We report on a long-term monitoring of the cool supergiant Betelgeuse, using the NARVAL and ESPaDOnS high-resolution spectropolarimeters, respectively installed at Telescope Bernard Lyot (Pic du Midi Observatory, France) and at the Canada-France-Hawaii Telescope (Mauna Kea Observatory, Hawaii). The data set, constituted of circularly polarized (Stokes V) and intensity (Stokes I) spectra, was collected between 2010 and 2012. We investigate here the temporal evolution of magnetic field, convection and temperature at photospheric level, using simultaneous measurements of the longitudinal magnetic field component, the core emission of the Ca II infrared triplet, the line-depth ratio of selected photospheric lines and the radial velocity of the star.

Magnetic fields of cool stars can be directly investigated through the study of the Zeeman effect on photospheric spectral lines using several approaches. With spectroscopic measurement in unpolarised light, the total magnetic flux averaged over the stellar disc can be derived but very little information on the field geometry is available. Spectropolarimetry provides a complementary information on the large-scale magnetic topology. With Zeeman-Doppler Imaging (ZDI), this information can be retrieved to produce a map of the vector magnetic field at the surface of the star, and in particular to assess the relative importance of the poloidal and toroidal components as well as the degree of axisymmetry of the field distribution.

The development of high-performance spectropolarimeters associated with multi-lines techniques and ZDI allows us to explore magnetic topologies throughout the Hertzsprung-Russel diagram, on stars spanning a wide range of mass, age and rotation period. These observations bring novel constraints on magnetic field generation by dynamo effect in cool stars. In particular, the study of solar twins brings new insight on the impact of rotation on the solar dynamo, whereas the detection of strong and stable dipolar magnetic fields on fully convective stars questions the precise role of the tachocline in this process.

Using spectropolarimetric data acquired with the ESPaDOnS and NARVAL instruments at CFHT and at TBL, we present a detailed spectral synthesis analysis of HD 232 862, a field giant classified as a G8II star hosting a magnetic field. This star is the first lithium-rich field giant hosting a magnetic field. Stellar evolution models suggest that HD 232 862 should be a 1.5 to 2.0 M⊙ star at the bottom of the red giant branch. Its unsually high lithium content (A(Li) = 2.45 ± 0.25 dex) is even more puzzling and challenges our understanding of the evolution of this star.

From spectropolarimetric data and spectral synthesis analysis, we report the serendipitous discovery of an unusually high lithium content field giant. HD 232862, classified as a G8II star, appears to be the first Lithium-rich field giant star hosting a surface magnetic field.

We present the results of high resolution spectroscopic observations of Li I resonance doublet at λ 6707.8 Å for fast rotating single stars of luminosity class II and Ib. We present a discussion on the link between rotation and Li content in intermediate mass giant stars, with emphasis on their evolutionary status. At least one of the observed stars, HD 232862, a G8II with an unusual vsini of 20 km/s, present a Li-rich behavior.

Alternaria alternata, A. radicina and A. dauci are important seed-borne fungi on carrot, with the first two species having a high toxigenic potential, for which a specific and sensitive detection method is required. Because both the traditional deep-freeze-blotter method and plating on selective medium are time consuming and laborious, a PCR-based assay was developed. Sequences of the internal transcribed spacer regions of the ribosomal gene repeat (rDNA) from 45 different Alternaria isolates were determined, a restriction fragment length polymorphism analysis was performed and a phylogenetic tree was constructed. Based on the sequences, specific primers for detection and identification of the three Alternaria species on carrot seeds and roots were designed. The primers were highly sensitive and were shown to be able to differentiate between the three Alternaria species. A. alternata and A. radicina could be detected in DNA isolated from carrot material applying the specific primers, even at low infection levels. The PCR-assay was compared to the deep-freeze-blotter method (DFBM) and plating on Alternaria radicina Selective Agar (ARSA, for A. radicina) by testing naturally infected seed samples and root material. Results of the PCR-assay were similar to those of the blotter method and plating on ARSA for the detection of A. alternata and A. radicina. A positive correlation was found between the percentage of seed infection established by the blotter method and the intensity of the amplified, specific product. The PCR-assay based on the specific primers developed seems to be a good alternative for the deep-freeze-blotter method and plating on ARSA, especially when time is an important issue.