The Cerrado is a Neotropical savanna where grasses are a major biomass component in the open vegetation physiognomies. Invasive grasses are widely used as pastures in the Cerrado, and their presence may displace native species. The persistence of native grasses relies also on reproduction via seeds, which is often dependent on seeds found buried in the soil seed bank. The literature about the effects of light availability on the germination of Neotropical savanna grasses is scarce, and germination may lead to abnormal seedlings that develop only the root or the shoot. Germination trials that overlook this fact may overestimate the potential for seedling recruitment. Therefore, we tested the effects of light availability on the germination of nine native and two invasive grasses, addressing the production of normal seedlings. Seeds were germinated in the complete absence or the presence of light (12 h photoperiod under white light) for 30 days. Germination was defined as the sum of normal and abnormal seedlings. Eight species were light-dependent, decreasing the production of normal seedlings in the dark. Two native and one invasive species were non-responsive to the dark treatment, showing no change in germination or production of normal seedlings. Our results suggest that seeds buried in the soil seed bank are likely to show reduced germination and develop abnormal seedlings, reinforcing a bottleneck for the recruitment of native grasses. For invasive species, however, the potential of seedling recruitment was minimally reduced by light, suggesting a competitive advantage for the recruitment of these species.

Digitaria exilis is an important indigenous cereal in West Africa. The first fonio reference transcriptome was released and became a key tool for developing new molecular markers contributing to a better understanding of its genetic diversity. A total of 126 new putative primer pairs were successfully designed in 37,327 unigenes from the D. exilis transcriptome. Thirty-seven primer pairs were randomly selected and tested for their ability to cross-amplify to related species. Clear amplification patterns were observed on 24 primer pairs. Of these, 71, 74 and 35% showed polymorphism in three species: D. exilis, D. longiflora and D. iburua. The transferability from D. exilis was 96% to D. longiflora and 71% to D. iburua. The new SSR markers confirmed the close genetic proximity of D. exilis with D. longiflora and its stronger genetic difference of D. exilis from D. iburua. These markers will be valuable for completing future knowledge on Digitaria evolutionary history, and for testing gene flows between related species.

Systemic uptake of organic compounds from roots to leaves follows a Gaussian distribution in relation to the lipophilicity, as measured by the log Kow. Quantification of compound uptake with different lipophilicities, and applied as a seed treatment that diffuses through the seed coat into the embryo during imbibition, has not been reported. The aim of this investigation was to quantify the uptake of non-ionic compounds into seeds of soybean and corn. A series of fluorescent piperonyl amides were synthesized and a novel combinatorial pharmacodynamic technique was developed that provided a range of compounds from log Kow 0.02 to 5.7. Seeds were treated with a mixture of amides, imbibed and compounds chemically extracted and quantified by high-performance liquid chromatography using a fluorescence detector. The maximum uptake efficiency of the applied amide mixture from whole soybean and corn seeds was 67% at log Kow 2.9, and 43% at log Kow 3.4, respectively. The critical partition coefficient for uptake for both species was <4.2 log Kow. Seeds were dissected and separated as soybean embryo and testa, and corn internal tissues (embryo + endosperm) or seed covering layers (pericarp + testa), and >75% of the amides were found in the soybean embryo or corn internal tissues compared with the covering layers at log Kow <4.2. The distribution of amides showed that the corn seed covering layer had similar hydrophilic/lipophilic properties as internal tissues, while soybean tissues had different hydrophilic/lipophilic properties. Collectively, the Gaussian uptake pattern for systemic uptake into plants was not found for either seed species.

Severe leaf blight of Japanese stiltgrass (JSG) from Bipolaris disease, causing significant decline in population density at some locations, has been reported sporadically in the field. Even so, much of the JSG in the mid-Atlantic is not diseased. Six populations of JSG from the field, one that was severely diseased by B. microstegii and the others “healthy,” were tested by artificial inoculation for susceptibility to both B. microstegii (five isolates) and B. drechsleri (three isolates). Populations of JSG in this study differed in their response to the two Bipolaris species, but within species of Bipolaris the plant responses were consistent. Plants from the diseased population of JSG from Frederick, MD, were very susceptible to B. microstegii, and plants from other populations from Maryland (three locations), Delaware, and Indiana were not. In contrast, B. drechsleri caused moderate disease on plants from all accessions but one, and it was significantly less aggressive than was B. microstegii on the susceptible accession of JSG. Results of a limited host range determination only with B. microstegii revealed hypersensitive responses, and therefore high levels of resistance, in corn (four cultivars) and sorghum (three accessions). The native, sympatric grass deertongue was not diseased in these tests. Results reveal a distinct differential response among populations of JSG to disease from B. microstegii, while in contrast, B. drechsleri is capable of causing disease on a broader range of JSG populations.

