Plant Genetic Resources Conservation Unit Research Articles

Screening and growth assessment of indigenous and exotic sesame genotypes under osmotic stress

Drought stress decrease plant growth especially during germination and seedling stages in dry areas. The plants of Sesame are moderately tolerant to drought although it is sensitive at germination and seedling stages. About 102 different sesame genotypes were acquired from the Ayub Agriculture Research Institute Faisalabad Pakistan and Plant Genetic Resources Conservation Unit (USDA) Griffin Georgia United States. Including two local varieties as check screened against drought tolerant were conducted in central lab of PMAS-Arid Agriculture University Rawalpindi, Pakistan during July 2019 by using 3 levels of osmotic potential (0, -0.18, and -0.36Mpa) created through Polyethylene Glycol (PEG 8000) following the complete randomized design and data were collected on growth and early seedling indices of sesame. The Hierarchical Cluster Analysis was performed by using IBM SPSS Statistics 23 software on the basis of drought tolerance index (DTI) and Membership Function Value (MFV). Results showed significant decline by increasing osmotic potential regarding studied traits. Ten (10) drought tolerant sesame genotypes namely PI – 153509PI – 154304 PI – 158053 PI – 158059 PI – 175907 PI – 158902 PI – 164142 PI – 164317 PI – 164763 PI – 180340 were selected which exhibited the DTI value (0.451 - 0.525) with the mean MFV value ranged from (0.856 - 0.913) and 5 genotypes had DTI value ranging from (0.075 - 0.150). The genotypes with average DTI ≥ 0.525 were considered as highly drought tolerant genotypes. Contrary, the genotypes with an average DTI ≤ 0.225 were considered drought sensitive and 20 genotypes were highly drought sensitive (HDS) with mean MFV value ranged from 0.103 - 0.196. Genotypes with drought tolerance characteristics can be used for future breeding programs to develop drought tolerant varieties for increasing growth and yield of sesame in drought prone areas.

Ticktrefoil (Desmodium) species as a nutraceutical forage resource for animals

AbstractTicktrefoil (Desmodium) species from the USDA, ARS, Plant Genetic Resources Conservation Unit (PGRCU) germplasm collection in Griffin, GA, were evaluated for their potential livestock nutraceutical (nutritional + pharmaceutical) value in a field small plot study at the Fort Valley State University (FVSU) Agricultural Research Station, Fort Valley, GA. Horse marmalade (Desmodium discolor Vogel), greenleaf ticktrefoil (Desmodium intortum [Mill.] Urb.), panicledleaf ticktrefoil (Desmodium paniculatum [L.] DC.), Hawaii ticktrefoil (Desmodium sandwicense E. May) and twisted ticktrefoil (Desmodium tortuosum [Sw.] DC.) were established in a greenhouse and transplanted to field plots, with plant material from each species harvested, freeze‐dried, ground and analyzed for nutrient content and bioactivity. Crude protein (CP) levels in D. discolor and D. tortuosum averaged 233 g/kg, whereas CP in D. intortum, D. paniculatum and D. sandwicense ranged from 99 to 157 g/kg. The Desmodium species had in vitro true digestibility values of 755 to 878 g/kg. There were no detectable condensed tannins in D. discolor and D. tortuosum, whereas D. intortum, D. paniculatum and D. sandwicense averaged 88, 89 and 73 g/kg total condensed tannin, respectively. There were species differences in flavonoid content (p < .01), with the highest delphinidin and cyanidin concentrations in D. sandwicense and D. paniculatum, respectively. There were no detectable levels of delphinidin or cyanidin for D. discolor or D. tortuosum. Quercitin and kaempferol concentrations were highest in D. intortum and D. paniculatum, respectively, whereas D. discolor and D. tortuosum had the lowest values. The highest protein precipitable phenolics and total phenolic concentrations were for D. paniculatum. Desmodium species have potential as nutraceutical forage for livestock and warrant further investigation.

Genetic diversity, population structure, and selection of breeder germplasm subsets from the USDA sweetpotato (Ipomoea batatas) collection.

