In the present study, bivalent nanovaccines of S. iniae and F. covae were administered by immersion vaccination at 30 and 40 days after hatching (DAH), and the third vaccination was orally administered by feeding at 50 DAH. Five different groups were designed: group 1 was set as the control group, and groups 2-4 were vaccinated using the same protocols. ELISA revealed that the levels of total IgM and specific IgM to S. iniae, and F. covae were significantly elevated in groups 2-4 at 10, 20, and 30 days after vaccination (DAV). A qRT‒PCR analysis of immune-related genes revealed significantly higher IgT expression in the vaccinated groups compared with the control group, as revealed by 44-100-fold changes in the vaccinated groups compared with the control (p < 0.001) at every tested time point after vaccination. All vaccinated groups expressed IgM, MHCIIα and TCRα at significantly higher levels than the control group at 10 and/or 20 DAV (p < 0.05). In the S. iniae challenge tests, the survival of vaccinated groups 2-4 ranged from 62.15 ± 2.11 to 75.70 ± 3.36%, which significantly differed from that of the control group (44.44 ± 1.92%). Similarly, all vaccinated groups showed higher survival rates of 68.89 ± 3.85 to 77.78 ± 5.09% during F. covae challenge than the control groups (50.00 ± 3.33%) (p < 0.05).

Enteric septicemia of catfish, columnaris disease, and streptococcosis, caused by Edwardsiella ictaluri, Flavobacterium columnare, and Streptococcus iniae, respectively, are the most common bacterial diseases of economic significance for the pond-raised channel catfish Ictalurus punctatus industry. Several management practices are used by catfish farmers to prevent large financial losses from these diseases such as the use of commercial antibiotics and other chemicals. In order to discover environmentally benign alternatives, using a rapid bioassay, we evaluated a crude extract from the roots of muscadine Vitis rotundifolia against these fish pathogenic bacteria and determined that the extract was most active against F. columnare. Subsequently, several isolated compounds from the root extract were further evaluated against F. columnare. Among these isolated compounds, (+)-hopeaphenol (2) and (+)-vitisin A (3) were found to be the most active against F. columnare, with 24-h 50% inhibition concentrations of 4.0±0.7 and 7.7±0.6 mg/L, respectively, and minimum inhibitory concentrations of 9.1±0 mg/L for each compound. Efficacy testing of 2 and 3 is necessary to further evaluate the potential for these compounds to be used as antibacterial agents for managing columnaris disease.

Aegilops columnaris Zhuk. is tetraploid grass species (2n=4x=28, UcUcXcXc) closely related to Ae. neglecta and growing in Western Asia and a western part of the Fertile Crescent. Genetic diversity of Ae. columnaris was assessed using C-banding, FISH, nuclear and chloroplast (cp)DNA analyses, and gliadin electrophoresis. Cytogenetically Ae. columnaris was subdivided into two groups, C-I and C-II, showing different karyotype structure, C-banding and FISH patterns. Group C-I was more similar to Ae. neglecta. All types of markers revealed significant heterogeneity of the C-II group, although group C-I was also polymorphic. Two chromosomal groups were consistent with plastogroups identified in a current study based on sequencing of three chloroplast intergenic spacer regions. The similarity of group C-I of Ae. columnaris with Ae. neglecta and their distinctness from C-II indicate that divergence of the C-I group was associated with minor genome modifications. Group C-II could emerge from C-I relatively recently, probably due to introgression from another Aegilops species followed by a reorganization of the parental genomes. Most C-II accessions were collected from the very narrow geographic region, and they might originate from a common ancestor. We suggest that the C-II group is at the initial stage of species divergence and undergoing an extensive speciation process.