U.S. Department Of Agriculture Agricultural Research Service Research Articles

Seeing the Forest for the Trees: Threats, Vulnerabilities, and Opportunities for Woody Landscape Plant Genetic Resources

Genetic resources are the foundation of American agriculture’s ongoing success—the diversity, security, health, and genetic integrity of these resources must be safeguarded. However, in contrast to other crops, protecting, managing, and using collections of woody landscape plant genetic resources present significant challenges. These include conservation of at-risk populations that have high genetic diversity, evaluation of taxa with an unknown potential to invade, and management of large specimens that have long generation times and often recalcitrant or difficult-to-store seeds. The wide diversity of taxa and the limited number of specialist curators and scholars present further challenges. Thus, effective collection, preservation, evaluation, and distribution of woody landscape plant germplasm require substantial and specialized resources. The most fundamental challenge is simple: too many built landscapes have low taxonomic diversity and are often dominated by a single taxon, or monoculture. In turn, these taxonomically and genetically depauperate landscapes are vulnerable to a host of biotic and abiotic threats and are less likely to provide ecosystem and societal services for which they were designed. To develop more resilient landscapes, there is an urgent need to expand taxonomic diversity, which requires the horticultural community to effectively acquire, curate, evaluate, distribute, and use diverse woody landscape plant genetic resources. The role of the US Department of Agriculture-Agricultural Research Service (USDA-ARS) National Plant Germplasm System (NPGS) Woody Landscape Plant Crop Germplasm Committee (WLPCGC) is to identify vulnerabilities and threats that compromise WLP crops in the United States and make recommendations for prioritization of germplasm acquisition, evaluation, research, and management priorities through regular interaction with stakeholders. Due to the breadth of genera and shifting plant genetic resource needs of the nursery industry, it is impractical to list specific threatened or priority genera in a broadly applicable crop vulnerability statement. Instead, the WLPCGC has identified themes of threats and vulnerabilities providing a foundation upon which to support prioritization as threats to specific genera emerge.

The evolution of a partnership-based breeding program for organic corn

This paper describes decades of research develop­ing a new type of corn (maize) cultivar that utilizes partnerships with seed-borne, bacterial endophytes to create environmentally friendly, nutritious corn that is better adapted to organic farming. Over time the project engaged and formed multiple, evolving networks of corn breeders and other scientists, organic farmers, nongovernmental organizations (NGOs), private companies, the U.S. Department of Agriculture Agricultural Research Service (USDA-ARS), and state agricultural univer­sities in several states. It addressed and partly resolved the need for developing (a) yield-competi­tive hybrids with greater nutrient density (methio­nine and minerals), (b) better adapted inbreds for organic production conditions, and (c) reduced pollution from nitrogen fertilizers. The partnership approach taken also differs from usual top-down mechanistic breeding approaches in that the methods of breeding entailed holistic attention, learning, and respect for what turned out to be corn plants evolving in symbiogenesis with beneficial microbial partners. Initial studies indicate that the resulting corn from the program is competitive in yield but has better nutritional value. It obtains more of its nitrogen from microbial biomass and organic matter and nitrogen fixation than does conventional corn. Its performance partially depends on seed-borne plant/microbial partnerships. This corn continues to be developed at the Mandaamin Institute but is also being commercially introduced for testing by farmers.

