Grapevine breeding for resistance to powdery mildew: Bioassay system for evaluation of plant resistance and for characterization of different Uncinula necator strains

Several isolates of Uncinula necator were separated and kept in vitro. The pathogenicity of these isolates was compared by a bioassay system using small leaves issued from in vitro plants; 2 µl of spore suspension was inoculated on these leaves. Significative differences in sporulation time, aggressiveness, sporulation rate and resistance to fungicide triadimenol were observed between these isolates. Host plant variety also affects some of these characters of pathogenicity. The isolates were classified into 2 mating types concerning the aspect of perithecia formation by paired combination between 2 isolates. Productivity of perithecia varied in response to the combination of isolates and to host plant variety

Sensibilité de variétés de vigne (Vitis vinifera L.) à l'excoriose (Phomopsis viticola Sacci). Distribution du caractère dans quelques descendances

On sait que l'excoriose ne présente pas la même gravité sur tous les cépages. Cependant, les observations qui sont relatées sont rares et fragmentaires c'est pourquoi nous avons entrepris de préciser le comportement d'un certain nombre de cépages de notre collection (plus de 200) vis-à-vis de cette maladie. Les notations effectuées confirment l'existence de grandes différences et ont permis de les chiffrer (notes de O à 5). On peut citer les cépages les moins sensibles: Pinot Meunier, Mourvèdre, Riesling, Cinsaut, Cabernet Franc, Ugni blanc; et parmi les plus sensibles: Chasselas, Semillon, Baroque, Gros Vert, Alphonse Lavallée, Cardinal.Ces observations, lorsqu'elles seront confirmées, pourront orienter, nous semble-t-il, l'application des méthodes de lutte à chaque cépage.Nous avons cherché, dautre part, à préciser le mode de transmission héréditaire de la réaction variétale à la maladie. Pour celà, nous avons mis au point une technique d'inoculation artificielle de rameaux herbacés en survie, assortie d'un mode de notation approprié.Les observations effectuées sur des descendants issus d'autofécondation des deux cépages Merlot et Alicante Bouschet ainsi que sur ceux issus du croisement entre ceux-ci, semblent indiquer une dominance de la moindre sensibilité à l'excoriose. Sensibility of grape varieties (Vitis vinifera L.) to excoriose (Phomopsis viticola Sacc.). Distribution of the character in some progenies It is known that excoriose is not equally severe to ail grape varieties. However, published observations are scanty and fragmentary; we therefore started a study on the behaviour of a number of varieties in our collection (more than 200) to this parasite.Visual scoring on a O to 5 scale confirmed the existence of important differences: Pinot Meunier, Mourvèdre, Riesling, Cinsaut, Cabernet Franc, Ugni blanc ranged among the least susceptible varieties; Baroque, Gros Vert, Alphonse Lavallée, Cardinal, Chasselas, Semillon were among the most susceptible ones.Once these observations are confirmed, they might be useful in adjusting of control methods to each variety.On the other hand, we tried to investigate the inheritance of the varietal response to the parasite. For that purpose, we devised an artificial inoculation technique using eut herbaceous shoots and a scoring scale.Observations on progenies from selfings of the varieties Merlat and Alicante Bouschet, as well as on those of the crossing between these varieties, indicate that low susceptibility to excoriose might be dominant

A technique for improving the germinability of grape seeds for breeding purposes

A method, using bunches from pre-rooted cuttings which are defoliated very early during bud burst, allows the cultivation of fruiting plants in the glasshouse. The germinability of the seeds obtained in this way is improved, which permits, in particular, progenies of an early mutant of the cultivar "Cot", the seeds of which obtained in the field do practically never germinate.Une technique pour améliorer la germinabilité des graines de vigne pour les besoinsde l'améliorationUne technique, consistant à obtenir des grappes sur des boutures préenracinées puis soumises à un effeuillage très précoce au débourrement, permet de cultiver des plantes fructifères en serre. Les graines ainsi obtenues ont une proportion de germination meilleure, ce qui a permis en particulier d'obtenir des descendants d'un mutant précoce du Cot dont les graines obtenues au champ ne germent pratiquement jamais.

