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The next generation of bioenergy crops will be grown on marginal lands. Prairie cordgrass (Spartina pectinata Link) is well suited to marginal land because of its tolerance to stresses such as salinity and water fluctuations. Developing prairie cordgrass as an energy crop requires genomic information such as genomic size and ploidy level. The 2C nuclear genome size of 11 prairie cordgrass populations, originating from Illinois, North Dakota, and South Dakota, were determined by flow cytometry using somatic G1 nuclei, and the ploidy variation confirmed by counting the chromosome number. One population from each of North Dakota and South Dakota, as well as the Red River, had genome sizes of 3.1 pg of DNA per G1 somatic nucleus whereas, the majority of the eight populations from Illinois had a genome size of 1.6 pg. One plant from one of the Illinois populations had an estimated genome size of 2.3 pg. These genome sizes of 3.1 and 1.6 pg, along with their respective chromosome numbers of 80 and 40 indicate octoploid and tetraploid plants. The chromosome number of 60 observed in the plant with 2.3 pg indicated that this plant was hexaptoid. This study provides the first estimates of genome size for prairie cordgrass and is also the first to report observed hexaploidy in this species. This genomic information provides critical knowledge for designing efficient breeding schemes for plant improvement. doi: 10.2135/cropsci2010.03.0140

The genus Malus has anywhere between 25 and 33 species along with several subspecies. Malus species as well as clones within the same species have varying ploidy levels, as these are more than likely collected from different trees and (or) from different locations. In recent years, large numbers of Malus germplasm accessions have been collected and maintained at the United States National Germplasm Clonal Repository; however, genome sizes of this material have not yet been determined. In this study, leaf tissues from young grafted trees of 100 Malus species and hybrids growing in a nursery at the University of Illinois were collected and immediately used for extracting nuclei. Leaf tissues from apple and maize line W-22, used as an internal standard, were co-chopped and prepared for flow cytometric analysis. Apple nuclei were stained with propidium iodide, an intercalating dye, and a minimum of 8000 nuclei per sample were analyzed. Mean fluorescence of apple nuclei was then determined. A total of four replications per sample was used. Among 100 Malus accessions analyzed, one tetraploid, three triploid, and 96 diploid genotypes were identified. Significant differences in genome size were identified among the three ploidy types observed and also within diploid genotypes. The 2C mean value for tetraploids was 3.13 pg and ranged from 2.27 to 2.41 pg for triploids, whereas 2C values for diploids ranged between 1.44 and 1.72 pg. In addition, leaf impressions of young, fully expanded leaves were collected from young trees of 10 selected genotypes based on their ploidy and flow cytometric analysis and used to measure the nucleotypic parameter stomatal length. Ten stomata were measured per slide, three slides were analyzed per leaf, and three leaves were analyzed per accession. Overall, mean length of stomata ranged between 19.47 Rm (diploid) and 27.6 [tm (tetraploid), indicating that stomatal length in a tetraploid Malus genotype was 1.4-fold higher than that of a diploid genotype. A positive correlation between genome size and the nucleotypic parameter stomatal length was observed. Key words: apple, Malus species, nuclear DNA content, nucleotypic effects. Le genre Malus contient entre 25 et 33 especes, ainsi que plusieurs sous-especes. Les especes du genre Malus ainsi que les clones au sein d'une meme espece presentent des niveaux variables de ploidie puisque ceux-ci sont le plus vraisemblablement echantillonnes a partir de differents arbres ou localites. Dernierement, de grandes quantites de ressources genetiques pour le genre Malus ont ete collectees et maintenues au sein du United States National Germplasm Clonal Repository bien que les tailles des genomes au sein de ce materiel n' aint pas encore ete determinees. Dans ce travail, des tissus foliaires de jeunes greffons appartenant a 100 especes ou hybrides cultives dans une pepiniere a la University of Illinois ont ete preleves et utilises immediatement pour extraire des noyaux. Les tissus foliaires de pommiers et de la lignee W-22 du mais, cette derniere etant utilisee comme temoin, ont ete haches ensemble et prepares en vue d'une analyse de cytometrie en flux. Les noyaux de pommiers ont ete colores au propidium iodure, un colorant intercalaire, et un minimum de 8 000 noyaux par echantillon ont ete analyses. La fluorescence moyenne des noyaux de pommiers a ensuite ete determinee. Un total de quatre replications par echantillon a ete realise. Parmi les 100 accessions examinees, un tetraploide, trois triploides et 96 diploides ont ete identifies. Des differences significatives en ce qui a trait a la taille du genome ont ete observees entre les trois niveaux de ploidie ainsi qu'au sein des genotypes diploides. La valeur 2C moyenne chez le tetraploide etait de 3,13 pg alors que celle-ci variait entre 2,27 et 2,41 pg chez les triploides et entre 1,44 et 1,72 pg chez les diploides. De plus, des empreintes de jeunes feuilles pleinement developpees ont ete prelevees sur de jeunes arbres de 10 genotypes, choisis en fonction de leur ploidie et l'analyse de cytometrie en flux, afin de mesurer un parametre nucleotypique : la longueur des stomates. Dix stomates ont ete mesures sur chaque lame, trois lames ont ete examinees par feuille et trois feuilles ont ete analysees par accession. Globalement, la longueur moyenne des stomates variait entre 19,47 [micro]m (diploide) et 27,6 [micro]m (tetraploide) montrant que la longueur des stomates etait 1,4 fois superieure chez le tetraploide. Une correlation positive entre la taille du genome et la longueur des stomates a ete observee. Mots-cles : pommier, especes du genre Malus, contenu en ADN nucleaire, effets nucleotypiques., Introduction The genus Malus belongs to the family Rosaceae, and subfamily Maloideae, which includes several important genera and accounts for most deciduous fruit crops including apple and pears. It has [...]

