Molecular and morphological phylogenetic analysis of Brachiaria and Urochloa (Poaceae)

The taxonomic relationships of Brachiaria and Urochloa have been questioned based on previous morphological studies. In this paper, we reconsider the phylogenetic relationships of these genera using 22 species of Brachiaria and Urochloa and six species of Paniceae as out-groups. The ITS1, 5.8S, and ITS2 region (internal transcribed spacer) of nuclear ribosomal DNA and eight morphological characters of the inflorescence were compiled into a data matrix. The cladistic analyses suggest that Urochloa-Brachiaria as a complex is paraphyletic with Eriochloa and Melinis. Species of all these genera share molecular synapomorphies and belong to the same monophyletic groups. The results confirm the continuous gradation between those genera previously found in several morphological studies. Therefore, the following eight new combinations are made: Urochloa bovonei (Chiov.) A.M. Torres & C.M. Morton, Urochloa dura (Stapf) A.M. Torres & C.M. Morton, Urochloa dura var. dura (Stapf) A.M. Torres & C.M. Morton, Urochloa dura var. pilosa (J.G. Anderson) A.M. Torres & C.M. Morton, Urochloa lachnantha (Hochst.) A.M. Torres & C.M. Morton, Urochloa leersioides (Hochst.) A.M. Torres & C.M. Morton, Urochloa nigropedata (Munro ex Ficalho & Hiern) A.M. Torres & C.M. Morton, and Urochloa subulifolia (Mez) A.M. Torres & C.M. Morton.     

The grasses Urochloa multiculma and U. fusca (Poaceae) in the Galapagos archipelago

Abstract

Confusion has existed over the validity of the taxon Urochloa multiculma (Andersson) Morrone & Zuloaga, which was originally described from Galapagos, and over the presence in the islands of the closely related U. fusca (Sw.) B.F. Hansen & Wunderlin. An examination of 14 characters in 182 specimens leads to the conclusions that U. multiculma is a valid taxon endemic to Galapagos, and that U. fusca is probably a recent human‐mediated introduction to the archipelago, which may now be hybridising with multiculma. Leaf pubescence and spikelet structure are used to construct an identification key.     

Inflorescence, spikelet, and floral development in Panicum maximum and Urochloa plantaginea (Poaceae)

Inflorescence development in Panicum maximum and Urochloa plantaginea was comparatively studied with scanning electron and light microscopy to test the transfer of P. maximum to Urochloa and to look for developmental features applicable to future cladistic studies of the phosphoenol pyruvate carboxykinase (PCK) subtype of C(4) photosynthesis clade (P. maximum and some species of Brachiaria, Chaetium, Eriochloa, Melinis, and Urochloa). Eleven developmental features not discernable in the mature inflorescence were found: direction of branch differentiation; origins of primary branches; apical vs. intercalary development of the main axis; direction of spikelet differentiation; direction of glume, lemma and palea differentiation; position of the lower glume (in some cases); size of the floret meristem; pattern of distal floret development; pattern of gynoecium abortion; differential pollen development between proximal and distal floret; and glume elongation. Inflorescence homologies between P. maximum and U. plantaginea are also clarified. Panicum maximum and U. plantaginea differ not only in their mature inflorescence structure but also in eight fundamental developmental features that exclude P. maximum from Urochloa. The following developmental events are related to sex expression: size of floret meristem, gynoecium abortion, pollen development delay in the proximal floret, glume elongation and basipetal floret maturation at anthesis.     

GISH-based comparative genomic analysis in Urochloa P. Beauv.

