Progress 09/01/17 to 08/31/21
Outputs
Target Audience:This grant funded a Clemson University PhD graduate student (Sophia Conzemius) who gave presentations at several professional meetings, including at the national meeting of the Entomological Society of America, regional meeting (southeastern branch) of the Entomological Society of America, the annual meeting of the South Carolina Entomological Society, a University wide three-minute thesis event, and a graduate student field day at an experiment station. The research was also mentioned to cotton growers at several extension meetings. The COVID-19 pandemic prevented the student from giving several other presentations at professional meetings. Changes/Problems:As outlined under accomplishments, an error in application of insecticide to treated plots occurred at both locations in 2019 only, a portion of the data from 2019 was therefore not usable. To address this, the trial was repeated for an additional 3rd year in 2020 in Florence. Since these field trials ended up lasting 3 years rather than the planned 2 years, this also delayed the completion of objective 2. Results from plant samples for metabolomics and VOC are either pending or to be completed by October 2021. We can provide updates on these results as needed. A draft manuscript for a peer-reviewed journal summarizing the fields trials is currently being reviewed internally. Manuscript(s) for the greenhouse trials will be completed over the winter. What opportunities for training and professional development has the project provided?PhD graduate student Sophia Conzemius continued her program, which included passing her comprehensive exams in September 2021. Sophia has worked closely with the PIs onthis grant in conducting all aspects of the research, including collecting data from thrips field trials (sampling of thrips, assessment of injury), rearing of thrips in the laboratory, and conducting greenhouse choice and no-choice trials. How have the results been disseminated to communities of interest?This grant funded a Clemson University PhD graduate student (Sophia Conzemius) who gave presentations at several professional meetings, including at the national meeting of the Entomological Society of America, regional meeting (southeastern branch) of the Entomological Society of America, the annual meeting of the South Carolina Entomological Society, a University wide three-minute thesis event, and a graduate student field day at an experiment station. The research was also mentioned to cotton growers at several extension meetings. The COVID-19 pandemic prevented the student from giving several other presentations at professional meetings. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
1. Evaluate cotton landraces maintained by the US National Plant Germplasm system for resistance to thrips in field trials in Florence, SC, and in Jackson Springs, NC. - Major activities completed: A total of 164 cotton landraces from the U.S. National Plant Germplasm System were used, in addition to two commercial varieties and two breeding lines with partial thrips-resistance. Field evaluations were performed at the NCSU Sandhills Research Station in Jackson Springs, NC, in 2018 and 2019 and at the Clemson University Pee Dee REC in Florence, SC, in 2018, 2019, and 2020. Because an error in application of insecticide to treated plots occurred at both locations in 2019 only, a portion of the data from 2019 was therefore not usable. To address this, the trial was repeated for an additional 3rd year in 2020 in Florence. Cotton was planted on May 2 in NC in 2018, May 9 in SC in 2018, and April 28 in SC in 2020 using an alpha-lattice split-plot design with the main plot as treatment (insecticide treated or untreated) and the subplot as genotype, with three replications, for a total of 1,008 plots in each experiment. All seeds were treated with fungicides; in the insecticide treated plots, seeds were additionally coated with 0.375 mg AI imidacloprid per seed before planting, and emerged seedlings were foliar sprayed with 210 g ha-1 of acephate insecticide at the first true leaf stage (TLS). - Data collected: Nine variables were measured in 2018: plant vigor rating, thrips plant damage rating, immature thrips counts, and adult thrips counts were evaluated at both the 1st TLS and 3rd TLS. Plant dry biomass was measured 42 days after planting. In SC in 2020, the same variables were measured except plant vigor was not recorded. A total of 25 variables were measured over the three field trials. Thrips species were identified from untreated plots using a dichotomous key for 2018 collections and using a probe-based qPCR in 2020. A two-way ANOVA (genotype, insecticide, and the interaction) was used to analyze the different variables. In addition, a selection index was created to quantify genotypes' relative vulnerability to thrips to determine putative thrips resistance that combined all 25 variables. For each variable, scores of '+1' (resistant), '0' (intermediate), and '-1' (susceptible) were assigned. - Summary statistics and discussion of results: across all trials, thrips species were dominated by Frankliniella fusca. These results are consistent with previous surveys showing that F. fusca is the dominant pest thrips species of seedling cotton