Evaluation of the durability of the <Emphasis Type="Italic">Barley yellow dwarf virus</Emphasis>-resistant <Emphasis Type="Italic">Zhong ZH</Emphasis> and <Emphasis Type="Italic">TC14</Emphasis> wheat lines

Serial passage experiments (SPE) of a Barley yellow dwarf virus-PAV (BYDV-PAV) isolate were performed on Zhong ZH and TC14 wheat lines to evaluate the durability of their resistance to BYDV. At different passage numbers (from the 2nd to the 114th), biological properties of the produced isolates were recorded either by monitoring infection percentages and virus titers of the first 3 weeks of viral infection or by measuring their impact on yield components. Statistical analyses using the area under pathogen progress curves and the area under concentration progress curves demonstrated that these two resistant lines induce, after only a few passages, a selection of variant(s) with significantly modified infection abilities. Isolates resulting from SPE performed on these lines induced important decreases of yield components. These results indicate that the use of Zhong ZH and TC14 lines in BYDV-resistant breeding programmes should be approached with caution.     

Variability in response to toosendanin in a laboratory colony of<Emphasis Type="Italic">Trichoplusia ni</Emphasis>

Laboratory rearing of insects for scientific research ensures a constant supply of insects. However, laboratory colonies may diverge genetically and/or phenotypically from wild populations due to selection pressures in their artificial environment. This study examined how variation in a colony ofTrichoplusia ni influenced reproducibility over time of bioassays of toosendanin (a limonoid extracted from the bark ofMelia azedarach). In four of five experiments insect growth was reduced significantly (P=0.05) by the presence of toosendanin in the diet. The fifth experiment showed the same trend, but the effect was not significant. Mean larval mass of both control and treated insects also varied greatly among experiments. The considerable variability observed in this population highlights the importance of replicating experiments in time, and not just space, to confirm reproducibility of treatment effects. http://www.phytoparasitica.org posting Jan. 23, 2007.     

Multi-scale study of bird species distribution and of their response to vegetation change: a Mediterranean example

Land use changes operate at different scales. They trigger a cascade of effects that simultaneously modify the composition or structure of the landscape and of the local vegetation. Mobil animals, and birds in particular, can respond quickly to such multi-scalar changes. We took advantage of a long term study on the response of songbirds to land-use changes on four Mediterranean islands in Corsica and Sardinia to explore the benefits of a multi-scale analysis of the relationships between songbird distribution, vegetation structure and landscape dynamics. Field data and aerial photographs were used to describe the vegetation at three different scales. Birds were censused by point counts. We used statistical variance decomposition to study how bird distribution and vegetation at various scales were linked. We analysed multi-scale vegetation changes (floristic composition, plot vegetation type, and landscape structure) and their consequences on bird distribution with multivariate and non-parametrical tests. The distribution of most species was linked to at least two spatial scales. The weight of a given scale was consistent with life-history traits for species whose biology was well-known. In the examples studied, vegetation composition, vegetation type and landscape changes that resulted from land abandonment negatively affected birds depending on open or heterogeneous areas. Our results emphasize that multi-scale analyses can greatly enhance our understanding of bird distribution and of their changes. Management of these populations should take into account measures at various spatial scales depending on the sensitivity of the species.     

Development and characterization of a cell line TTCF from endangered mahseer Tor tor (Ham.)

Tor tor is an important game and food fish of India with a distribution throughout Asia from the trans-Himalayan region to the Mekong River basin to Malaysia, Pakistan, Bangladesh and Indonesia. A new cell line named TTCF was developed from the caudal fin of T. tor for the first time. The cell line was optimally maintained at 28°C in Leibovitz-15 (L-15) medium supplemented with 20% fetal bovine serum (FBS). The propagation of TTCF cells showed a high plating efficiency of 63.00%. The cytogenetic analysis revealed a diploid count of 100 chromosomes at passage 15, 30, 45 and 60 passages. The viability of the TTCF cell line was found to be 72% after 6 months of cryopreservation in liquid nitrogen (-196°C). The origin of the cell lines was confirmed by the amplification of 578- and 655-bp sequences of 16S rRNA and cytochrome oxidase subunit I (COI) genes of mitochondrial DNA (mtDNA) respectively. TTCF cells were successfully transfected with green fluorescent protein (GFP) reporter plasmids. Further, immunocytochemistry studies confirm its fibroblastic morphology of cells. Genotoxicity assessment of H?O? in TTCF cell line revealed the utility of TTCF cell line as in vitro model for aquatic toxicological studies.     

