Structure of herbivore communities in two oak (Quercus spp.) hybrid zones

Summary We examined patterns of density and species diversity for leaf-mining Lepidopterans and gall-forming Hymenopterans in two oak (Quercus spp.) hybrid zones: Quercus depressipes x Q. rugosa and Q. emoryi x Q. coccolobifolia. In both species complexes, hybrid hosts typically supported significantly lower densities and species diversity of parasites than did parental types. This contradicts the findings of Whitham (1989) that suggested that hybrid hosts may act as parasite sinks both in ecological and evolutionary time. We discuss features of hybrid zones that are likely to influence patterns of herbivory.     

Quercus tuitensis (Fagaceae, Quercus sect. Lobatae), a new deciduous oak from western Jalisco, Mexico

Quercus tuitensis, a deciduous red oak known only from the Sierra El Tuito on the Pacific slopes of western Jalisco, Mexico, is described, illustrated, and compared toQ. praineana Trel. In addition,Q. aequivenulosa andQ. coffeaecolor are reaffirmed as synonyms ofQ. praineana.     

Reduced parasitism of a leaf-mining moth on trees with high infection frequencies of an endophytic fungus

We investigated relationships between endophytic fungi and a leaf-mining moth, Phyllonorycter sp., along an elevational gradient from 2255 to 2895 m. The fungi and moth larvae inhabit leaves of Quercus gambelii. Fungal frequencies and larval densities varied with elevation. However, larval densities were not associated with the frequencies of infection by endophytic fungi. Survival of larvae was positively associated with the most dominant fungus, Gnomonia cerastis, owing to reduced parasitism of moth larvae on trees with high frequencies of Gnomonia.     

Interactions of Taxol-producing endophytic fungus with its host (Taxus spp.) during Taxol accumulation

Endophytic fungi (Fusarium mairei) culture broth (EFCB) was added to cell suspension cultures of Taxus cuspidata. After 5 days, cultures of T. cuspidata given 4 ml of EFCB produced a maximal yield of 6.11 mg/l paclitaxel, with a release ratio of 75%, 2- and 6.8-fold, respectively, greater than the controls. The active element in EFCB is an exopolysaccharide of ∼79 kD. Endophytic fungi produced 0.19 mg/l of paclitaxel in its producing medium. However, when the supernatant of Taxus cell suspension cultures from day 20 was added to the paclitaxel-producing medium, the biomass of fungi decreased by 24% and the yield of paclitaxel by 45%. In a co-culture system of plant and fungus, the yield of paclitaxel (12.8 mg/l) was >2-fold higher than that in the EFCB-treatment system.     

Characterization of highly variable (GA/CT) n microsatellites in the bur oak,Quercus macrocarpa

The objective of this study was to ascertain the usefulness of polymerase chain reaction (PCR)-based microsatellite analysis for studying pollination and parentage in a wind-pollinated temperate tree. A small insert genomic library of the bur oak (Quercus macrocarpa) was constructed and screened for the presence of (CA/GT) _n and (GA/CT) _n repeats. The proportion of positive clones yielded estimates of 3×10⁵ such dinucleotide repeats per genome, roughly comparable to abundances reported in other eukaryotic genomes. Thirteen positive clones were sequenced. In contrast to mammalian genomes, the (GA/CT) _n motif was more abundant than the (CA/GT) _n motif in these clones. The (GA/CT) _n repeats also showed longer average repeat length (mean n=16.2 versus 7.3), suggesting that they are better candidates for yielding polymorphic genetic markers in oak genomes. Indeed, a survey of adult bur oaks and offspring in a small stand in northern Illinois at 3 of these (GA/CT) _n microsatellite loci revealed Mendelian inheritance and extremely high levels of polymorphism, with the number of alleles at each locus ranging from 11–20 and heterozygosity ranging from 0.66 to 0.75. These results, indicating that (GA/CT) _n microsatellites are both abundant and highly polymorphic in the bur oak genome, suggest that such genetic markers have tremendous potential for applications for studies of parentage, pollination and dispersal in temperate trees.     

