Molecular evidence of symbiotic activity between <Emphasis Type="Italic">Symbiodinium</Emphasis> and <Emphasis Type="Italic">Tridacna maxima</Emphasis> larvae

Dinoflagellates in the genus Symbiodinium (zooxanthellae) provide the photosynthesis that sustains the majority of primary production in coral reefs. They occur symbiotically with several phyla, including mollusks such as giant clams (Tridacna spp.). This mutualistic association is obligatory for the giant clams, but the exact point in which this symbiosis is established and the main translocated photosynthate are unknown. In this study, we tracked the expression of specific genes for symbiosis and glycerol synthesis during a time course experiment. Giant clam larvae were raised until 75 h post-fertilization and then infected with cultured isolates of Symbiodinium clade A3. Expression of symbiosis-specific and housekeeping genes was monitored at four time points. The expression of H⁺-ATPase, a symbiosis-specific gene in Symbiodinium, was observed at 24 h after symbiont acquisition by the clam larvae. The expression of an enzyme responsible for glycerol synthesis was also observed. Together, these results show that the symbiotic relationship was already in place 24 h after Symbiodinium acquisition, during veliger larval stage. This is the first report using a molecular symbiosis-specific marker that supports symbiotic activity between Symbiodinium and a metazoan larva of an organism that acquires symbionts horizontally. From the expression of the glycerol-synthesizing gene, it was qualitatively determined that Symbiodinium cells may produce glycerol regardless of whether they are free-living or in symbiosis.     

Phylogenetic analyses of <Emphasis Type="Italic">Symbiodinium</Emphasis> isolated from <Emphasis Type="Italic">Waminoa</Emphasis> and their anthozoan hosts in the Ryukyu Archipelago,southern Japan

It is known that the genus Waminoa (order Acoela, Family Convolutidae) associates with anthozoans (Scleractinia, Octocorallia, Zoantharia) and feeds on the mucus of their host. Despite the close relationship between Waminoa and its host species, it is known from phylogenetic analyses of sequences of the internal transcribed spacer 2 of ribosomal DNA (ITS-2) that photosymbiotic Symbiodinium isolated from Waminoa are different from the Symbiodinium of their anthozoan hosts. Additionally, Waminoa inherit their Symbiodinium and Amphidinium via vertical transmission. In the current study, we looked for and collected Waminoa from different anthozoan hosts from the Ryukyu Archipelago in southern Japan, and then examined the Symbiodinium of Waminoa as well as hosts’ Symbiodinium, and utilized sequences of the hyper-variable non-coding region of the plastid minicircle (psbA^ncr) in order to re-examine the diversity of Symbiodinium within Waminoa. In the resulting psbA^ncr phylogenetic tree, all Symbiodinium within Waminoa comprised a unique group within Clade C, all with the same genotype in the psbA^ncr phylogenetic tree. Our results reconfirm that most Waminoa host their own lineage of Symbiodinium, and demonstrate that Waminoa are also found on azooxanthellate anthozoan hosts, as we found Waminoa on Siphonogorgia sp., expanding their potential known habitat. Additionally, two Symbiodinium from Waminoa from both shallow (4 m) and mesophotic (32 m) depths were not included in main group of Symbiodinium from Waminoa in the ITS-2 phylogenetic tree, although we could not acquire psbA^ncr sequences for these specimens. Therefore it is possible that undetected Symbiodinium diversity may yet exist within Waminoa, and future work at shallow to mesophotic depths examining both zooxanthellate and azooxanthellate hosts may find more Waminoa and Symbiodinium diversity.     

Nitrification in intertidal sponge <Emphasis Type="Italic">Cinachyrella cavernosa</Emphasis>

