Anatomy and variability of "Cuvierichelys parisiensis", a geoemydid turtle that crosses the Eocene-Oligocene boundary in Belgium

Abundant material of turtles from the early Oligocene site of Boutersem-TGV (Boutersem, Belgium), is presented here. No information on the turtles found there was so far available. All the turtle specimens presented here are attributable to a single freshwater taxon that is identified as a member of Geoemydidae, Cuvierichelys. It is the first representative of the ‘Palaeochelys s. l.–Mauremys’ group recognized in the Belgian Paleogene record. This material, which allows to know all the elements of both the carapace and the plastron of the taxon, cannot be attributed to the only species of the genus Cuvierichelys so far identified in the Oligocene, the Spanish form Cuvierichelys iberica. The taxon from Boutersem is recognized as Cuvierichelys parisiensis. Thus, both the paleobiogeographic and the biostratigraphic distributions of Cuvierichelys parisiensis are extended, its presence being confirmed for the first time outside the French Eocene record. The validity of some European forms is refuted, and several characters previously proposed as different between Cuvierichelys iberica and Cuvierichelys parisiensis are recognized as subjected to intraspecific variability.

Pl2 resistance gene differentiates the pathogenicity in four "Plasmopara halstedii" (sunflower downy mildew) races 304, 704, 314 and 714

In order to clarify the role of Pl2 resistance gene in differentiation the pathogenicity in Plasmopara halstedii (sunflower downy mildew), analyses were carried out in four pathotypes: isolates of races 304 and 314 that do not overcome Pl2 gene, and isolates of races 704 and 714 that can overcome Pl2 gene. Based on the reaction for the P. halstedii isolates to sunflower hybrids varying only in Pl resistance genes, isolates of races 704 and 714 were more virulent than isolates of races 304 and 314. Index of aggressiveness was calculated for pathogen isolates and revealed the presence of significant differences between isolates of races 304 and 314 (more aggressive) and isolates of races 704 and 714 (less aggressive). There were morphological and genetic variations for the four P. halstedii isolates without a correlation with pathogenic diversity. The importance of the Pl2 resistance gene to differentiate the pathogenicity in sunflower downy mildew was discussed.