Comparative analysis of micromorphological characters in two distantly related Mexican oaks, Quercus conzattii and Q. eduardii (Fagaceae), and their hybrids

Interspecific hybridization occurs with high frequency in the genusQuercus, but few studies have analyzed and compared micromorphological characters in putative parental species and their hybrids.Quercus eduardii andQ. conzattii are two Mexican black oak species that, although distantly related, have formed at least one population of hybrid origin, where individuals with intermediate macromorphology are present. The purpose of this investigation was to analyze the degree of differentiation in micromorphological characters between the two species and to assess the expression of these characters in individuals with intermediate macromorphology. Foliar trichomes, epicuticular waxes, stomata, and pollen grains, were examined using scanning electron microscopy (SEM) in the three types of individuals (Q. conzatti, Q. eduardii, and intermediates). Trichome density was quantified with light microscopy. Types of trichomes present, length of trichome arms, types of epicuticular wax on the leaf surfaces, and the position of stomata with respect to the foliar surface were characters useful to differentiate betweenQ. conzattii andQ. eduardii. Plants with intermediate macromorphology displayed a pattern of micromorphological characters that were identical to one parental species (Q. conzattii), or extreme or novel relative to both species.     

Early seedling growth of pine (Pinus densiflora) and oaks (Quercus serrata,Q. mongolica,Q. variabilis) in response to light intensity and soil moisture

In climatic chambers seed germination and seedling growth of Pinus densiflora Sieb. et Zucc., Quercus serrata Thunb., Quercus mongolica Fisch. ex Turcz. and Quercus variablilis Bl. were investigated as functions of light intensity and soil moisture. In Korea these tree species occur widely and form mixed forests with different distributions. Species clearly differed in the pattern of germination and early seedling growth between light and soil treatments. The germination of pine did not differ between the experimental treatments until the breaking of the primary buds. After that, light intensity was the deciding factor for further development. In the most moist treatment (approx. field capacity) growth of the pine seedlings was strongly inhibited. For the three oak species, differences between experimental treatments first occurred after complete formation of primary leaves. Seed development strongly correlated with the weight of the acorn. The large seeded Q. variabilis (acorns with mean weight of 4.7 g) developed faster and reached larger dimensions towards the end of the experiment than Q. mongolica (2.8 g per acorn) and Q. serrata (0.9 g per acorn). Regarding height and biomass growth, the oak species showed a higher shade tolerance than pine. The proleptic shoot growth was clearly influenced by the light intensity. Root formation was favoured by a high exposure to light. In case of the oak species reduction of soil moisture increased the length of primary roots and the number of secondary roots.     

Genetic variability of fragmented stands of pedunculate oak (Quercus robur) in Finland

The genetic structure of 33 natural Quercus robur stands in Finland was studied using 13 allozyme loci to analyze the effects of fragmentation in a wind-pollinated tree species. The present fragmented and discontinuous distribution of oak is a result of both short-term human impact and long-term climatic and geological change, including post-glacial land uplift. In accordance with general expectations, genetic diversity in small populations was lower than that in large populations, and differentiation among small populations was higher than that among large populations. Heterozygote deficiency was more pronounced in large populations, which is proposed to be a Wahlund effect created by either spatial sub-structuring or the existence of synchronized flowering lineages. Also genetic differentiation was higher and diversity lower in Finland than the estimates reported for Central Europe. There were differences in the genetic structure on sites of different geological age. We suggest that on most geologically old sites drift has a prominent effect whereas on younger sites also founder effects may be important.     

Deciduous and semi-deciduous oak forests (<Emphasis Type="Italic">Quercus robur,Q. petraea</Emphasis> and <Emphasis Type="Italic">Q. pyrenaica</Emphasis>) floristic composition in the Northwest Iberian Peninsula