The nitrification process in different sections of the sponges remains unresolved, despite several studies on the nitrogen cycling pathways in the tissues of temperate and Arctic sponges. In this study, the abundance, diversity and activity of the associated nitrifying organisms in intracellular, intercellular, extracellular and cortex of a tropical intertidal sponge, Cinachyrella cavernosa, were investigated using most probable number, next-generation sequencing and incubation method, respectively. The nitrification rate and the abundance of nitrifying bacteria showed significant difference among different sections. The nitrification rate in C. cavernosa was 2–12× higher than the reported values in other sponge species from temperate and Arctic regions. Nitrification rate in sponge cortex was 2× higher than in intercellular and extracellular sections. Ammonium and nitrite oxidisers ranged from 10³ to 10⁴ CFU g^?1 in the sponge with a high number of ammonium and nitrite oxidisers in the cortex. Nitrifiers belonging to Nitrosomonas, Nitrospira, Nitrospina, Nitrobacter and Nitrosopumilus were present in different sections of the sponge, with nitrifying archaea dominating the intracellular section and nitrifying bacteria dominating other sections. This study reports for the first time the nitrification inside the sponge cells. The study also suggests that the intertidal sponge, C. cavernosa, harbours metabolically active nitrifiers in different sections of the sponge body with different rates of nitrification. Thus, nitrifiers play an important role in ammonia detoxification within the sponge and also contribute to the nitrogen budget of the coastal ecosystem.     

<Emphasis Type="Italic">Megaviridae</Emphasis>-like particles associated with <Emphasis Type="Italic">Symbiodinium</Emphasis> spp. from the endemic coral <Emphasis Type="Italic">Mussismilia braziliensis</Emphasis>

Coral reefs are one of the most dynamic and productive marine ecosystems. The coral holobiont consists of the coral animal and a variety of associated microorganisms that include symbiotic dinoflagellates of the genus Symbiodinium, bacteria, archaea, fungi and viruses. The interactions among these components are crucial for coral health and, consequently, to the coral reef resilience to disturbance. Environmental stressors such as elevated temperature, high irradiance and ultraviolet (UV) radiation can lead to the breakdown of the coral-Symbiodinium symbiosis in a phenomenon known as “coral bleaching”. The present study provides evidence for virus-like particles (VLPs) induced in UV-irradiated Symbiodinium spp. cultures (clades A and C) that were isolated from the coral Mussismilia braziliensis, suggesting a latent viral infection in these strains. Scanning and transmission electron microscopy images of the UV stressed cultures revealed the presence of giant (ca. 450 nm) and small (ca. 40 nm) VLPs. Morphological features link the giant VLPs to the family Megaviridae. Symbiodinium spp. Megaviridae giant viruses and other associated viruses may represent dynamic forces driving and influencing health of the coral holobiont.     

Genetic diversity of free-living <Emphasis Type="Italic">Symbiodinium</Emphasis> in the Caribbean: the importance of habitats and seasons

Although reef corals are dependent of the dinoflagellate Symbiodinium, the large majority of corals spawn gametes that do not contain their vital symbiont. This suggests the existence of a pool of Symbiodinium in the environment, of which surprisingly little is known. Reefs around Curaçao (Caribbean) were sampled for free-living Symbiodinium at three time periods (summer 2009, summer 2010, and winter 2010) to characterize different habitats (water column, coral rubble, sediment, the macroalgae Halimeda spp., Dictyota spp., and Lobophora variegata, and the seagrass Thalassia testudinum) that could serve as environmental sources of symbionts for corals. We detected the common clades of Symbiodinium that engage in symbiosis with Caribbean coral hosts A, B, and C using Symbiodinium-specific primers of the hypervariable region of the chloroplast 23S ribosomal DNA gene. We also discovered clade G and, for the first time in the Caribbean, the presence of free-living Symbiodinium clades F and H. Additionally, this study expands the habitat range of free-living Symbiodinium as environmental Symbiodinium was detected in T. testudinum seagrass beds. The patterns of association between free-living Symbiodinium types and habitats were shown to be complex. An interesting, strong association was seen between some clade A sequence types and sediment, suggesting that sediment could be a niche where clade A radiated from a free-living ancestor. Other interesting relationships were seen between sequence types of Symbiodinium clade C with Halimeda spp. and clades B and F with T. testudinium. These relationships highlight the importance of some macroalgae and seagrasses in hosting free-living Symbiodinium. Finally, studies spanning beyond a 1-yr cycle are needed to further expand on our results in order to better understand the variation of Symbiodinium in the environment through time. All together, results presented here showed that the great diversity of free-living Symbiodinium has a dynamic distribution across habitats and time.     