Bamboo shoots and leaves are valuable food sources for both humans and livestock. The USDA-ARS NPGS (National Plant Germplasm System) collections hold 93 bamboo species in 20 genera. Total leaf protein, amino acid composition and elemental content for these important genetic resources had never been quantified. Lack of nutrition information hinders germplasm utilization. The above-mentioned nutritional traits were evaluated from these 93 species in this study. Leaf protein content among bamboo species ranged from 8.12 to 16.33% with an average of 12.84%. This average was higher than 9.0% observed for switchgrass leaves, but considerably lower than 32.48% in cassava leaves. For 18 quantified amino acids, there was more than a twofold variation among the samples evaluated. For 12 quantified mineral elements, there was significant variability from the low end (4.2-fold, 2.27–9.52 mg/g calcium; 4.4-fold, 56.17–246.43 µg/g sodium) to the high end (61.5-fold, 17.67–1087.0 µg/g manganese; 40.8-fold, 42.0–1713.5 µg/g aluminium). Due to their variability in leaf nutritive value, bamboo species should be carefully chosen when they are used as a feedstock. The results from this study will be useful for the bamboo industry, producers and consumers.

Propagule pressure significantly contributes to and limits the potential success of a biological invasion, especially during transport, introduction, and establishment. Events such as multiple introductions of foreign parent material and gene flow among them can increase genetic diversity in founding populations, often leading to greater invasion success. We applied the tools and theory of population genetics to better understand the dynamics of successful biological invasion. The focal species, cogongrass, is a perennial invasive grass species significantly affecting the Gulf Coast and southeastern region of the United States. The literature indicates separate, allopatric introductions of material from East Asia (Philippines and Japan) into the U.S. states of Mississippi and Alabama. Molecular analysis of samples from those two states utilized amplified fragment length polymorphism (AFLP) markers on 388 individuals from 21 localities. We hypothesized that previously isolated lineages of cogongrass are present and crossing in the Southeast. We observed genetic variation within localities (0.013 ≤ heterozygosity (He) ≤ 0.051, mean = 0.028 ± 0.001) with significant and substantial population structure (FST = 0.534, P < 0.001). Population structure analyses detected two genetically defined and statistically supported populations, which appear to have experienced some admixture. The geographic distribution of those populations was consistent with the two-introduction scenario reported previously. These results are also consistent with contact in the invasive range of previously isolated lineages from the native range.

The study of colonizing and of dominant grass species is essential for prairie conservation efforts. We sought to answer how naturalized Kentucky bluegrass in the northern Great Plains has become successful in the last 20 yr despite its long history in the northern Great Plains. We tested for evidence of geographical differentiation using flow cytometry and microsatellite markers to ascertain the population genetics of Kentucky bluegrass. Across all tested wild populations, high levels of genetic diversity were detected along with moderate levels of structure. Mantel tests of geographical patterns were not significant. Using clonal assignment, we found two major clones that made up the majority of the tested wild populations. When we compared the wild individuals to pedigree cultivars, we found virtually no genetic overlap across all tests, which did not support our hypothesis of developed cultivars contributing to high genetic diversity in natural populations. Furthermore, DNA content tests indicated a narrow range in ploidy in wild populations compared with lawn cultivars, further supporting a hypothesis of divergence between wild and pedigree cultivars. These results indicate the recent invasion of Kentucky bluegrass in the northern Great Plains is not because of adaptation or propagule pressure, but rather likely an environmental or land use shift.

The noctuid stem borer Busseola fusca is an important pest of maize and sorghum in Sub-Saharan Africa. The presence of this species occurred mostly on cultivated than on wild habitats. Busseola fusca is oligophagous having a narrow range of a wild grass species. This might be due, in part, to differences in silicon (Si) content in plant tissues between cultivated and wild grasses. In the present study, we have tested this hypothesis by studying the survival and the relative growth rate (RGR) expressed as daily weight gains of B. fusca larvae on maize and six wild host plants, mostly present in the natural habitat where B. fusca occurred, and correlated with their Si contents. Survival and RGR of B. fusca larvae were considerably higher on maize and wild sorghum than on the other grass species, and they were negatively related to plant Si content. This was corroborated with results on RGR from artificial diets amended with increasing levels of Si. In addition, if Si was added to maize growing substrate B. fusca larval growth was significantly reduced confirming the involvement of Si in B. fusca larvae – Poaceae interactions. The results provide insight into the possible mechanisms of oligophagy of B. fusca and provide a correlative support for a physical role of plant endogenous Si in impeding feeding of B. fusca larvae.