Amélioration du rendement du bouturage des extrémités après thermothérapie sur plantes en pots par l'utilisation de la culture sur milieu nutritif gélosé stérile

L'enracinement sous brouillard d'extrémités de tiges prélevées sur des plantes en pots après le traitement thermique se révèle souvent décevant (20 à 25%). Ces extrémités, mises stérilement en culture sur milieu nutritif gélosé, ne sont que rarement contaminées par des champignons ou des bactéries (moins de 3%), et l'on obtient ainsi un nombre élevé de plantes établies au champ à partir des extrémités implantées (82%).lmprovement of the shoot-tip yield of heat treated pot plants using culture on agar nutrient medium under sterile conditionsRooting shoot-tips from heat treated pot plants under mist proved very unsuccessfull (20 to 25%). Use of culture on agar nutrient medium under sterile conditions with these shoot tips resulted in a surprisingly low fungal and bacterial contamination rate (less than 3°/o) and a very high proportion of successfull establishment of plants in the field from the shoot-tip inplants (82%)

Relationship and patterns of distribution among grapevine viroids from California and Europe

Analyses of California and European grapevine sources indicated a ubiquitous occurrence of viroids in these materials. Hybridization results indicated sequence homology to both GV-1 and GV-3 for viroids of varieties grown in California as well as from European sources. Wine and rootstock varieties contained a greater proportion of the more common GV-1 plus GV-3 viroid profile, whereas the table varieties contained a larger proportion of the relatively unusual viroid profile of GV-1, -2, and-3. An unexpected divergence of four viroid profiles emerged in the rootstock species. These profiles were 1) Gv-1, -2, and -3, 2) GV-1 plus GV-3, 3) GV-3, and 4) viroid-free. V. californica was the only grapevine analyzed which was found to be viroid-free

Estimation de la capacité photoautotrophique de vitroplants de porte-greffe de vigne (var. Gravesac): mise au point d'un système de mesure de la photosynthèse nette de vitroplants

La capacité photosynthétique de vitroplants de vigne (var. Gravesac) a été déterminée à l'aide d'un dispositif de mesures des échanges gazeux en circuit ouvert. L'activité photosynthétique et la respiration de la plante sont importantes en culture in vitro. La photosynthèse nette maximale est de 2 µmol m-2 s-1 a 500 µ11-1 de CO2. A 350 µ11-1 de CO2 la photosynthèse est de 1,6 µmol m-2 s-1. La respiration a l'obscurité est de 0,018 µmol s-1 g-1 de poids sec total. La quantité totale des sucres solubles dans le milieu de culture reste constante pendant les deux mois de culture. Le saccharose est totalement hydrolysé en glucose et en fructose. Les vitroplants de Gravesac ne prélèvent pas de sucres dans le milieu, ce qui confirme leur degré élevé d'autotrophie dans ces conditions de culture. La comparaison entre les échanges gazeux de vitroplants et des plantes cultivées en serre met en évidence une réduction de 80% de l'activité in vitro.Evaluation of the photoautotrophic ability of Vitis plantlets (rootstock var Gravesac): Set-up of a special open flow gas exchange systemThe photosynthetic ability of Vitis rootstock plantlets (var. Gravesac) was estimated in vitro with an open flow system specially designed for in vitro culture. CO2 response curves were established and respiration was also measured. The maximum net photosynthetic rate, reached at 500 µ11-1 of CO2, is 2 µmol m-2 s-1. At 350 µ11-1 CO2 the photosynthetic activity is 1.6 µmol m-2 s-1. The dark respiration rate is 0.018 µmol s-1 g-1 of total dry weight. The total amount of soluble carbohydrates in the medium remains the same whether plantlets were present or not. In the medium with plantlets, the sucrose is entirely hydrolysed in glucose and fructose within two months. No carbohydrate uptake from the medium was recorded indicating an autotrophic behaviour. Measurements of CO2 exchange were also performed at leaves of plants cultivated in a greenhouse. The photosynthetic activity of in vitro plants accounts only for 20% of the level of greenhouse-grown plants

The Remarkable Be Star HD110432

HD110432 has gained considerable attention because it is a hard, variable X-ray source similar to gamma Cas. From time-serial echelle data obtained over two weeks during 2005 January and February, we find several remarkable characteristics in the star's optical spectrum. The line profiles show rapid variations on some nights which can be most likely be attributed to irregularly occurring and short-lived migrating subfeatures. Such features have only been observed to date in gamma Cas and AB Dor, two stars for which it is believed magnetic fields force circumstellar clouds to corotate over the stellar surface. The star's optical spectrum also exhibits a number of mainly FeII and HeI emission features with profiles typical of an optically thin disk viewed edge-on. Using spectral synthesis techniques, we find that its temperature is 9800K +/-300K, that its projected area is a remarkably large 100 stellar areas, and its emitting volume resides at a distance of 1 AU from the star. We also find that the star's absorption profiles extend to +/-1000 km/s, a fact which we cannot explain. Otherwise, HD110432 and gamma Cas share similarly peculiar X-ray and optical characteristics such as high X-ray temperature, erratic X-ray variability on timescales of a few hours, optical emission lines, and submigrating features in optical line profiles. Because of these similarities, we suggest that this star is a new member of a select class of "gamma Cas analogs."Comment: 31 pages, 9 figures, accepted by ApJ (3/20/06

