Publications

4482

ABSTRACT The stolbur disease associated with “ Candidatus Phytoplasma solani” (CaPsol) is very common in Europe and the Mediterranean regions and adversely affects perennial or annual plants but is rarely reported on cucurbits. We report the first multilocus genetic characterisation of CaPsol strains infecting cucurbit plants and the presence of some RNA viruses prevalent in cucurbits. Between 2019 and 2020, 156 symptomatic and nine asymptomatic plant samples were collected during surveys in cucurbit‐growing areas. Symptomatic plants exhibited leaf deformation, growth retardation, yellowing, flower deformation and other virus‐like symptoms. Molecular testing detected potyviruses, tobamoviruses and Cucumis melo endornavirus (CmEV) as single and double infections in 108 samples, but CaPsol was determined only in seven plants as a single infection. CaPsol strains infecting squash and watermelon in the Marmara region of Türkiye were genetically characterised by describing their tuf, vmp1 and stamp gene sequences. All cucurbit‐associated CaPsol strains were of the tuf ‐b1 genotype and five different stamp genotypes previously reported in other crops and wild plant reservoirs in Europe. Cucurbit CaPsol strains had vmp1 gene sequences corresponding to RFLP types V4 and V14, previously detected in the Mediterranean basin. These strains were not novel cucurbit‐specific genotypes but shared similarities with genotypes from diverse plant hosts across Europe. This indicated that CaPsol is not restricted to cucurbits and may persist in alternative plant hosts. Thus, disease management should include monitoring alternative plant reservoirs, rather than focusing solely on cucurbit production areas. Viral infections showed significantly higher prevalence compared to phytoplasma infections in the region.

Abstract Citrus Huanglongbing (HLB) is one of the most devastating diseases in the citrus industry and is caused primarily by ‘Candidatus Liberibacter asiaticus’ (CLas), a phloem-restricted gram-negative bacterium transmitted via citrus psyllids in the field. Precise CLas detection is crucial for HLB control, particularly during extensive surveys in new emerging regions. Unfortunately, the lack of a practical on-site detection method for CLas due to the limited specificity of immunostrips and the costive non-user friendliness approaches prevent the effective disease control. In this study, a probe-based recombinase polymerase amplification (RPA) targeting the CLas five-copy nrdB gene (β-subunit of ribonucleotide reductase, RNR) was developed and evaluated for its specificity, sensitivity, and reliability. To enhance user-friendliness and facilitate widely use, an All-in-one kit was premade as freeze-dried pellets in individual tubes, containing all necessary components except DNA template. The applicability of the All-in-one kit for CLas detection was confirmed using plant or psyllid crude DNA extracts. Collectively, the All-in-one kit offers a specific, sensitive, rapid, cost-effective, and practical alternative for diagnosing CLas in field conditions when coupled with simplified crude DNA extraction method, providing an alternative approach for on-site CLas detection in the context of HLB.

[Pasteurella] langaaensis has been found to be polyphyletic in relation to the type species Pasteurella multocida, as endicated by 16S rRNA gene sequence comparisons and a number of other comparisons (enclosing the genus name in brackets). 16S rRNA gene sequence-based phylogeny confirmed that [P.] langaaensis is unrelated to other members of Pasteurellaceae at the genus level and may be a candidate for a new genus with 95% 16S rRNA gene sequence identity to the closest related sequence belonging to the type strain of [Actinobacillus] rossii. The highest digital DNA–DNA hybridization value predicted from the whole-genomic sequence of the type strain of [P.] langaaensis was to the type strain of Acinobacillus suis with 26%, confirming a separate taxonomic status at the species level. The phylogenetic comparison of concatenated conserved protein sequences determined in a previous study showed a unique position of the taxon investigated, which qualified for the status of a new genus since the highest conserved protein sequence identity was found to [A.] rossii with 86%. A new genus with one species, Alitibacter langaaensis gen. nov., comb. nov., is proposed. The genus can be separated from other genera in the family Pasteurellaceae by from 1 up to 12 phenotypic characters, and it is monotypic from other genera with respect to analysis of 16S rRNA gene sequences as well as of predicted core genomic proteins. The type strain of Alitibacter langaaensis is F73T (=NCTC 11411T=CCUG 15566T=DSM 22999T=CPI 102678T=ATCC 43328T).

Abstract Fer.men.ti.micr.ar.chae'um. L. gen. neut. n. fermenti , of a fermentation process; N.L. masc. adj. micros , small [probably better: micrus]; N.L. neut. n. archaeum , ancient one, archaeon; from Gr. adj. archaîos ‐a ‐on , ancient; N.L. neut. n. Fermentimicrarchaeum , a small archaeon performing fermentation processes. Microcaldota / Microcaldia / Candidatus Fermentimicrarchaeales / Candidatus Fermentimicrarchaeaceae / Candidatus Fermentimicrarchaeum The genus Candidatus Fermentimicrarchaeum was established based on complete genome sequence assembled from a freshwater lake sediment metagenome. Ca . Fermentimicrarchaeum is phylogenetically affiliated with the phylum Microcaldota (previously known as Candidatus Micrarchaeota) of the archaeal DPANN superphylum. Analysis of the 1.2 Mb genome of Ca . Fermentimicrarchaeum suggests that, contrary to the ARMAN group of Microcaldota and most DPANN members, this organism has complete glycolytic pathways and ATP generation mechanisms in substrate phosphorylation, the capacities to utilize some sugars and amino acids as substrates, and pathways for de novo nucleotide biosynthesis but lacks an aerobic respiratory chain. We suppose that Ca . Fermentimicrarchaeum is a free‐living scavenger rather than an obligate parasite or symbiont, and its functional role in lake sediments consists of the fermentation of low molecular weight organic compounds. 16S rRNA gene sequences and metagenome‐assembled genomes affiliated with Ca . Fermentimicrarchaeum were recovered from freshwater lake sediments and soils. DNA G + C content (mol%) : 46.4–48.5 (genome sequence). Type species : Candidatus Fermentimicrarchaeum limneticum Kadnikov et al. 2020, CL3.