Sweetpotato (Ipomoea batatas) is the sixth most important food crop and plays a critical role in maintaining food security worldwide. Support for sweetpotato improvement research in breeding and genetics programs, and maintenance of sweetpotato germplasm collections is essential for preserving food security for future generations. Germplasm collections seek to preserve phenotypic and genotypic diversity through accession characterization. However, due to its genetic complexity, high heterogeneity, polyploid genome, phenotypic plasticity, and high flower production variability, sweetpotato genetic characterization is challenging. Here, we characterize the genetic diversity and population structure of 604 accessions from the sweetpotato germplasm collection maintained by the United States Department of Agriculture (USDA), Agricultural Research Service (ARS), Plant Genetic Resources Conservation Unit (PGRCU) in Griffin, Georgia, United States. Using the genotyping-by-sequencing platform (GBSpoly) and bioinformatic pipelines (ngsComposer and GBSapp), a total of 102,870 polymorphic SNPs with hexaploid dosage calls were identified from the 604 accessions. Discriminant analysis of principal components (DAPC) and Bayesian clustering identified six unique genetic groupings across seven broad geographic regions. Genetic diversity analyses using the hexaploid data set revealed ample genetic diversity among the analyzed collection in concordance with previous analyses. Following population structure and diversity analyses, breeder germplasm subsets of 24, 48, 96, and 384 accessions were established using K-means clustering with manual selection to maintain phenotypic and genotypic diversity. The genetic characterization of the PGRCU sweetpotato germplasm collection and breeder germplasm subsets developed in this study provide the foundation for future association studies and serve as precursors toward phenotyping studies aimed at linking genotype with phenotype.

Genetic Diversity for Quercetin, Myricetin, Cyanidin, and Delphinidin Concentrations in 38 Blackeye Pea (Vigna unguiculata L. Walp.) Genotypes for Potential Use as a Functional Health Vegetable

Blackeye peas (Vigna unguiculata L. Walp.) are mainly used as a vegetable throughout the world, however they may contain significant concentrations of quercetin, myricetin, cyanidin, and delphinidin for potential use as a functional vegetable. Thirty-eight blackeye pea genotypes were selected from the core collection in the USDA, ARS, Plant Genetic Resources Conservation Unit’s cold storage at 4 °C during 2016. Information regarding concentrations of quercetin, myricetin, cyanidin, delphindin, and correlations among these as well as additional seed traits including seed coat color, seed pattern color, seed pattern, seed texture, and years in storage would add value to the blackeye pea genotypes for use as a functional vegetable. Using high performance liquid chromatography (HPLC), the red seeded accession originating from Mozambique, PI 367927 produced the highest quercetin (469.53 µg/g) and myricetin (212.23 µg/g) concentrations. The black seeded genotype, PI 353236, originating from India, produced the highest cyanidin (1,388.82 µg/g) concentration. However, PI 353236 and the brown seeded genotype, PI 353352 from India produced the highest concentrations of delphinidin (1,343.27 and 1,353.94 µg/g), respectively. Several correlations were observed and interestingly only delphinidin showed a significant negative correlation (r = −0.293*) with years in cold storage indicating that delphinidin declined in the seeds stored the longest (from 4-45 years) at 4 °C. Principal component analysis (PCA) explained how the flavonols, anthocyanidins, and the additional seed traits contributed to the variation of the blackeye pea genotypes. The cluster analysis showed six clusters representing low to high phytochemical concentrations. The genetic parameters including σ2g, σ2p, GCV, PCV, h2 h, and GG indicate that improvement in these phytochemical traits is possible through selection. The genotypic and phenotypic correlations showed that improving one phytochemical significantly improved the other except for cyanidin with delphinidin. These results can be used by scientists to develop blackeye pea cultivars with high flavonol and anthocyanidin concentrations.

Multivariate Analysis of Butterfly Pea (Clitoria ternatea L.) Genotypes With Potentially Healthy Nutraceuticals and Uses

Butterfly pea (Clitoria ternatea L.) is a legume used as tea, forage, ornamental, salad, and medicinal plant. The flowers range from white to dark purple with little known about the variation for seed and flower color in the United States Department of Agriculture, Agricultural Research Service, Plant Genetic Resources Conservation Unit germplasm collection. Therefore, 26 butterfly pea accessions were analyzed using a principal component analysis (PCA) and average linkage cluster analysis (ALCA). These butterfly pea genotypes ranged from 56% to 99% for viabilities, 2.57 to 5.88 g for 100 seed weight, 34.07 to 226.26 g for total seed weight, and 1,326 to 3,874 for total seed numbers. PCA accounted for 40%, 57%, 70%, 79%, and 86% of the variation using principal components (PCs) 1 through 5, respectively. PC1 was most correlated with 100 and total seed weight, while PC2 correlated with blue, white, and purple flowers. PC3 correlated mostly with germination, purple flowers, and total seed weight. PCs 4 and 5 primarily correlated with blue and purple flowers, respectively. Several significant correlations were also observed. ALCA grouped the 26 butterfly pea genotypes into four distinct seed number–producing clusters. Clusters 1 to 4 represent the lowest to highest seed numbers produced by the butterfly pea genotypes. Several potential health benefits from butterfly pea flowers, leaves, seeds, and roots for human use were identified from the literature.