Properties and nature of Be stars: 27. Orbital and recent long-term variations of the Pleiades Be star Pleione = BU Tauri

Radial-velocity variations of the H-alpha emission measured on the steep wings of the H-alpha line, prewhitened for the long-time changes, vary periodically with a period of (218.025 +/- 0.022)d, confirming the suspected binary nature of the bright Be star Pleione, a member of the Pleiades cluster. The orbit seems to have a high eccentricity over 0.7, but we also briefly discuss the possibility that the true orbit is circular and that the eccentricity is spurious owing to the phase-dependent effects of the circumstellar matter. The projected angular separation of the spectroscopic orbit is large enough to allow the detection of the binary with large optical interferometers, provided the magnitude difference primary - secondary is not too large. Since our data cover the onset of a new shell phase up to development of a metallic shell spectrum, we also briefly discuss the recent long-term changes. We confirm the formation of a new envelope, coexisting with the previous one, at the onset of the new shell phase. We find that the full width at half maximum of the H-alpha profile has been decreasing with time for both envelopes. In this connection, we briefly discuss Hirata's hypothesis of precessing gaseous disk and possible alternative scenarios of the observed long-term changes

Ultraviolet Spectrophotometry of Variable Early-Type Be and B stars Derived from High-Resolution IUE Data

High-dispersion IUE data encode significant information about aggregate line absorptions that cannot be conveniently extracted from individual spectra. We apply a new technique in which fluxes from each echelle order of a short wavelength IUE spectrum are binned together to construct low-resolution spectra of a rapidly varying B or Be star. The ratio of binned spectra obtained bright- star and faint-star phases contains information about the mechanism responsible for a star's variability, such as from pulsations or occultations of the star by ejected matter. We model the variations caused by these mechanism by means of model atmosphere and absorbing-slab codes. Line absorptions strength changes are sensitive to conditions in circumstellar clouds with T = 8,000--13,000K. To demonstrate proofs of concept, we construct spectral ratios for circumstellar structures associated with flux variability in various Be stars: (1) Vela X1 has bow-shock wind trailing its neutron star companion and shows signatures of gas at 13,000K or 26,000K medium in different sectors, (2) 88 Her undergoes episodic outbursts as its UV flux fades, followed a year later by a dimming in visible wavelengths, a result of a gray opacity that dominates as the shell expands and cools, and (3) zeta Tau and 60 Cyg exhibit periodic spectrum and flux changes, which match model absorptions for occulting clouds. Also, ratioed UV spectra of strongly pulsating stars show unique spectrophotometric signatures which can be simulated with models. An analysis of ratioed spectra obtained for a typical sample of 18 classical Be stars known to have rapid periodic flux variations indicates that 13 of them have ratioed spectra which are relatively featureless or have signatures of pulsation. Ratioed spectra of 3 others in the sample are consistent with the presence of co-rotating clouds.Comment: Latex 49 dbl-spaced pages plus 9 figures. Accepted by ApJ. Files available at ftp://nobel.stsci.edu/pub/uv

X-ray and Optical Variations in the Classical Be Star gamma Cas

gamma Cas (B0.5e) is known to be a unique X-ray source because ot its moderate L_x, hard X-ray spectrum, and light curve punctuated by ubiquitous flares and slow undulations. Its X-ray peculiarities have led to a controversy concerning their origin: either from wind infall onto a putative degenerate companion, as for typical Be/X-ray binaries, or from the Be star per se. Recent progress has been made to address this: (1) the discovery that gamma Cas is an eccentric binary system (P = 203.59 d) with unknown secondary type, (2) the accumulation of RXTE data at 9 epochs in 1996-2000, and (3) the collation of robotic telescope B, V-band photometric observations over 4 seasons. The latter show a 3%, cyclical flux variation with cycle lengths 55-93 days. We find that X-ray fluxes at all 9 epochs show random variations with orbital phase. This contradicts the binary accretion model, which predicts a substantial modulation. However,these fluxes correlate well with the cyclical optical variations. Also, the 6 flux measurements in 2000 closely track the interpolated optical variations between the 2000 and 2001 observing seasons. Since the optical variations represent a far greater energy than that emitted as X-rays, the optical variability cannot arise from X-ray reprocessing. However, the strong correlation between the two suggests that they are driven by a common mechanism. We propose that this mechanism is a cyclical magnetic dynamo excited by a Balbus-Hawley instability located within the inner part of the circumstellar disk. In our model, variations in the field strength directly produce the changes in the magnetically related X-ray activity. Turbulence associated with the dynamo results in changes to the density distribution within the disk and creates the observed optical variations.Comment: 30 dbl-spaced pages, Latex, plus 11 figures. Accepted by Ap