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Bacterial canker and spot of stone fruits and bacterial blight of walnut, caused by different pathovars of Xanthomonas arboricola, namely X. arboricola pv. pruni and X. arboricola pv. juglandis, respectively, are considered among quarantine or regulated (nonquarantine) agents in different countries. The two pathogens were initially reported in Iran in 2005 and 1977, respectively. However, the precise identity, pathogenicity status and geographic distribution of these pathogens have been questioned. In this study, we have employed a series of comprehensive field surveys and samplings over a course of 5 years (2015–2019) across 16 provinces to reassess and clarify the occurrence and distribution of X. arboricola on fruit and nut trees in Iran. Besides dozens of non‐Xanthomonas and nonpathogenic bacterial strains, 27 X. arboricola strains were isolated from stone fruits (n = 13) and walnut (n = 14). Except for the strains Peh35, Peh78 and Peh79, the stone fruit strains were nonpathogenic on their host of isolation as well as several other plant species, while the walnut strains were pathogenic on their host of isolation. Multilocus sequence analysis (MLSA) of four housekeeping genes, atpD, dnaK, gyrB and rpoD, revealed that among the stone fruit strains only Peh78 and Peh79 could be assigned into X. arboricola pv. pruni, while the walnut strains were identified as X. arboricola pv. juglandis. Based on the results of pathogenicity assays and phylogenetic analyses, we confirm the occurrence of X. arboricola pv. juglandis in Iran, while X. arboricola pv. pruni was absent in the plant samples evaluated in this study. [ABSTRACT FROM AUTHOR]

Bacterial blight and leaf spot of geraniums is a destructive disease of cultivated Pelargonium species around the world. During 2020 to 2021, surveys were conducted in seven geranium-growing provinces of Iran to monitor the status of bacterial blight and leaf spot disease. The disease was observed in six surveyed provinces varying in the extent of occurrence and severity. Twenty-two gram-negative pale-yellow bacterial strains resembling members of Xanthomonas were isolated from symptomatic leaves and stems. Pathogenicity and host range assays showed that the bacterial strains were pathogenic on Pelargonium grandiflorum , P. graveolens , P. peltatum , and P. zonale . All strains were positive for a PCR test using the primer pair XcpM1/XcpM2, which is specific for X. hortorum pv. pelargonii . Phylogenetic analysis using the sequences of gyrB and lepA genes showed that the 22 strains clustered in a clade among the sequences of X. hortorum pv. pelargonii strains retrieved from GenBank but were distinct from the other pathovars of X. hortorum . BOX-PCR-based fingerprinting using BOX-A1R primer revealed that the strains isolated in this study were grouped into two clusters, while no distinct correlation was observed between the host/area of isolation and BOX-PCR fingerprinting. None of the strains obtained in this study nor the reference strain of the pathogen produced bacteriocin against each other. Results obtained in this study shed light on the geographic distribution, taxonomic status, and host range of the bacterial blight and leaf spot pathogen of geraniums in Iran, paving the path for further research on disease management., Competing Interests: The author(s) declare no conflict of interest.

Curtobacterium flaccumfaciens (Microbacteriaceae), a plant-pathogenic coryneform species includes five pathovars with valid names and a number of proposed – but unvalidated – new members. In this study, phenotypic features and DNA similarity indexes were investigated among all C. flaccumfaciens members. Results showed that the C. flaccumfaciens pv. poinsettiae strains causing bacterial canker of Euphorbia pulcherrima in the USA as well as the orange-/red-pigmented strains of C. flaccumfaciens pv. flaccumfaciens pathogenic on dry beans in Iran are too distinct from each other and from the type strain of the species to be considered members of C. flaccumfaciens. Hence, the latter two groups were elevated at the species level as C. poinsettiae sp. nov. (ATCC 9682T = CFBP 2403T = ICMP 2566T = LMG 3715T = NCPPB 854T as type strain), and C. aurantiacum sp. nov. (50RT = CFBP 8819T = ICMP 22071T as type strain). Within the emended species C. flaccumfaciens comb. nov., yellow-pigmented strains causing bacterial wilt of dry beans and those causing bacterial canker of Euphorbia pulcherrima in Europe were retained as C. flaccumfaciens pv. flaccumfaciens and C. flaccumfaciens pv. poinsettiae, respectively; while taxonomic position of the sugar beet pathogen C. flaccumfaciens pv. beticola ATCC BAA144PT was confirmed. The newly described onion pathogen C. allii was also reclassified as C. flaccumfaciens pv. allii with the pathotype strain LMG 32517PT. Furthermore, C. flaccumfaciens pv. basellae causing bacterial leaf spot of malabar spinach (Basella rubra) was transferred to C. citreum pv. basellae with ATCC BAA143PT as pathotype. [ABSTRACT FROM AUTHOR]