Evaluation of the USDA sweetpotato [Ipomoea batatas (L.) Lam.] germplasm collection for tolerance to the herbicide clomazone

Sweetpotato [Ipomoea batatas (L.) Lam.], is an important food crop worldwide. Weed management is consistently ranked among the top priorities of the sweetpotato industry in the United States (U.S.). Unfortunately, weed management of sweetpotato in the U.S. can be challenging as there are few herbicides labeled for use on the crop. Clomazone is one of the most widely used herbicides on sweetpotato in the U.S. and is effective in controlling several annual broadleaf weed and grass species and there is interest in developing germplasm that is tolerant to the herbicide. There is a lack of information concerning clomazone tolerance for sweetpotato plant introductions (PIs) that are contained within the germplasm collection of the USDA, ARS, Plant Genetic Resources Conservation Unit. The present study evaluated 564 sweetpotato PIs for tolerance to clomazone under a recommended rate in a field plot, with the objective of identifying sources of tolerance to clomazone. Clomazone injury ratings [1 = no chlorosis, 3 = minor chlorosis ( 50%)] of the 564 sweetpotato PIs indicated that the majority (N = 497 PIs) had either no chlorosis or minor damage. There is ample phenotypic diversity for periderm (skin) and stele (flesh) color and dry matter present within the clomazone tolerant PIs. Additionally, there is sufficient genetic diversity present, as 108 PIs have been characterized and assigned to four genetic clusters with another 81 PIs having high levels of mixed ancestry. The results reported here provide critical baseline data for future studies of resistance and practical breeding for tolerance to clomazone.

259 Screening of Lespedeza germplasm for forage quality and bioactivity

Abstract Interest in the condensed tannin-containing legume sericea lespedeza (Lespedeza cuneata) as a nutraceutical (bioactive) forage for livestock has been increasing in the United States but other Lespedeza species have not been adequately evaluated. A study was completed to determine the nutritional and bioactivity potential of Lespedeza species obtained from the USDA Plant Genetic Resources Conservation Unit in Griffin, GA. Accessions from 15 Lespedeza species were planted in small plots at Fort Valley State University in Fort Valley, GA. After establishment, forage was harvested, freeze-dried, ground and analyzed for neutral detergent fiber (NDF), acid detergent fiber (ADF), in vitro true digestibility (IVTD), total phenolics (TP), and protein precipitable phenolics (PPP). Species differences were significant (P < 0.01) for all parameters measured. Lespedeza cuneata accessions, including “AUGrazer,” the cultivar most commonly used as an anti-parasitic crop in the United States had NDF, ADF, and IVTD values of 35.7±0.4%, 26.8±0.4%, and 74.3±1.2%, while L. virginica, a native species, had 34.9±3.0%, 26.0±2.5%, and 74.9±4.2%, respectively. The L. cuneata accessions averaged 179.6±4.3 and 133.6±3.5 mg/g of forage material for TP and PPP, while L. virginica averaged 564.2±24.6 and 306.5±19.9 mg/g, respectively. Other species varied from 30.5±3.0 to 47.4±4.2% NDF, 22.9±1.6 to 36.4±3.6% ADF, 55.2±5.9 to 81.6±3.4% IVTD, and 107.7±17.4 to 283.5±34.7 and 55.2±14.0 to 139.4±28.1 mg/g of forage for TP and PPP, respectively. Based upon these results, Lespedeza species tested in this study, particularly L. virginica, have potential as nutraceutical forages for livestock production systems. As L. cuneata accessions established and grew much better than other Lespedeza species in this study, agronomic testing of this germplasm collection in other environments is warranted. In addition, determining potential anti-parasitic properties of these species using in vitro and in vivo testing would be beneficial.