Agricultural Research Service Weed Science Research: Past, Present, and Future

AbstractThe U.S. Department of Agriculture–Agricultural Research Service (USDA-ARS) has been a leader in weed science research covering topics ranging from the development and use of integrated weed management (IWM) tactics to basic mechanistic studies, including biotic resistance of desirable plant communities and herbicide resistance. ARS weed scientists have worked in agricultural and natural ecosystems, including agronomic and horticultural crops, pastures, forests, wild lands, aquatic habitats, wetlands, and riparian areas. Through strong partnerships with academia, state agencies, private industry, and numerous federal programs, ARS weed scientists have made contributions to discoveries in the newest fields of robotics and genetics, as well as the traditional and fundamental subjects of weed–crop competition and physiology and integration of weed control tactics and practices. Weed science at ARS is often overshadowed by other research topics; thus, few are aware of the long history of ARS weed science and its important contributions. This review is the result of a symposium held at the Weed Science Society of America’s 62nd Annual Meeting in 2022 that included 10 separate presentations in a virtual Weed Science Webinar Series. The overarching themes of management tactics (IWM, biological control, and automation), basic mechanisms (competition, invasive plant genetics, and herbicide resistance), and ecosystem impacts (invasive plant spread, climate change, conservation, and restoration) represent core ARS weed science research that is dynamic and efficacious and has been a significant component of the agency’s national and international efforts. This review highlights current studies and future directions that exemplify the science and collaborative relationships both within and outside ARS. Given the constraints of weeds and invasive plants on all aspects of food, feed, and fiber systems, there is an acknowledged need to face new challenges, including agriculture and natural resources sustainability, economic resilience and reliability, and societal health and well-being.

Fifty years of collecting wild Helianthus species for cultivated sunflower improvement

Abstract Wild Helianthus species have been undeniably beneficial in sustaining the sunflower crop by providing plant breeders with a diverse genetic pool of potentially useful traits. Exploration to collect populations of wild sunflowers is one of the more difficult and challenging activities in the conservation and utilization of these valuable genetic resources. The logistics of collecting requires careful planning, locating the target species, obtaining permission to access and collect, and timing the exploration to ensure the availability of mature seed. The US Department of Agriculture, Agricultural Research Service (USDA-ARS) established the wild Helianthus seed collection in 1976 at Bushland, Texas with the goal of collecting and conserving the broadest representative genetic diversity possible and serving as a central repository of germplasm and related information. In 1985 this collection was transferred to UDSA-ARS, North Central Regional Plant Introduction Station, Ames, Iowa. Over the last half century, 37 explorations were undertaken covering 175,000 km to collect the 53 Helianthus species from their distributional ranges in the forty-eight conterminous states in the US, three Canadian Providences (Manitoba, Saskatchewan, and Alberta), Argentina and Australia. The many explorations have created a global crop wild relatives (CWR) genebank collection. The current wild CWR sunflower genebank contains 2562 accessions of 53 species with 1065 wild Helianthus annuus accessions (42 %), 617 accessions representing populations of the 13 other wild annual species (24 %), and 880 accessions representing 39 perennial species (34 %). This collection is the largest and most genetically diverse ex situ sunflower collection in the world and is vital to the conservation of wild sunflower species for the global sunflower community.

Pseudotemporal and spatial organization of B cell activation and differentiation in Peyer's patches

Abstract Organized lymphoid tissues are important sites of immune induction where B cells activate and differentiate. High-resolution transcriptomic technology has revolutionized current understandings of B cell activation and differentiation in organized lymphoid tissues such as lymph nodes but has not been used to dissect B cell activation and differentiation in Peyer’s patches, important sites of intestinal immune induction. We utilized single-cell RNA sequencing and spatial transcriptomics to define pseudotemporal and spatial organization, respectively, of B cell activation and differentiation in porcine jejunal and ileal Peyer’s patches (JPPs and IPPs). IPPs had greater follicular mass and more defined follicular borders than JPPs, resulting in greater follicular B cell abundance in IPPs and non-follicular B cell abundance in JPPs. Despite follicular morphology and B cell abundances varying between JPPs and IPPs, pseudotemporal trajectories and predicted spatial locations of B cell activation and differentiation were similar between intestinal locations. Transition of resting into follicular B cells was demarcated by increased expression of follicle- and cell cycle-associated genes and movement of cells from interfollicular zones (IFZs) into follicles. Another trajectory indicated transition of resting B cells located in IFZs directly into antibody-secreting cells located in IFZs and crypts, suggesting a route of extrafollicular B cell activation and differentiation. Altogether, results indicate conserved patterns of both follicular and extrafollicular B cell activation and differentiation in Peyer’s patches across intestinal locations, despite differences in cellular abundances and follicular morphology. Research was funded by (1) USDA-ARS CRIS project #5030-3200- 225-00D, (2) the SCINet project of the USDA ARS project number 0500-00093-001- 00-D, and (3) an appointment to the Agricultural Research Service (ARS) Research Participation Program administered by the Oak Ridge Institute for Science and Education (ORISE) through an interagency agreement between the U.S. Department of Energy (DOE) and the U.S. Department of Agriculture (USDA). ORISE is managed by ORAU under DOE contract number DE-SC0014664. All opinions expressed in this paper are the authors’ and do not necessarily reflect the policies and views of USDA, ARS, DOE, or ORAU/ORISE.

