Publications

4774

Long-term sustainable management of zebra chip (ZC) disease of potato requires development of tolerant or resistant germplasm. To this end, 283 potato varieties and breeding clones were infected with the ZC putative causal agent ‘Candidatus Liberibacter solanacearum’ (Lso) by potato psyllid vector inoculations in 2010, 2011, 2012, and 2013. Potato germplasm was then examined for development of fresh and fried ZC symptoms. Over multiple years 29 breeding clones exhibited little to no symptoms in freshly cut tuber slices, and five exhibited little to no symptoms in fried slices. These five presumed tolerant breeding clones were chosen for further screening to determine whether the lack of physiological responses to Lso infection was the cause of observed tolerance. To this end, tuber amino acid, sugar, and phenolic levels were compared between noninfected and Lso-infected plants. The five putative tolerant clones had less dramatic shifts in host physiology following Lso infection than the susceptible Atlantic cultivar. This suggested lack of host responses to Lso infection that result in major changes in tuber biochemistry is a potential mechanism of ZC resistance. However, the susceptible Atlantic cultivar did have consistently greater Lso titers compared with two of the tolerant entries, so for these reductions in Lso pathogen progression also might be a factor. Regardless, lack of host responses could still remain one trait that could be used to aid in selection of ZC-resistant potato varieties, as other tolerant lines had infection levels consistent with susceptible Atlantic cultivar. These results also suggest that germplasm derived from relatives of cultivated potato plants are viable sources of ZC disease resistance.

A Gram-stain-negative, non-motile, non-spore-forming, long rod-shaped bacterium, designated strain GYP-15T, was isolated from the culture broth of a marine microalga,Picochlorumasp. 122. Phylogenetic analyses revealed that strain GYP-15Tshared 90.6 % 16S rRNA gene sequence similarity with its closest relative,Kangiella aquimarinaKCTC 12183T, and represents a distinct phylogenetic lineage in a robust clade consisting of GYP-15Tand members of the generaKangiellaandPleioneain the orderOceanospirillales. Chemotaxonomic and physiological characteristics, including major cellular fatty acids, NaCl tolerance and pattern of carbon source utilization, could also readily distinguish strain GYP-15Tfrom all established genera and species. Thus, it is concluded that strain GYP-15Trepresents a novel species of a new genus, for which the nameAliikangiella marinagen. nov., sp. nov. is proposed. The type strain ofAliikangiella marinais GYP-15T( = MCCC 1K01163T = KCTC 42667T). Based on phylogenetic results, 16S rRNA gene signature nucleotide pattern and some physiological characteristics, the three generaKangiella,PleioneaandAliikangiellaare proposed to make up a novel family,Kangiellaceaefam. nov., in the orderOceanospirillales.

To improve the knowledge base of Borrelia in north Africa, we tested 257 blood samples collected from febrile patients in Oran, Algeria, between January and December 2012 for Borrelia species using flagellin gene polymerase chain reaction sequencing. A sequence indicative of a new Borrelia sp. named Candidatus Borrelia algerica was detected in one blood sample. Further multispacer sequence typing indicated this Borrelia sp. had 97% similarity with Borrelia crocidurae, Borrelia duttonii, and Borrelia recurrentis. In silico comparison of Candidatus B. algerica spacer sequences with those of Borrelia hispanica and Borrelia garinii revealed 94% and 89% similarity, respectively. Candidatus B. algerica is a new relapsing fever Borrelia sp. detected in Oran. Further studies may help predict its epidemiological importance.

‘Candidatus Phytoplasma cynodontis’ is widespread in bermudagrass and has only been found in monocotyledonous plants. Molecular studies carried out on strains collected in Italy, Serbia, and Albania enabled verification of molecular variability in the 16S ribosomal RNA (rRNA) gene. Based on restriction fragment length polymorphism and sequence analyses, the strains from Serbia were clearly differentiated from all others and assigned to a new ribosomal DNA (rDNA) subgroup designated as 16SrXIV-C. A system for amplification of fragments containing the ‘Ca. P. cynodontis’ groEL gene was developed to enable study of its variability in related strains belonging to different 16SrXIV subgroups. Despite the fact that the groEL gene exhibited a greater sequence variation than 16S rRNA, the phylogenetic tree based on groEL gene sequence analysis was highly congruent with the 16S rDNA-based tree. The groEL gene analyses supported differentiation of the Serbian strains and definition of the new subgroup 16SrXIV-C. Phylogenetic analyses of both genes confirmed distinct phylogenetic lineages for strains belonging to 16SrXIV subgroups. Furthermore, groEL is the only nonribosomal marker developed for characterization of ‘Ca. P. cynodontis’ thus far, and its application in molecular surveys should provide better insight into the relationships among these phytoplasmas and correlation between strain differentiation and their geographical distribution.