in the southeastern U.S. Thrips densities, thrips injury, plant vigor, and biomass varied among cotton genotypes in all trials. Using our selection index, 11 genotypes were considered putatively thrips-resistant due to their relatively high number of variables, i.e., index sums of +17 to +13, exhibiting desirable outcomes. The four putatively thrips-susceptible genotypes were defined by a score of 0 to -4. The two commercial varieties were scored +12 and +10, respectively. The two breeding lines with partial thrips-resistance were scored +9 and +10, respectively. The variables with greatest separations among genotypes were plant vigor and biomass. These variables had similarly been examined in previous thrips trials in cotton, where thrips resistance had been associated with a faster relative growth rate and greater plant biomass. By assessing cotton across several variables, we aimed to identify genotypes that may be characterized by multiple types of thrips resistance. - Key outcomes: Our research investigated the relatively unexplored diversity of exotic, uncultivated day-neutral G. hirsutum for their resistance to thrips in the southeastern U.S., leading to a change in knowledge. We quantified thrips resistance traits in wild Upland landraces using intensive screening methods. The genotypes with resistance to thrips can now be used in the cotton breeding program led by USDA ARS co-PI. To further examine thrips resistance in these genotypes, we continued this research in choice and no-choice laboratory tests to identify types of resistance (obj. 2). 2. Investigate mechanisms of resistance among susceptible and resistance genotypes. Genotypes will be selected based on results of field trials conducted in objective 1. Antibiosis, antixenosis, and tolerance mechanisms of resistance will be investigated. In order to identify potential mechanisms of resistance, chemical analyses will include volatile analysis and metabolomics. - Major activities completed: Greenhouse trials at the Clemson University Edisto REC in Blackville, SC were initiated in May 2019. A colony of tobacco thrips (F. fusca) was established in the laboratory using insects from a colony provided by Dr. George Kennedy (NCSU). Because greenhouse trials could be conducted with only a subset of the 168 genotypes used in field trials, a key necessity was an appropriate selection of both resistant and susceptible genotypes using the selection index developed from our field trials. Since these field trials ended up lasting 3 years rather than the planned 2 years, this delayed the completion of this objective. However, this gave us time to fine tune the methodology in the greenhouse. A brief outline of trials is provided here: 2019: efforts focused on troubleshooting both the rearing of F. fusca and developing methods for choice and no-choice trials. Assays were conducted using 5 resistant and 5 susceptible lines from the combined 2018 field data. 2020: choice and no-choice tests were conducted with 10 putatively resistant genotypes, 3 putatively susceptible genotypes, and 3 standards with 10 replicates for choice trials and 8-10 replicates for no-choice trials. 2021: once combined field data had been analyzed, we selected 11 putatively resistant genotypes, 4 putatively susceptible genotypes, and 3 standards with 17 replicates for choice trials and 16 replicates for no-choice trials. In addition, separate sets of the same 18 genotypes were grown in order to submit plant samples for metabolomics and volatile organic compounds (VOCs). The goal of this component is to identify potential mechanisms of resistance. Because of the delay in completing these trials, plant samples were submitted to the Clemson University Multi-User Analytical Laboratory for metabolomics on 1 September 2021 (6 replicates for each genotype) for VOC on 16 September 2021 (initial trial run at 300 ml/min sampling rate: 3hr, 6hr, and 24hr; final samples will be submitted in October 2021). - Data collected: Plant height was measured prior to starting experiments. For choice trials, 90 female thrips were introduced into a cage with the 18 genotypes. After 3 days, plant height, leaf stage, biomass and eggs per plant (after staining leaves) were measured. For no-choice trials, 5 female thrips were introduced into each cage. After 10 days, plant height, leaf stage, biomass, injury, and eggs per plant (after staining leaves) were measured. We expect to receive metabolomics data in the next few weeks. - Summary statistics: eggs per plant varied among genotypes, in addition to plant height before and after experiments for choice trials. For no-choice trials, adult and immature thrips varied among genotypes, in addition to biomass. We look forward to exploring associations of the metabolomics and VOC data with these findings. - Key outcomes: Our research investigated potential thrips resistance mechanisms diversity among exotic, uncultivated day-neutral G. hirsutum, leading to a change in knowledge. Our identification of antixenosis (based on egg laid per plant) and antibiosis resistance mechanisms (based on development of thrips), combined with the forthcoming chemical analyses, will help to identify potential resistance mechanisms, which can be used to accelerate cotton breeding programs for thrips resistance.