Structural and functional leaf diversity lead to variability in photosynthetic capacity across a range of Juglans regia genotypes.

Similar to other cropping systems, few walnut cultivars are used as scion in commercial production. Germplasm collections can be used to diversify cultivar options and hold potential for improving crop productivity, disease resistance and stress tolerance. In this study, we explored the anatomical and biochemical bases of photosynthetic capacity and response to water stress in 11 Juglans regia accessions in the U.S. department of agriculture, agricultural research service (USDA‐ARS) National Clonal Germplasm. Net assimilation rate (A n) differed significantly among accessions and was greater in lower latitudes coincident with higher stomatal and mesophyll conductances, leaf thickness, mesophyll porosity, gas‐phase diffusion, leaf nitrogen and lower leaf mass and stomatal density. High CO2‐saturated assimilation rates led to increases in A n under diffusional and biochemical limitations. Greater A n was found in lower‐latitude accessions native to climates with more frost‐free days, greater precipitation seasonality and lower temperature seasonality. As expected, water stress consistently impaired photosynthesis with the highest % reductions in lower‐latitude accessions (A3, A5 and A9), which had the highest A n under well‐watered conditions. However, A n for A3 and A5 remained among the highest under dehydration. J. regia accessions, which have leaf structural traits and biochemistry that enhance photosynthesis, could be used as commercial scions or breeding parents to enhance productivity.

#mediterraneandiet: A Content Analysis of Mediterranean Diet – Related Information on TikTok

ObjectivesThe Mediterranean diet (MD) is associated with reduced cardiovascular disease risk and is widely recommended by heart-health organizations. A consistent definition of MD in the literature is lacking; thus, misinformation and consumer confusion about MD is likely. To examine how the MD is interpreted in popular discourse, we conducted a social media content analysis of MD-related video posts. MethodsThis is one of the first nutrition studies to apply content analysis techniques to TikTok, a social media app with over a billion active global users offering continuous streams of curated short-form videos. In August 2021, two independent coders downloaded the first-appearing 200 TikTok videos under the hashtag #mediterraneandiet. This approach resulted in a pre-varied sample that mirrored the natural experience of a new TikTok user. Each video was coded for 62 variables across four main categories: account details of posters, engagement statistics, video characteristics, and video content specific to the MD. ResultsIntercoder reliability across two coders was high (k = .84). Preliminary results suggest two main interpretations of the MD on TikTok. One set of posts presents the MD as a heart-healthy eating pattern, dominated by posters claiming medical or nutrition credentials. The other set of posts presents the MD as cuisines from countries surrounding the Mediterranean Sea. Clear examples emerged of individuals conflating these two concepts, with dieters actively promoting the MD for health, yet promoting cultural foods that are not typically considered part of the MD dietary pattern (i.e., lamb kebab and pita bread). ConclusionsAlthough promoting the MD dietary pattern may benefit those at risk of cardiovascular disease, there remains consumer confusion on social media about what the MD entails. As the internet is the primary source of nutrition information for many Americans, innovative strategies are needed to help consumers navigate potentially-misleading online content. Funding SourcesThis research was supported in part by the U.S. Department of Agriculture/Agricultural Research Service (USDA/ARS) under Cooperative Agreement No. 58-3092-0-001.