Oak forests in the Northwest Iberian Peninsula represent climax communities with a high floristic diversity of vascular plants. This study presents data from 189 botanical samples randomly collected in stands of deciduous and semi-deciduous oak as Quercus robur (98), Q. petraea (50) and Q. pyrenaica (41). Within these stands, 187 species or subspecies were identified, in addition to 20 genera and 68 families, all of them present in forests of Quercus robur. A total of 126 species occur in more than five relevés. The largest number of species corresponds to Poaceae (22), Fabaceae (19) and Rosaceae (14). The biological spectrum is dominated by hemicryptophytes, with mainly Atlantic and Sub-Atlantic floristic elements. The distribution of the stands has been studied by using Two-Way Indicator Species Analysis, obtaining like pseudo-species, with shrubby and arborea form, the following ones: Fagus sylvatica, Castanea sativa, Sorbus aucuparia, Corylus avellana, Crataegus monogyna, Pyrus cordata, Erica arborea, Frangula alnus and Cytisus scoparius.     

A phenetic study of the taxonomic delimitation of Quercus acutifolia and Q. conspersa (Fagaceae)

A phenetic study ofQuercus acutifolia andQ. conspersa (Fagaceae) is carried out. The study was based on morphological characters, and included cluster analysis and principal component analysis. The results revealed that the characters employed so far to separateQuercus acutifolia andQ. conspersa seem to be quite unreliable. Nevertheless, both species can still be recognized as taxonomically different entities, although mostly based on characters of leaf margins. We propose that the individuals that have leaves with dentate-aristate margins correspond toQ. acutifolia, whereas those that have leaves with entire and not dentate-aristate margins belong toQ. conspersa.     

Interspecific somatic hybrid plants between eggplant (Solanum melongena) and Solanum torvum

Summary Mesophyll protoplasts of eggplant (cv Black Beauty) and of Solanum torvum (both 2n=2x=24) were fused using a modification of the Menczel and Wolfe PEG/DMSO procedure. Protoplasts post-fusion were plated at 1 × 10⁵/ml in modified KM medium, which inhibited division of S. torvum protoplasts. One week prior to shoot regeneration, ten individual calluses had a unique light-green background and were verified as cell hybrids by the presence of the dimer isozyme patterns for phosphoglucoisomerase (PGI) and glutamate oxaloacetate transaminase (GOT). Hybridity was also confirmed at the plant stage by DNA-DNA hybridization to a pea 45S ribosomal RNA gene probe. The ten somatic hybrid plants were established in the greenhouse and exhibited intermediate morphological characteristics such as leaf size and shape, flower size, shape, color and plant stature. Their chromosome number ranged from 46–48 (expected 2n=4x=48) and pollen viability was 5%–70%. In vitro shoots taken from the ten hybrid plants exhibited resistance to a verticillium wilt extract. Total DNA from the ten hybrids was restricted and hybridized with a 5.9 kb Oenothera chloroplast cytochrome f gene probe, a 2.4 kb EcoRI clone encoding mitochondrial cytochrome oxidase subunit II from maize and a 22.1 kb Sal I mitochondrial clone from Nicotiana sylvestris. Southern blot hybridization patterns showed that eight of ten somatic hybrids contained the eggplant cpDNA, while two plants contained the cpDNA hybridization patterns of both parents. The mtDNA analysis revealed the presence of novel bands, loss of some specific parental bands and mixture of specific bands from both parents in the restriction hybridization profiles of the hybrids.Michigan Agricultural Experiment Station Journal Article No. 12545     

Cytological study of interspecific hybrid between Brassica campestris x B. hirta (Sinapis alba)

Interspecific hybrids from the crossing Brassica campestris x B. hirta are reported in our study for the first time. F₁ plants were obtained by using ovary culture. The phenotype of hybrids was similar to B. napus; the plants were self-fertile. Investigation of meiotic division and nuclear DNA content measurements showed the amphidiploid origin of these hybrids. The relationship between genome A and D, as well as the spontaneous amphidiploidization of the hybrids, are discussed.     

Cadinane sesquiterpenoids of Phomopsis cassiae, an endophytic fungus associated with Cassia spectabilis (Leguminosae)

Five cadinane sesquiterpenes derivatives were isolated by bioassay-guided fractionation from Phomopis cassiae, an endophytic fungus isolated from Cassia spectabilis. The structures of the two diastereoisomeric 3,9,12-trihydroxycalamenenes (1, 2); 3,12-dihydroxycalamenene (3); 3,12-dihydroxycadalene (4) and 3,11,12-trihydroxycadalene (5) were established on the basis of analyses of 1D and 2D NMR and HRTOFMS experiments. Antifungal activity of the isolates was evaluated against Cladosporium sphaerospermum and Cladosporium cladosporioides, revealing 5 as the most active compound.     

