French isolates of Phytophthora infestans from potato and tomato differ in phenotype and genotype

Prior to 1996, the A2 mating type of Phytophthora infestans was not detected on potato in France, but was found at one site on tomato in 1995. This finding lead to the question of the extent of differences and relationships existing between the populations of P. infestans present on each host. A collection of 76 isolates collected in France, mainly in 1996, from potato and tomato was characterised for mating type, allozyme genotype at the Gpi and Pep loci, and mitochondrial DNA haplotype; 74 of these isolates were also characterised for multilocus RFLP fingerprint, and 62 for virulence. All isolates except four showed allozyme genotypes (Gpi 90/100 or 100/100, Pep 83/100 or 100/100) and mtDNA haplotypes (Ia or IIa) characteristic of the populations introduced into Europe in the late 1970s. The four exceptions were isolates collected from tomato in Southern France in 1988-1991, which showed some characteristics of the former European populations (Gpi 86/100, Pep 92/100, mtDNA Ib). Both mating types were present among the collections from both hosts, but isolates with the A2 mating type were found on potato only in one garden crop, adjacent to tomato. Nine different RG57 fingerprints were observed, with a greater diversity among tomato isolates. Furthermore, tomato and potato collections differed markedly in the frequencies of genotypes present. Finally, tomato isolates generally had a lower virulence complexity than potato isolates. These data suggest that P. infestans populations on tomato and potato are largely separated, despite the occurrence of limited gene flow.     

Impact of wheat straw decomposition on successional patterns of soil microbial community structure

The dynamics of indigenous bacterial and fungal soil communities were followed throughout the decomposition of wheat straw residue. More precisely, such dynamics were investigated in the different soil zones under the influence of decomposing wheat straw residue (i.e. residues, soil adjacent to residue = detritusphere, and bulk soil). The genetic structures of bacterial and fungal communities were compared throughout the decomposition process long by applying B- and F-ARISA (for bacterial and fungal-automated ribosomal intergenic spacer analysis) to DNA extracts from these different zones. Residue decomposition induced significant changes in bacterial and fungal community dynamics with a magnitude of changes between the different soil zones ordered as followed: residue > detritusphere > bulk soil, confirming the spatial structuration of the sphere of residue influence to the 4-6 mm soil zone in contact with residue. Furthermore, significant differences in the structure of bacterial and fungal communities were apparent between the early (14 and 28 days) and late (from 56 to 168 days) stages of decomposition. These could be related to ecological attributes such as the succession of r- (copiotrophs) and K- (oligotrophs) strategists. Microbial diversity at the early (28 days) and late (168 days) stages of degradation was further analysed by a molecular inventory of 16S and 18S rDNA in DNA extracts from the residue zone. This confirmed the succession of different populations during residue decomposition. Fluorescent Pseudomonas spp. and Neurospora sp. were dominant in the early stage with subsequent stimulation of Actinobacteria and Deltaproteobacteria taxa, as well as Basidiomycota fungal taxa and Madurella spp. According to the ecological attributes of these populations, microbial succession on fresh organic residue incorporated in soil would be dominated by copiotrophs and r-strategists in the early stages, with oligotrophs (K-strategists) increasing in relative abundance as substrate quantity and/or quality declines over time.     

Larval instars determination for the European Grapevine Moth (Lepidoptera: Tortricidae) based on the frequency distribution of head-capsule widths

Morphological measurements such as head-capsule (HC) width can be very useful and accessible tools that may be employed for classifying Lepidopteran larval instars according to stage of life history. The availability of such measures is crucial in the management of larval pests, because their control relies upon making accurate assessment of the life history stage at which larvae has reached in various environmental conditions. Such forecasts are then used in order to estimate the timing of emergence for future adult populations. Previous studies investigated the use of head-capsule widths from field larvae of European Grapevine Moth (EGVM), Lobesia botrana Den. and Schiff., to describe the distributions of the five instars during three generations of the insect. The observations were performed in 1998 and 2002 in a vineyard near Bordeaux. The results presented here increase the scope of earlier methods by providing statistical confidence. Our method was calibrated on a large number of individuals (N = 552) issued from our insect culture and uses a nonlinear least-squares parameter estimation to describe the distribution of each larval instar inside each generation. The model was tested on a wild larval population (n = 3007) occurring in our experimental vineyard during two complete years. The instar class ranges and boundaries were characterized with the associated probabilities of misclassification. A final classification statistical model is developed for each instar and each generation. From this study, we conclude that larval HC sizes increase statistically according to the generation of the year, and thus is influenced by grape phenology.     