Weedy Amaranthus species pose a serious threat to agriculture. One of the areas that causes the greatest concern is development of herbicide resistance and subsequent transfer of herbicide resistance genes among the species. To determine the potential impact of interspecific hybridization, one must first be able to detect such hybrids. To determine if genome size could be useful in the detection of interspecific hybrids among the weedy Amaranthus species, the genome sizes of the weedy Amaranthus species sympatric in Illinois were analyzed. In a series of experiments, the genome sizes of these species were determined by flow cytometric analysis. A significant variation was observed with respect to nuclear DNA content in the eight species examined. The genome sizes ranged from ≅ 0.95 pg in A. palmeri to ≅ 1.4 pg in A. tuberculatus. Overlap of genome sizes among the species does exist; however, due to the reproductive biology of the species, this overlap does not preclude the detection of interspecific hybrids. Any dioecious weedy Amaranthus plant in Illinois that has a genome size between 1.3 pg and 1.1 pg is probably a hybrid. Thus, the potential for genome size determination to reveal interspecific hybrids among weedy Amaranthus species has been demonstrated., WEEDY AMARANTHUS species (pigweeds) have been and continue to be a major problem in agronomic production. A major contributor to the noxious nature of these weedy species is their ability [...]

Reports of genome size variation in soybean [Glycine max (L.) Merr.] have ranged from 40 to 0%. This wide range has resulted in doubts of the existence of intraspecific DNA variation in soybean. Eighteen soybean lines were analyzed by flow cytometry to determine their genome size. The lines were selected on the basis of diversity of origin. Intraspecific genome size variation was observed at approximately 4%. To ensure that the variation observed was reproducible and not due to technique error, the two highest and lowest genomes size accessions were reanalyzed. The order and variation observed between the high and low genome size accessions were maintained. To ensure further that the differences were reproducible, seeds from the two highest and lowest genome size accessions were planted in different locations in the USA, grown to maturity, harvested, and the seeds returned to Illinois. The harvested seed was analyzed and again the order and variation in genome size between the high and low genome size accessions were similar to the previous two analyses even though more than 1 yr had passed between the analysis. In addition, two experiments using Amaranthus palmeri S. Wats as an internal standard were conducted. In both of these experiments, the observed variation between the previously reported high and low genome size soybean lines was approximately 1 to 2%. The variation between the high and low genome size soybean lines is reproducible. The variation reported here indicates that the DNA amount variation is between 1 and 4%, lower than was originally reported., OVER THE PAST SEVERAL YEARS, a controversy has been occurring within the literature with respect to intraspecific nuclear DNA content variation in plants. While certain species such as maize (Zea [...]

For improvement of hairy vetch (Vicia villosa Roth) as a winter cover crop, it is necessary to gain insight into the magnitude of variability present in the species. This study was conducted to assess the sources of genetic and phenotypic variability of V. villosa accessions. Thirteen morphological and agronomic traits were measured on 42 populations of V. villosa and two populations of V. pannonica Crantz in field studies at Urbana, IL, for 2 yr. These measurements include initial seed weight, germination, stem length, stem width, leaf length, and leaf width in the fall and spring, winter survival, biomass, and a ratio of organic C to total N (C:N ratio) of the plants. The multivariate data set was analyzed by canonical discriminant analysis (CDA) in combination with a clustering procedure. In this analysis, the first two canonical variates were significant and accounted for 94% of the among-accession variability. The canonical variates indicated that fall and spring measurements of the leaf and stem, and C:N ratio are the most differentiating traits among the accessions. The canonical variates were used to duster the accessions into four subgroups on the basis of the differentiating traits. Canonical discriminant analysis was useful in identifying the genetic variation and the traits that better describe the variation among hairy vetch populations. Cluster analysis was successful in differentiating the accessions into similar subgroups on the basis of the measured traits. Plant breeders can use the information on variation among Vicia accessions and focus on traits of particular significance., WINTER COVER CROPS have long been recognized as possible tools for maintaining and improving soil quality and consequently addressing production and environmental concerns in agriculture (Wagger et al., 1998). Leguminous [...]

Prairie cordgrass (Spartina pectinata), a perennial C4 grass native to the North American prairie, has several distinctive characteristics that potentially make it a model crop for production in stressful environments. However, little is known about the transcriptome dynamics of prairie cordgrass despite its unique freezing stress tolerance. Therefore, the purpose of this work was to explore the transcriptome dynamics of prairie cordgrass in response to freezing stress at -5°C for 5 min and 30 min. We used a RNA-sequencing method to assemble the S. pectinata leaf transcriptome and performed gene-expression profiling of the transcripts under freezing treatment. Six differentially expressed gene (DEG) groups were categorized from the profiling. In addition, two major consecutive orders of gene expression were observed in response to freezing; the first being the acute up-regulation of genes involved in plasma membrane modification, calcium-mediated signaling, proteasome-related proteins, and transcription regulators (e.g., MYB and WRKY). The follow-up and second response was of genes involved in encoding the putative anti-freezing protein and the previously known DNA and cell-damage-repair proteins. Moreover, we identified the genes involved in epigenetic regulation and circadian-clock expression. Our results indicate that freezing response in S. pectinata reflects dynamic changes in rapid-time duration, as well as in metabolic, transcriptional, post-translational, and epigenetic regulation. [ABSTRACT FROM AUTHOR]