Antimicrobial potentials of endophytic fungi residing in <Emphasis Type="Italic">Quercus variabilis</Emphasis> and brefeldin A obtained from <Emphasis Type="Italic">Cladosporium</Emphasis> sp.

Among 67 endophytic fungi isolated from Quercus variabilis, 53.7% of endophytic fungal fermentation broths displayed growth inhibition on at least one test microorganism, such as pathogenic fungi (Trichophyton rubrum, Candida albicans, Aspergillus niger, Epidermophyton floccosum, Microsporum canis) and bacteria (Escherichia coli, Bacillus subtilis, Pseudomonas fluorescens). Moreover, 19.4% of strains showed a broader antimicrobial spectrum, such as Aspergillus sp., Penicillium sp., Alternaria sp., 20.9% of strains showed strong inhibition (+++) to pathogenic bacteria, while only 7.5% displayed that to test fungi. The most active antifungal strain I(R)9-2, Cladosporium sp. was selected and fermented. From the broth, a secondary metabolite, brefeldin A was obtained. This is the first report on the antimicrobial potentials of endophytic fungi residing in Q. variabilis and isolation of brefeldin A produced by Cladosporium sp.     

Endophytic fungi from a pharmaceutical plant, Camptotheca acuminata: isolation, identification and bioactivity

About 174 endophytic fungi were isolated from the pharmaceutical plant, Camptotheca acuminata. Of the 18 taxa obtained, non-sporulating fungi (48.9%), Alternaria (12.6%), Phomopsis (6.9%), Sporidesmium (6.3%), Paecilomyces (4.6%) and Fusarium (4.6%) were dominant. ITS rDNA assay indicated that most of the non-sporulating fungi belonged to the Pyrenomycetes and Loculoascomycetes ascomycetes or their anamorph Coelomycetes. The results of the bioactivity test showed that 27.6% of the endophytic fungi displayed inhibition against more than one indicator microorganism. 4.0% and 2.3% of the endophytic fungi showed cytotoxicity and protease inhibition, respectively. The endophytic fungi with bioactivities were distributed in more than 12 taxa including non-sporulating fungi, which are reliable sources for bioactive agents.     

Cytogenetics of a Hordeum vulgare x Elymus patagonicus hybrid (n=4x=28)

Summary Hordeum vulgare L. (2n=2x=14) was hybridized with Elymus patagonicus Speg. (2n=6x=42). The hybrid had 28 chromosomes, genomically represented as HSH₁H₂, and was perennial with a codominant phenotype. The chromosomes were meiotically associated as 19.6 univalents + 0.004 ring bivalents + 2.6 rod bivalents + 0.8 trivalents + 0.14 quadrivalents in 1,129 meiocytes, with a chiasma frequency of 4.77 per cell. The bivalent pairing presumably is an autosyndetic but modified expression of the H₁H₂ genomes of E. patagonicus, since ring bivalents were rare. This does not preclude the association of the H. vulgare H genome chromosomes with either H₁ and/or H₂ genomes of E. patagonicus to form bivalent or multivalent associations. A further evaluation of the genome homologies of H. vulgare, H. bogdanii, E. canadensis and E. patagonicus is proposed.     

