Can drifting objects drive the movements of a vulnerable pelagic shark?

1. Juvenile silky sharks (Carcharhinus falciformis) regularly associate with floating objects yet the reasons driving this behaviour remain uncertain. Understanding the proportion of time that silky sharks spend associated with floating objects is essential for assessing the impacts of the extensive use of fish aggregating devices (FADs) in the tropical tuna purse-seine fisheries, including increased probability of incidental capture and the potential of an ecological trap.
2. Previous studies provided insight into the amount of time that silky sharks spent at an individual FAD but were unable to assess neither the time spent between two associations nor the proportion of time spent associated/unassociated.
3. The percentage of time that juvenile silky sharks spend unassociated with floating objects was estimated through the analysis of horizontal movements of 26 silky sharks monitored with pop-up archival tags. Under the assumption that a high association rate with drifting FADs would align the trajectories of tracked sharks with ocean surface currents, a novel methodology is proposed, based on the comparison of shark trajectories with simulated trajectories of passively drifting particles derived using a Lagrangian model.
4. Results revealed that silky shark trajectories were divergent from surface currents, and thus unassociated with FADs, for at least 30% of their time. The potential of the methodology and the results are discussed in the context of increasing FAD densities in the Indian Ocean.

     

Detection of quantitative trait loci for fat androstenone levels in pigs

A QTL analysis of fat androstenone levels from a three-generation experimental cross between Large White and Meishan pig breeds was carried out. A total of 485 F2 males grouped in 24 full-sib families, their 29 parents and 12 grandparents were typed for 137 markers distributed over the entire porcine genome. The F2 male population was measured for fat androstenone levels at 100, 120, 140, and 160 d of age and at slaughter around 80 kg liveweight. Statistical analyses were performed using two interval mapping methods: a line-cross (LC) regression method, which assumes alternative alleles are fixed in founder lines, and a half- full-sib (HFS) maximum likelihood method, where allele substitution effects were estimated within each half- and full-sib family. Both methods revealed genomewide significant gene effects on chromosomes 3, 7, and 14. The QTL explained, respectively, 7 to 11%, 11 to 15%, and 6 to 8% of phenotypic variance. Three additional significant QTL explaining 4 to 7% of variance were detected on chromosomes 4 and 9 using LC method and on chromosome 6 using HFS method. Suggestive QTL were also obtained on chromosomes 2, 10, 11, 13, and 18. Meishan alleles were associated with higher androstenone levels, except on chromosomes 7, 10, and 13, although 10 and 13 additive effects were near zero. The QTL had essentially additive effects, except on chromosomes 4, 10, and 13. No evidence of linked QTL or imprinting effects on androstenone concentration could be found across the entire porcine genome. The steroid chromosome P450 21-hydroxylase (CYP21) and cytochrome P450 cholesterol side chain cleavage subfamily XIA (CYP11A) loci were investigated as possible candidate genes for the chromosome 7 QTL. No mutation of coding sequence has been found for CYP21. Involvement of a candidate regulatory mutation of CYP11A gene proposed by others can be excluded in our animals.     

Osmotic adjustment in three-year-old seedlings of five provenances of maritime pine (Pinus pinaster) in response to drought

Three-year-old seedlings of five provenances of Pinus pinaster Ait. that differed in climatic conditions at their geographical origin were subjected to decreasing soil water availability. The degree of needle osmotic adjustment (OA) was estimated based on logarithmic plots of needle relative water content (RWC) against needle osmotic potential (Psi(pi)); i.e., lnRWC versus -ln(-Psi(pi)). There were significant differences among provenances in active OA (0.13 to 0.30 MPa for a decrease in RWC to 80%), and a clear negative relationship was found between OA and precipitation (650 to 1280 mm of mean annual rainfall) at the geographical origins of the provenances. A high osmoregulatory capacity contributes to the maintainance of positive turgor at low water potentials. We conclude that OA is one of the mechanisms underlying adaptation to drought in P. pinaster. Solute accumulation was about 2.3 times higher in the provenance from the driest site than in the provenance from the wettest site. The contribution of osmotic adjustment to differences in drought tolerance mechanisms among provenances is discussed.     

