USDA National Plant Germplasm System Research Articles

‘Newell’ bermudagrass: A public release from the USDA Cynodon collection

AbstractWarm‐season perennial grasses are the backbone of the pasture‐based livestock industry in the lower southeastern United States, and bermudagrass (Cynodon spp.) is the most widely planted forage species, covering ∼15 million ha. The genus Cynodon is native to southern Africa, and germplasm collections possess high genetic and phenotypic variability. The USDA National Plant Germplasm System maintains a collection of bermudagrass plant introductions (PIs) in Griffin, GA, and USDA‐ARS, Tifton, GA, maintains additional germplasm. Multi‐location trials were established in four states (Florida, Georgia, North Carolina, and Oklahoma) to screen Cynodon germplasm for herbage accumulation (HA), nutritive value (NV), and bermudagrass stem maggot (BSM) (Atherigona reversura Villeneuve). Due to the large genotype × environment interaction for HA, we focused on selecting accessions adapted to South Georgia and Florida, and further studies were performed in Florida. Several PIs showed improved HA and NV compared with ‘Tifton 85’. PI 316510, originally introduced from Ingelheim, Germany, produced high HA in Citra, FL, and Tifton, GA, with improved NV traits. In addition, PI 316510 had faster establishment and similar BSM tolerance to Tifton 85. We confirmed PI 316510 as tetraploid (2n = 4x = 36) through chromosome counts and flow cytometry, and it is genetically distinct from other commercial cultivars. PI 316510 has been publicly released under the name ‘Newell’, and it is vegetatively propagated. Planting material can be requested from the UF‐IFAS Forage Breeding program.

Unraveling phenotypic diversity in Cynodon spp. germplasm for forage accumulation and nutritive value in the transition zone

AbstractCharacterizing phenotypic variation in germplasm collections is crucial for plant breeding. Cynodon spp. accessions maintained at the USDA National Plant Germplasm System (NPGS), and the core forage collection were screened in a replicated trial under two nitrogen rates (0 and 150 kg ha−1 per harvest) in Ardmore, OK. The goals for this study were to: (a) estimate genetic parameters for forage accumulation (FA) and nutritive value (NV), (b) estimate genotype × harvest (rgh) and genotype × environment (rge) interaction for all traits, (c) quantify FA and NV for commercial cultivars and selected accessions. The experiment was setup as a row‐column design with two replicates and augmented representation of controls: Tifton 85, Wrangler, Midland, and Cheyenne. The trial was harvested five times (twice in 2016 and three times in 2017) and data were analyzed using linear mixed models. Genetic parameters revealed the presence of significant phenotypic variation for FA and NV. Low genotype × harvest and genotype × environment interactions indicated genotypic stability and potential for selecting improved accessions for FA and NV. Several plant introductions (PIs) were identified for their improved FA and NV. The application of N increased FA and CP concentration in all harvests but did not significantly impact phenotypic variation in other NV traits. Phenotypic data will be deposited in the Germplasm Resource Information Network (GRIN)‐Global database.

Genetic fingerprinting identifies apple (Malus domestica Borkh.) fruit cultivars in historic orchards on public lands

The National Historic Preservation Act of 1966 mandates that historic resources, including orchards, on federal lands be evaluated for potential significance. Evaluations include assessments and documentation of an orchard’s layout and location, as well as the architecture, ages, conditions, and cultivars of trees. These factors may reveal an orchard’s history and uniqueness and determine an orchard’s historic importance. Fruit tree cultivar identities are a key piece of this puzzle. They reveal information about an orchard’s use, origin, and uniqueness. In the past, historic preservationists relied on pomologists to identify cultivars based primarily on the phenotypic traits of the tree. DNA fingerprinting technologies, in combination with high-quality reference cultivar collections, have dramatically improved the accuracy of heritage cultivar identification. We demonstrate the utility of using DNA technologies for cultivar identifications on federal lands using examples from trees in orchards of Redwood National and State Parks and the Eldorado National Forest. A total of 87 historic apple trees from these locations were genotyped and cultivar names were determined for 35 trees, using a reference set of 1319 apple cultivars from the USDA National Plant Germplasm System, Washington State University, Seed Savers Exchange, and Temperate Orchard Conservancy. Some of the trees that were not identified may be cultivars that are not included in the reference sets and others may be unique trees derived from seeds. The information derived from genetic fingerprinting analyses will aid in the determination of the historic significance of orchards on public lands.