Phytoanticipins from banana (<Emphasis Type="Italic">Musa acuminata</Emphasis> cv. Grande Naine) plants,with antifungal activity against <Emphasis Type="Italic">Mycosphaerella fijiensis</Emphasis>, the causal agent of black Sigatoka

The previously detected antifungal activity against Mycosphaerella fijiensis of aqueous infusions of healthy banana (Musa acuminata cv. Grande Naine) leaves, suggested the production of phytoprotectants by the plant. The bioassay-guided VLC-purification of the lyophilized infusion of the leaves of 4-month old healthy banana (M. acuminata cv. Grande Naine) plants, resulted in the purification of a phytoanticipin with strong antifungal activity against M. fijiensis Morelet, the causal agent of black Sigatoka, the most destructive and devastating disease of bananas and plantains in the world. The LC-MS analysis of the purified phytoanticipin suggests a steroidal saponin structure with four sugar units attached to the C-3 position of a diosgenin-like aglycone. This represents the first report of phytoanticipins occurring in M. acuminata.     

Lymphocytic Thyroiditis in the Dog

Abstract— —A 0.4 per cent incidence of lymphocytic thyroiditis was seen in 4,500 dogs examined. The haematological and biochemical investigations failed to reveal any results of diagnostic significance. The histological features were reminiscent of a human Hashimoto's disease. Whilst the condition was similar to that seen in man, several significant differences were noted. A genetically linked auto-immune aetiology was considered the most likely.
Résumé— —La morbidité de la thyroïdite lymphocytaire constatée au cours de l'examen de 4.500 chiens atteignait 0,4 pour cent. Les examens hématologiques et biochimiques n'ont donné aucun résultat d'intérêt diagnostique. Les caractéristiques histologiques constatées évoquaient la maladie de Hashimoto chez I'homme. L'état des chiens étudiés ressemblait en principe à la maladie rencontrée chez I'homme, mais plusieurs différences ont été nottés. Il y a lieu de croire à une auto-immunitéà corrélation génétique.
Zusammenfassung— —Bei 4500 untersuchten Hunden wurde lymphocytische Thyreoiditis mit einer Häufigkeit von 0,4% beobachtet. Die hämatologischen und biochemischen Untersuchungen lieferten keine Ergebnisse von diagnostischer Bedeutung. Die histologischen Besonderheiten erinner-ten an die Hashimotosche Krankheit des Menschen. Obwohl der Zustand dem beim Menschen auftretenden glich, wurden doch mehrere Unterschiede bemerkt. Eine genetisch bedingte autoimmune Ätiologie wurde für am wahrscheinlichsten gehalten.     

Mycobacterium szulgai infection in a captive population of African clawed frogs (Xenopus tropicalis).

A colony of captive Xenopus tropicalis became infected with Mycobacterium szulgai. Clinical signs, when observed, were lethargy, weight loss, and emaciation. Visceral granulomas were common findings at laparoscopy and necropsy. The diagnosis of mycobacteriosis was based on histologic appearance and Ziehl-Neelsen staining of tissues. The identification of M. szulgai organisms was based on comparison of the 16S rRNA gene sequence with several GenBank databases. There have been no reports of this mycobacterial species as the causative agent of naturally occurring disease in amphibians.     

Transmission of bovine viral diarrhea virus to adult goats from persistently infected cattle.

The transmission of bovine viral diarrhea virus (BVDV) from persistently infected (PI) heifers to adult seronegative goats was examined in this study. Ten seronegative adult goats were exposed to 4 PI heifers. None of the goats developed any clinical signs but all goats seroconverted by 42 days after exposure to the PI cattle. Results indicate that goats are susceptible to BVDV infection when housed with PI cattle.