Oidium neolycopersici: Intra-specific variability inferred from AFLP analysis and relationship with closely related powdery mildew fungi infecting various plant species

Previous works indicated a considerable variation in the pathogenicity, virulence, and host range of Oidium neolycopersici isolates causing tomato powdery mildew epidemics in many parts of the world. In this study, rDNA internal transcribed spacer (ITS) sequences, and amplified fragment length polymorphism (AFLP) patterns were analyzed in 17 O. neolycopersici samples collected in Europe, North America, and Japan, including those which overcame some of the tomato major resistance genes. The ITS sequences were identical in all 10 samples tested and were also identical to ITS sequences of eight previously studied O. neolycopersici specimens. The AFLP analysis revealed a high genetic diversity in O. neolycopersici and indicated that all 17 samples represented different genotypes. This might suggest the existence of either a yet unrevealed sexual reproduction or other genetic mechanisms that maintain a high genetic variability in O. neolycopersici. No clear correlation was found between the virulence and the AFLP patterns of the O. neolycopersici isolates studied. The relationship between O. neolycopersici and powdery mildew anamorphs infecting Aquilegia vulgaris, Chelidonium majus, Passiflora caerulea, and Sedum alboroseum was also investigated. These anamorphs are morphologically indistinguishable from and phylogenetically closely related to O. neolycopersici. The cross-inoculation tests and the analyses of ITS sequences and AFLP patterns jointly indicated that the powdery mildew anamorphs collected from the above mentioned plant species all represent distinct, but closely related species according to the phylogenetic species recognition. All these species were pathogenic only to their original host plant species, except O. neolycopersici which infected S. alboroseum, tobacco, petunia, and Arabidopsis thaliana, in addition to tomato, in cross-inoculation tests. This is the first genome-wide study that investigates the relationships among powdery mildews that are closely related based on ITS sequences and morphology. The results indicate that morphologically indistinguishable powdery mildews that differed in only one to five single nucleotide positions in their ITS region are to be considered as different taxa with distinct host ranges

Precise energy of the 9.4 keV gamma transition observed in the 83Rb decay

The energy of the 9.4 keV γ-transition observed in the 83Rb decay was established to be 9405.8(3) eV. This energy value was obtained from photon spectrometry measurements of the differences in the energies of closely spaced lines. The result allows one to determine more precisely the energy of conversion electrons of the 9.4 keV transition, which represent a unique tool for energy calibration of the tritium beta spectrum and systematic measurements in the KATRIN neutrino mass determination experiment

POPULATION DEMOGRAPHICS OF SILVER CARP Hypophthalmichthys molitrix IN KENTUCKY LAKE

Invasive species continue to threaten aquatic ecosystems in the United States. Silver Carp Hypophthalmichthys molitrix have successfully infiltrated much of the Mississippi River Basin, including Kentucky Lake – a large reservoir located on the Tennessee River in Western Kentucky. Although Silver Carp have been present in Kentucky Lake for at least a decade, until recently, very little was known about the population, how often successful reproduction is occurring, or the environmental conditions that facilitate strong year-classes. Hence, it is difficult for managers to predict the potential impact of Silver Carp on native species. Silver Carp were collected from Kentucky Lake using gill nets, cast nets/anglers, boat electrofishing, and commercial fishing. Population demographics (size, age, growth, condition, and mortality) of Silver Carp within Kentucky Lake were examined by measuring total length and weight for all fish and removing a pectoral fin ray for aging. Additionally, spawning periodicity of mature Silver Carp in Kentucky Lake was examined by calculating gonadosomatic index (GSI) or the weight of the gonads relative to the fish’s body weight each month for just over a year. Fecundity (number of eggs per female) was estimated by multiplying the average number of eggs within six 1-g sub-samples by the combined weight of both ovaries. Silver Carp in Kentucky Lake were larger sized, faster growing, relatively heavy, and comparatively unexploited compared to other populations in the United States. Female Silver Carp in Kentucky Lake also exhibited higher fecundity than Silver Carp from other populations in the United States. Silver Carp appear to spawn in mid-spring in conjunction with warming water temperatures and rising water flows similar to other populations. Additionally, the capture of young-of-the-year Silver Carp suggests that successful natural reproduction is occurring in Kentucky Lake. These data provide a snapshot of a relatively recent invasion of Silver Carp and are among the first to characterize reproduction in a large mesotrophic reservoir. Therefore, the results of this study may serve as a model for other large mesotrophic systems such as the embayments of the Great Lakes

Cucurbits (Cucurbitaceae; Cucumis spp., Cucurbita spp., Citrullus spp.)

The Cucurbitaceae is a remarkable plant family, deserving of attention because of its economic, aesthetic, cultural, medicinal, and botanical significance. In the Old and New Worlds, cucurbits have been associated with human nutrition and culture for more than 12,000 years (Brothwell and Brothwell 1969; Lira-Saade 1995). Thus, the Cucurbitaceae, along with the Brassicaceae and Asteraceae, can be considered families of extraordinary importance to humans, and they follow cereals and legumes in their economic significance to human economy (Whitaker and Davis 1962; Nayar and More 1998)

Positronic lithium, an electronically stable Li-e+^+ ground state

Calculations of the positron-Li system were performed using the Stochastic Variational Method and yielded a minimum energy of -7.53208 Hartree for the L=0 ground state. Unlike previous calculations of this system, the system was found to be stable against dissociation into the Ps + Li$^+$ channel with a binding energy of 0.00217 Hartree and is therefore electronically stable. This is the first instance of a rigorous calculation predicting that it is possible to combine a positron with a neutral atom and form an electronically stable bound state.Comment: 11 pages, 2 tables. To be published in Phys.Rev.Let