Gene signatures for intestinal and peripheral innate lymphoid cells in pigs reveal tissue-specific imprinting and similarities to human cells via single-cell RNA sequencing

Abstract Intestinal innate lymphoid cells (iILCs) impact intestinal health outcomes, but study of iILCs in humans is limited. Human peripheral ILCs (pILCs) are easily obtained but may vary substantially from iILCs, thus requiring comparison of iILCs and pILCs to determine applicability of pILCs as surrogates to study iILC function. Pigs have anatomic, physiological, nutritional, and immune similarities to humans that are lacking in rodent models, making pigs a relevant biomedical model; however, ILCs are poorly defined in pigs. Single-cell RNA sequencing was performed to compare porcine iILCs to pILCs and determine potential similarities of porcine to human ILCs. Porcine pILCs matched porcine natural killer (NK) cell descriptions, while iILCs were annotated as group 1 and group 3 ILCs. Gene modules obtained independent of cell annotations were distilled to core signatures of genes most highly specific to pILCs, pan-iILCs, group 1 iILCs, and group 3 iILCs. The pILC signature included conventional NK cell genes, while the group 3 iILC signature included genes associated with type 3 immunity. Pan-iILC and group 1 iILC signatures included genes associated with tissue residency, cell activation, and metabolism, indicating tissue-specific, activation-associated imprinting. Gene profiles were used to develop in situ iILC detection methods, establishing group 1 iILCs were intraepithelial, while group 3 iILCs resided in lamina propria/gut-associated lymphoid tissue. Findings indicated iILCs were ILC subsets distinct from pILCs, thus opposing pILCs as surrogates to study iILC dynamics. Moreover, gene profiles and in situ locations of iILCs drew close parallels to human iILCs functions, supporting pigs as a biomedical model for iILC research. Research was supported by appropriated funds from USDA-ARS CRIS 5030-31320-004-00D, an appointment to the Agricultural Research Service (ARS) Research Participation Program administered by the Oak Ridge Institute for Science and Education (ORISE) through an interagency agreement between the U.S. Department of Energy (DOE) and the U.S. Department of Agriculture (USDA). ORISE is managed by ORAU under DOE contract number DE-SC0014664. All opinions expressed in this paper are the authors’ and do not necessarily reflect the policies and views of USDA, ARS, DOE, or ORAU/ORISE. This research used resources provided by the SCINet project of the USDA ARS project number 0500-00093-001-00-D.

‘Cordial’ Strawberry

Cordial, a late-season, short-day strawberry (Fragaria ×ananassa Duch. ex Rozier), follows Keepsake as the second cultivar resulting from a U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS) effort at Beltsville, MD, to develop strawberries with increased shelf life (Lewers et al., 2019). ‘Cordial’ and ‘Keepsake’ strawberries had similarly low proportions of fruit rot and degradation in 2 weeks of refrigerated storage compared with other cultivars and breeding selections. ‘Cordial’ has consistently provided very high yields and very low rot with no fumigation or fungicides in an annual plasticulture system at Beltsville, MD. ‘Cordial’ strawberries are

Improved runoff curve numbers for a large number of watersheds of the USA

ABSTRACT This study presents a procedure to determine improved curve numbers (CNImp) for application of the enhanced Soil Conservation Service - Curve Number (SCS-CN) model developed by Verma et al. for improved runoff prediction. To this end, five different mathematical relationships, i.e. linear, exponential, power, logarithmic and polynomial, are developed for 57 US Department of Agriculture – Agricultural Research Service (USDA-ARS) watersheds to compute CNImp with the aid of CN derivable from the National Engineering Handbook, Section-4 (NEH-4) table (CNT) and from the enhanced SCS-CN model (CNV) with significant R 2 values. Using these relationships, CNImp values are computed for another 57 watersheds for validation. Based on common performance criteria, all five developed relationships for CNImp are found to be superior to the original model in runoff computation. When compared, CNImp are close to CNV and very different from CNT. Despite the fact all the relationships performed equally well, with similar performance statistics, the exponential relationship performed the best of all and the power relationship was the worst.

