Preliminary studies of<Emphasis Type="Italic">in vitro</Emphasis> stimulation of sexual mating among isolates of<Emphasis Type="Italic">Mycosphaerella fijiensis</Emphasis>, causal agent of black sigatoka disease in bananas and plantains

Single-ascospore-derived isolates ofMycosphaerella fijiensis Morelet from false horn ‘Agbagba’ plantain leaves obtained from five different villages in southern Nigeria were stimulated to mate under artificial conditions. Pairs of isolates were incubated under blacklight on potato dextrose agar (PDA) with surface-sterilized plantain leaves or on PDA with autoclaved plantain leaves. Some isolates were observed to be sexually compatible by their ability to produce spherical to bulb-shaped fruiting body structures (FBS) and ascospores on pairing. FBS were observed to measure between 39–65 μm (smallest diameter) and 39–104 μm (largest diameter; mean 55.3×71.1 μm) in diameter, whereas ascospore lengths measured between 13.0 and 14.9 μm. Length of incubation time required for FBS production was dependent on the pair of isolates involved, the average being 40.1 days. With some pairs, ascospores were observed after 35 days of incubation. http://www.phytoparasitica.org posting Dec. 16, 2002.     

Poorly differentiated cutaneous carcinoma of non-sebaceous origin in a 3-year-old Mongolian gerbil (Meriones unguiculatus)

A 3-year-old female gerbil developed a non-healing skin wound due to a malignant neoplasm. Histology, immunohistochemistry (cytokeratin 19 positive; vimentin, estrogen, and progesterone receptor negative), and electron microscopy (no desmosomes or melanosomes) revealed an undifferentiated carcinoma with pulmonary metastasis. Unlike in previous reports, it did not arise from the abdominal pad’s sebaceous gland.     

Profiling of isoflavonoids in Iris germanica rhizome extracts by microprobe NMR and HPLC-PDA-MS analysis

Lipophilic and polar extracts of iris rhizomes (Iris germanica) were submitted to a phytochemical profiling by a combination of HPLC–PDA–MS and semi-preparative HPLC/off-line microprobe NMR measurements. A total of 20 compounds were purified in sub-milligram to milligram amounts via two successive chromatographic steps. They were identified as isoflavones, isoflavone glycosides and acetovanillone by analysis of on-line MS and PDA, and off-line NMR data. A new isoflavone glycoside, iriflogenin-4′-O-gentiobioside, was subsequently isolated at preparative scale for full chemical characterization. This study demonstrates the applicability of the HPLC/off-line microprobe NMR approach as a robust means for rapid phytochemical profiling of plant extracts.     

BiKF AdaMus: a novel research project studying the response and adaptive potential of single species and communities to climate change in combination with other stressors

Introduction

How will the combination of climate-induced physical/chemical changes and anthropogenic pollution impact key species and biodiversity, and thus the ecosystem functions in future?

Discussion

The project AdaMus within the newly founded Biodiversity and Climate Research Centre BiK^F aims to understand the prospective ecosystem stress responses and adaptive potential of species and communities to multiple stressors to provide reliable predictions of future developments in terrestric, aquatic and marine environments.

Conclusion

Long-term experiments with terrestrial, aquatic and marine species and communities will be conducted under IPCC predicted climate conditions. In terrestric and limnic experiments, additional co-stressors such as pesticides and alien species are introduced to test for interactions. In the case of marine plankton, potential consequences of multiple climate-related changes in the physical environment (temperature, salinity and oxygen) will be analysed.     

Study of precursors responsible for off-flavor formation during storage of potato flakes

Off-flavors frequently appear during the storage of potato flakes. Volatile profile analysis performed by solid-phase microextraction-gas chromatography-mass spectrometry revealed that hexanal is the main compound that appears during the storage period. Hexanal may be a degradation product of linoleic acid formed through linoleic acid hydroperoxide cleavage. Profiles of hexanal precursors were determined from potato flakes at different storage time points. Linoleic acid-derived oxylipins are predominant in potato flakes. The free oxylipins identified, in descending order, are as follows: hexanal, hydroxy polyunsaturated fatty (PUFAs), oxo PUFAs, divinyl ether PUFAs, and hydroperoxy PUFAs. However, the main oxylipins detected were esterified: esterified hydroxy, hydroperoxy, and oxo PUFAs. Oxylipins reveal different evolutions during the storage period. Chiral high-performance liquid chromatography analysis of the precursors of hexanal and other oxylipins revealed a racemic composition that supports the nonenzymatic formation of hexanal and most of the other oxylipins identified.     

