BackgroundDowny mildews are the most speciose group of oomycetes and affect crops of great economic importance. So far, there is only a single deeply-sequenced downy mildew genome available, from Hyaloperonospora arabidopsidis. Further genomic resources for downy mildews are required to study their evolution, including pathogenicity effector proteins, such as RxLR effectors. Plasmopara halstedii is a devastating pathogen of sunflower and a potential pathosystem model to study downy mildews, as several Avr-genes and R-genes have been predicted and unlike Arabidopsis downy mildew, large quantities of almost contamination-free material can be obtained easily.ResultsHere a high-quality draft genome of Plasmopara halstedii is reported and analysed with respect to various aspects, including genome organisation, secondary metabolism, effector proteins and comparative genomics with other sequenced oomycetes. Interestingly, the present analyses revealed further variation of the RxLR motif, suggesting an important role of the conservation of the dEER-motif. Orthology analyses revealed the conservation of 28 RxLR-like core effectors among Phytophthora species. Only six putative RxLR-like effectors were shared by the two sequenced downy mildews, highlighting the fast and largely independent evolution of two of the three major downy mildew lineages. This is seemingly supported by phylogenomic results, in which downy mildews did not appear to be monophyletic.ConclusionsThe genome resource will be useful for developing markers for monitoring the pathogen population and might provide the basis for new approaches to fight Phytophthora and downy mildew pathogens by targeting core pathogenicity effectors.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1904-7) contains supplementary material, which is available to authorized users.

No abstract

In this review, we present a critical analysis of the current status of wild Lactuca L. germplasm in relation to its utility for lettuce breeding. We discuss wild Lactuca germplasm in ex situ collections from the perspectives of taxonomy, biogeography, biology and ecology, gene pools, field exploration and acquisition, descriptor development, characterization and evaluation, and enhancement. Future research and other activities related to wild Lactuca germplasm and their continued exploitation in lettuce breeding are considered.

Dandelions (genus Taraxacum) comprise a group of sexual diploids and apomictic polyploids with a complicated reticular evolution. Apomixis (clonal reproduction through seeds) in this genus is considered to be obligate, and therefore represent a good model for studying the role of asexual reproduction in microevolutionary processes of apomictic genera. In our study, a total of 187 apomictic individuals composing a set of nine microspecies (sampled across wide geographic area in Europe) were genotyped for six microsatellite loci and for 162 amplified fragment length polymorphism (AFLP) markers. Our results indicated that significant genetic similarity existed within accessions with low numbers of genotypes. Genotypic variability was high among accessions but low within accessions. Clustering methods discriminated individuals into nine groups corresponding to their phenotypes. Furthermore, two groups of apomictic genotypes were observed, which suggests that they had different asexual histories. A matrix compatibility test suggests that most of the variability within accession groups was mutational in origin. However, the presence of recombination was also detected. The accumulation of mutations in asexual clones leads to the establishment of a network of clone mates. However, this study suggests that the clones primarily originated from the hybridisation between sexual and apomicts.

This chapter presents a brief history of the uses of lettuce (Lactuca sativa L.) and its wild North American relatives, and reviews the agricultural importance of lettuce and challenges in its cultivation, in relation to nutritional quality, diseases, pests, and edaphic and climatic limitations. The evolution and taxonomy of the genus Lactuca are presented, with a primary focus on the wild Lactuca species of North America, their characterization, biogeography and distribution, habitat ecology, and genepools. Specific examples of phenotypic variability, genetic diversity and disease resistance of wild Lactuca taxa from both published reports and recent evaluations conducted in our laboratory are also presented. The past (and future) exploitation of wild Lactuca relatives in lettuce breeding is examined and discussed in the broader context of crop improvement. The current status of in situ and ex situ conservation of wild and weedy North American Lactuca is reviewed, along with recommendations on how these genetic resources could be better conserved and utilized.

Filamentous epipelic cyanobacteria were isolated from ponds and lakes in the Czech Republic, Austria and Italy. Morphological and genetic variation of 20 isolated strains within the genera Geitlerinema, Microcoleus and Phormidium were studied. Partial sequences of the 16S rRNA gene were used for phylogenetic analyses, and secondary structure of the 16S-23S ITS region was used to additionally define clades. Morphological and molecular were congruent, and we were able to identify the majority of strains correctly to species on the basis of morphological features. Overall diversity and morphological/genetic variation of epipelic species is not as high as described from other benthic habitats, possibly due to the relative microhabitat uniformity of lake/pond bottom sediments. The M. vaginatus clade is well defined by an 11 bp insert in 16S rRNA gene (bp 423-433) and populations from different ecological conditions differ in secondary structure in the 16S-23S ITS regions, particularly in Box-B helices. Ph. autumnale and the genus Geitlerinema appear to be polyphyletic as presently defined.

No abstract

No abstract