Using NASA Earth observations and Google Earth Engine to map winter cover crop conservation performance in the Chesapeake Bay watershed

Winter cover crops such as barley, rye, and wheat help to improve soil structure by increasing porosity, aggregate stability, and organic matter, while reducing the loss of agricultural nutrients and sediments into waterways. The environmental performance of cover crops is affected by choice of species, planting date, planting method, nutrient inputs, temperature, and precipitation. The Maryland Department of Agriculture (MDA) oversees an agricultural cost-share program that provides farmers with funding to cover costs associated with planting winter cover crops, and the U.S. Geological Survey (USGS) and the U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS) have partnered with the MDA to develop satellite remote sensing techniques for measuring cover crop performance. The MDA has developed the capacity to digitize field boundaries for all fields enrolled in their cover crop programs (>26,000 fields per year) to support a remote sensing performance analysis at a statewide scal,e and has requested assistance with the associated imagery processing from the National Aeronautics and Space Administration (NASA). Using the Google Earth Engine (GEE) cloud computing platform, scripts were developed to process Landsat 5/7/8 and Harmonized Sentinel-2 imagery to measure winter cover crop performance. We calibrated cover crop performance models using linear regression between satellite vegetation indices and USGS / USDA-ARS field sampling data collected on Maryland farms between 2006 and 2012 (1298 samples). Satellite-derived Normalized Difference Vegetation Index (NDVI) values showed significant correlation with the natural logarithm of cover crop biomass (p ≤0.01, R2 = 0.56) and with observed percent vegetative ground cover (p ≤0.01, R2 = 0.68). The GEE scripts were used to composite seasonal maximum NDVI values for each enrolled cover crop field and calculate performance metrics for the winter and spring seasons of three enrollment years (2014–15, 2015–16, and 2017–18) for four Maryland counties. Results from winter 2017–18 demonstrate that rye and barley fields had higher biomass than wheat fields, and that early planting, along with planting methods that increase seed-soil contact, increased performance. The processing capabilities of GEE will support the MDA in scaling up remote sensing performance analysis statewide, providing information to evaluate the environmental outcomes associated with various agronomic management strategies. The tool can be modified for different seasonal cutoffs, utilize new sensors to capture phenology in winter and spring, and scale to larger regions for use in adaptive management of winter cover crops planted for environmental benefit. Project supportThis project was supported by the USGS Land Change Science Program within the Land Resources Mission Area, the USDA Choptank River Conservation Effects Assessment Project (CEAP), the USDA Lower Chesapeake Bay Long Term Agricultural Research (LTAR) Project; the Maryland Department of Agriculture; and the NASA DEVELOP National Program.

‘Crimson Joy’ Peach

The U.S. Department of Agriculture–Agricultural Research Service (USDA-ARS) stone fruit breeding program at Byron, GA, is one of the few public programs that remain active in developing new peach cultivars adapted to the southeastern climate and suitable for the regional shipping industry. The “prince” series peach cultivars, most of which produce large, firm, melting, freestone fruit with yellow flesh, normal acidity, and high blush, were released to meet this need (Okie, 1993; Okie and Layne, 2008a, 2008b; Okie et al., 1982; Okie and Reilly, 1987). As a continuation of this effort, ‘Crimson Joy’ (tested as BY99P3866) is released, along with two other “Joy” cultivars (Chen and Okie, 2020a, 2020b). This cultivar has a chilling requirement estimated at ≈700 chill hours (CH) and is suited for areas with medium to high chill accumulation. ‘Crimson Joy’ is well adapted to the southeastern climate, has performed well in Georgia and South Carolina, and is suggested for trial wherever ‘GaLa’ or ‘Harvester’ are grown.

Detection of chalk in single kernels of long‐grain milled rice using imaging and visible/near‐infrared instruments