Variability for Sennoside A and B concentrations in eight Senna species

Some Senna species are important medicinal plants used worldwide and may show variation for sennoside concentrations. The USDA, ARS, PGRCU (United States Department of Agriculture, Agricultural Research Service, Plant Genetic Resources Conservation Unit) curates several Senna species including candlebush [S. alata (L.) Roxb.], Alexandrian senna [S. alexandrina Mill.], S. angulata (Vogel) H.S. Irwin & Barneby, S. covesii (A. Gray) H.S. Irwin & Barneby, S. hirsuta var. hirta H.S. Irwin & Barneby, S. hirsuta var. leptocarpa (Benth.) H.S. Irwin & Barneby, S. occidentalis (L.) Link, and S. uniflora (Mill.) H.S. Irwin & Barneby. The natural products including sennoside A and B are the primary laxative ingredients in many medicinal products. However, it is unknown if sennoside A and B are found in many of these Senna species and at what concentrations. The objective of this study was to evaluate sennoside A and B content from leaves of 14 and pods of four accessions including eight Senna species over two years and locations. Sample analysis was performed by HPLC (high performance liquid chromatography) on an Agilent 1100 with an auto-sampler and diode array detector. Significant accession and location x accession effects were observed for sennoside A and B. Mean separations revealed that leaves from S. alata produced significantly more sennoside A (8.55 mg/g) than all other species. However, immature pods from S. alexandrina produced the significantly highest sennoside B (16.19 mg/g) content. While this is a preliminary analysis, it provides evidence for higher levels of sennoside A and B in S. alata and S. alexandrina than in S. angulata, S. covesii, S. hirsuta var. hirta, S. hirsuta var. leptocarpa, S. occidentalis, and S. uniflora. These results show that both S. alata and S. alexandrina produced the highest sennoside concentrations. However, additional studies are required to verify sennoside content in other Senna species and organs including Senna pods.

Genetic Diversity and Population Structure of the USDA Sweetpotato (Ipomoea batatas) Germplasm Collections Using GBSpoly.

Sweetpotato (Ipomoea batatas) plays a critical role in food security and is the most important root crop worldwide following potatoes and cassava. In the United States (US), it is valued at over $700 million USD. There are two sweetpotato germplasm collections (Plant Genetic Resources Conservation Unit and US Vegetable Laboratory) maintained by the USDA, ARS for sweetpotato crop improvement. To date, no genome-wide assessment of genetic diversity within these collections has been reported in the published literature. In our study, population structure and genetic diversity of 417 USDA sweetpotato accessions originating from 8 broad geographical regions (Africa, Australia, Caribbean, Central America, Far East, North America, Pacific Islands, and South America) were determined using single nucleotide polymorphisms (SNPs) identified with a genotyping-by-sequencing (GBS) protocol, GBSpoly, optimized for highly heterozygous and polyploid species. Population structure using Bayesian clustering analyses (STRUCTURE) with 32,784 segregating SNPs grouped the accessions into four genetic groups and indicated a high degree of mixed ancestry. A neighbor-joining cladogram and principal components analysis based on a pairwise genetic distance matrix of the accessions supported the population structure analysis. Pairwise FST values between broad geographical regions based on the origin of accessions ranged from 0.017 (Far East – Pacific Islands) to 0.110 (Australia – South America) and supported the clustering of accessions based on genetic distance. The markers developed for use with this collection of accessions provide an important genomic resource for the sweetpotato community, and contribute to our understanding of the genetic diversity present within the US sweetpotato collection and the species.

Color analysis of storage roots from the USDA, ARS sweetpotato (Ipomoea batatas) germplasm collection

The United States Department of Agriculture (USDA), Agricultural Research Service (ARS), Plant Genetic Resources Conservation Unit in Griffin, GA maintains the United States germplasm collection for Ipomoea spp. (Convolvulaceae). During 2012–2014, 737 sweetpotato, Ipomoea batatas (L.) Lam., plant introductions (PI) were acquired as tissue-culture plantlets and then acclimated to greenhouse conditions at the USDA, ARS, U. S. Vegetable Laboratory (USVL), Charleston, SC. Single plants were transferred to plastic-covered plant beds to produce cuttings for replicated field trials. Storage roots were harvested from 690 PIs grown in the field and 695 PIs grown in pots. Color coordinates were obtained for each PI using a tristimulus colorimeter. Hue angle values (h*) ranged from 8.2° to 88.3° ( $$ \bar{x} $$ = 54.9°) for the periderm (peel or skin) of field-grown storage roots (n = 690 PIs) and − 9.4° (= 350.6°) to 96.2° ( $$ \bar{x} $$ = 51.3°) for pot-grown roots (n = 695 PIs). The red–green coordinate (a*) ranged from 0.8 to 30.7 ( $$ \bar{x} $$ = 12.8) for the periderm of field-grown roots and − 2.0 to 44.9 ( $$ \bar{x} $$ = 16.1) for pot-grown roots. The yellow–blue coordinate (b*) ranged from 2.8 to 33.1 ( $$ \bar{x} $$ = 19.4) for the periderm of field-grown roots and − 7.4 to 38.1 ( $$ \bar{x} $$ = 19.3) for pot-grown roots. Color saturation (chroma, C*) ranged from 13.7 to 35.8 ( $$ \bar{x} $$ = 24.9) for the periderm of field-grown roots and 14.9–45.5 ( $$ \bar{x} $$ = 29.3) for pot-grown roots. Lightness (white–black, L*) ranged from 32.6 to 81.7 ( $$ \bar{x} $$ = 54.6) for the periderm of field-grown roots and 32.1–88.2 ( $$ \bar{x} $$ = 64.0) for pot-grown roots. Hue angles ranged from − 13.1° (= 346.9°) to 100.9° ( $$ \bar{x} $$ = 80.9°) for the stele (flesh) of field-grown storage roots (n = 672 PIs) and − 29.9° to 103.5° ( $$ \bar{x} $$ = 81.6°) for pot-grown roots (n = 676 PIs); a* ranged from − 5.6 to 35.0 ( $$ \bar{x} $$ = 8.0) for the stele of field-grown roots and − 6.0 to 41.0 ( $$ \bar{x} $$ = 7.6) for pot-grown roots; and b* ranged from − 7.7 to 56.1 ( $$ \bar{x} $$ = 34.6) for the stele of field-grown roots and − 12.6 to 56.1 ( $$ \bar{x} $$ = 31.8) for pot-grown roots. C* ranged from 12.7 to 65.8 ( $$ \bar{x} $$ = 37.2) for the stele of field-grown roots and 8.9–65.7 ( $$ \bar{x} $$ = 34.5) for pot-grown roots; and L* ranged from 27.8 to 91.1 ( $$ \bar{x} $$ = 77.7) for the stele of field-grown roots and 28.2–91.9 ( $$ \bar{x} $$ = 80.4) for pot-grown roots. There were significant relationships between stele color (h*) and percent dry matter, with orange stele having a significantly lower % dry matter ( $$ \bar{x} $$ = 25.6%, n = 183) compared with roots with cream/white stele ( $$ \bar{x} $$ = 30.8%, n = 373). There appears to be wide genetic diversity for root color characteristics for the United States sweetpotato germplasm collection.