Optimization of in vitro germination and cryopreservation conditions for preserving date palm pollen in the USDA National Plant Germplasm System

Date palm (Phoenix dactylifera L.) is a staple crop across arid and semi-arid regions around the world. Both genebanks and date palm breeders benefit by having clearly defined methods for the long-term preservation of pollen. Methods were developed to cryopreserve pollen from date palm trees in the USDA-ARS National Plant Germplasm System. First, in vitro pollen germination conditions were optimized using five cultivars. Then, date palm pollen equilibrated over saturated salt solutions of Ca(NO3)2 or MgCl2 at 23 °C (46% and 33% RH, respectively) or in a room set at 23% RH and 5 °C. Pollen was kept at these conditions for one to 56 days and then placed into liquid nitrogen vapor (LNV). Viability was assessed for fresh, moisture-equilibrated (non-LNV and LNV-exposed), and pollen stored in LNV for 9 months. The highest level of in vitro pollen germination was observed for date palm cultivar Thoory BC3 (60 ± 2%) when it was rehydrated for 2 h and then incubated at 23 °C on Marquard medium with 15% sucrose. Viability remained stable for pollen that was stored in LNV for 9 months. In addition, pollen also remained viable if it was cooled to and warmed from LNV for up to 60 cycles. These data suggest that date palm pollen can be successfully placed in genebank cryostorage. Using optimized in vitro germination conditions, date palm pollen can survive at least 9 months in LNV and can be cooled to and warmed from LNV at least 60 times.

Genotyping by sequencing for SNP marker development in onion.

Onion (Allium cepa) is not highly tractable for development of molecular markers due to its large (16 gigabases per 1C) nuclear genome. Single nucleotide polymorphisms (SNPs) are useful for genetic characterization and marker-aided selection of onion because of codominance and common occurrence in elite germplasm. We completed genotyping by sequencing (GBS) to identify SNPs in onion using 46 F2 plants, parents of the F2 plants (Ailsa Craig 43 and Brigham Yellow Globe 15-23), two doubled haploid (DH) lines (DH2107 and DH2110), and plants from 94 accessions in the USDA National Plant Germplasm System (NPGS). SNPs were called using the TASSEL 3.0 Universal Network Enabled Analysis (UNEAK) bioinformatics pipeline. Sequences from the F2 and DH plants were used to construct a pseudo-reference genome against which genotypes from all accessions were scored. Quality filters were used to identify a set of 284 high quality SNPs, which were placed onto an existing genetic map for the F2 family. Accessions showed a moderate level of diversity (mean He = 0.341) and evidence of inbreeding (mean F = 0.592). GBS is promising for SNP discovery in onion, although lack of a reference genome required extensive custom scripts for bioinformatics analyses to identify high quality markers.

DNA content and ploidy estimation of Festuca ovina accessions by flow cytometry

AbstractFestuca ovina L. is a fine fescue that is used as a low‐input turfgrass. The ploidy levels of F. ovina accessions held by the USDA National Plant Germplasm System (NPGS) are unknown, limiting the use of the germplasm in breeding programs. The objective of this study was to determine DNA content and estimate ploidy of these accessions. Among 127 accessions, we identified a wide range of ploidy levels from diploid to octoploid. We also found the accessions with higher ploidy levels usually had larger seed size. These results will be informative to plant breeders and researchers using germplasm from the F. ovina collection and point to challenges in maintaining polyploid, outcrossing germplasm seed stocks in common nurseries.