Plant sugars are often considered as primary feeding stimuli, conditioning host plant acceptance by herbivorous insects. Of the nine sugars identified from methanolic extracts of seven grass species, only turanose, a sucrose isomer, was negatively correlated with the survival and growth of the noctuid larva of cereal stemborer, Busseola fusca. Sucrose was the most abundant sugar, although it did not vary significantly in concentration among the plant species studied. Using Styrofoam™ cylinders impregnated with increasing concentrations of turanose or sucrose, the two sugars had opposing effects: turanose appeared phagodeterrent while sucrose was phagostimulatory. Electrophysiological studies indicated that B. fusca larvae were able to detect both sugars via their styloconic sensilla located on the mouthparts. The findings indicate that, whereas sucrose is a feeding stimulant and positively influences food choice by B. fusca larvae, turanose negatively contributes to larval food choice. The balance in concentrations of both sugars, however, somehow influences the overall host plant choice made by the larvae. This can partly explain host plant suitability and choice by this caterpillar pest in the field.

The cereal rust mite, Abacarus hystrix, is one of the most notable among mites causing losses in cultivated grasslands. It is one of a few eriophyoid species for which a broad host range has been reported. Recent studies, however, have shown that host specialization is very likely in this species. For two populations of A. hystrix (one inhabiting perennial ryegrass, the second inhabiting quackgrass), host-associated differences correlated with strong host fidelity, distinct phenotypes and reproductive barriers have been found. In the present study, the ability of wheat colonization by quackgrass- and ryegrass-adapted cereal rust mite was studied. The hypothesis that the potential for wheat colonization by the quackgrass strain is more likely was tested by comparing the colonization performance (assessed by female survival and fecundity) of quackgrass- and ryegrass-associated A. hystrix on their familiar hosts and on wheat. The ryegrass population had no success in wheat colonization (expressed by extremely low fecundity and female survival). Fecundity and survival of quackgrass strain were similar on wheat and the familiar host, or even higher on wheat. Phylogenetic similarity of quackgrass and wheat is discussed as a possible factor that might influence such patterns of host colonization. Since A. hystrix is the only vector of the ryegrass mosaic virus (RgMV), the presented results may be helpful in explaining the inability of RgMV to successfully infest wheat. The conclusions are that (i) quackgrass- and ryegrass-adapted strains of the cereal rust mite have different physiological host ranges and (ii) phylogenetic relationships between host plant species appear to be drivers for host specialization in this mite species.

Surveys were completed in Eritrea, Ethiopia, Kenya, Madagascar, Mozambique, Tanzania, Uganda and Zanzibar to assess the lepidopteran stem borer species diversity on wild host plants. A total of 24,674 larvae belonging to 135 species were collected from 75 species of wild host plants belonging to the Poaceae, Cyperaceae and Typhaceae. Amongst them were 44 noctuid species belonging to at least nine genera, 33 crambids, 15 pyralids, 16 Pyraloidea species not yet identified, 25 tortricids and three cossids. The noctuid larvae represented 73.6% of the total number of larvae collected, with 66.3, 3.5 and 3.8% found on Poaceae, Cyperaceae and Typhaceae, respectively. The Crambidae, Pyralidae, Tortricidae and Cossidae represented 19.8, 1.9, 2.5 and 0.1% of the total larvae collected, respectively, with 90.4% of the Crambidae and Pyralidae collected from Poaceae, and 99.7% of the Tortricidae collected from Cyperaceae. The lepidopteran stem borer species diversity in the wild host plants was far more diverse than previously reported.

A major challenge for the molecular characterization and evaluation of minor grass species germplasm is the lack of sufficient DNA markers. A set of 210 simple sequence repeat (SSR) markers developed from major cereal crops (self-pollinated wheat and rice, mainly self-pollinated sorghum and out-crossing maize) were evaluated for their transferability to minor grass species (finger millet, Eleusine coracana; seashore paspalum, Paspalum vaginatum; and bermudagrass, Cynodon dactylon). In total, 412 cross-species polymorphic amplicons were identified. Over half of the primers generated reproducible cross-species or cross-genus amplicons. The transfer rate of SSR markers was correlated with the phylogenetic relationship (or genetic relatedness) of these species. The average transfer rate of genomic SSR markers was different from the average transfer rate of expressed sequence tag (EST)-SSR markers. The level of polymorphism was significantly higher among species (67%) than within species (34%), and was related to the degree of out-crossing for each species. The level of polymorphism detected within species was 57% from self-incompatible species, 39% from out-crossing species and 20% from self-pollinated species. Genomic SSRs detected a higher level of polymorphism than EST-SSRs. The use of transferred polymorphic SSR markers for the characterization and evaluation of germplasm is discussed.