Rohitukine,a chromone alkaloid and a precursor of flavopiridol,is produced by endophytic fungi isolated from Dysoxylum binectariferum Hook.f and Amoora rohituka (Roxb).Wight & Arn

Rohitukine, a chromone alkaloid, has gained considerable international attention in recent years because of its novel semi-synthetic derivative, flavopiridol and P-276-00. Both these molecules are in advanced stages of clinical development and trial for cancer treatment. Recently, flavopiridol was approved as an orphan drug for treatment of chronic lymphocytic leukemia cancer. The natural occurrence of rohitukine is restricted to only four plant species, Amoora rohituka and Dysoxylum binectariferum (both from the Meliaceae family) and from Schumanniophyton magnificum and Schumanniophyton problematicum (both from the Rubiaceae family). Recently, an endophytic fungi isolated from D. binectariferum was reported to produce rohitukine in culture. In this study, we report the production of rohitukine and its subsequent attenuation by endophytic fungi, Fusarium oxysporum (MTCC-11383), Fusarium oxysporum (MTCC-11384) and Fusarium solani (MTCC-11385), all isolated from D. binectariferum and Gibberella fujikuroi (MTCC-11382) isolated from Amoora rohituka. The fungal rohitukine which was analyzed by HPLC, LC–MS and LC–MS/MS was identical to reference rohitukine and that produced by the plant. The rohitukine content in the mycelial samples ranged from 192.78 μg to 359.55 μg 100 g⁻¹ of dry weight of and in broth it ranged from 14.10 to 71.90 μg 100 ml⁻¹. In all the fungal cultures, the production declined from first to fourth sub-culture. Studies are underway to unravel the mechanism by which the fungi produce the host metabolite in culture.     

Bioactive metabolites from Alternaria brassicicola ML-P08, an endophytic fungus residing in Malus halliana

A total of 48 strains were isolated from the normal tissues of Malus halliana and the EtOAc extracts of their cultures were subjected to primary antimicrobial screening against four test bacteria and three fungi. As a result, 22 strains exhibited antimicrobial activity against at least one test microbe. Among them, Alternaria brassicicola ML-P08 showing strong activity (MICs: 0.31–2.50 mg/ml) was selected for further investigation on its secondary metabolites. Bioassay-guided fractionation of the EtOAc extract of its liquid culture afforded seven compounds, which were identified as alternariol (1), alternariol 9-methyl ether (2), altechromone A (3), herbarin A (4), cerevisterol (5), 3β,5α-dihydroxy-(22E,24R)-ergosta-7,22-dien-6-one (6) and 3β-hydroxy-(22E,24R)-ergosta-5,8,22-trien-7-one (7), respectively, by spectral means (MS, IR, ¹H- and ¹³C-NMR). In vitro antimicrobial assay showed that compound 3 was substantially active against Bacillus subtilis, Escherichia coli, Pseudomonas fluorescens and Candida albicans with the MICs of 3.9, 3.9, 1.8, and 3.9 μg/ml, respectively. Compound 4 also showed pronounced antifungal activity against Trichophyton rubrum and C. albicans with MICs of both 15.6 μg/ml. In addition, compound 1 exhibited strong xanthine oxidase inhibitory activity with the IC₅₀ of 15.5 μM, comparable to that of positive control, allopurinol (IC₅₀: 10.7 μM).     

Spatial distribution of cpDNA and mtDNA haplotypes in a hybrid zone betweenPinus pumila andP. parviflora var.pentaphylla (Pinaceae)

Pinus species exhibit paternal chloroplast inheritance and maternal mitochondrial inheritance. This independent inheritance of two cytoplasmic genomes provides an exceptional environment for discriminating female (seeds) and male (pollen) components of gene flow across hybridizing species. We obtained mitochondrial genetic markers diagnostic toP. parviflora var.pentaphylla andP. pumila by PCR amplification of the intron ofnad1 on mtDNA, and examined the spatial-distribution pattern of the mtDNA haplotypes in a hybrid zone betweenP. parviflora var.pentaphylla andP. pumila in the Tanigawa Mountains of Japan. These data, in conjunction with previous information on cpDNA haplotypes and needle morphology, revealed contrastive patterns of introgression of two cytoplasmic genomes. CpDNA introgression has occurred uni-directionally fromP. parviflora var.pentaphylla toP. pumila. Conversely, mtDNA introgression has occurred in the opposite direction, fromP. pumila toP. parviflora var.pentaphylla. Levels of introgression are roughly equivalent for cpDNA and mtDNA. The contrastive spatial distribution pattern of cpDNA and mtDNA haplotypes could be caused by differential movement of seeds and pollen for interspecific genetic exchange.