AbstractBackground and objectivesTo maintain the competitiveness of U.S. long‐grain rice in U.S. and foreign markets, having translucent whole milled grain is critical. An objective technique to detect grain chalk, opaque areas in the grain, will provide breeders and industry with an effective tool for developing low‐chalk varieties or agronomic practices that reduce chalk occurrence. Two instruments developed at the Center for Grain and Animal Health Research, U.S. Department of Agriculture‐Agricultural Research Service (USDA‐ARS), a single‐kernel near‐infrared (SKNIR) tube instrument and a silicon‐based light‐emitting diode (SiLED) high‐speed sorter, were compared with two commercially available imaging instruments, WinSEEDLE and SeedCount used for chalk quantification. Three 2‐way chalk classifications were defined for single kernels based on visual inspection: (a) <50% or ≥50% opacity or chalk (modified Grain Inspection, Packers & Stockyards Administration [GIPSA]), (b) <10% or ≥10% opacity (10% cutoff), and (c) 100% opacity or 100% translucent (MaxLevel).FindingsThe SKNIR method provided the best classification for the modified GIPSA definition with an 82.4% average correct classification (CC), that is, 89% and 76% for nonchalky and chalky kernels, respectively. The WinSEEDLE had the best classification for the 10% cutoff definition, with an 84% CC for nonchalky kernels and a 96% CC for chalky kernels. For the MaxLevel definition, average CCs of both the SKNIR and SiLED methods were similar, at 93% and 95%, respectively. The average CCs were lower for both the WinSEEDLE method and the SeedCount method at 14% and 58%, respectively. These low CC values are a result of using a threshold of 100% for chalky or nonchalky kernels, where a single misclassified pixel within the image will cause misclassification. Calibration models developed for both the SKNIR and SiLED methods indicate that their classifications were based mainly on spectral differences near the adsorption bands for starch, protein, and water content.ConclusionsAll of the instruments can be used to classify chalk, but their level of accuracy depends on how chalk is defined.Significance and noveltyThe SiLED has the capability to process seeds at a high rate, and the SKNIR has the potential to measure compositional traits in addition to chalk measurements.

Host Response to Black Leaf Streak and Agronomic Performance of Banana Genotypes in Puerto Rico

Bananas are one of the most important fruits, serving as a cash crop and staple food in many regions of the world. In Puerto Rico, bananas are an important agricultural industry, supplying all the fruit needed for local demand. Diseases significantly limit production, and the evaluation and adoption of improved genetic resistance in bananas might provide an avenue for long-term sustainable production. To this end, nine enhanced genotypes from international selection and breeding programs were introduced and evaluated for their response to black leaf streak (BLS) (Pseudocercospora fijiensis Morelet) and for their agronomic performance. Bananas were evaluated as part of a collaborative effort between the U.S. Department of Agriculture Agricultural Research Service (USDA-ARS) Tropical Agriculture Research Station (TARS) and Bioversity International’s International Musa Testing Program (IMTP). Improved genotypes were compared with disease-resistant and disease-susceptible reference genotypes across two cropping cycles. Field plants were grown following commercial production practices with no BLS management. Significant differences in disease reactions were observed during both cropping cycles for test and reference genotypes. Under high disease pressure, ‘FHIA-21’, ‘FHLORBAN 916’, and ‘FHLORBAN 920’ test genotypes showed higher numbers of functional leaves and lower disease severity at harvest in both cycles. Short cycling times were also observed for the two FHLORBAN genotypes. Larger bunches with a high number of fruits were produced by the ‘IBP 12’, ‘IBP 5-B’, and ‘IBP 5-61’ selections. Several of the GCTCV test genotypes were extremely susceptible to BLS, did not perform as expected, and appeared to be off-types. Several of the test genotypes performed well, although currently none possessed all needed traits for a commercial banana substitute. Regardless, several test genotypes have agronomic potential because they have been selected for disease resistance to other important pathogens (e.g., fusarium wilt) and therefore have become part of the permanent TARS collection. Future efforts will continue to focus on the IMTP collaboration and introduction of promising banana genotypes for evaluations.

