Production and measurement of fission product noble gases.

Gaseous fission products have been produced via thermal neutron irradiation of a highly-enriched uranium target and extracted using a custom gas processing system for measurement on a prototype, high-resolution ß - Î³ coincidence detection system. The gas was extracted and measured in two stages in order to measure the prompt and ß--delayed fission products. This paper presents an overview of the system used to produce gaseous fission products, and the results of the advanced coincidence spectrometry techniques used to identify and quantify decays from the radionuclides produced, including the noble gases 85Kr, 85mKr, 88Kr, 133Xe, 135Xe, 133mXe and 135mXe, as well as 133I and 88Rb. The measurements were validated by determination of the nuclear decay half-lives, specifically for the ground state decay of 135Xe, which was found to be 9.15(49) hours and consistent with the literature value. This work demonstrates the UK capability to produce gaseous radionuclides for quality assurance and calibration purposes in Radionuclide Laboratories supporting the Comprehensive Nuclear-Test-Ban Treaty (CTBT).

Evaluation of buffalograss genotypes and full-sibs for chinch bug resistance.

Fifteen buffalograss, Buchloe dactyloides (Nutt.) Engelm, genotypes and 94 diploid full-sib progeny were evaluated for western chinch bug, Blissus occiduus Barber (Hemiptera: Lygaeidae), resistance in two separate studies. The experimental design for each study was a completely randomized design. Adult chinch bugs were introduced onto caged single clone genotypes and progeny in the greenhouse. Chinch bug damage was assessed using a 1-5 visual damage rating scale with 1 = < or = 10%; 2 = 11-30%; 3 = 31-50%; 4 = 51-70%; and 5 = > or = 70% of the buffalograss leaf area with severe discoloration, or dead tissue. Highly significant differences were found among the genotypes and progeny for chinch bug damage. Among the genotypes, Legacy, Prestige, 184, 196, Bowie, NE 3297, NE 2769, and NE 2768 were moderately resistant with damage ratings of > 1, but < 3, while NE 2990, NE 2838, and 1-57-19 were moderately susceptible with damage ratings of > or = 3, but < 4. Among the progeny, one progeny (MP45) was highly resistant with a chinch bug damage rating of 1.0, 78 progeny (83%) had moderate resistance, with damage ratings of > 1.0 and < 3.0, 13 progeny (14%) were moderately susceptible with damage ratings ranging from 3.0 to 3.9, while only two were highly susceptible with damage ratings of > or = 4.0. The significant variability among genotypes and progeny for chinch bug resistance indicates the ability to improve buffalograss resistance to chinch bugs through selection or hybridization of selected genotypes.

Genome-wide profiling and analysis of Festuca arundinacea miRNAs and transcriptomes in response to foliar glyphosate application.

Glyphosate is a broad spectrum herbicide which has been widely used for non-selective weed control in turfgrass management. Festuca arundinacea cv. Falcon was shown to be one of the tolerant turfgrass species in response to varying levels of glyphosate [5% (1.58 mM), 20% (6.32 mM)] recommended for weed control. However, there is a lack of knowledge on the mRNA expression patterns and miRNA, critical regulators of gene expression, in response to varying levels of glyphosate treatments. Here, we investigate the transcriptome and miRNA-guided post-transcriptional networks using plant miRNA microarray and Affymetrix GeneChip Wheat Genome Array platforms. Transcriptome analysis revealed 93 up-regulated and 78 down-regulated genes, whereas a smaller number showed inverse differential expressions. miRNA chip analysis indicated a number of (34 out of the 853) plant miRNAs were differentially regulated in response to glyphosate treatments. Target transcripts of differentially regulated miRNAs were predicted and nine of them were quantified by quantitative real-time PCR (qRT-PCR). Target transcripts of miRNAs validate the expression level change of miRNAs detected by miRNA microarray analysis. Down-regulation of miRNAs upon 5 and 20% glyphosate applications led to the up-regulation of their target observed by qRT-PCR or vice versa. Quantification of F. arundinacea miRNA, homologous of osa-miR1436, revealed the agreement between the Affymetrix and miRNA microarray analyses. In addition to miRNA microarray experiment, 25 conserved F. arundinacea miRNAs were identified through homology-based approach and their secondary structures were predicted. The results presented serve as analyses of genome-wide expression profiling of miRNAs and target mRNAs in response to foliar glyphosate treatment in grass species.

Polyploidy creates higher diversity among Cynodon accessions as assessed by molecular markers.

Developing a better understanding of associations among ploidy level, geographic distribution, and genetic diversity of Cynodon accessions could be beneficial to bermudagrass breeding programs, and would enhance our understanding of the evolutionary biology of this warm season grass species. This study was initiated to: (1) determine ploidy analysis of Cynodon accessions collected from Turkey, (2) investigate associations between ploidy level and diversity, (3) determine whether geographic and ploidy distribution are related to nuclear genome variation, and (4) correlate among four nuclear molecular marker systems for Cynodon accessions' genetic analyses. One hundred and eighty-two Cynodon accessions collected in Turkey from an area south of the Taurus Mountains along the Mediterranean cost and ten known genotypes were genotyped using sequence related amplified polymorphism (SRAP), peroxidase gene polymorphism (POGP), inter-simple sequence repeat (ISSR), and random amplified polymorphic DNA (RAPD). The diploids, triploids, tetraploids, pentaploids, and hexaploids revealed by flow cytometry had a linear present band frequency of 0.36, 0.47, 0.49, 0.52, and 0.54, respectively. Regression analysis explained that quadratic relationship between ploidy level and band frequency was the most explanatory (r = 0.62, P < 0.001). The AMOVA results indicated that 91 and 94% of the total variation resided within ploidy level and provinces, respectively. The UPGMA analysis suggested that commercial bermudagrass cultivars only one-third of the available genetic variation. SRAP, POGP, ISSR, and RAPD markers differed in detecting relationships among the bermudagrass genotypes and rare alleles, suggesting more efficiency of combinatory analysis of molecular marker systems. Elucidating Cynodon accessions' genetic structure can aid to enhance breeding programs and broaden genetic base of commercial cultivars.