The genus Urochloa P. Beauv. [syn. Brachiaria (Trin.) Griseb.] comprises species of great economic relevance as forages. The genomic constitution for the allotetraploid species Urochloa brizantha (cv. Marandu) and Urochloa decumbens (cv. Basilisk) and the diploid Urochloa ruziziensis was previously proposed as BBB¹B¹, B¹B¹B²B² and B²B², respectively. Evidence indicates U. ruziziensis as the ancestral donor of genome B² in U. decumbens allotetraploidy, but the origin of the genomes B and B¹ is still unknown. There are diploid genotypes of U. brizantha and U. decumbens that may be potential ancestors of the tetraploids. The aim of this study was to determine the genomic constitution and relationships between genotypes of U. brizantha (2x and 4x), U. decumbens (2x and 4x) and U. ruziziensis (2x) via genomic in situ hybridization (GISH). Additionally, chromosome number and genome size were verified for the diploid genotypes. The diploids U. brizantha and U. decumbens presented 2n?=?2x?=?18 chromosomes and DNA content of 1.79 and 1.44 pg, respectively. The GISH analysis revealed high homology between the diploids U. brizantha and U. decumbens, which suggests relatively short divergence time. The GISH using genomic probes from the diploid accessions on the tetraploid accessions’ chromosomes presented similar patterns, highlighting the genome B¹ present in both of the tetraploids. Based on GISH results, the genomic constitution was proposed for the diploid genotypes of U. brizantha (B¹B¹) and U. decumbens (B¹′B¹′) and both were pointed as donors of genome B¹ (or B¹′), present in the allotetraploid genotypes.

     

Anther development in Brachiaria brizantha (syn. Urochloa brizantha) and perspective for microspore in vitro culture

Protoplasma - Brachiaria, a genus from the Poaceae family, is largely cultivated as forage in Brazil. Among the most cultivated varieties of Brachiaria spp., B. brizantha cv. Marandu (syn. Urochloa...     

Aluminum tolerance measured by root growth and mucilage protection in Urochloa brizantha and Urochloa decumbens

Aluminum toxicity on root systems was analyzed through comparing root growth and evaluating the protective function of mucilage in Urochloa decumbens and Urochloa brizantha. Seedlings were grown in a solution with different concentrations of AlCl₃ and with mucilage removed or present. The root elongation rate, total length, number of roots and presence of aluminum at the root apex were measured. Root development was inhibited by aluminum and the elongation rate was maintained without any difference between the two species. A significant reduction in root length was found in U. brizantha. Aluminum did not influence root branching in either species and accumulated mostly in the rhizosphere of U. brizantha, where the mucilage has less of a protective function. The greatest aluminum tolerance was found in U. decumbens, observed through maintenance of total root system growth from lower to higher aluminum toxicity.     

Chemical Characterization and Phytotoxic Effects of the Aerial Parts of Ruzigrass (Urochloa ruziziensis)

Studies of the phytotoxic effects between plants can be a crucial tool in the discovery of innovative compounds with herbicide potential. In this sense, we can highlight ruzigrass (Urochloa ruziziensis), which is traditionally used in the crop rotation system in order to reduce weed emergence. The aim of this work was to characterize the secondary metabolites of ruzigrass and to evaluate its phytotoxic effects. In total, eight compounds were isolated: friedelin, oleanolic acid, α‐amyrin, 1‐dehydrodiosgenone, sitosterol and stigmasterol glycosides, tricin and p‐coumaric acid. Phytotoxic effects of the crude methanolic extract and fractions of ruzigrass were assessed using germination rate, initial seedling growth, and biomass of Bidens pilosa, Euphorbia heterophylla and Ipomoea grandifolia. Chemometric analysis discriminated the weed species into three groups, and B. pilosa was the most affected by fractions of ruzigrass. The phytotoxic activities of 1‐dehydrodiosgenone, tricin, and p‐coumaric acid are also reported, and p‐coumaric acid and 1‐dehydrodiosgenone were active against B. pilosa.     

Epigenetic Marks Associated to the Study of Nucleolar Dominance in Urochloa P. Beauv.

The genus Urochloa P. Beauv. presents a prominent role in the tropical agricultural scenario being composed of species with different ploidy levels. Studies on the genomic relationship within this genus as well as specific analysis involving epigenetic marks are limited. The aim of the present study was to identify the cytosine methylation (5-mCyt) and histone H3 lysine 9 dimethylation (H3k9me2) in the different modulations of 45S ribosomal DNA (rDNA) sites in interphase nuclei and to associate these results with gene expression analysis in Urochloa ruziziensis (2n = 4x = 36), Urochloa brizantha cv. Marandu (2n = 4x = 36), and their respective interspecific hybrid H1863 (2n = 4x = 36). Immunolocalization techniques were performed in combination with Fluorescence in situ hybridization (FISH) for the location of the 45S rDNA sites. Predominantly, we observed intra- and perinucleolar sites, mostly hypomethylated and/or hyper/hypomethylated, decondensed or partially condensed. The gene expression analysis was performed qualitatively through the conventional PCR using complementary DNA and confirmed by the RT-qPCR technique and primers designed for the ITS-1 region of U. brizantha and U. ruziziensis. The molecular analyses performed on leaves showed that there is dominance of U. brizantha 45S rDNA gene expression on U. ruziziensis in the H1863 hybrid. In roots, the analyses showed that the 45S rDNA genes of the two parents are expressed in the hybrid genome. Thus, it is plausible to infer a tissue-specific nuclear dominance model in which the pattern of hypermethylated cytosine sites with heterochromatic marks and, therefore, silenced were mostly inherited from U. ruziziensis, whereas the rDNA originated from U. brizantha was characterized by cytosine and H3k9 hypomethylation.

