Identification of Genetic Variation between Obligate Plant Pathogens Pseudoperonospora cubensis and P. humuli Using RNA Sequencing and Genotyping-By-Sequencing.

RNA sequencing (RNA-seq) and genotyping-by-sequencing (GBS) were used for single nucleotide polymorphism (SNP) identification from two economically important obligate plant pathogens, Pseudoperonospora cubensis and P. humuli. Twenty isolates of P. cubensis and 19 isolates of P. humuli were genotyped using RNA-seq and GBS. Principle components analysis (PCA) of each data set showed genetic separation between the two species. Additionally, results supported previous findings that P. cubensis isolates from squash are genetically distinct from cucumber and cantaloupe isolates. A PCA-based procedure was used to identify SNPs correlated with the separation of the two species, with 994 and 4,231 PCA-correlated SNPs found within the RNA-seq and GBS data, respectively. The corresponding unigenes (n = 800) containing these potential species-specific SNPs were then annotated and 135 putative pathogenicity genes, including 3 effectors, were identified. The characterization of genes containing SNPs differentiating these two closely related downy mildew species may contribute to the development of improved detection and diagnosis strategies and improve our understanding of host specificity pathways.

Lead and cadmium in the blood of nine species of seabirds, Marion Island, South Africa.

Levels of lead (Pb) and cadmium (Cd) were investigated as potential stressors in nine species of breeding seabirds on Marion Island, South Africa. The majority of blood Pb levels (95 %) were below background exposure levels. Species was a significant factor in ranked means analysis for mean blood Pb levels. Fewer individual blood Cd levels (<60 %) were within background exposure levels and species was not significant. Elevated levels of Cd have been documented in other seabird species without apparent outward effects, which suggests that seabirds may be adapted to high cadmium environments, particularly from their diets. Overall, the results suggest Pb and Cd are not primary causes for concern in these seabirds.