Effect of sunn hemp (Crotalaria juncea L.) cutting date and planting density on weed suppression in Georgia, USA

A field study was conducted in 2008 and 2009 at the USDA, ARS, Plant Genetic Resources Conservation Unit in Griffin, GA, to investigate weed suppression by sunn hemp (Crotalaria juncea L). The objectives were to (1) evaluate the effects of apical meristem removal (AMR) at three dates [5, 6, and 7 wks after planting (WAP) on May 14, 2008 and May 21, 2009] and (2) assess the impact of seeding rates (11, 28, and 45 kg ha−1) on weed biomass reduction. Weed species were identified at 4, 8, and 12 wks after sunn hemp planting. Sunn hemp cutting date had no significant effect on weed suppression in 2008 but significant differences for grass weeds at 4, 8, and 12 WAP and for yellow nutsedge at 8 and 12 WAP did occur when compared to the control in 2009. In comparison to the sunn hemp-free control plot in 2009, all three seeding rates had reduced grass weed dry weights at 4, 8, and 12 WAP. The total mass of yellow nutsedge when grown with sunn hemp was reduced compared to the total mass of yellow nutsedge grown in the weedy check for all seeding rates at 8 and 12 WAP. Lower grass weed biomass was observed by 12 WAP for cutting dates and seeding rates during 2008 and 2009. Sunn hemp cutting date and seeding rate reduced branch numbers in both years. The reduction in sunn hemp seeding rates revealed a decrease in weed populations.

First Report of Puccinia emaculata Infection on Switchgrass in Virginia.

During the spring of 2007, approximately 2,000 switchgrass plants, representing 168 core switchgrass germplasm, were established in a field nursery at the Virginia Tech Kentland Farm Research Center in Montgomery County, VA. These germplasms were originally obtained from the USDA Plant Genetic Resources Conservation Unit (Griffin, GA) and included both lowland and upland ecotypes. After planting, the switchgrass plants were allowed to establish for 3 years. In the summers of 2009, 2010, and 2011, a substantial infection of a foliar rust pathogen was observed on more than 90% of switchgrass lines in the field. The infected leaves had dark brown pustules that were arranged in a linear fashion between the veins and mainly located on the adaxial surface of the leaf. We observed the infected leaf samples under a microscope and isolated the urediniospores. The urediniospores were brown, round, and averaged 26.08 ± 1.67 μm long and 24.65 ± 1.66 μm wide. Teliospores were observed late in the summers of 2009 and 2010. The teliospores were two-celled, oblong to ellipsoid in shape, and averaged 32.23 ± 3.07 μm in length. The apical cell width averaged 17.6 ± 1.83 μm and the basal cell width averaged 15.08 ± 1.75 μm. The morphology of both the urediniospores and teliospores were similar to Puccinia emaculata Schw. (P. emaculata) (2,3). Using previously established rust disease scoring methods (1), the infected switchgrass lines were evaluated and scored for infection severity on a 0 to 9 scale based on the percentage of leaf area infected, with 0 being either highly resistant or escaping infection and 9 being highly susceptible. The majority of upland switchgrass cultivars, including Caddo, Cave-in-rock, Blackwell, Sunburst, Pathfinder, and Dacotah, were moderately to highly susceptible to this rust pathogen and on average, scored between 7 and 8. However, the majority of lowland switchgrass cultivars, including Alamo, Kanlow, TEM-SEC, TEM-SLC, and TEM-LoDorm, were moderately to highly resistant and scored on average between 3 and 4. This result is consistent with previous reports that show that lowland ecotypes are more resistant to rust diseases (1). To further validate the identity of the rust pathogen, we designed two primers (5'-CCAGTAACGGCGAGTGAAGAG-3' and 5'-CGACTTCCATGGCCACCGTGCGGCTGTCT-3') based on the 18S rDNA sequence of P. emaculata (3). DNA was extracted from bulk infected leaf material for PCR amplification. The 1.2 kb PCR product was isolated and sent for DNA sequencing. The DNA sequence was 98% identical to the 18S rDNA sequence of P. emaculata (EU915294.1). To our knowledge, this study represents the first report of rust on a wide range of various switchgrass cultivars in Virginia.