Molecular cloning and sequence analysis of cDNAs encoding for Boophilus microplus, Haemaphysalis longicornis and Rhipicephalus appendiculatus actins

The nucleotide and deduced amino acid sequences of the actins from ticks, Boophilus microplus, Haemaphysalis longicornis and Rhipicephalus appendiculatus, have been determined. Nucleotide sequence analysis showed open reading frames of 1128-nucleotide-long encoding proteins of 376 amino acids with a predicted molecular weight of 41.82 kDa each. Comparison between the nucleic acid and deduced amino acid sequences as well as structural and phylogenetic analyses of these genes confirmed the high similarity among actins from ticks in comparison to other species.     

Methods of conserving gametes and embryos of farm mammalsLes méthoses de conservation des gamètes et embryons de mammifères de fermeKonservierungsmethoden für gameten und embryonen von haus-säugetieren

There are several methods of preserving domestic animal genes. In the present paper methods using frozen germ plasm are considered. Except in the mare, birth rates of more than 50% are obtained from deep-freezing spermatozoa. The freezing of oocytes has not been used yet in all domestic animals, but the techniques of freezing cattle, sheep, goat, rabbit and recently horse embryos are being developed. It is not yet possible to use these techniques in the pig. The success of gene preservation programmes depends not only on the technique used, but also on the efforts made by breeders and official organizations.     

A Field Method for Evaluating the Potential Durability of New Resistance Sources: Application to the Leptosphaeria maculans-Brassica napus Pathosystem

ABSTRACT To increase the longevity of new resistance genes by avoiding a rapid change in pathogen populations, we established a new field method to determine, before the release of a resistant cultivar, whether and how rapidly the pathogen population is capable of responding to the selective pressure we impose. This method was applied to the Leptosphaeria maculans-Brassica napus pathosystem. The potential durability of two new major resistance genes introgressed into B. napus from the Brassica B genome was tested separately for each gene under field conditions for 4 years. Successive inoculations with residues of the resistant lines mixed with susceptible contaminated plant material recovered at harvest the previous year were performed in autumn. The Jlm1 resistance gene originating from B. juncea conferred complete resistance on the B. napus-B. juncea recombinant lines MX and MXS to inoculation of the cotyledons with a large diversity of L. maculans isolates. It also gave a high level of stem canker resistance in the field against natural populations of the pathogen. A similar level of resistance was obtained in the B. napus-B. nigra addition line LA4+, containing B. nigra chromosome 4 in a B. napus background. In the second year of the field experiment (i.e., the first in which residues from the resistant lines were included in the inoculation material), both MX and LA4+ maintained a high level of resistance. In the third and fourth years of the field experiment, the resistance of MX and MXS exposed to inoculum produced from their own residues broke down, but against fungal populations from susceptible B. napus or resistant B. nigra material remained effective. In contrast, LA4+ remained highly resistant to all sources of inoculum for the 4-year experiment.     

Cytological Investigation of Resistance to Leptosphaeria maculans Conferred to Brassica napus by Introgressions Originating from B. juncea or B. nigra B Genome

ABSTRACT Introgressions into Brassica napus from the B genome, either the B. nigra chromosome B4 or the B. juncea fragment carrying the Jlm1 gene, have given rise to the B. napus-B. nigra addition line (LA4+) and the B. napus-B. juncea recombinant line (MXS), respectively. The resistance of these two lines to Leptosphaeria maculans is characterized by a hypersensitive reaction (HR) on both the cotyledons and leaves, while the collar displays a high degree of resistance. Responses induced in cotyledons of the two lines by L. maculans inoculation were investigated with emphasis on cytological events underlying the HR and on host defense reactions. Features of host cell changes including condensation and lobing of nuclei, fragmentation of chromatin, disruption of the nuclear membranes, and plasma membrane withdrawal were reminiscent of HR cell death in MXS and LA4+ plants. Restriction of pathogen growth to the infection areas in LA4+ was correlated to reinforcement of cell wall barriers, including wall apposition, papillae, and vessel plugging. In MXS, the lower expression of resistance was associated with a delay in plant responses. These results indicate that mechanisms underlying the HR in the B. napus recombinant and addition lines are differently controlled according to the introgressed genes.     