First Report of Cercospora Leaf Spot Caused by Cercospora chenopodii on Spinacia oleracea in the U.S.A.

In November 2017, leaf spots were observed in a fresh market spinach crop of cultivar SV2157VB in New Jersey at ∼20% incidence but not in the adjacent crop of Unipack-151. Pale tan lesions (3 to 8 mm in diameter) had gray sporulation at the centers. Symptomatic leaf pieces were surface-sterilized in 0.6% NaOCl for 60 s, triple-rinsed in sterilized water, dried, and plated onto PDA and water agar (each with 100 µg of chloramphenicol/ml). Seven isolates all produced hyaline, straight to slightly curved conidia, mostly two- to three-septate, 20.0 to 82.0 µm (45.2 ± 11.3 µm, mean ± standard deviation) × 6.0 to 11.0 µm (8.1 ± 1.0 µm) (n = 312), with no significant differences among isolates. Spore characteristics matched those of Cercospora spp. (Świderska-Burek 2015). The consensus sequence of the calmodulin gene (cmdA) amplified from all seven isolates using primers CALDF1 and CALDR (Lawrence et al. 2013) (GenBank accession no. MN422444) was 99.78% identical to that of Cercospora cf. chenopodii (JX142839.1), which is not differentiated from C. chenopodii by this gene (Groenewald et al. 2013). Actin (actA) primers ACT-512F and ACT-783R generated an identical sequence for the isolates (MN422442) that was 99.55% identical to that of C. chenopodii (JX143081.1) (Carbone and Kohn 1999). The translation elongation factor 1-α (TEF1-α) sequence of the isolates (MN422445) had 99.45% identity to the sequence of a voucher specimen of C. chenopodii (JX143327.1). C. beticola-specific primers CbCALF and CbCALR did not amplify DNA of these isolates, only DNA of control isolates of C. beticola (Knight et al. 2019). Based on a phylogenetic tree inferred from concatenated actA, cmdA, ITS rDNA, and TEF1-α sequences, the isolates clustered with the voucher strain C. chenopodii CBS 132620. Six isolates were each tested for pathogenicity on four 33-day-old plants of each of spinach cultivars Mandolin, SV2157VB, Unipack-151, and Viroflay; sugar beet cultivar KDH4-9 (USDA National Plant Germplasm System PI 683513, homozygous susceptible to C. beticola), red beet cultivars Red Ace and Ruby Queen, and Swiss chard cultivar Silverado. Plants were enclosed in plastic bags for 24 h, atomized with a spore suspension (1 × 10⁴ conidia/ml) prepared from clarified V8 agar plates of each isolate, and returned to the bags for 24 h. Four non-inoculated control plants of each cultivar were atomized with water as control treatments. Beet and chard plants were placed in a greenhouse and spinach plants in a growth chamber with 10 h lighting/day to avoid bolting under 16-h summer days in Washington. Symptoms had not developed after 7 days, at which time spinach plants were moved to the greenhouse. By 9 days, leaf spots resembling those on the original leaves were observed on Mandolin and SV2157VB. By 14 days, there were leaf spots on all four spinach cultivars. Symptoms were most severe on SV2157VB (18.3 ± 2.0% mean ± standard error of leaf area), followed by Mandolin and Viroflay (8.8 ± 1.6%), and then Unipack-151 (2 ± 0.5%). Symptoms did not develop on non-inoculated spinach or inoculated and non-inoculated sugar beet, table beet, and Swiss chard. Cercospora could only be reisolated from symptomatic spinach plants, with the isolates confirmed as C. chenopodii based on actA sequences. Although C. beticola has been reported to cause Cercospora leaf spot of spinach (Knight et al. 2018), this is the first report of C. chenopodii causing a leaf spot of spinach in the United States. Research is needed to evaluate impacts of this species on additional spinach cultivars and management options.