Molecular evidence for hybridization between invasive <Emphasis Type="Italic">Solidago canadensis</Emphasis> and native <Emphasis Type="Italic">S</Emphasis>. <Emphasis Type="Italic">virgaurea</Emphasis>

Hybridization between alien and native species is biologically very important and could lead to genetic erosion of native taxa. Solidago × niederederi was discovered over a century ago in Austria and described by Khek as a natural hybrid between the alien (nowadays regarded also as invasive) S. canadensis and native S. virgaurea. Although interspecific hybridization in the genus Solidago is considered to be relatively common, hybrid nature of S. × niederederi has not been independently proven using molecular tools, to date. Because proper identification of the parentage for the hybrid Solidago individuals solely based on morphological features can be misleading, in this paper we report an additive polymorphism pattern expressed in the ITS sequences obtained from individuals representing S. × niederederi, and confirm the previous hypothesis that the parental species of this hybrid are S. canadensis and S. virgaurea. Additionally, based on variability at the cpDNA rpl32-trnL locus, we showed that in natural populations hybridization occurs in both directions.     

Distribution and habitats of <Emphasis Type="Italic">Phengaris</Emphasis> (<Emphasis Type="Italic">Maculinea</Emphasis>) butterflies and population ecology of <Emphasis Type="Italic">Phengaris</Emphasis><Emphasis Type="Italic">teleius</Emphasis> in China

Many species of the butterfly genus Phengaris are regarded as endangered in many parts of their distribution. Several species are also widely distributed across northern China. Due to land use change and overgrazing, their habitats are declining and many patches have been lost. This paper investigates the distribution and habitats of the Chinese Phengaris species (of the subgenus Maculinea). Shrub-grassland near forests seem the most frequent habitat for Phengaris, while flat open grasslands are mostly over-grazed and thus survival for Phengaris butterflies there seems difficult. Throughout Europe, P. teleius is an endangered species, while there is still no information on its status in China. To improve the knowledge on the population ecology of P. teleius, its population structure, adult behaviour and movement were studied through mark–release–recapture methods in the Qinling Mountains of Taibai County. Eight grassland patches which were potentially suitable were found in the area in 2013. In total, 480 individuals (274 females) were marked, resulting in an overall recapture rate of 16 %. The average daily population size was 44 butterflies (±23 SD) during the adult flight period. Sixty-seven percent of the females and 38 % of the males moved less than 50 m, and 17 % of recaptured females and 38 % of males moved more than 200 m. The mean movement distance was 107 ± 177 m for males and 182 ± 122 m for females. The majority of the recaptures (86 %) were made within the patches, only a few individuals (14 %) moved between patches. Due to human disturbance and destruction, all of the eight potentially suitable patches are becoming smaller and increasingly isolated, thus these populations of P. teleius may face an increasing risk of extinction, which may well be a tip of the iceberg of habitat loss and fragmentation of P. teleius in Taibai County and possibly beyond. Hence we hope our initial study of P. teleius could have positive impacts on the conservation of Phengaris butterflies in China.     

Complete chloroplast genome sequence of <Emphasis Type="Italic">Capsicum</Emphasis><Emphasis Type="Italic">baccatum</Emphasis> var. <Emphasis Type="Italic">baccatum</Emphasis>

Molecular markers derived from the complete chloroplast genome can provide effective tools for species identification and phylogenetic resolution. Complete chloroplast (cp) genome sequences of Capsicum species have been reported. We herein report the complete chloroplast genome sequence of Capsicum baccatum var. baccatum, a wild Capsicum species. The total length of the chloroplast genome is 157,145 bp with 37.7 % overall GC content. One pair of inverted repeats, 25,910 bp in length, was separated by a small single-copy region (17,974 bp) and large single-copy region (87,351 bp). This region contains 86 protein-coding genes, 30 tRNA genes, 4 rRNA genes, and 11 genes contain one or two introns. Pair-wise alignments of chloroplast genome were performed for genome-wide comparison. Analysis revealed a total of 134 simple sequence repeat (SSR) motifs and 282 insertions or deletions variants in the C. baccatum var. baccatum cp genome. The types and abundances of repeat units in Capsicum species were relatively conserved, and these loci could be used in future studies to investigate and conserve the genetic diversity of the Capsicum species.     