The diversity of visitors to flowers of the grass Brachiaria ruziziensis R. Germ and Evrard is very low in Ngaoundéré, Cameroon. Bees (Hymenoptera) and syrphids (Diptera) were observed gathering pollen, and each insect group had its own strategy depending on the prevailing environmental conditions. Syrphids are early-morning flower visitors and take time to feed on wet pollen. They visit flowers from 0630 h when the relative humidity is higher than 80% and temperature lower than 25°C. Bees gather dry pollen from 0930 h when the relative humidity is <50% and temperature>30°C, and carry it to the nests for feeding.

Deschampsia antarctica Desv. is one of two vascular plants from the Maritime Antarctic. It is usually exposed to cold, salt, and desiccating winds. We hypothesize that D. antarctica has genes that encode dehydrin proteins and their expression is regulated by low temperature, salt or osmotic stress. To test this hypothesis a fragment of a dehydrin gene from D. antarctica was identified and used as a probe to study dehydrin expression under low temperature, salt, and osmotic stress, and exogenous ABA (abscisic acid) treatments. An anti-dehydrin antibody was also used to study dehydrin protein accumulation under the same treatments. Southern analysis of genomic DNA treated with different endonucleases showed more than four bands recognized by the probe, suggesting that D. antarctica has several dehydrin genes. Northern analysis showed two putative dehydrin transcripts of 1.0 kb accumulated only under exogenous ABA and 1.6 kb under osmotic and salt treatments, suggesting that D. antarctica would have ABA-dependent and - independent pathways for regulation of dehydrin expression. Western analysis showed seven dehydrin proteins (58, 57, 55, 53, 48, 30 and 27 kDa) under the different stress treatments. Cold-accumulated dehydrin proteins were immunolocalized, showing that they are associated with vascular and epidermal tissue, which are preferential ice nucleation zones.

Deschampsia antarctica is a freezing-tolerant plant and the only native Poaceae that grows in the Maritime Antarctic. During the long days of the growing season this plant accumulates sucrose (Suc) in the leaves to 36% of the dry weight. The mechanism that leads to this high accumulation is unknown. The effect of day length and low temperature on sucrose phosphate synthase (SPS) (EC: 2.4.1.14) activity and sugar accumulation was studied in D. antarctica and compared with other Poaceae. Three different day lengths: short (SD) (8/16 h), medium (MD) (16/8 h) and long (LD) (21/3 h); and two temperatures: 4°C (cold-acclimated) and 15°C (non-acclimated) were tested. The highest contents in total soluble sugars (TSS) and Suc were reached in crowns and leaves, respectively, in cold-acclimated plants under LD. TSS and Suc contents and SPS activity with cold acclimation were higher in D. antarctica than in other agricultural (wheat, oat and barley) and non-agricultural (D. caespitosa and D. beringensis) Poaceae species. Suc/TSS ratio was higher in all Deschampsia species than in agricultural Poaceae species. SPS activity and sucrose content in leaves were positively correlated only in LD cold acclimated plants. This result shows that SPS activity is responsive to day length in D. antarctica.

Of the three component organs of the grass leaf – blade, sheath and ligule – the ligule is the least studied and the least understood. Traditionally, it has been assumed to act in a passive way in protecting the culm and leaves that it encloses from the entry of water, dust and harmful spores. However, ultrastructural and cytochemical studies of the membranous ligules of several taxa, particularly Lolium species, have challenged that rather simplistic view and suggest that these ligules play a more active role in the life of the grass plant as a secretory tissue. This review summarizes the evidence for the latter notion, assesses the validity of both the passive and active hypotheses of membranous ligule function and notes similarities between membranous grass ligules, root caps and lycopsid ligules.