Variation for Heat Tolerance During Seed Germination in Diverse Carrot [Daucus carota (L.)] Germplasm

Carrot production is constrained by high levels of heat stress during the germination stage in many global regions. Few studies have been published evaluating the effect of heat stress on carrot seed germination or screening for genetic heat stress tolerance. The objectives of this study were to evaluate the response of diverse carrot germplasm to heat stress, identify heat-tolerant germplasm that may be used by plant breeders, and define the appropriate temperature for assessing heat tolerance in germinating carrot seed. To identify an appropriate screening temperature, three commercial hybrids and an open pollinated variety were evaluated at five temperatures (24, 32.5, 35, 37.5, and 40 °C). In preliminary studies, 35 °C was identified as the optimal temperature for screening heat tolerance of carrot seed. Cultivated and wild carrot plant introductions (PIs) (n = 270) from the U.S. Department of Agriculture (USDA) National Plant Germplasm System (NPGS) representing 41 countries, inbred lines from the USDA Agricultural Research Service (n = 15), and widely grown commercial hybrids (n = 8) were evaluated for heat tolerance under heat stress and nonstress conditions (35 °C and 24 °C, respectively) by calculating absolute decrease in percent germination (AD), inhibition index (II), relative heat tolerance (RHT), and heat tolerance index (HTI). All measurements of heat tolerance identified significant differences among accessions; AD ranged from −13.0% to 86.7%, II ranged from 35.7% to 100.0%, RHT ranged from 0 to 1.36, and HTI ranged from 0.0 to 1.45. The broad-sense heritability (H2) calculations ranged from 0.64 to 0.86 for different traits, indicating a moderately strong genetic contribution to the phenotypic variation. Several wild carrot accessions and inbred lines displayed low levels of heat tolerance, whereas cultivated accessions PI 643114 (United States), PI 652400 and PI 652403 (Turkey), PI 652208 (China), and PI 652403 (Russia) were most heat tolerant. This is the first evaluation of heritability for heat stress tolerance during carrot seed germination, the first measure of HTI, and the first correlation calculation between heat and salt tolerance during germination in carrot.

Using adaptive management to guide multiple partners in TCE remediation using a permeable reactive barrier

The US Department of Agriculture-Agricultural Research Service (USDA-ARS) worked together with the University of Maryland, College Park and BMT Designers and Planners (Consultant) to design a biowall to remediate the groundwater of a Superfund site located in Beltsville, MD. The US Environmental Protection Agency (US EPA) oversaw the remediation plan as per the regulations of the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) program. A hybrid adaptive management strategy was employed to to guarantee the use of a science-based approach to the remediation efforts, to ensure that new information could be incorporated into the remediation plan, and to avoid the shortcomings of other remediation efforts elsewhere. Laboratory experiments and a historic-data assessment were conducted in conjunction with the monitoring plan to provide the Consultant and USDA with comprehensive feedback, to strengthen and to modify the monitoring and biowall construction plans as the requirements of the site changed. This feedback mechanism was repeated multiple times to make certain that the highest quality and most effective methods were used. The scope of the project also grew to include investigations of the soil microbial community for future structural biostimulation and bioaugmentation activities. While the biowall has reduced the concentration of trichloroethylene (TCE) to levels at or below its Maximum Contaminant Level, work is on-going to improve the functionality of the biowall and to address emerging challenges.

Variation for Salinity Tolerance During Seed Germination in Diverse Carrot [Daucus carota (L.)] Germplasm

Global carrot production is limited by the crop’s high susceptibility to salinity stress. Not much public research has been conducted to screen for genetic salinity stress tolerance in carrot, and few resources exist to aid plant breeders in improving salinity tolerance in carrot. The objectives of this study were to evaluate the response of diverse carrot germplasm to salinity stress, identify salt-tolerant carrot germplasm that may be used by breeders, and define appropriate screening criteria for assessing salt tolerance in germinating carrot seed. Carrot plant introductions (PIs) (n = 273) from the U.S. Department of Agriculture (USDA) National Plant Germplasm System representing 41 different countries, inbred lines from the USDA Agricultural Research Service (n = 16), and widely grown commercial hybrids (n = 5) were screened for salinity tolerance under salinity stress and nonstress conditions (150 and 0 mm NaCl, respectively) by measuring the absolute decrease (AD) in the percent of germination, inhibition index (II), relative salt tolerance (RST), and salt tolerance index (STI) of germinating seeds. All salt tolerance measurements differed significantly between accessions; AD ranged from −4.2% to 93.0%; II ranged from −8.0% to 100.0%; RST ranged from 0.0 to 1.08; and STI ranged from 0.0 to 1.38. Broad sense heritability calculations for these measurements were 0.87 or more, indicating a strong genetic contribution to the variation observed. Six accessions identified as salt-tolerant or salt-susceptible were evaluated in a subsequent experiment conducted at salt concentrations of 0, 50, 100, 150, 200, and 250 mm NaCl. Variations between mean AD, II, RST, and STI of tolerant and susceptible lines were greatest at 150 mm NaCl, validating the use of 150 mm NaCl concentrations during salt tolerance screening of carrot seed. Wild carrot accessions displayed little tolerance, and PI 256066, PI 652253, PI 652402, and PI 652405 from Turkey were most salt-tolerant.