Trans Situ Conservation of Crop Wild Relatives

ABSTRACTIn the face of unprecedented climatic disasters, social conflict, and political uncertainty, integrating in situ and ex situ strategies may become increasingly necessary to effectively conserve crop wild relatives (CWR). We introduce the concept of trans situ conservation to safeguard CWR genetic diversity and accessibility for crop improvement. Building on initiatives to combine in situ protection with ex situ backup in genebanks, trans situ conservation dynamically integrates multiple in situ and ex situ measures, from conservation to research to education, spanning local to global scales. Two important features emerge from a trans situ approach. First, integrating in situ and ex situ studies of CWR genetic diversity, adaptation, and ecological interactions can lead to advances in crop improvement and in situ management. Second, the complementarity, redundancy, and synergy gained through trans situ conservation buffer climatic, economic, political, and institutional instabilities. Focusing on a case study in the United States–Mexico desert borderlands, we evaluate three components of trans situ conservation: in situ protection on working and public lands; seed and living plant collections in local and regional botanical gardens, arboreta, and nurseries; and genebank accessions in the USDA National Plant Germplasm System. We discuss gaps, tensions, and synergies that emerge when coordinating these three components and offer the conservation of the wild chile [Capsicum annuum L. var. glabriusculum (Dunal) Heiser & Pickersgill] in southern Arizona as an example of concerted in situ and ex situ research integrated in a trans situ framework

Seeds of Success: Collateral Benefits to Agricultural Crop Improvement, Research, and Education

ABSTRACTThe need to restore natural landscapes impacted by environmental perturbations such as wildfires, and droughts, gave rise to Seeds of Success (SOS), a collaborative effort led by the Bureau of Land Management to collect seed of US wild native species since 2001. These collected native species are also important for agricultural activities; however, this has not been fully assessed. The SOS National Collection was evaluated for potential as sources of traits for crop improvement and direct development for agricultural purposes. Use of the collection was examined using information provided in seed requests from the USDA National Plant Germplasm System. From 2001 to 2017, SOS collected 23,577 accessions of 4761 different species, representing almost 30% of the native species in the United States. Collecting efforts have filled gaps in the conservation of native crop wild relatives; 12% of species and 18% of accessions are close and distant relatives of major and minor crops. Almost a third of the National Collection includes species with potential use in ornamental, food, medicinal, forage and feed, or material and industrial plant production. Of these species, those with ornamental potential are the most abundant in the National Collection. Requests for seed have been increasing over time, with the top three uses categorized as genetic studies, botanical or taxonomic investigations, and varietal development. Seeds of Success has positively affected the availability of native, wild plant genetic resources that have many potential uses in support of agricultural crop improvement, research, and education.

Genetic Parameters for Phenotypic Traits in Annual Ryegrass

Characterizing phenotypes in germplasm collections and making data publicly available is crucial to ensure the utilization of the accessions in breeding programs. Variance component estimates are used to calculate genetic parameters needed to make strategic decisions for germplasm conservation and its utilization in plant breeding. This information is lacking for annual ryegrass (Lolium multiflorum Lamarck) germplasm from the USDA National Plant Germplasm System (NPGS). In this study, we estimated variance components, repeatability, genotypic values, genetic correlations, and genotype × year correlations for 18 traits in 167 annual ryegrass populations. Repeatability (H2) ranged from 0.11 to 0.93 for single‐year analyses, and from 0.03 to 0.86 for traits evaluated during two growing seasons, evidencing the presence of genetic variability. Genotype × year correlations ranged from 0.17 up to 0.99, demonstrating variable consistency in phenotypic performance across years. Combining multiple traits in one cultivar is a challenge for breeders, particularly for traits negatively correlated. Establishment, plant vigor, leaf width and length, and chlorophyll content were negatively correlated with disease traits. Heading date was positively correlated with number of tillers, crown size, and biomass production. High positive correlations were also found between biomass and plant height, crown size, tiller number and size, and leaf/stem ratio. The data presented in this study will become publicly available via the Germplasm Resource Information Network (GRIN)‐Global database of the NPGS.

