Proposal of strain CFBP 7900 as the neopathotype strain of X. hortorum pv. carotae Because the holopathotype strain of X. hortorum pv. carotae is no longer available due to the storage of a contaminant (Enterobacter) in international collections, we propose replacing it with the strain CFBP 7900, also known as M081, as the neopathotype strain of the pathovar carotae (Kimbrel et al. 2011). Strain CFBP 7900 was isolated in 2008 in a carrot plant in the United States, which is the same country as the X. hortorum pv. carotae holopathotype strain (Kendrick 1934). The genome of this strain was previously sequenced (GenBank accession number AEEU00000000) and analyzed and is highly characteristic of that of a pathogenic Xanthomonas (Kimbrel et al. 2011). In our study, this strain was identified using the Meng's PCR test (Meng et al. 2004), and the identification was confirmed by a taxonomic assignation using an MLSA based on seven housekeeping genes that included all other pathotype strains of pathovars of X. hortorum. This strain represents one of the two clusters forming the pathovar carotae (Fig. 1). Moreover, the presence of three hrc genes was confirmed and indicates a functional TTSS, which was confirmed by the induction of an HR on tobacco. The strain was also found to be pathogenic on carrot and induced typical symptoms of leaf blight (i.e., water-soaked lesions that evolved into necrotic spots and were then dry and brittle, fitting the initial description) (Kendrick 1934). Moreover, the strain CFBP 7900 was phenotypically characterized by standard biochemical tests and metabolic profiling on Biolog GEN III microplates (Morinière et al. 2020). All these data are consistent with the first description of the holopathotype made by Kendrick (1934). As of 11 August 2023, only three genome sequences of X. hortorum pv. carotae were publicly available in the National Center for Biotechnology Information (NCBI). Two of them are from the strain CFBP 7900 (= M081) and the third from a strain named MAFF 301101 isolated in Japan (BioSAmple: SAMN02470773, SAMEA6962650, and SAMN16925265) (Dia et al. 2020; Kimbrel et al. 2011). Only the first one, deposited in 2013 and published by Kimbrel et al. (2011), presents a high quality level, and the chromosome is circularized. Moreover, strain M081 was deposited at the CIRM-CFBP, under the name CFBP 7900. It is publicly available and maintained by this international open collection. The holopathotype strain of X. hortorum pv. carotae has been reported to be unsuitable as the pathotype strain of this pathovar since at least 1991, leading to the use of other strains as references when studying the pathovar carotae (Young et al. 1991). Thus, since 2011 and the genome sequencing of the strain CFBP 7900, it was used in a majority of studies designing molecular detection tests (Dia et al. 2022; Kimbrel et al. 2011; Temple et al. 2013), in studies using these molecular tests to confirm X. hortorum pv. carotae identification (Myung et al. 2014; Palomo et al. 2021), as a reference strain or reference genome to identify X. hortorum pv. carotae strains (Palomo et al. 2021), or in papers of other Xanthomonas species or pathovar as the reference for the pathovar carotae (Dhakal et al. 2019; Dia et al. 2021; Hébert et al. 2021; Morinière et al. 2021; Rosenthal et al. 2022).