Rhizobial Symbiovars

Some members of the Sc published a paper “Guidelines for the description of rhizobial symbiovars”. In this paper, they discussed the requirements and guidelines to describe symbiovars, propose a set of rules, provide a list of all symbiovars published so far, and offer a mechanism to maintain a list in the future.

Proposed guidelines for the description and naming of symbiovars

1. Description

1a. Plant specificity is the essential basis to define a symbiovar. Symbiovars should be described in relation to the symbiosis phenotypes, not only referring to nodulation but also to effectiveness by considering nitrogen fixation.

1b. A symbiovar must have a representative strain, and the genome sequence of that strain must be publicly available and of sufficient quality. It is recommended (but not obligatory) that the representative strain be available in an international culture collection.

1c. It must be demonstrated that the symbiosis genes are recognizably distinct from those of all previously described symbiovars in sequence or in the presence/absence of specific genes.

2. Naming

2a. The name of a new symbiovar must be distinct from all previously recognised symbiovar names in all genera.

2b. Symbiovar names that are adjectival always take the feminine gender.

2c. In other respects, the names of symbiovars follow the same rules as those of species epithets.

2d. A proposal for a new symbiovar must be published in the body (not supplementary files) of an article in a peer-reviewed journal, and must include all the information required by these guidelines.

3. Recognition

3a. The ICSP Subcommittee for Rhizobia and Agrobacteria undertakes to maintain a list of recognized symbiovars and to appoint persons to manage this.

3b. After publication, authors should submit the publication to the Secretary of the ICSP Subcommittee for Rhizobia and Agrobacteria.

3c. New symbiovars that conform to the guidelines and have priority will be added to the online list of recognized symbiovars on the Subcommittee website (currently https://sites.google.com/view/taxonomyagrorhizo/home).

3d. The priority of names is established by the date of inclusion in the list.

Conclusion

In view of the large number of symbiovars described so far, and the likelihood that the number will increase in the future when more legumes are thoroughly studied, we felt the need to consider some appropriate standards and to clarify the status of the symbiovars already described.  We have proposed guidelines for the description and naming of symbiovars and offered to set up and maintain a public list as a service to the rhizobial research community. Our aim is to make it easier to understand and use the symbiovar concept. As with any new venture, we may find we need to make adjustments in the light of experience, and we welcome feedback from users.

List of recognized symbiovars

A list of all symbiovars (in alphabetical order) proposed to date is given in the following Table (Table 1 in the published paper).