     

A New Species of Rhynchohyalus from the Southeastern Pacific Ocean with Notes on R. natalensis (Opisthoproctidae)

Journal of Ichthyology - A new species Rhynchohyalus parbevs sp. nov. from the Southeast Pacific, which differs from R. natalensis in the greater number of gill rakers, the relative...     

Effects of the exotic macrophyte, para grass (Urochloa mutica), on benthic and epiphytic macroinvertebrates of a tropical floodplain

1. We examined the effect of the exotic macrophyte, para grass (Urochloa mutica), on benthic and epiphytic macroinvertebrates of a tropical floodplain in northern Australia. Macroinvertebrates were sampled from four grass communities: (1) para grass, (2) hymenachne (Hymenachne acutigluma), a native perennial; (3) rice (Oryza meridionalis), a native annual, and (4) areas where para grass had been sprayed with herbicide. 2. Macroinvertebrate richness, abundance and community similarity showed very few differences among the grass communities, particularly in the epiphytic habitat. Benthic invertebrates showed some differences among grasses, with lower richness and abundance and different community structure associated with hymenachne. Herbicide control of para grass had no apparent effect on benthic invertebrates but reduced the abundance of epiphytic invertebrates in the short term. 3. The results of this study indicate that para grass has very little impact on macroinvertebrate communities, despite the changes to macrophyte communities. This is probably because para grass has similar physical structure to the native grasses and because none of these grasses contribute directly to aquatic food webs. Control of para grass using herbicide has little impact on aquatic invertebrates. This suggests that predicting the impact of weed invasion in wetlands requires an understanding of both the functional properties of macrophytes and the habitat preferences of the macroinvertebrates.     

Early growth of Brazilian tree Dimorphandra wilsonii is also threatened by African grass Urochloa decumbens

The conversion of the Brazilian savannas for pastures and agricultural use has caused the species Dimorphandra wilsonii (Fabaceae-Caesalpinioideae) to become isolated and restricted to areas occupied by African grasses of Urochloa sp. This highly endangered tree species was cultivated in the presence of Bradyhizobium japonicum (symbiont 1), Glomus etunicatum (symbiont 2), and Urochloa decumbens in low nitrogen (N) availability in order to evaluate its growth in these experimental conditions. Even though the nodulation and mycorrhization was of low occurrence, the inoculated plants with symbionts had the greatest nitrogen and chlorophyll content, photosynthetic radiation use efficiency, and biomass accumulation in relation to the plants which had not been inoculated and/or cultivated in the presence of U. decumbens. The results suggest effective N₂ fixation, independent of the localization of bacteria, whether in the root tissue interior or free in the rhizosphere. Therefore, the presence of N₂-fixing bacteria can benefit the early growth of D. wilsonii, whereas the occurrence and aggressive persistence of U. decumbens can limit this development, increasing the threat of extinction of this species in their habitat.     

An integrative insight on dormancy alleviation in diaspores of Urochloa humidicola (Rendle) Morrone & Zuloaga,a tropical grass with great economic and ecological impact