Training in Plant Genetic Resources Management: A Way Forward

Plant genetic resource collections are national treasures that are critical to the success of breeding programs and the long‐term resiliency of agriculture in the United States and worldwide. The USDA National Plant Germplasm System (NPGS) is a coordinated network of 19 genebank locations throughout the United States that conserve and protect nearly 600,000 accessions representing ∼16,000 plant species. The expertise of current curators must be captured, and training materials must be developed to educate the next generation of those who maintain and use plant genetic resources. A group of experts convened in April 2018 to discuss the needs, pedagogical approaches, educational content, delivery platforms, and mechanisms for sustaining a possible future plant genetic resources management training program. A three‐component approach was envisioned to achieve the task of educating current and future genebank managers, as well as those who use genetic resources in their research and breeding programs. The proposed training program will include the development of online Resource Libraries, online courses, and workshops. Resource Libraries, hosted by GRIN‐Global, will make learning objects, downloadable information, and links to other online sources publicly available. These Resource Libraries will be available for use in existing classes, as well as for the development of new workshops and online courses. Development of, and public access to, training resources will capture key information about genebanking, make it more widely available, and secure its long‐term viability.

Oil concentration and fatty-acid profile of naturalized Helianthus annuus populations from Australia

Although wild annual sunflower (Helianthus annuus L.) is indigenous to North America, it has been both inadvertently and intentionally introduced into other countries, such as Australia, where it has become naturalized. Prior to this research, there were no collections of naturalized H. annuus from Australia in the USDA National Plant Germplasm System gene bank. The possibility exists that naturalized Australian populations may contain distinct traits, such as oil content and fatty-acid composition, differing from their North American progenitors due to the different environments, diseases, and insect-pest complexes. The objective of this study was to collect naturalized H. annuus populations from the five states of Australia and to analyze them for oil content and fatty-acid composition. Fifty-six populations were collected throughout the broad distributional range of this species and then analyzed for oil content and fatty-acid composition. The mean oil content of the H. annuus populations was 28%, ranging from a low of 19% to a high of 31%, similar to populations of this species in its native North American habitats. Fatty-acid profiles were also similar for North American wild populations, Australian naturalized populations, and improved cultivars. Oil concentration of hybrids can be rapidly increased to acceptable levels by backcrossing with cultivated sunflower. Based on this fact, there should be little concern about the relatively low oil content of these naturalized populations when they are used as a source of other unique traits for cultivated sunflower improvement.

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.

Genetic diversity analysis of Gossypium arboreum germplasm accessions using genotyping-by-sequencing.

The diploid cotton species Gossypium arboreum possesses many favorable agronomic traits such as drought tolerance and disease resistance, which can be utilized in the development of improved upland cotton cultivars. The USDA National Plant Germplasm System maintains more than 1600 G. arboreum accessions. Little information is available on the genetic diversity of the collection thereby limiting the utilization of this cotton species. The genetic diversity and population structure of the G. arboreum germplasm collection were assessed by genotyping-by-sequencing of 375 accessions. Using genome-wide single nucleotide polymorphism sequence data, two major clusters were inferred with 302 accessions in Cluster 1, 64 accessions in Cluster 2, and nine accessions unassigned due to their nearly equal membership to each cluster. These two clusters were further evaluated independently resulting in the identification of two sub-clusters for the 302 Cluster 1 accessions and three sub-clusters for the 64 Cluster 2 accessions. Low to moderate genetic diversity between clusters and sub-clusters were observed indicating a narrow genetic base. Cluster 2 accessions were more genetically diverse and the majority of the accessions in this cluster were landraces. In contrast, Cluster 1 is composed of varieties or breeding lines more recently added to the collection. The majority of the accessions had kinship values ranging from 0.6 to 0.8. Eight pairs of accessions were identified as potential redundancies due to their high kinship relatedness. The genetic diversity and genotype data from this study are essential to enhance germplasm utilization to identify genetically diverse accessions for the detection of quantitative trait loci associated with important traits that would benefit upland cotton improvement.