Showy partridge pea [Chamaecrista fasciculata (Michx.) Greene] with potential for cultivation as a multi-functional species in the United States

Showy partridge pea, Chamaecrista fasciculata is used in the USA for cover cropping, ornate flowers in native gardens, honey crop, as an annual reseeding legume for restoration and conservation plantings, and wildlife food. However, its greatest potential may be as a bio-control plant for the control of mole crickets, cactus moth, and additional pest species. The United States Department of Agriculture, Agricultural Research Service, Plant Genetic Resources Conservation Unit (USDA, ARS, PGRCU) conserves 36 accessions originating from the USA.

Morphological and reproductive characterization of guar (Cyamopsis tetragonoloba) genetic resources regenerated in Georgia, USA

Guar, Cyamopsis tetragonoloba is used worldwide for food stabilization, fiber source, food, and industry. The United States Department of Agriculture, Agricultural Research Service, Plant Genetic Resources Conservation Unit (USDA, ARS, PGRCU) conserves 1,298 accessions originating from India, Pakistan, and breeding lines from the USA. My objectives were to determine: (1) if these guar accessions can successfully be regenerated in Georgia, USA, (2) which traits contribute the most variation, and (3) to provide estimates for genetic relatedness among these accessions. Guar accessions were directly seeded to the field in Griffin, GA between early May and mid June 2006-2008. At 50% maturity, 73 accessions were characterized for morphological, phenological, and reproductive traits during the regeneration cycles. High quality plants regenerated from most of the accessions and produced 80 to more than 9,300 seeds per accession. Guar can be successfully grown and regenerated in Griffin, GA. Coefficients of variation and principal component analysis revealed variability among accessions for these traits evaluated. Cluster analysis separated guar accessions into three groups (clusters) based on low, intermediate or high seed numbers. Guar accessions clustered in groups 2 and 3 appear to be more genetically related than those in group 1.

Characterization of sesame (Sesamum indicum L.) germplasm regenerated in Georgia, USA

Sesame, Sesamum indicum L. is used worldwide for cooking oil and food. The United States Department of Agriculture, Agricultural Research Service, Plant Genetic Resources Conservation Unit (USDA, ARS, PGRCU) conserves 1,226 accessions originating from Europe, Africa, Asia, North America, and South America. Sesame accessions were directly seeded to the field in Griffin, GA between 15 May and 01 June 2003–2007. At 50% maturity, 192 accessions were characterized for morphological, phenological, and reproductive traits during the regeneration cycles. High quality plants regenerated from all accessions produced 131 to more than 80,000 seeds per accession. Sesame can be successfully grown and regenerated in Griffin, GA. Coefficients of variation and principal component analysis revealed considerable variability among accessions for phenological, morphological and reproductive traits. Assuming appropriate levels of heritability, sufficient variation among sesame accessions exists for days to maturity, plant height, and reproductive traits among these sesame accessions to warrant breeding programs for new sesame cultivar development.

