Protein variability in cereal cyst nematodes from different geographic regions assessed by two-dimensional gel electrophoresis

La variabilité protéique de douze populations de nématodes à kyste des céréales provenant de sept pays (quatre continents) a été étudiée à partir de trois échantillons par population, chacun constitué de 40 femelles blanches âgées de 50 jours, produites sur le même blé, #Triticum aestivum cv. Arminda, en conditions contrôlées. La pathogénie de chaque isolat est précisée par référence à la littérature ou/et à des tests d'hôtes complémentaires. Trois électrophorèses sont réalisées par échantillon protéique avec de légères modifications apportées aux techniques de migration (O'Farrell, 1975) et de coloration (Oakley et al., 1980). 320 polypeptides sont détectés sur l'ensemble des populations. Les profils protéiques sont comparés par analyse d'images informatisée à l'aide d'une station Vax (4000.60), d'un scanner (Eikonix, Kodak) et du logiciel Kepler (L.S.B. Corporation). Différents degrès de sévérité dans l'acceptation de la détection des spots ont été établis selon leur volume et/ou une gamme d'amplitudes. Les indices de similarité (F) et les distances génétiques (D = 1-F) sont calculés à partir des spots homologues. Les dendrogrammes correspondants sont construits selon la méthode UPGMA. Les résultats montrent une grande variabilité protéique entre populations et une séparation nette entre le groupe #Heterodera avenae sensu stricto et le groupe Gotland. Dans le groupe #H. avenae$ sensu stricto, les deux populations françaises et un isolat d'Australie du sud sont fortement apparentés. Des protéines spécifiques des deux pathotypes français Ha12 et Ha12/FR2 sont caractérisées. La comparaison des profils protéiques par analyse d'images informatisée est discutée. (Résumé d'auteur

Host responses of different Triticeae to species of the cereal cyst nematode complex in relation to breeding resistant durum wheat

Vingt-huit lignées ou cultivars de #Triticum diploïdes (génomes A, D, S(I), U), tétraploïdes (génomes AB, D(V)M(V), UM, US(V)) et hexaploïdes (génome ABD) ont été étudiés pour leur capacité à permettre le développement de neuf populations d'#Heterodera avenae originaires de six pays (Algérie, France, Espagne, Australie, Israël et Inde), deux populations d'#Heterodera filipjevi provenant de Russie et de Bulgarie et une population d'#Heterodera latipons provenant d'Israël. Les tests ont été conduits dans des conditions artificielles selon une technique miniaturisée. Les résultats ont montré une résistance élevée à l'encontre des populations d'#H. avenae sensu stricto au sein des trois niveaux de ploïde et dans les différents génomes S(1) (#T. longissimum), D(V)M(V) (#T. ventricosum), UM (#T. ovatum), US(V) (#T. variabile) et ABD (#T. aestivum AUS 4930). Des sources de résistance complète ou partielle ont été trouvées dans le génome D (#T. tauschii CPI 110813 ou AUS 18913), mais leur expression dans les blés hexaploïdes synthétiques est incomplète. Il a été confirmé que le gène #Cre1 du blé cv. Loros est inefficace contre les populations d'#H. avenae d'Australie, d'Inde, et d'Israël, ainsi que contre les populations d'#H. filipjevi. La différenciation inter- et intraspécifique dans ce complexe de nématodes à kystes des céréales pour leur (a)virulence vis-à-vis de #Triticeae$ et leur capacité reproductive intrinsèque sont discutées, ainsi que l'utilisation de résistances complète et partielle dans les programmes de sélection. (Résumé d'auteur

Detection of Heterodera avenae infestations on winter wheat by radiothermometry

International audienc

An Euler-type formula for β(2n)\beta(2n) and closed-form expressions for a class of zeta series