Differential effect of elicitors on biphenyl and dibenzofuran formation in Sorbus aucuparia cell cultures

The Rosaceous subtribe Pyrinae (formerly subfamily Maloideae) is well-known for its economically important fruit trees, such as apple and pear, and also includes Sorbus aucuparia. Elicitor-treated S. aucuparia cell cultures are used to study the biosynthesis of the Pyrinae-specific phytoalexins, biphenyls and dibenzofurans. Three biphenyls (aucuparin, noraucuparin, 2'-hydroxyaucuparin) and a dibenzofuran (eriobofuran) were isolated and structure elucidated using GC-MS and NMR. A second dibenzofuran of low abundance was tentatively assigned as noreriobofuran. Treatment of S. aucuparia cell cultures with yeast extract induced the formation of aucuparin as the major phytoalexin. In contrast, addition of preparations from the fire blight bacterium, Erwinia amylovora, and the scab-causing fungus, Venturia inaequalis, resulted in accumulation of eriobofuran as the major inducible constituent. Methyl jasmonate was a poor elicitor. The observations are suggestive of a biogenic relationship between biphenyls and dibenzofurans. Elicitor-treated S. aucuparia cell cultures provide an interesting in vitro system for studying biphenyl and dibenzofuran metabolism in the economically valuable Pyrinae.     

Decomposition of plant tissue submerged in an extremely acidic mining lake sediment: phenolic CuO-oxidation products and solid-state C NMR spectroscopy

In extremely acidic mining sediments of the Lusatian mining district, the alkalinisation process relies on organic C, which can serve as electron donor for microbially induced sulfate reduction. Plant material of the pioneer plant Juncus bulbosus is an important organic matter source in lake sediments. Therefore, decomposition of the plant tissue was assessed during the exposure of litterbags for 30 months in the 0-5 cm layer of waterlogged mining sediments, which have a pH between 2.5 and 3. The ash free dry weight (AFDW) and elemental content of the plant tissue were recorded several times during the exposure. Changes in chemical structure were analyzed by solid-state ¹³C cross polarization magic angle spinning nuclear magnetic resonance (CPMAS NMR) spectroscopy and the lignin component characterized by wet-chemical CuO oxidation. The AFDW accounted for about 34% of initial biomass after field exposure for 30 months. Mass loss of biomass occurred in two phases with decomposition rates varying between 30 and 430 mg AFDW d⁻¹. The mass loss increased considerably after 5-7 months when litterbags were invaded by fresh J. bulbosus plants. With respect to higher mass loss, ¹³C CPMAS NMR spectroscopy, showed slight changes of the bulk chemical composition after 11 months, indicating that microorganisms present in the sediments or in the rhizosphere degrade plant material as a whole, rather than selectively. During the second phase from about 11 months until the end of the exposure period, contribution of O-alkyl C most probably assignable to easily degradable polysaccharides decreased. In contrast, the contribution of alkyl, aromatic and carboxyl C increased. CuO oxidation showed that the lignin component of J. bulbosus is degraded oxidatively during field exposure. Our results indicate that the exposed plant material is decomposed in the sediment due to changes in sediment conditions that followed plant invasion of the litterbags. It is suggested that the rhizosphere of J. bulbosus by its influence on the redox potential, pH and the microbial component plays a crucial role in organic matter degradation in acidic mining sediments.     

Effect of plant density on the inflorescence production of stems and the distribution of flower production in potato

Summary A knowledge of the pattern of flowering and seed production is required for the development of large-scale field production of True Potato Seed (TPS). At the highland experimental station of the International Potato Center in Peru, data on flowering and seed production were collected from three cultivars planted at three densities. Main stems in which flowering was delayed ceased shoot growth at an earlier stage and produced fewer inflorescences. Inflorescences produced later had fewer flowers, a lower berry set and yielded less seed. Inflorescences flowering at the same time performed similarly, irrespective of their position on the plant. Increasing plant density resulted in cessation of shoot growth at an earlier stage and concentrated inflorescence and flower production at primary positions of early-flowering shoots. With cvs Renacimiento and Yungay a higher plant density increased the percentage of flowers produced in the first three weeks of the flowering period, but with cv. Atzimba the effect of plant density on the distribution of flower production was off-set by a slower stem development.