Association between <Emphasis Type="Italic">cagA</Emphasis>, <Emphasis Type="Italic">vacAi</Emphasis>, and <Emphasis Type="Italic">dupA</Emphasis> genes of <Emphasis Type="Italic">Helicobacter pylori</Emphasis> and gastroduodenal pathologies in Chilean patients

In addition to the already known cagA gene, novel genetic markers have been associated with Helicobacter pylori (H. pylori) virulence: the dupA and vacAi genes. These genes might play an important role as specific markers to determine the clinical outcome of the disease, especially the vacAi gene, which has been expected to be a good marker of severe pathologies like gastric adenocarcinoma. In the present study, the association of cagA, dupA, and vacAi genes with gastroduodenal pathologies in Chilean patients was studied. One hundred and thirty-two patients positive for H. pylori were divided into two groups—non-severe and severe gastric pathologies—and investigated for the presence of cagA, dupA, and vacAi H. pylori virulence genes by PCR. The cagA gene was detected in 20/132 patients (15.2%), the vacAi1 gene was detected in 54/132 patients (40.9%), the vacAi2 gene was detected in 26/132 patients (19.7%), and the dupA gene was detected in 50/132 (37.9%) patients. Logistic regression model analysis showed that the vacAi1 isoform gene in the infected strains and the severity of the diseases outcome were highly associated, causing severe gastric damage that may lead to gastric cancer (p < 0.0001; OR = 8.75; 95% CI 3.54–21.64). Conversely, cagA (p = 0.3507; OR = 1.62; 95% CI 0.59–4.45) and vacAi2 (p = 0.0114; OR = 3.09; 95% CI 1.26–7.60) genes were not associated with damage, while the dupA gene was associated significantly with non-severe clinical outcome (p = 0.0032; OR = 0.25; 95% CI 0.09–0.65). In addition, dupA gene exerts protection against severe gastric pathologies induced by vacAi1 by delaying the outcome of the disease by approximately 20 years.     

Regional chronologies of <Emphasis Type="Italic">Cedrela</Emphasis><Emphasis Type="Italic">fissilis</Emphasis> and <Emphasis Type="Italic">Cedrela angustifolia</Emphasis> in three forest types and their relation to climate

Key message

Although tree-ring chronologies of Cedrela fissilis and Cedrela angustifolia showed a common climatic signal, local conditions influence growth, suggesting that forest guidelines should be appropriate to the species and context.

Abstract

Cedrela species are highly valued because of the quality of their timber. Understanding the behaviour of each different Cedrela species and their ecology is of importance to ensuring that forest harvesting and management do not endanger the survival of natural populations. These species grow in a wide range of environmental gradients and different types of forests in Bolivia. This study used dendrochronological methods to analyse growth–precipitation relationships of two Cedrela species coming from three locations with different environmental conditions: dry Chiquitano (Concepción), Chiquitano transitional Amazonian (Guarayos), and Bolivian-Tucuman montane forests (Postrervalle). The rainy season in all locations runs from October to April and the dry season runs from May to September. Twelve Cedrela fissilis specimens were sampled from dry Chiquitano, 11 Cedrela fissilis specimens from Chiquitano transitional Amazonian, and 30 Cedrela angustifolia specimens from Bolivian-Tucuman montane forests. The samples were crossdated and exhibited a common signal between trees from three sites, despite tree rings from the Chiquitano transitional Amazonian forest being narrower and displaying blurred bands of parenchyma in the boundaries. Significant inter-series correlation was found for the C. fissilis species series from dry Chiquitano with r = 0.261 (p < 0.01) and Chiquitano transitional Amazonian forests with r = 0.284 (p < 0.01), and for Cedrela angustifolia from Bolivian-Tucuman montane forests with r = 0.374 (p < 0.01). Mean annual growth was 2.07, 1.92, and 2.82 mm year^?1 at the three sites, respectively. Cedrela species from dry Chiquitano and Bolivian-Tucuman montane forests were sensitive to precipitation from October to April of the current growth year (wettest season) and to low temperatures from May to July of the current growth year (driest season). Samples from Chiquitano transitional Amazonian were more sensitive to precipitation during late rainy season (March, April, and May of the current growth year) and high temperatures during the rainy months (November–December). Growth differences between sites and species in response to climate variations and local conditions should be taken into account and handled with different forest management guidelines.

     

<Emphasis Type="Italic">Metschnikowia</Emphasis> mating genomics

Genes involved in mating type determination and recognition were examined in Metschnikowia and related species, to gather insights on factors affecting mating compatibility patterns among haplontic, heterothallic yeast species of the genus. We confirmed the universality of the special mating locus organisation found in Clavispora lusitaniae across and exclusive to the family Metschnikowiaceae (i.e., Metschnikowia and Clavispora). Timing of the divergence between idiomorphs was confirmed to coincide with the origin of the larger (CUG-ser) clade comprising the Debaryomycetaceae and the Metschnikowiaceae, exclusive of Cephaloascus fragrans. The sequence of the a mating pheromone is highly conserved within the large-spored Metschnikowia species, including Metschnikowia orientalis and Metschnikowia hawaiiana, but not Metschnikowia drosophilae or Metschnikowia torresii, which have a pattern of their own, as do other clades in the genus. In contrast, variation in α pheromones shows a more continuous, although imperfect correlation with phylogenetic distance as well as with in vivo mating compatibility.     