History of Bermudagrass Turfgrass Breeding Research in Tifton, GA

Bermudagrass (Cynodon spp.) is the foundation of the turfgrass industry in most tropical and warm-temperate regions. Development of bermudagrass as a turfgrass began in the early 1900s. Many of the cultivars commercially available today have been cooperatively released by the U.S. Department of Agriculture Agricultural Research Service (USDA-ARS) and the University of Georgia at the Coastal Plain Experiment Station in Tifton, GA.

Validating Blackberry Seedling Pedigrees and Developing an Improved Multiplexed Microsatellite Fingerprinting Set

Confirming parentage and clonal identity is an important aspect of breeding and managing germplasm collections of clonally propagated, outcrossing crops, like blackberry (Rubus subgenus Rubus). DNA fingerprinting sets are used to identify off-cross progeny and confirm clonal identity. Previously, a six-simple sequence repeat (6-SSR) fingerprinting set was developed for blackberry using a small number of samples. The usefulness of the 6-SSR fingerprinting set for pedigree confirmation had not been evaluated. Therefore, it was used in this study to validate parentage for 6 and 12 biparental populations from the University of Arkansas (UA) and US Department of Agriculture Agricultural Research Service (USDA-ARS), Horticultural Crops Research Unit (HCRU) breeding programs, respectively. Twenty-seven of the 489 individuals in these breeding populations were identified as off-cross. The 6-SSR fingerprinting set was sufficient for parentage confirmation; however, a total of 61 plants distributed across 28 sets of genotypes could not be distinguished from each other. An 8-SSR fingerprinting set with improved resolution was subsequently developed and used to evaluate 177 Rubus accessions from the USDA-ARS National Clonal Germplasm Repository, UA, and USDA-ARS HCRU programs. The 8-SSR fingerprinting set distinguished all samples expected to have unique genotypes and identified differing DNA fingerprints for two sets of accessions suspected to have identical fingerprints. Cluster analysis grouped the accessions from the eastern and western US breeding programs based on geography and descent. Future work will focus on establishing a database of DNA fingerprints for germplasm identification and for determining pedigree relationships between blackberry accessions.

Cryopreserved storage of clonal germplasm in the USDA National Plant Germplasm System

The US Department of Agriculture-Agricultural Research Service (USDA-ARS), National Plant Germplasm System (NPGS) plant collections are a critical source of genetic diversity for breeding and selection of improved crops, including vegetatively propagated plants. Information on these collections is readily accessible to breeders and researchers on the internet from the Germplasm Resources Information Network (GRIN). The clonal collections are at risk for loss due in part to their genetic diversity that makes growing them in one location a challenge, but also because it is difficult to have duplicate collections without incurring great expense. The development of cryopreservation techniques during the last two decades provides a low maintenance form of security backup for these collections. National plant collections for vegetatively propagated crop plants and their wild relatives are maintained by the USDA-ARS, NPGS at 15 sites across the country. These sites include various combinations of field, greenhouse, screenhouse, and in vitro collections. Cryopreserved backup collections in liquid nitrogen storage were instituted in the 1990s, increased greatly in the 2000s with the advent of new techniques, and are continuing today. Collections of dormant buds of temperate trees, shoot tips of in vitro cultures of many crops, and embryonic axes of some large seeded or recalcitrant seeded plants are all part of the clonal backup storage system.