In a recent work, Dancs and He found an Euler-type formula for $\,\zeta{(2\,n+1)}$, $\,n\,$ being a positive integer, which contains a series they could not reduce to a finite closed-form. This open problem reveals a greater complexity in comparison to $\zeta(2n)$, which is a rational multiple of $\pi^{2n}$. For the Dirichlet beta function, the things are `inverse': $\beta(2n+1)$ is a rational multiple of $\pi^{2n+1}$ and no closed-form expression is known for $\beta(2n)$. Here in this work, I modify the Dancs-He approach in order to derive an Euler-type formula for $\,\beta{(2n)}$, including $\,\beta{(2)} = G$, the Catalan's constant. I also convert the resulting series into zeta series, which yields new exact closed-form expressions for a class of zeta series involving $\,\beta{(2n)}$ and a finite number of odd zeta values. A closed-form expression for a certain zeta series is also conjectured.Comment: 11 pages, no figures. A few small corrections. ACCEPTED for publication in: Integral Transf. Special Functions (09/11/2011

Environmental control of terpene emissions from Cistus monspeliensis L. in natural Mediterranean shrublands

The large amount of volatile organic compound (VOC) emitted by vegetation modifies air quality contributing to both tropospheric ozone and secondary organic aerosol production. A better understanding of the factors controlling VOC emissions by vegetation is mandatory in order to improve emission estimates derived from tropospheric chemistry models. Although the Mediterranean shrublands are particularly abundant and rich in emitting species, their emission potential is poorly known. Focusing on a VOC-emitting shrub species widespread in the Mediterranean area (Cistus monspeliensis L.), we measured and analysed its emissions of terpenes taking into account the age of individuals, the season of sampling and the soil type. Sampling was done under natural environmental conditions. Species of the genus Cistus are frequently reported to be storing species, although we found only one stored monoterpene and three sesquiterpenes in very low amount. Major emitted compounds were a-pinene and b-myrcene. Total terpene emissions were not influenced by plant age but emission of some individual terpenes was positively correlated with age. A strong seasonal effect was evidenced. A larger amount of terpenes was emitted during spring and summer than during fall and winter. Summer emission rates were nearly 70 times higher than winter emission rates. Total and individual terpene emissions were influenced by soil type; emissions on siliceous substrate were ca. seven times higher than those on calcareous substrate. In conclusion, it appears clearly that environmental factors such as soil nature and season should be taken into account in order to achieve improved modelling of terpene emissions by shrub species

Resistance to the cereal cyst nematode (Heterodera avenae) transferred from the wild grass Aegilops ventricosa to hexaploid wheat by a "stepping-stone" procedure

Transfer of resistance toHeterodera avenae, the cereal cyst nematode (CCN), by a stepping-stoneprocedure from the wild grassAegilops ventricosa to hexaploid wheat has been demonstrated. The number of nematodes per plant was lower, and reached a plateau much earlier, in the resistant introgression line H93-8 (1–2 nematodes per plant) than in the recipient H10-15 wheat (14–16 nematodes per plant). Necrosis (hypersensitive reaction) near the nematode, little cell fusion, and few, often degraded syncytia were observed in infested H93-8 roots, while abundant, well-formed syncytia were present in the susceptible H10-15 wheat. Line H93-8 was highly resistant to the two Spanish populations tested, as well as the four French races (Fr1-Fr4), and the British pathotype Hall, but was susceptible to the Swedish pathotypes HgI and HgIII. Resistance was inherited as though determined by a single quasi-dominant factor in the F2 generations resulting from crosses of H93-8 with H10-15 and with Loros, a resistant wheat carrying the geneCre1 (syn.Ccn1). The resistance gene in H93-8 (Cre2 orCcn2) is not allelic with respect to that in Loros. RFLPs and other markers, together with the cytogenetical evidence, indicate that theCre2 gene has been integrated into a wheat chromosome without affecting its meiotic pairing ability. Introduction ofCre2 by backcrossing into a commercial wheat backgroud increases grain yield when under challenge by the nematode and is not detrimental in the absence of infestation