Usefulness of the Non-conventional <Emphasis Type="Italic">Caenorhabditis elegans</Emphasis> Model to Assess <Emphasis Type="Italic">Candida</Emphasis> Virulence

Invasive candidiasis is caused mainly by Candida albicans, but other Candida species have increasing etiologies. These species show different virulence and susceptibility levels to antifungal drugs. The aims of this study were to evaluate the usefulness of the non-conventional model Caenorhabditis elegans to assess the in vivo virulence of seven different Candida species and to compare the virulence in vivo with the in vitro production of proteinases and phospholipases, hemolytic activity and biofilm development capacity. One culture collection strain of each of seven Candida species (C. albicans, Candida dubliniensis, Candida glabrata, Candida krusei, Candida metapsilosis, Candida orthopsilosis and Candida parapsilosis) was studied. A double mutant C. elegans AU37 strain (glp-4;sek-1) was infected with Candida by ingestion, and the analysis of nematode survival was performed in liquid medium every 24 h until 120 h. Candida establishes a persistent lethal infection in the C. elegans intestinal tract. C. albicans and C. krusei were the most pathogenic species, whereas C. dubliniensis infection showed the lowest mortality. C. albicans was the only species with phospholipase activity, was the greatest producer of aspartyl proteinase and had a higher hemolytic activity. C. albicans and C. krusei caused higher mortality than the rest of the Candida species studied in the C. elegans model of candidiasis.     

The ectomycorrhizae of <Emphasis Type="Italic">Lactarius rimosellus</Emphasis> and <Emphasis Type="Italic">Lactarius acatlanensis</Emphasis> with the endangered <Emphasis Type="Italic">Fagus grandifolia</Emphasis> var. <Emphasis Type="Italic">mexicana</Emphasis>

Gut bacterium Pantoea sp. is one of the predominant bacterial species in the larval gut of the diamondback moth, Plutella xylostella. The phenotypic characters of Pantoea sp. were investigated with BIOLOG phenotype MicroArray (PM) in this study. Totally 950 different metabolic phenotypes were tested using the PM plates 1–10. Results exhibited that Pantoea sp. was able to metabolize 37.37 % of the tested carbon sources, 91.32 % of nitrogen sources, 100 % of sulfur sources, and 98.31 % of phosphorus sources. Most informative utilization patterns for carbon sources of Pantoea sp. were organic acids and carbohydrates, and for nitrogen were various amino acids. The bacterium had 94 different biosynthetic pathways. It had a wide range of adaptabilities, and could still metabolize in osmolytes with up to 9 % sodium chloride, 6 % potassium chloride, 5 % sodium sulfate, 20 % ethylene glycol, 4 % sodium formate, 4 % urea, 5 % sodium lactate, 200 mmol/L sodium phosphate (pH 7.0), 100 mmol/L ammonium sulfate (pH 8.0), 100 mmol/L sodium nitrate, and 100 mmol/L sodium nitrite, respectively. It also exhibited active metabolism under pH values between 4.5 and 10. Pantoea sp. showed active decarboxylase activities while poor deaminase activities in the presence of various amino acids. The phenotypic characterization of Pantoea sp. increased our knowledge of the bacterium, in particular its interactions with insect hosts and the adaptability in gut environments, and showed us some possible approaches to controlling diamondback moth through decreasing Pantoea sp. density.     

Phosphoenolpyruvate-supply module in <Emphasis Type="Italic">Escherichia coli</Emphasis> improves <Emphasis Type="Italic">N</Emphasis>-acetyl-<Emphasis Type="SmallCaps">d</Emphasis>-neuraminic acid biocatalysis

Objectives

N-Acetyl-d-neuraminic acid (Neu5Ac) is often synthesized from exogenous N-acetylglucosamine (GlcNAc) and excess pyruvate. We have previously constructed a recombinant Escherichia coli strain for Neu5Ac production using GlcNAc and intracellular phosphoenolpyruvate (PEP) as substrates (Zhu et al. Biotechnol Lett 38:1–9, 2016).