• Even though exhaustively studied, dormancy alleviation in diaspores of Urochloa humidicola (Rendle) Morrone & Zuloaga remains a mystery. To clarify this, we asked the following question: could dormancy alleviation in diaspores of this species be associated with ageing, GA/ABA balance and remaining structures of the panicoid spikelet?
• We answer this question using diaspores of U. humidicola cv. BRS Tupi as a biological model, a cultivar with a wide edaphoclimatic range in Neotropical areas and whose diaspores possess ‘deep dormancy’ when dispersed. We analysed both germination and early plant development using a split‐plot model.
• Our findings demonstrate that dormancy alleviation in diaspores of U. humidicola is a synergic phenomenon driven by crosstalk between age, GA/ABA balance and remaining structures of the panicoid spikelet covering caryopses, since this interaction acts on the dynamics of germination and early plant development.
• We demonstrate that: (i) spreading germination time is a maternal survival mechanism of this species, which has repercussions for occupational aggressiveness of the species; (ii) remaining structures of the panicoid spikelet covering caryopses are the main modulator of embryo development. These structures control the after‐ripening process, which is modulated by some molecular factor. We also highlight that it is necessary to review concepts about dormancy of dispersal units in this grass species.

     

Genetic diversity of Oxytropis section Xerobia (Fabaceae) in one of the centres of speciation

Genetica - The genetic diversity and phylogenetic relationships of Oxytropis caespitosa, O. grandiflora, O. eriocarpa, O. mixotriche, O. nitens,...     

A cytogenetic study of R. constantinopolitanus and R. sericeus (Ranunculaceae) in Iran

With 600 species Ranunculus is the largest genus in Ranunculaceae, and has a broad global distribution. We studied the karyotypes of R. constantinopolitanus and R. sericeus species of Ranunculaceae and identified their symmetry level. New chromosome numbers of 2n = 21 (Nodeh woods population) and 2n ca. 63 (Javaherdeh population) are reported for R. constantinopolitanus. Two different populations of R. sericeus had two different chromosome results. We investigated morphological and karyological studies along with pollens micromorphology. Different populations of R. constantinopolitanus and R. sericeus, with different chromosome numbers showed morphological and micromorphological differences. Therefore, we considered the two populations of R. sericeus as cytotypes. There was a correlation between the studied morphological characters and pollen size with ploidy levels in the two R. constantinopolitanus populations.     

Low-temperature (77 K) phosphorescence of triplet chlorophyll in isolated reaction centers of photosystem II

Photosynthesis Research - Phosphorescence characterized by the main emission band at 952 ± 1 nm (1.30 eV), the lifetime of...     

New microsatellite markers developed from <Emphasis Type="Italic">Urochloa humidicola</Emphasis> (Poaceae) and cross amplification in different <Emphasis Type="Italic">Urochloa</Emphasis> species

Background

Urochloa humidicola is a forage grass that grows in tropical regions and is recognized for its tolerance to seasonal flooding. It is a polyploid and apomictic species with high phenotypic plasticity. As molecular tools are important in facilitating the development of new cultivars and in the classification of related species, the objectives of this study were to develop new polymorphic microsatellite markers from an enriched library constructed from U. humidicola and to evaluate their transferability to other Urochloa species.

Findings

Microsatellite sequences were identified from a previously constructed enriched library, and specific primers were designed for 40 loci. Isolated di-nucleotide repeat motifs were the most abundant followed by tetra-nucleotide repeats. Of the tested loci, 38 displayed polymorphism when screened across 34 polyploid Urochloa sp. genotypes, including 20 accessions and six hybrids of U. humidicola and two accessions each from U. brizantha, U. dictyoneura, U. decumbens and U. ruziziensis. The number of bands per Simple Sequence Repeat (SSR) locus ranged from one to 29 with a mean of 11.5 bands per locus. The mean Polymorphism Information Content (PIC) of all loci was 0.7136, and the mean Discrimination Power (DP) was 0.7873. Six loci amplified in all species tested. STRUCTURE analysis revealed six different allelic pools, and the genetic similarity values analyzed using Jaccard's coefficient ranged from 0.000 to 0.913.

Conclusions

This work reports new polymorphic microsatellite markers that will be useful for breeding programs for Urochloa humidicola and other Urochloa species as well as for genetic map development, germplasm characterization, evolutionary and taxonomic studies and marker-assisted trait selection.

     

Henneguya michiganensis n. sp. (Cnidaria: Myxosporea) from the gills of muskellunge Esox masquinongy Mitchill(Esociformes: Esocidae)

Systematic Parasitology - Henneguya Thélohan, 1892&nbsp;is the second most species rich genus of myxozoans, with reports from freshwater and marine fish worldwide. In the Great Lakes...     

