Colonization in action: genetic characteristics of <Emphasis Type="Italic">Daphnia magna</Emphasis> Strauss (Crustacea,Anomopoda) in two recently restored ponds

New habitats are an interesting tool to monitor colonization processes in the light of changes in genetic structure and evolutionary potential of populations. Cladocerans are cyclical parthenogens that offer the possibility to track genetic changes during the colonization process due to the alternation of sexual and asexual phases. The locally called “malladas” are shallow and temporary peridunal ponds in Eastern Spain that were silted in the 1960s and have been recently dug to their original basin. We here describe the colonization process in two of these newly restored ponds by the cladoceran Daphnia magna during their first 3 years. This colonization process followed three critical steps: population founding by the initial colonists, arrival of secondary immigrants and consolidation of the population structure. We found a low number of genotype colonists followed by the establishment of secondary immigrants and a slight decrease in gene flow with time. We discuss the importance of dispersal, founder effects, natural selection, inbreeding depression and genetic drift during the colonization process in the light of the most recent literature.     

First Report of Pythium indigoferae and P. irregulare Associated to Apple Trees Decline in Tunisia

Pythium indigoferae and Pythium irregulare, identified based on morphological and physiological characteristics, were isolated from necrotic roots, crown tissues and the rhizosphere of apple trees in Tunisia from 23 apple orchards in spring and autumn 2007–2009. The virulence assays on excised twigs, using different Pythium species isolated demonstrated that these oomycetes were pathogenic on the Anna, Lorka and Meski varieties and the MM106 rootstock. However, the biggest lesion area was noted on MM106 rootstock. Thus, it appeared that this rootstock is more susceptible to Pythium infections than Anna, Meski and Lorka apple varieties. Furthermore, it is important to note that in vitro tests showed that P. indigoferae seems to be more virulent than P. irregulare.     

Oligonucleotide Arrays vs. Metaphase-Comparative Genomic Hybridisation and BAC Arrays for Single-Cell Analysis: First Applications to Preimplantation Genetic Diagnosis for Robertsonian Translocation Carriers

Comprehensive chromosome analysis techniques such as metaphase-Comparative Genomic Hybridisation (CGH) and array-CGH are available for single-cell analysis. However, while metaphase-CGH and BAC array-CGH have been widely used for Preimplantation Genetic Diagnosis, oligonucleotide array-CGH has not been used in an extensive way. A comparison between oligonucleotide array-CGH and metaphase-CGH has been performed analysing 15 single fibroblasts from aneuploid cell-lines and 18 single blastomeres from human cleavage-stage embryos. Afterwards, oligonucleotide array-CGH and BAC array-CGH were also compared analysing 16 single blastomeres from human cleavage-stage embryos. All three comprehensive analysis techniques provided broadly similar cytogenetic profiles; however, non-identical profiles appeared when extensive aneuploidies were present in a cell. Both array techniques provided an optimised analysis procedure and a higher resolution than metaphase-CGH. Moreover, oligonucleotide array-CGH was able to define extra segmental imbalances in 14.7% of the blastomeres and it better determined the specific unbalanced chromosome regions due to a higher resolution of the technique (≈20 kb). Applicability of oligonucleotide array-CGH for Preimplantation Genetic Diagnosis has been demonstrated in two cases of Robertsonian translocation carriers 45,XY,der(13;14)(q10;q10). Transfer of euploid embryos was performed in both cases and pregnancy was achieved by one of the couples. This is the first time that an oligonucleotide array-CGH approach has been successfully applied to Preimplantation Genetic Diagnosis for balanced chromosome rearrangement carriers.     

Detection of black-foot and Petri disease pathogens in soils of grapevine nurseries and vineyards using bait plants

Background and aims

Little information is currently available regarding the number of species of black-foot and Petri disease pathogens present in soil and their capacity to infect grapevine roots and reach the xylem vessels.

Methods

Seedlings of grapevine rootstock 41-B, and cvs. Bobal and Palomino were planted both in pots containing soil samples collected from commercial vineyards and in nursery fields. Roots and xylem vessels were later analyzed for fungal isolation.

Results

Black-foot pathogens: Ilyonectria alcacerensis, I. macrodidyma, I. novozelandica and I. torresensis were frequently isolated from roots of seedlings grown in all soils evaluated, whereas Petri disease pathogens: Cadophora luteo-olivacea, Phaeoacremonium aleophilum, Pm. parasiticum and Phaeomoniella chlamydospora were only isolated from xylem vessels of seedlings grown in nursery soils, with a low incidence. Ilyonectria alcacerensis, I. novozelandica and I. torresensis were isolated for the first time from grapevines in Spain, and Pm. parasiticum and Ca. luteo-olivacea were detected for the first time in nursery soils.

Conclusions

Our results confirm nursery and vineyard soils as an important inoculum source for black-foot pathogens and demonstrate the presence of several Petri disease pathogens in nursery soils.     

Phosphorus budgets and forms of phosphorus in the Sau reservoir sediment: An interpretation of the limnological record

The phosphorus compounds in the sediment of Sau reservoir have been analysed and related to the annual phosphorus budgets from 1965 to 1969. With the increase of eutrophy, the phosphorus inputs leave the water in two ways: to the sediment and to the water outflow. The second way becomes more important throughout the eutrophication process.Of the three phosphorus forms studied, apatite-P is related to annual water flow, which is also directly related to sedimentation rate. By contrast, the other two phosphorus forms (organic-P and inorganic non apatite-P) are linked to phosphorus outputs. These relationships enable us to propose an historical sequence for the sediment. Finally, the dating of sediment allows us to develop an equation relating the total phosphorus in the sediment to the annual phosphorus inputs and water flow into the reservoir (r = 0.94).     

Ventilation by external high-frequency oscillation in cats

Eight anesthetized tracheostomized cats were placed in an 8.2-liter airtight chamber with the trachea connected to the exterior. Thirty-two combinations of high-frequency oscillations (HFO) (0.5-30 Hz; 25-100 ml) were delivered for 10 min each in random order into the chamber. Arterial blood gas tensions during oscillation were compared with control measurements made after 10 min of spontaneous breathing without oscillation when the mean arterial PCO2 (PaCO2) was 30.1 Torr. Ventilation due to spontaneous breathing (Vs) and oscillation (Vo) were derived from the chamber pressure trace and a pneumotachograph, respectively. As the oscillation frequency increased, oscillated tidal volume (Vo) decreased from a mean of 39 (0.5 Hz) to 3.3 ml (30 Hz) when 100 ml was delivered to the chamber. From 6-25 Hz, apnea occurred with Vo less than estimated respiratory dead space (VD); the minimum effective Vo/VD ratio was 0.37 +/- 0.05. Although Vo was maximal at 10 Hz at each oscillation volume, the lowest PaCO2 occurred at 2-6 Hz, and arterial PO2 rose as expected during hypocapnia. Above 10 Hz, PaCO2 was determined by Vo and was independent of frequency, whereas at lower frequencies, PaCO2 was related to Vo; below 6 Hz, PaCO2 varied inversely with the calculated alveolar ventilation. As oscillations became more effective, both PaCO2 and Vs fell progressively and were highly correlated; apnea occurred when PaCO2 was reduced by a mean of 4.5 Torr. Mean chamber pressure remained near zero up to 15 Hz, indicating functional residual capacity did not change. We conclude that externally applied HFO can readily maintain gas exchange in vivo, with Vo less than VD at frequencies over 2 Hz.