Switchgrass Germplasm Resources

ABSTRACTSwitchgrass (Panicum virgatum L.) is an important native grass and dominant member of the tallgrass prairie ecosystem. It is used for conservation, restoration, livestock feed production, and bioenergy feedstock production. The purpose of this review is to describe the biological and geographical basis for switchgrass germplasm diversity and to provide a resource for scientists and outreach personnel to find switchgrass germplasm to meet their needs. Upland and lowland ecotypes represent the most important polymorphism in switchgrass, with distinct but overlapping geographic distributions. Variation in ploidy exists within both ecotypes, with 2n = 4x = 36 the dominant ploidy in the lowland ecotype and 2n = 8x = 72 the dominant ploidy in the upland ecotype. Ploidy is a strong barrier to gene flow, but ecotype is a weak barrier, with up to 10% of random individuals demonstrating some evidence for upland‐lowland hybridization in their ancestry. Latitudinal and, to a lesser extent, longitudinal differentiation exists within each ecotype, such that most wild populations and cultivars are not well adapted more than one hardiness zone from their place of origin. Plant breeding can alter this relationship by creating populations with improved cold tolerance, for example, increasing the adaptation range of an individual cultivar. The USDA National Plant Germplasm System maintains the national switchgrass collection, which is available for research and breeding purposes.

Screening USDA Lettuce (Lactuca sativa L.) Germplasm for Ability to Germinate under Cold Conditions

Low temperatures can slow down emergence, decrease weed competitiveness, and lead to uneven crop maturity in direct-seeded crops such as baby leaf lettuce (Lactuca sativa L.). In this study, seeds of 103 single-parent lineage, homozygous lettuce accessions (53 cos and 50 leaf type) from the USDA National Plant Germplasm System (NPGS) and six commercial standard lettuce cultivars (three cos and three leaf type) were evaluated in replications for percent germination after 7 and 10 days at 5 °C in a germination chamber. Cos and leaf types were selected for this study as they are most commonly used for baby leaf lettuce production. Differences were observed among entries in percent seeds germinated after both 7 and 10 days. Overall, an average of 68% of seeds germinated after 7 days and 94% germinated after 10 days. Although several NPGS accessions had higher percent germination than the commercial cultivars, the average percent germination was not statistically different between the two seed sources at 7 or 10 days. Percent germination also did not differ between entries of cos and leaf type after 7 or 10 days. Similarly, no difference in percent germination between entries of dark and white seed color was observed after 7 or 10 days. No relationship between 100 seed weight and percent germination was observed after 7 days (r2 = 0.07) or 10 days (r2 = 0.13). Thus, lettuce seed type, color, and 100 seed weight do not appear to be good predictors of germination under cold conditions in lettuce. The accessions with the highest percent germination after 7 days at 5 °C have the potential to be used for the development of new lettuce cultivars suitable for an extended, early season production in temperate climates when soil temperature is lower than optimal for lettuce germination. Further studies are needed to assess the ability of these accessions to germinate rapidly under cold field soil conditions.

Musa spp. Germplasm Management: Microsatellite Fingerprinting of USDA–ARS National Plant Germplasm System Collection