Results

PEP synthesis-related genes, pck and ppsA, were overexpressed within different modes to construct PEP-supply modules, and their effects on Neu5Ac production were investigated. All the PEP-supply modules enhanced Neu5Ac production. For the best module, pCDF-pck-ppsA increased Neu5Ac production to 8.6 ± 0.15 g l^?1, compared with 3.6 ± 0.15 g l^?1 of the original strain. Neu5Ac production was further increased to 15 ± 0.33 g l^?1 in a 1 l fermenter.

Conclusions

The PEP-supply module can improve the intracellular PEP supply and enhance Neu5Ac production, which benefited industrial Neu5Ac production.

     

<Emphasis Type="Italic">Talaromyces heiheensis</Emphasis> and <Emphasis Type="Italic">T. mangshanicus</Emphasis>, two new species from China

Two new species, Talaromyces heiheensis from rotten wood and T. mangshanicus isolated from soil, are illustrated and described as new to science in sections Trachyspermi and Talaromyces. The phylogenetic positions of the two new species inferred from the internal transcribed spacer, beta-tubulin, calmodulin and RNA polymerase II second largest subunit regions were carried out. Talaromyces heiheensis is phylogenetically closely related to T. albobiverticillius, T. rubrifaciens, T. solicola and T. erythromellis, and characterised by slow growth on Czapek yeast autolysate agar at 25 °C, orange conidia en masse on malt extract agar at 25 °C, biverticillate and terverticillate conidiophores, acerose phialides and subglobose to ellipsoidal, smooth-walled conidia. Talaromyces mangshanicus is related to T. kendrickii, T. qii and T. thailandensis, and characterised by slow-growing colonies with absent or sparse sporulation on CYA agar at 25 °C, conidia en masse greyish purple, purplish red soluble pigment on yeast extract agar (YES) at 25 °C, biverticillate conidiophores, ampulliform phialides and subglobose to ellipsoidal conidia with echinulate walls. They are distinguished from the known species in culture characteristics on four standard media, microscopic features and sequence data.     

Simple Sequence Repeat and <Emphasis Type="Italic">S</Emphasis>-locus Genotyping to Explore Genetic Variability in Polyploid <Emphasis Type="Italic">Prunus spinosa</Emphasis> and <Emphasis Type="Italic">P. insititia</Emphasis>

Polyploid Prunus spinosa (2n = 4×) and P. insititia (2n = 6×) represent enormous genetic potential in Central Europe, which can be exploited in breeding programmes. In Hungary, 17 cultivar candidates were selected from wild-growing populations including 10 P. spinosa, 4 P. insititia and three P. spinosa × P. domestica hybrids (2n = 5×). Their taxonomic classification was based on their phenotypic characteristics. Six simple sequence repeats (SSRs) and the multiallelic S-locus genotyping were used to characterize genetic variability and reliable identification of the tested accessions. A total of 98 SSR alleles were identified, which presents 19.5 average allele number per locus, and each of the 17 genotypes could be discriminated based on unique SSR fingerprints. A total of 23 S-RNase alleles were identified. The complete and partial S-genotype was determined for 8 and 9 accessions, respectively. The identification of a cross-incompatible pair of cultivar candidates and several semi-compatible combinations help maximize fruit set in commercial orchards. Our results indicate that the S-allele pools of wild-growing P. spinosa and P. insititia are overlapping in Hungary. A phylogenetic and principal component analysis confirmed the high level of diversity and genetic differentiation present within the analysed genotypes and helped clarify doubtful taxonomic identities. Our data confirm that S-locus genotyping is suitable for diversity studies in polyploid Prunus species. The analysed accessions represent huge genetic potential that can be exploited in commercial cultivation.     