Avian predation on wild and cultured sea urchin <Emphasis Type="Italic">Strongylocentrotus intermedius</Emphasis> in a rocky shore habitat

ABSTRACT:   The present study reports the annual variation in consumption of the sea urchin Strongylocentrotus intermedius by avian predators on a rocky shore where the culture of sea urchins has been conducted. Carrion crow and a few gull species were the most abundant avian predators and consumed a large number of sea urchins. Crows consumed mostly natural sea urchins, approximately 36 kg ww/ha per year on the intertidal rocky bench, but the gull species consumed mostly cultured sea urchins, approximately 100 kg ww/ha per year in the culture area. The seasonal variation in the amount of sea urchins consumed by crows was higher than that by the gull species, presumably because of the difference in foraging behavior in association with the seasonal tidal cycle. The natural sea urchins consumed are an allochthonous input from the subtidal to the intertidal habitat, and thus, crow predation may not affect the natural and the cultured populations of the sea urchin. The gull species consumed much of the cultured sea urchin, and thus, may be regarded as an effective predator causing damage to sea urchin culture. The results suggest that further studies are needed to determine why the gull species selectively feed on cultured sea urchins.     

The role of flatfishes in the organization and structure of the eastern Bering Sea ecosystem

We evaluated the role of flatfishes in the organization and structure of the eastern Bering Sea ecosystem using the Ecopath/Ecosim approach. As basic input data for the Ecopath/Ecosim model, we used estimates of biomass from bottom trawl surveys and age-structured population models, production/biomass (P/B) ratio, consumption/biomass (Q/B) ratio, diet composition (DC), and fisheries harvests for each component of species or species groups. We estimated the trophic level of each component, niche overlaps among flatfishes, and the impacts of competition and predation on flatfish species in the eastern Bering Sea ecosystem. Based on those estimates, we developed the tropho-dynamic structure of the ecosystem, and the model was used to simulate ecological effects of fishery exploitation patterns. No single flatfish species appeared to have a profound and uniquely important role in the organization and structure of the ecosystem. Instead, the most important component among the guild of flatfish species appeared to be yellowfin sole Pleuronectes asper, which had greater biomass than other flatfish and a relatively diverse diet among the small flatfish species. Pacific halibut Hippoglossus stenolepis, Greenland turbot Reinhardtius hippoglossoides, and arrowtooth flounder Atheresthes stomias were important keystone predators in the eastern Bering Sea ecosystem together with some groups of marine mammals and sea birds. Intra flatfish complex cannibalism was not observed, however, substantial diet overlaps were common in the flatfish guild system.     

A new primer for 16S rDNA analysis of microbial communities associated with <Emphasis Type="Italic">Porphyra yezoensis</Emphasis>

To construct high-quality 16S rDNA clone libraries for microbial communities associated with Porphyra yezoensis and to minimize the detection of rDNA from leafy gametophytes of P. yezoensis, we designed a new 16S rDNA universal primer (75F). Of the clones prepared using 75F, which was designed to distinguish between bacteria and P. yezoensis, 95% were classified into four groups, namely, β-proteobacteria, γ-proteobacteria, Lentisphaerae, and Flavobacteria. PCR-based analysis of the 16S rDNA primer constructed in this study can be used to implement 16S rDNA-based methodologies for the investigation of microbial community composition and diversity related to the Porphyra group.