Agrobotanical Attributes, Nitrogen-Fixation, Enzyme Activities and Nutraceuticals of Hyacinth Bean (Lablab purpureus L.): A Bio-Functional Medicinal Legume

Hyacinth bean (Lablab purpureus L.) accessions of different origins received from USDA, ARS, Plant Genetic Resources Conservation Unit, Griffin, GA, USA were evaluated for agrobotanical attributes, enzyme activities, nutraceuticals and quality in calcium deficient soil of Aligarh, Western Uttar Pradesh, India. Fresh and dry weights per plant, leaf-area, number and dry weight of nodules per plant, net photosynthetic rate, stomatal conductance and transpiration rate, total chlorophyll and carotenoid content, activities of nitrate reductase and carbonic anhydrase, leaf - N, P, K and Ca contents and nodule-nitrogen and leghaemoglobin contents, respectively were analyzed at 60, 90 and 120 day after sowing. Photosynthesis was measured only at 90 DAS. Yield attributes including pod number per plant, seed number per pod, 100-seed weight and seed-yield per plant were recorded at harvest (150 DAS). Protein and carbohydrate content as well as tyrosinase activity in hyacinth bean seeds were also determined. Among the five accessions, EC-497619 (A4) showed superior performance over the rest of the accessions. Accession A4 showed the highest values for growth, yield, physiological, biochemical and quality attributes in comparison to the other accessions. Net photosynthetic rate, stomatal conductance and transpiration rate were found maximum in the A4 accession. Chlorophyll and carotenoid content were also reported higher in accession A4. Accession A4 showed higher nitrate reductase and carbonic anhydrase activities than the other accessions. Nodule-nitrogen and leghaemoglobin content ranged from 5.267-5.314% and 0.110-0.130 mM, respectively. Mineral profiles, viz., nitrogen, phosphorus, potassium and calcium content varied from 3.610-3.643, 0.338-0.356, 3.020-3.124 and 1.764-1.804%, respectively. Seed protein of all accessions varied from 24.70-25.06%. Carbohydrate content ranged from 50.83-53.16% across all accessions tested. Accession A4 produced the highest tyrosinase activity in the seeds.

First Report of Tomato spotted wilt virus Infecting African Clover (Trifolium tembense) in Georgia.

Tomato spotted wilt virus (TSWV; family Bunyaviridae, genus Tospovirus), which is vectored by several species of thrips (order Thysanoptera, family Thripidae), causes a destructive disease that affects many economically important host plants such as tomatoes, peppers, and peanuts. Controlling the spread of this disease is challenging, and currently, only limited strategies are available to prevent and/or control its dissemination, including early diagnosis, destruction of infected material, and elimination of the vector. TSWV has been previously reported in subterranean clover (Trifolium subterraneum), white clover (T. repens), and various unidentified wild clovers (Trifolium spp.) in North America and Australia (1,3), but never before in an African species. T. tembense (Fresen.), an herbaceous annual African clover that is mainly used for grazing, is part of the national germplasm collection housed at the Plant Genetic Resources Conservation Unit in Griffin, GA. TSWV was found naturally infecting several accessions of this species being grown for regeneration in a greenhouse during 2008. Initial putative identification of the virus was done by visual inspection of host symptoms that included ringspots, necrotic and chlorotic local lesions, sometimes mild systemic wilting, and eventually an overall decline of healthy tissue in the infected plants. This was subsequently confirmed by double-antibody sandwich (DAS)-ELISA and reverse transcription (RT)-PCR. Primers (5'-ATGTCTAAGGTTAAGCTC-3' forward and 5'-TTAAGCAAGTTCTGTGAG-3' reverse) targeted the nucleocapsid gene of TSWV and amplified an expected product of approximately 800 bp (2). No product was amplified in any of the negative controls. Twenty-six individuals representing twelve plant accessions (PI 517788, 517790, 517792, 517793, 517809, 517832, 517842, 517845, 517851, 517871, 517876, and 517889) were screened for TSWV. Two to three individuals were targeted from each accession. Samples were chosen on the basis of the availability of leaf tissue to perform two diagnostic assays, ELISA and RT-PCR. Samples chosen for this study were all naturally infected by thrips. All but four individuals representing two plant accessions tested positive for the virus. The RT-PCR data substantiated the DAS-ELISA results and confirmed the suspected infection. More than 26% of the positive samples naturally infected by TSWV were further characterized by purifying and sequencing (bidirectionally) the RT-PCR product on an automated CEQ 8000 sequencer (Beckman Coulter, Fullerton, CA). The resulting sequences were aligned and edited using AlignIR (LI-COR, Lincoln, NE). More than 700 bp of sequence data (GenBank Accession No. FJ183743-FJ183746) was compiled and they displayed 98% identity with deposited TSWV nucleocapsid gene sequences in GenBank, with no similarity to any other targets. To our knowledge, this is the first report of TSWV infection in T. tembense. Accessions potentially resistant to TSWV within this species were identified and need to be further substantiated. T. tembense is a wild, native clover in Africa and could serve as a weed host for infection of nearby agronomically important crops.