Nitrogen (N) allocated to leaf growth in forage grasses and legumes following severe defoliation is predominately mobilized from the remaining root and leaf sheath tissues, since both N uptake from the soil and N2 fixation are severely down-regulated for several days. The hypothesis that a low N reserve status at the time of defoliation limits N remobilization and leaf regrowth was tested with contrasting cultivars of Lolium perenne (cvs Aberelan and Cariad) in flowing solution culture. Plants were grown under ‘high’ or ‘low’ (uptake of N decreased by 50%) regimes of N supply for 10 d before a single severe defoliation. Labelling with 15N was used to assess the importance of N reserves, including putative vegetative storage proteins, relative to N translocated from concurrent uptake, as a source of leaf N during regrowth. Leaf regrowth, N uptake and N mobilization were all affected by previous N supply. Low plant N status at the time of defoliation increased regrowth dry weight of ‘Aberelan’ by 10% and translocation of N absorbed from the medium by 23%, while mobilization of N reserves was decreased by 56%. On the contrary, regrowth dry weight of ‘Cariad’ was decreased by 23%, and translocation of N absorbed by 21% in low plant N status, compared with high plant N status. Concentrations of soluble protein in roots and remaining leaf sheaths decreased after defoliation in plants only under optimal N supply. Analysis of soluble proteins in sheath material by SDS–PAGE suggested that three polypeptides (55, 36.6 and 24 kDa) might function as vegetative storage proteins, although they were of low abundance in plants, subjected to monthly harvests, grown in controlled conditions and in the field. The apparent antagonism between uptake of NH4+ or NO3− by roots and mobilization of N reserves is discussed together with evidence for functional vegetative storage proteins in L. perenne.

Two tetraploid subspecies of Dactylis glomerata L., subsp. reichenbachii (Hausm.) Stebbins et Zohary and subsp. glomerata, occur in the French Alps. The former is confined to dolomitic, south-facing, alpine lawns above 2000 m, whereas the latter occurs in non-dolomitic habitats in subalpine meadows mainly below 1900 m. Previous studies of allozyme variation have shown that genetic introgression between the two subspecies occurs over large areas. By contrast, morphologically intermediate individuals only occur in an extremely narrow area, suggesting that the morphological and physiological differences between the two subspecies is of adaptive significance. A reciprocal clone transplant experiment was set up to examine (1) any genetic differences between subspecies indicative of ecotypic differentiation in relation to habitat characteristics and (2) the level of phenotypic plasticity in the two subspecies. Genetic differentiation was confirmed by a statistically significant taxon × site interaction effect in anova for all traits studied. The glomerata populations produced more tillers, longer leaves and higher culms in all sites, especially in their home environment. However, reichenbachii populations produced more seeds than the glomerata populations in the original reichenbachii environment, suggesting ecotypic differentiation between the two subspecies. This result might also explain why the glomerata subspecies is unable to colonize dolomitic habitats occupied by the reichenbachii subspecies. The reichenbachii populations showed less plasticity than the glomerata populations for leaf length and floriferous tiller number, a result which is discussed in the context of the response of plants from productive and non-productive habitats to environmental variation.

To test the hypothesis that fructan structure can be used as a taxonomic character for the Poaceae we examined the accumulation of the linear, β-2,6-linked fructan series with a terminal glucose residue within the tribes Aveneae and Poeae. Only Dactylis glomerata L. (Poeae) has been shown to contain this series, making it unique among fructan structures and a potential taxonomic marker. To this end, 13 members of the tribes Aveneae and Poeae were surveyed for the presence of this fructan series by comparing extracts of water-soluble carbohydrate by TLC with an extract of D. glomerata. The fructans of four species were similar to those of D. glomerata, as determined by TLC. Further comparison by anion-exchange chromatography and linkage analysis demonstrated that Phalaris aquatica L., Puccinellia stricta (Hook. f.) C. H. Blom and Holcus lanatus L. contained a linear, β-2,6-linked series of fructan with a terminal glucose residue but that Lagurus ovatus L., although containing predominantly β-2,6-linked fructan was composed of more than one series of fructan, one with a terminal glucose residue and one with an internal glucose residue. A linear β-2,6-linked series of fructans with a terminal glucose residue was the dominant fructan accumulated by some species of genera belonging to both the Aveneae (Phalaris and Holcus) and the Poeae (Dactylis and Puccinellia). As both of these tribes also contain genera that accumulate fructans with an internal glucose residue, e.g. Avena and Lagurus (Aveneae) and Lolium (Poeae), structure of fructan cannot be used to distinguish these tribes. Review of the literature, however, showed that it is possible to separate the supertribes Triticodae and Poodae on the basis of the structure of the fructan that they accumulate.