Litter decomposition in peatlands is promoted by mixed plants

Purpose

The carbon sink function of peatlands is primarily driven by a higher production than decomposition of the litter Sphagnum mosses. The observed increase of vascular plants in peatlands could alter the decomposition rate and the carbon (C) cycle through a litter mixing effect, which is still poorly studied. Here, we examine the litter mixing effect of a peat moss (Sphagnum fallax) and two vascular plants (Pinus uncinata and Eriophorum vaginatum) in the field and laboratory-based experiment.

Materials and methods

During the laboratory incubation, mass loss, CO₂ production, and dissolved organic carbon concentration were periodically monitored during 51 days. The collected data were then processed in a C dynamics model. The calculated enzymatic activity was correlated to the measured β-glucosidase activity in the litter. In the field experiment, mass loss and CO₂ production from litter bags were annually measured for 3 years.

Results and discussion

Both laboratory and field experiments clearly show that the litter mixture, i.e., Sphagnum-Pinus-Eriophorum, had a synergistic effect on decomposition by enhancing the mass loss. Such enhanced mass loss increased the water extractable C and CO₂ production in the litter mixture during the laboratory experiment. The synergistic effect was mainly controlled by the Sphagnum-Eriophorum mixture that significantly enhanced both mass loss and CO₂ production. Although the β-glucosidase activity is often considered as a major driver of decomposition, mixing the litters did not cause any increase of the activity of this exo-enzyme in the laboratory experiment suggesting that other enzymes can play an important role in the observed effect.

Conclusions

Mixing litters of graminoid and Sphagnum species led to a synergistic effect on litter decomposition. In a context of vegetation dynamics in response to environmental change, such a mixing effect could alter the C dynamics at a larger scale. Identifying the key mechanisms responsible for the synergistic effect on litter decomposition, with a specific focus on the enzymatic activities, is crucial to better predict the capacity of peatlands to act as C sinks.

     

Growth phenology in <Emphasis Type="Italic">Pinus halepensis</Emphasis> Mill.: apical shoot bud content and shoot elongation

Key message

The chronology of periods of organogenesis and elongation is highlighted in Pinus halepensis.The two first growth units of an annual shoot are preformed inside the bud during the previous year. The following growth units are formed during the spring or summer of the current year.

Context

Analysis of annual shoot length growth phenology is crucial to assess the impact of climate change on tree production. Little is known about the basic growth characteristics and the phenology of pines.

Aims

The present study disentangles the roles of shoot organogenesis vs elongation in the annual growth cycle of the polycyclic Aleppo pine.

Methods

Growth of young Pinus halepensis trees was monitored monthly for 1 year. At each monitoring date, the bud content and meristem dimensions of the main stem shoots apices were analyzed.

Results

The two first growth units of an annual shoot are preformed inside the bud during the previous year. The following growth units are formed during the spring or summer of the current year. The gap between a shoot organogenesis and its elongation may vary from 1 month, for the last growth unit, to half a year, for the first growth units.

Conclusion

Our results underline the importance of taking seasonal environmental conditions from both the previous and the current year into account, in order to study the plasticity of annual shoot growth and its response to climate change and variability.

     

The novel elicitor COS‐OGA enhances potato resistance to late blight

Phytophthora infestans is the causal agent of potato late blight. This pathogen is usually controlled by fungicides, but new European regulations have imposed changes in crop protection management that have led to a search for alternative control measures. The induction of plant defence responses by elicitors is a promising new strategy compatible with sustainable agriculture. This study investigated the effect of eliciting a defence response in potato against P. infestans using a formulation of the COS‐OGA elicitor that combines cationic chitosan oligomers (COS) and anionic pectin oligomers (OGA). Trials were conducted under greenhouse conditions to assess the ability of COS‐OGA to control P. infestans. The results showed that three foliar applications with this elicitor significantly increased potato protection against late blight in controlled conditions. The activation of potato defence genes was also evaluated by RT‐qPCR during these trials. Two pathogenesis‐related proteins, basic PR‐1 and acidic PR‐2, were rapidly and significantly up‐regulated by the elicitor treatment. Therefore, these results suggest that the COS‐OGA elicitor increases the protection of potato against P. infestans and that this protection could be explained by an increase in the expression of potato defence genes rather than by biocide activity.