be completed if extramural funding can be obtained. Two other groups (one at UC Riverside and another the United Kingdom) are pursuing similar research goals using the CMV system. Therefore, it may be unwise to continue pursuit of these objectives without a collaboration in place to ensure that efforts are not duplicated. This will be evaluated over the remaining year and if necessary a project change will be submitted. What opportunities for training and professional development has the project provided?Training activities Members of the laboratory received training in molecular techniques and electrophysiological techniques for quantifying the feeding behavior of hemipteran vectors. Trainings were done on a one-on-one mentoring basis as well as through organized training sessions. A writing group is ongoing to provide regular training in scientific communication and to ensure progress on writing and publishing results of ongoing projects. Professional Development The post doctoral researcher assisted with organization of, and presentation within, a symposium (PracticalApplicationsof Research on Parasite Manipulation of Hosts and Vectors) for the Entomological Society of America annual meeting (2018) in Vancouver, BC. One graduate student presented her research at this meeting and the Pacific branch meeting of the Entomological Society of America. Undergraduate and graduate researchers presented their work at the UC Riverside Entomology department student seminar day. Graduate students participate in professional development training through coursework within the UCR Entomology Department graduate program (grant writing, presentation skills, research ethics, and job application strategies). How have the results been disseminated to communities of interest?Graduate student trainees regularly perform outreach to local schools and youth groups. Graduate students also presented research in the laboratory to freshman undergraduates participating in the PERSIST program, which is meant to attract and retain underrepresented minorities in STEM fields. Research has been presented at the UCR Entomology student seminar day, Entomological Society of America national and Pacific branch meetings (post-doctoral researcher, PD, and one graduate student), the Gordon Research Conference on Plant-herbivore interactions (PD), European Congress of Entomology (Post-doctoral researcher and PD) and to melon growers and agronomists at the California Melon Research Board annual meeting (PD). ? What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Impact statement: Understanding the effects of plant pathogens requires knowledge of both plant responses to infection and vector behavior in relation to infected and healthy hosts. During this reporting period we demonstrated that a plant virus enhances its own chances of transmission by changing the appearance and quality of host plants for whitefly vectors. The virus, CYSDV, causes millions of dollars in lost revenue due to effects on melon crops in California, and our findings have led to externally funded projects aimed at disrupting CYSDV effects on plants and vectors using environmentally safe compounds that enhance plant defenses, as well as a funded project to breed melon cultivars with resistance to both CYSDV and whitefly vectors. These efforts will lead to reduced insecticide inputs and recovery of lost production. Alongside this virus-focused work, we also made progress in understanding how the bacteria living inside whitefly vectors assist their host organisms in feeding on host plants. This work was partially completed by undergraduates participating in UC Riverside programs that help enhance inclusion and retention of underrepresented groups in science fields. It served as the basis for a successful NIFA proposal and provided new insights into how a globally devastating insect vector can feed on a wide variety of host plants. We also made great progress in understanding how viruses and vectors move from agricultural environments into preserved natural areas housing native vegetation. We found that drought-tolerant native plants are frequently infected by multiple plant viruses, some of which are new to science and some of which originate from adjacent crop habitats. The costs or benefits of these viruses for native vegetation are unknown, but our research suggests that nearly all wild plants are infected with multiple viruses and that these organisms are an entirely overlooked component of conservation strategies. 1. Quantify the effects of CYSDV infection on melon attractiveness to and resistance to whitefly vectors.We found that symptoms associated with later stages of disease progression are highly attractive to whiteflies, while ingestion of sap from the phloem is strongly enhanced at both early and late stages of infection. Our data suggest that CYSDV infection symptoms significantly enhance the probability of transmission by whitefly vectors. These findings provide insight into how vectors select among hosts and how virus pathology relates to transmission. Results have been presented to melon growers and at scientific conferences. 2. Quantify the effects of CYSDV infection on reservoir host attractiveness to and resistance to whitefly vectors. We screened several alfalfa cultivars for susceptibility to CYSDV infection. All cultivars became infected. Future efforts will pursue work on quantifying CYSDV effects on alfalfa attractiveness to insect vectors and virus acquisition/transmission from alfalfa. 3. Quantify the effects of CYSDV infection on abiotic stress resistance, survival, and fecundity of wild perennial reservoir hosts. Nothing to report. 4. Characterize the mechanisms of whitefly and CYSDV resistance in melon accessions PI 122847, TGR 1551 (PI 482420), and PI 313970. We measured insect preferences and CYSDV susceptibility among melon accessions in the laboratory. Our results confirm rough field observations that PI122847 is tolerant and/or resistant to CYSDV and that whiteflies avoid settling and feeding on this plant. A collaborator is crossing and backcrossing these accessions to create F2 and F2:3 generations. These will be used to map resistance traits. The long-term results of this project will provide virus-resistant cultivars and reduce insecticide inputs. 