Identifying, cloning and structural analysis of differentially expressed genes upon Puccinia infection of Festuca rubra var. rubra.

Differentially expressed genes in response to rust infection (Puccinia sp.) in creeping red fescue (Festuca rubra var. rubra) were identified and quantified using the mRNA differential display technique. The differentially induced genes were identified as homologs of mitogen-activated protein kinase (MAPK) 3 of Arabidopsis thaliana, stem rust resistance protein Rpg1 of barley and Hsp70 of Spinacia oleracea. The change in the steady state expression levels of these genes in response to rust infection was tested by Northern blot analysis and further quantified by real-time PCR. A steady accumulation of transcripts in the course of rust infection was observed. Full-length transcript of a fescue MPK-3 was obtained by RACE PCR. Its corresponding cDNA encodes a protein with a predicted MW of 42.5 kDa which was mapped onto the structural model of homologs MAPK to illustrate the corresponding MAPK signature motifs. This study, for the first time, presents evidence on the rust infection dependent metabolic pathways in creeping red fescue.

Molecular characterization of cDNA encoding resistance gene-like sequences in Buchloe dactyloides.

Current knowledge of resistance (R) genes and their use for genetic improvement in buffalograss (Buchloe dactyloides [Nutt.] Engelm.) lag behind most crop plants. This study was conducted to clone and characterize cDNA encoding R gene-like (RGL) sequences in buffalograss. This report is the first to clone and characterize of buffalograss RGLs. Degenerate primers designed from the conserved motifs of known R genes were used to amplify RGLs and fragments of expected size were isolated and cloned. Sequence analysis of cDNA clones and analysis of putative translation products revealed that most encoded amino acid sequences shared the similar conserved motifs found in the cloned plant disease resistance genes RPS2, MLA6, L6, RPM1, and Xa1. These results indicated diversity of the R gene candidate sequences in buffalograss. Analysis of 5' rapid amplification of cDNA ends (RACE), applied to investigate upstream of RGLs, indicated that regulatory sequences such as TATA box were conserved among the RGLs identified. The cloned RGL in this study will further enhance our knowledge on organization, function, and evolution of R gene family in buffalograss. With the sequences of the primers and sizes of the markers provided, these RGL markers are readily available for use in a genomics-assisted selection in buffalograss.

Evolution of Buchloë dactyloides based on cloning and sequencing of matK, rbcL, and cob genes from plastid and mitochondrial genomes.

Buffalograss (Buchloë dactyloides (Nutt.) Englem), a C4 turfgrass species, is native to the Great Plains region of North America. The evolutionary implications of buffalograss are unclear. Sequencing of rbcL and matK genes from plastid and the cob gene from mitochondrial genomes was examined to elucidate buffalo grass evolution. This study is the first to report sequencing of these genes from organelle genomes in the genus Buchloë. Comparisons of sequence data from the mitochondrial and plastid genome revealed that all genotypes contained the same cytoplasmic origin. There were some rearrangements detected in mitochondrial genome. The buffalograss genome appears to have evolved through the rearrangements of convergent subgenomic domains. Combined analyses of plastid genes suggest that the evolutionary process in Buchloë accessions studied was monophyletic rather than polyphyletic. However, since plastid and mitochondrial genomes are generally uniparentally inherited, the evolutionary history of these genomes may not reflect the evolutionary history of the organism, especially in a species in which out-crossing is common. The sequence information obtained from this study can be used as a genome-specific marker for investigation of the buffalograss polyploidy complex and testing of the mode of plastid and mitochondrial transmission in genus Buchloë.

Buffalograss germplasm resistance to Blissus occiduus (Hemiptera: Lygaeidae).

Plant germplasm collections may offer genetic variability useful in identifying insect resistance. The goal of this project was to evaluate buffalograss genotypes [Buchloë dactyloides (Nutt.) Engelm.] for resistance to the chinch bug, Blissus occiduus Barber (Hemiptera: Lygaeidae), and to relate resistance to ploidy level, chinch bug number, and pubescence. Forty-eight buffalograss genotypes from diverse geographic locations were evaluated in replicated studies under greenhouse conditions. Of the genotypes studied, four were highly resistant, 22 were moderately resistant, 19 were moderately susceptible, and three were highly susceptible to chinch bug damage. The mean number of chinch bugs was significantly different among the 48 genotypes. There was no significant correlation between chinch bug resistance and ploidy level or chinch bug resistance and pubescence. These results indicate the genetic source of resistance to chinch bugs exists in buffalograss germplasm. Highly resistant genotypes can be used in breeding programs to further improve buffalograss cultivars.