A survey of sesamin and composition of tocopherol variability from seeds of eleven diverse sesame (Sesamum indicum L.) genotypes using HPLC‐PAD‐ECD

The objective of this study was to determine the composition and content of sesamin and desmethyl tocopherols such as alpha-tocopherol (alphaT), delta-tocopherol (deltaT) and gamma-tocopherol (gammaT) in seeds of sesame (Sesamum indicum L.) for 11 genotypes conserved in the United States Department of Agriculture (USDA), Agricultural Research Service (ARS) and Plant Genetic Resources Conservation Unit (PGRCU) in Griffin, Georgia, USA. Seed accessions studied were collections from eight countries worldwide, including one landrace from Thailand and two cultivars from Texas, USA. Novel methodologies and analytical techniques described herein consisted of reverse-phase high-performance liquid chromatography (HPLC) connected in series with two detection systems specific for each analyte class. Photodiode array detection was employed for sesamin analysis and electrochemical array detection was used in the determination of tocopherols. A preliminary study was conducted to assess sesamin levels in 2003 and tocopherol levels in 2004 from sesame seed samples conserved at the USDA, ARS and PGRCU. In 2005, sesame seed samples were grown, harvested and evaluated for sesamin as well as tocopherol levels. The overall results (n = 3) showed that sesamin, alphaT, deltaT and gammaT levels were 0.67-6.35 mg/g, 0.034-0.175 microg/g, 0.44-3.05 microg/g and 56.9-99.3 microg/g respectively, indicating that the sesame seed accessions contained higher levels of sesamin and gammaT compared with alphaT and deltaT. Statistical analysis was conducted and significant differences were observed among the 11 different sesame genotypes. This suggests that genetic, environmental and geographical factors influence sesamin and desmethyl tocopherol content.

Evaluation of Sorghum Germplasm from China against Claviceps africana, Causal Agent of Sorghum Ergot

Forty Chinese sorghum landraces maintained by the USDA-ARS Plant Genetic Resources Conservation Unit, Griffin, GA were evaluated for ergot resistance at the Texas A&M Research Farm, College Station, Texas, during the 2005 and 2006 growing seasons. The male sterile line, ATx623, was included as a susceptible control and three IS8525 derived lines were included as resistant controls. The disease infection level was low in the susceptible check in 2005 due to unfavorable environmental conditions, but the majority of the Chinese accessions showed a higher level of tolerance than the resistant controls and in contrast, infection severity was high in 2006. The IS8525 resistant controls averaged 25% infection compared to an average infection of 18% for the 40 Chinese accessions. Four Chinese accessions, PI63923, PI511832, PI610749, and PI610688, recorded less than 10% ergot infection and thus, these four accessions may possess genes for ergot resistance. Further research is underway to evaluate these accessions under multi-environments to confirm resistance and to determine if the resistance is associated with pollination characteristics. Accepted for publication 19 February 2008. Published 19 May 2008.

ANTHOCYANIN AND POTENTIAL THERAPEUTIC TRAITS IN CLITORIA, DESMODIUM, CORCHORUS, CATHARANTHUS AND HIBISCUS SPECIES

The USDA, ARS, Plant Genetic Resources Conservation Unit curates several important nutraceutical and medicinal plant species. Anthocyanins are responsible for flower, leaf and seed coat color in plants, and are antioxidants as well. However, little is known about anthocyanin content in Clitoria ternatea, Desmodium adscendens, Corchorus olitorius, Catharanthus roseus, Hibiscus sabdariffa and Acer saccharum. This study was conducted to identify anthocyanin indexes and additional health enhancing components in these species. An anthocyanin meter with an LED diode of 520 nm was used to measure the anthocyanin index of leaves and flowers from plants growing in the field during July, September and October 2006. We found anthocyanin indexes ranging from 4.1 to 52.4 for leaves and 0.8 to 26.8 for flowers in all five species. The highest leaf anthocyanin index average of 14.6 was found in D. adscendens (PI 316623) followed by sugar maple (A. saccharum) with a leaf anthocyanin average index of 13.0. Catharanthus roseus (PI 608581) also had the highest flower anthocyanin index average of 17.3. These data were recorded at or prior to 50% maturity. In addition, potential health uses for these species are discussed. Phytochemicals identified include but are not limited to an antimicrobial protein from C. ternatea, anthocyanin rich extracts from H. sabdariffa for potential use as a chemopreventive agent, and antitumor promoters in C. olitorius leaves. These anthocyanins and phytochemicals have potential value in the nutraceutical and medical industries. These variable anthocyanin indexes among these species will assist breeders and other scientists with valuable germplasm for development of anthocyanin enriched cultivars.