Photosynthesis in phosphoenolpyruvate carboxykinase-type C4 plants: photosynthetic activities of isolated bundle sheath cells from Urochloa panicoides

A method has been developed for rapidly preparing bundle sheath cell strands from Urochloa panicoides, a phosphoenolpyruvate (PEP) carboxykinase-type C4 plant. These cells catalyzed both HCO3(-)- and oxaloacetate-dependent oxygen evolution; oxaloacetate-dependent oxygen evolution was stimulated by ATP. For this activity oxaloacetate could be replaced by aspartate plus 2-oxoglutarate. Both oxaloacetate- and aspartate plus 2-oxoglutarate-dependent oxygen evolution were accompanied by PEP production and both were inhibited by 3-mercaptopicolinic acid, an inhibitor of PEP carboxykinase. The ATP requirement for oxaloacetate- and aspartate plus 2-oxoglutarate-dependent oxygen evolution could be replaced by ADP plus malate. The increased oxygen evolution observed when malate plus ADP was added with oxaloacetate was accompanied by pyruvate production. These results are consistent with oxaloacetate being decarboxylated via PEP carboxykinase. We suggest that the ATP required for oxaloacetate decarboxylation via PEP carboxykinase may be derived by phosphorylation coupled to malate oxidation in mitochondria. These bundle sheath cells apparently contain diffusion paths for the rapid transfer of compounds as large as adenine nucleotides.     

Evidence of Allopolyploidy in Urochloa humidicola Based on Cytological Analysis and Genetic Linkage Mapping

The African species Urochloa humidicola (Rendle) Morrone & Zuloaga (syn. Brachiaria humidicola (Rendle) Schweick.) is an important perennial forage grass found throughout the tropics. This species is polyploid, ranging from tetra to nonaploid, and apomictic, which makes genetic studies challenging; therefore, the number of currently available genetic resources is limited. The genomic architecture and evolution of U. humidicola and the molecular markers linked to apomixis were investigated in a full-sib F₁ population obtained by crossing the sexual accession H031 and the apomictic cultivar U. humidicola cv. BRS Tupi, both of which are hexaploid. A simple sequence repeat (SSR)-based linkage map was constructed for the species from 102 polymorphic and specific SSR markers based on simplex and double-simplex markers. The map consisted of 49 linkage groups (LGs) and had a total length of 1702.82 cM, with 89 microsatellite loci and an average map density of 10.6 cM. Eight homology groups (HGs) were formed, comprising 22 LGs, and the other LGs remained ungrouped. The locus that controls apospory (apo-locus) was mapped in LG02 and was located 19.4 cM from the locus Bh027.c.D2. In the cytological analyses of some hybrids, bi- to hexavalents at diakinesis were observed, as well as two nucleoli in some meiocytes, smaller chromosomes with preferential allocation within the first metaphase plate and asynchronous chromosome migration to the poles during anaphase. The linkage map and the meiocyte analyses confirm previous reports of hybridization and suggest an allopolyploid origin of the hexaploid U. humidicola. This is the first linkage map of an Urochloa species, and it will be useful for future quantitative trait locus (QTL) analysis after saturation of the map and for genome assembly and evolutionary studies in Urochloa spp. Moreover, the results of the apomixis mapping are consistent with previous reports and confirm the need for additional studies to search for a co-segregating marker.     

Infraspecific chemical variability in the essential oils of Pimenta pseudocaryophyllus (Gomes) L.R. Landrum (Myrtaceae)

Leaf essential oils of Pimenta pseudocaryophyllus from the central Brazilian Cerrado were obtained by hydrodistillation and investigated by GC and GC–MS. A total of 57 constituents were identified, accounting for 96–100% of the volatile constituents. Principal component and cluster analysis identified three chemotypes: cluster I, characterized by high percentages of geranial (41.2 +/? 3.9%), neral (26.8 +/? 1.3%), caryophyllene oxide (3.8 +/? 2.5%), and spathulenol (3.7 +/? 1.8%); cluster II, with high contents of (E)-asarone (21.8 +/? 30.9%), (E)-caryophyllene (16.2 +/? 7.7%), and elemicin (8.8 +/? 2.4%); and cluster III, with high amounts of (E)-methyl isoeugenol (93.2 +/? 1%). The occurrence of these chemotypes at the same site indicates that chemovariation is genetically determined.