5. Based on 1-4 above, develop management recommendations for reducing CYSDV incidence and impacts on melon production. Presently, we are pursuing efforts to disrupt symptoms of virus infection, and thereby attraction of vectors, using hormone mimic products. We tested a product that mimics the plant hormone salicylic acid, but it did not have an appreciable effect on symptom expression or disruption of vector attraction. This suggests that other phytohormone pathways may be involved in CYSDV pathology. We are now pursuing work to test the effects of ethylene inhibitors on virus symptom expression alongside profiling of phytohormone changes along disease progression. This work will inform labeling and registration of plant hormone mimic products and provide guidance to growers on how to use these products as part of an integrated disease and vector management program. Results have been presented to growers and at scientific conferences. 6. Evaluate the role of a facultative endosymbiont in modifying whitefly feeding behavior and whitefly responses to CYSDV-infected and healthy melon plants. Using a unique system consisting of two lines of an invasive whitefly which differ only in the presence or absence of a facultative symbiont, we found evidence that the benefits of symbiont infection can include more effective suppression of plant defenses. By priming plants with feeding by symbiont-infected vs. symbiont-free whiteflies, we showed that feeding by whiteflies with the symbiont enhances the performance of symbiont-free whiteflies on systemic leaves. This work was presented at the European Congress of Entomology and was recently funded through a seed grant from the NIFA foundational program. Moving forward, we will characterize the salivary components responsible for plant defense suppression and test the functional significance of a subset of putative effectors. 7. Use CMV as a model pathogen to study the relationship among virus evolutionary history, virulence, and induction of transmission-enhancing chemical phenotypes in host plants. We performed behavioral experiments to measure the in-plant feeding behavior of insect vectors on different host plants infected with one of two different genotypes of CMV. We found that infection of a cucurbit host alters quality in ways that reduce palatability for vector aphids, but the opposite effect occurs in a solanaceous host. Experiments are ongoing in this system. 8. Use functional genomics approaches to identify the genetic determinants of CMV effects on host chemical phenotypes. Nothing to report. 9. Determine how beneficial rhizobacteria modify the behavioral responses of vectors to virus-induced changes in plant phenotypes. Final experiments have been completed to quantify the effects of beneficial microbe colonization on the ability of a plant virus to modify chemistry and vector behavior. We found that microbial colonization enhances transmission, but that this appears to be context dependent. The results are being written up for publication with an entomologically themed journal as the intended target for submission. Results have been presented at several scientific conferences. 10. Use perennial grasses as models for understanding how plant traits and virus infection status interact to determine vector behavior and virus spread.We determined that most studies on this topic are done in Poaceae systems. Therefore, we opted to pursue work on dicot perennial hosts native to California. For each species, we sampled vector communities using sticky traps placed out throughout the season. We also sampled tissue to perform next generation deep sequencing to characterize the virus communities. We found that all plants were infected with both known and novel viruses and that insect vectors can be very abundant on some hosts. Presently we are isolating and establishing pure cultures of a subset of viruses to pursue further work to determine vertical transmission rates, overwintering in root tissue, and virus effects on host traits. This objective included training and mentoring of one graduate student (for which this project serves as the thesis work) and one undergraduate student.
Publications
- Type:
Book Chapters
Status:
Published
Year Published:
2018
Citation:
Mauck, K. E., Chesnais, Q., & Shapiro, L. R. (2018). Evolutionary Determinants of Host and Vector Manipulation by Plant Viruses. Advances in Virus Research, 101, 189250. https://doi.org/10.1016/bs.aivir.2018.02.007
- Type:
Journal Articles
Status:
Published
Year Published:
2018
Citation:
Chesnais, Q., & Mauck, K. E. (2018). Choice of Tethering Material Influences the Magnitude and Significance of Treatment Effects in Whitefly Electrical Penetration Graph Recordings. Journal of Insect Behavior, 31(6), 656671. https://doi.org/10.1007/s10905-018-9705-x
- Type:
Journal Articles
Status:
Published
Year Published:
2018
Citation:
Shates, T. M., Sun, P., Malmstrom, C. M., Dominguez, C., & Mauck, K. E. (2018). Addressing Research Needs in the Field of Plant Virus Ecology by Defining Knowledge Gaps and Developing Wild Dicot Study Systems. Frontiers in Microbiology, 9, 3305. https://doi.org/10.3389/fmicb.2018.03305
- Type:
Journal Articles
Status:
Published
Year Published:
2019
Citation:
Mauck, K. E., Kenney, J., & Chesnais, Q. (2019). Progress and challenges in identifying molecular mechanisms underlying host and vector manipulation by plant viruses. Current Opinion in Insect Science. https://doi.org/10.1016/j.cois.2019.01.001
- Type:
Journal Articles
Status:
Published
Year Published:
2019
Citation:
Chesnais, Q., Mauck, K. E., Bogaert, F., Bami�re, A., Catterou, M., Spicher, F., & Ameline, A. (2019). Virus effects on plant quality and vector behavior are species specific and do not depend on host physiological phenotype. Journal of Pest Science. https://doi.org/10.1007/s10340-019-01082-z
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