Publications
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Progress 09/01/19 to 08/31/20
Outputs
Target Audience:Clemson University PhD student Sophia Conzemius gave a presentation on her research funded by this grant on cotton resistance to thrips at the national meeting of the Entomological Society of America in St Louis, MO,in November 2019, a meeting attended by scientists, graduate students, and other industry professionals. The COVID-19 pandemic has prevented the student from giving another presentation at a professional meeting that was cancelled. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest?Clemson University PhD student Sophia Conzemius gave a presentation on her research funded by this grant on cotton resistance to thrips at the national meeting of the Entomological Society of America in St Louis, MO, in November 2019, a meeting attended by scientists, graduate students, and other industry professionals. What do you plan to do during the next reporting period to accomplish the goals?We will continue to process thrips samples (count thrips and identify a sub-sample to species). We will continue to conduct greenhouse choice and no-choice trials, and will conduct leaf chemical analysis in order to identify potential resistance mechanisms.
Impacts
What was accomplished under these goals?
At the South Carolina location, a replicated trial with 168 cotton genotypes was conducted in 2020 in insecticide treated (seed treatment of imidacloprid and fungicide + foliar application of acephate at the cotyledon stage on 12 May 2020) and untreated plots (seed treatment of fungicide only), for a total of 1,008 plots per location. Thrips were sampled in each plot by submerging 5 plants per plot in jars with alcohol on two sampling dates (first [18 May] and third true leaf [1 June]). Injury from thrips and plant vigor were also recorded. At 42 days after emergence (9 June), dry weight biomass was recorded from 5 plants per plot, in addition to NDVI measured with a handheld sensor. Identification of thrips species is on-going from samples taken from untreated plots. All data (thrips, injury, vigor, NDVI, and biomass) have been collected from the fields trials for this objective. Samples of adult and immature thrips are being processed, as well identification of thrips species. Clemson University PhD student Sophia Conzemius is currently analyzing the data for a manuscript for a peer-reviewed journal article with the data from NC and SC. Greenhouse trials at the Clemson University Edisto REC in Blackville, SC are on-going, with trials initiated in May 2019. A colony of tobacco thrips was established in the laboratory. Based on the field data, a subset of 6 resistant and 6 susceptible genotypes was determined. Seeds from these genotypes were planted in the greenhouse and choice and no-choice trials are on-going. These trials will continue into the fall of 2020.
Publications
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Progress 09/01/18 to 08/31/19
Outputs
Target Audience:
Nothing Reported
Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest?
Nothing Reported
What do you plan to do during the next reporting period to accomplish the goals?We will continue to process thrips samples (count adult and immature thrips and identify a sub-sample of thripsto species). We have now completed the 2-years of field trials. During the next period, efforts will focus on continuing greenhouse and laboratory trials to identify mechanisms of resistance using choice and no-choice trials, and determining physical characteristics associated with resistance in addition to metabolomics analyses.
Impacts
What was accomplished under these goals?
At each locationin South Carolina and North Carolina, a replicated trial with 168 cotton genotypes was conducted in 2018 in insecticide treated (seed treatment of imidacloprid and fungicide + foliar application of acephate at the cotyledon stage) and untreated plots (seed treatment of fungicide only), for a total of 1,008 plots per location. Thrips were sampled in each plot by submerging 5 plants per plot in jars with alcohol on two sampling dates (first and third true leaf). Injury from thrips and plant vigor were also recorded. At 42 days after emergence, dry weight biomass was recorded from 5 plants per plot, in addition to NDVI measured with a handheld sensor. Identification of thrips species is on-going from the 2018 samples. At both locations, the trials were repeated in 2019 with identical methods. To date, all data (thrips, injury, vigor, NDVI, and biomass) from the 2019 trials have been collected. Samples of adult and immature thrips will be processed beginning in September 2019, as well as identification of thrips species. Clemson University PhD student Sophia Conzemius, began in May 2019 with greenhouse trials at the Clemson University Edisto REC in Blackville, SC. A colony of tobacco thrips was established in the laboratory. Based on the 2018 field data, a subset of 5 resistant and 5 tolerant genotypes was determined. Seeds from these genotypes were planted in the greenhouse;choice and no-choice trials have been initiated. These trials will continue into the Fall of 2019, and will be repeated in the summer of 2020.
Publications
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