Molecular evidence for a natural diploid hybrid between <Emphasis Type="Italic">Miscanthus</Emphasis><Emphasis Type="Italic">sinensis</Emphasis> (Poaceae) and <Emphasis Type="Italic">M. sacchariflorus</Emphasis>

The hybrid origin of Miscanthus purpurascens has previously been proposed, primarily because of its intermediate morphology. In this study, phylogenies based on the DNA sequences from the internal transcribed spacer region of nuclear ribosomal DNA (nrDNA ITS), on the DNA sequences of the trnL intron and trnL-F intergenic spacer of chloroplast DNA, and on amplified fragment length polymorphism (AFLP) fingerprinting confirm that M. purpurascens originated through homoploid hybridization between M. sinensis and M. sacchariflorus. Two different types of ITS sequences were identified from almost all plants of M. purpurascens. One type was found to be closely related to M. sinensis and the other to M. sacchariflorus. Miscanthus purpurascens was found to possess many M. sinensis- and M. sacchariflorus-specific AFLP bands but no band specific to itself. Clustering with the Unweighted Pair Group Method with Arithmetic Mean and principal coordinate analysis based on the AFLP data also demonstrated that M. purpurascens is an approximate intermediate of the two species. In addition, M. purpurascens has the plastid genome of M. sinensis or M. sacchariflorus, suggesting that either species could be its maternal parent. All specimens of M. purpurascens and its coexisting parental species are identified as diploids (2n = 2x = 38). Possible mechanisms of natural hybridization, hybrid status, chloroplast DNA recombination, and evolutionary implications of this hybridization are also discussed.     

Development and characterization of <Emphasis Type="Italic">japonica</Emphasis> rice lines carrying the brown planthopper-resistance genes <Emphasis Type="Italic">BPH12</Emphasis> and <Emphasis Type="Italic">BPH6</Emphasis>

The brown planthopper (Nilaparvata lugens Stål; BPH) has become a severe constraint on rice production. Identification and pyramiding BPH-resistance genes is an economical and effective solution to increase the resistance level of rice varieties. All the BPH-resistance genes identified to date have been from indica rice or wild species. The BPH12 gene in the indica rice accession B14 is derived from the wild species Oryza latifolia. Using an F₂ population from a cross between the indica cultivar 93-11 and B14, we mapped the BPH12 gene to a 1.9-cM region on chromosome 4, flanked by the markers RM16459 and RM1305. In this population, BPH12 appeared to be partially dominant and explained 73.8% of the phenotypic variance in BPH resistance. A near-isogenic line (NIL) containing the BPH12 locus in the background of the susceptible japonica variety Nipponbare was developed and crossed with a NIL carrying BPH6 to generate a pyramid line (PYL) with both genes. BPH insects showed significant differences in non-preference in comparisons between the lines harboring resistance genes (NILs and PYL) and Nipponbare. BPH growth and development were inhibited and survival rates were lower on the NIL-BPH12 and NIL-BPH6 plants compared to the recurrent parent Nipponbare. PYL-BPH6 + BPH12 exhibited 46.4, 26.8 and 72.1% reductions in population growth rates (PGR) compared to NIL-BPH12, NIL-BPH6 and Nipponbare, respectively. Furthermore, insect survival rates were the lowest on the PYL-BPH6 + BPH12 plants. These results demonstrated that pyramiding different BPH-resistance genes resulted in stronger antixenotic and antibiotic effects on the BPH insects. This gene pyramiding strategy should be of great benefit for the breeding of BPH-resistant japonica rice varieties.     

The diversity of rhizobia nodulating the <Emphasis Type="Italic">Medicago</Emphasis>, <Emphasis Type="Italic">Melilotus</Emphasis> and <Emphasis Type="Italic">Trigonella</Emphasis> inoculation group in Egypt is marked by the dominance of two genetic types

Twenty four rhizobial strains were isolated from root nodules of Melilotus, Medicago and Trigonella plants growing wild in soils throughout Egypt. The nearly complete 16S rRNA gene sequence from each strain showed that 12 strains (50 %) were closely related to the Ensifer meliloti LMG6133^T type strain with identity values higher than 99.0 %, that 9 (37.5 %) strains were more than 99 % identical to the E. medicae WSM419^T type strain, and that 3 (12.5 %) strains showed 100 % identity with the type strain of N. huautlense S02^T. Accordingly, the diversity of rhizobial strains nodulating wild Melilotus, Medicago and Trigonella species in Egypt is marked by predominance of two genetic types, E. meliloti and E. medicae, although the frequency of isolation was slightly higher in E. meliloti. Sequencing of the symbiotic nodC gene from selected Medicago and Melilotus strains revealed that they were all similar to those of the E. meliloti LMG6133^T and E. medicae WSM419^T type strains, respectively. Similarly, nodC sequences of strains identified as members of the genus Neorhizobium were more than 99 % identical to that of N. galegae symbiovar officinalis HAMBI 114.