ABSTRACTThe USDA–ARS Tropical Agriculture Research Station (TARS) is responsible for conserving germplasm of a number of important agricultural crop species. Its banana (Musa spp.) collection is comprised of diploid, triploid, and tetraploid accessions of cultivated, ornamental, wild, and synthetic hybrid accessions. To estimate genetic diversity, identify gaps, determine integrity, and generate clonal reference multilocus DNA profiles for a total of 175 accessions in the collection, a set of 22 microsatellite markers developed in the framework of the Generation Challenge Program (www.generationcp.org/, accessed 30 June 2014) by Centre de Coopération Internationale en Recherche Agronomique pour le Développement and recommended by the Global Musa Genomics Consortium were screened with an additional 15 reference DNA samples. Twenty‐one of the 22 microsatellite markers amplified well and generated a total of 302 alleles with an average number of 14.4 alleles per locus. In general, profiles were reproducible and consistent for the 21 loci when clonal field and tissue culture plants were compared with reference samples. The average number of alleles and gene diversity estimates demonstrated substantial genetic diversity in the collection. Principal coordinate and cluster analyses grouped accessions in the collection according to their ploidy level and genomic compositions. Markers that were used in the study distinguished accessions to the subgroup level and identified mislabeled accessions, notably in the tissue culture collection where phenotypic differences are difficult to observe. The accessions and fingerprint profiles for the TARS collection are available through the USDA National Plant Germplasm System, Germplasm Resource Information Network (GRIN‐Global) database www.ars‐grin.gov/ (accessed 30 June 2014).

Ploidy determination of buffel grass accessions in the USDA National Plant Germplasm System collection by flow cytometry

The DNA content of 568 accessions of buffel grass (Cenchrus ciliaris L. syn. Pennisetum ciliare (L.) Link) in the USDA National Plant Germplasm System was determined through flow cytometry. Based on DNA content, 308 accessions were determined as tetraploids with 36 chromosomes, 139 as pentaploids with 45 chromosomes, 20 as hexaploids with 54 chromosomes, two as septaploids with 63 chromosomes, and 99 as aneuploids.

Evaluating a Germplasm Collection of the Cover Crop Hairy Vetch for Use in Sustainable Farming Systems

ABSTRACTUnderstanding the association between genotype and agronomically important phenotypes (early flowering, hard seed, and winter hardiness) will facilitate cultivar selection and inform breeding programs concerned with the cover crop hairy vetch (Vicia villosa Roth). We used molecular, observational, and biochemical techniques to identify and evaluate 64 accessions of hairy vetch that originated throughout the world and comprise the USDA National Plant Germplasm System. Time to flowering, percent C, and percent N were measured on plants of each accession grown in the field at Beltsville, MD. Amplified fragment length polymorphisms were assayed on each accession. We related parameters of genetic, phenotypic, and biochemical diversity to the geographical origins of the accessions. Country of origin explained little of the marker genetic diversity in this collection. Climate factors of geographical origins, however, explained larger amounts of the marker genetic diversity observed. These results provide baseline information to identify a core genetic subset of the V. villosa germplasm collection. Information presented here may facilitate future V. villosa breeding efforts and directly assist farmers in cover crop varietal selection.

Identification of thickspike wheatgrass accessions with superior rhizome spread, seed production, and seed quality

Thickspike wheatgrass ( Elymus lanceolatus (Scribn. & J.G. Sm.) Gould [Poaceae]) accessions evaluated for performance in the Intermountain/Great Basin region of the US differed significantly ( P = 0.05) for several agronomic and seed quality traits. In this study, 50 accessions of thickspike wheatgrass, including all accessions in the USDA National Plant Germplasm System collection and 5 cultivars were characterized for rhizome spread and seed production at a site near Eureka, Utah, during 2007 and 2008. The resulting seeds from both production years were then further evaluated in laboratory and greenhouse experiments for germination percentage, seed weight, emergence rate, and total emergence after deep seeding. Significant interaction between the accessions and the year of production necessitated characterization of results within each year of production, rather than across years. The Utah Experimental population was among the highest performing accessions for 4 of the traits in at least one of the years of the study. None of the accessions, however, were among the high performers for all 6 evaluated traits. Based on summation of accession standard normalized mean variables for each trait, several accessions including 552794 from Colorado and 562039 from Wyoming showed promise for combining good performance for most of the traits for production in the Intermountain/Great Basin region. Accessions from outside this area were poorly adapted. Thus, untapped potential exists to cultivate thickspike wheat-grass seed sources with higher seed production and seed quality than are now commercially available.