Genome Designations in the Triticeae

Those attending the Second International Triticeae Consortium agreed to adopt a standard set of symbols for the individual haplomes of the Triticeae. A committee consisting of R.R.-C. Wang (Chair), R. von Bothmer, J. Dvorak, G. Fedak, I. Linde-Laursen, and M. Muramatsu met with two goals:

1) to develop a set of rules for designating haplome symbols for the Triticeae and

2) to develop a set of symbols that based on existing knowledge of the tribe.

The results of their deliberations were published in the Proceedings of the Symposium. The information presented here is based on that publication and subsequent discussions.

I have taken the liberty of proposing an additional rule. It is clearly identified as such in what follows. To my mind, preparation and citation of voucher specimens is essential if the designation of haplome symbols and publication of haplomic constitutions are to have the permanence and verifiability that is critical to scientific work.

Anyone wishing to propose changes or additions to the rules and symbols presented here should contact Dr. R.R.-C. Wang. For errors in the Web pages, contact Dr. Mary Barkworth.

Rules for Haplome Designation

1. Haplome symbols should be written in bold face.

2. Different basic haplomes in the Triticeae (with x = 7), defined as having less than 50% of complete meiotic pairing (i.e., c < 0.5) in a a diploid hybrid in the absence of the Ph or other pairing promoter/suppressor gene effect, should be designated with different symbols.

3. Single upper case letters of the Roman alphabet (A-Z) should, as far as possible, be used as symbols for the basic haplomes.

4. Additional basic haplomes should be designated by an upper case letter followed by a lower case letter.

5. The haplome designation of a polyploid taxon should be given as a combination of the symbols of its constituent basic diploid haplomes.

6. Unknown or unverified haplomes should be designated X followed by a lower case letter (e.g., Xu for Hordeum murinum). When a haplome has been sufficiently identified as distinct from all other established basic haplomes, it should be given its own haplome symbol.

7. The letter Y has previously been used to designate unknown haplomes, but it has also been extensively used to designate on the haplomes present in species of Elymus sensu lato. It is now restricted to use in Elymus sensu lato.

8. Modified versions of a basic haplome should be indicated by superscripts in lower case that are indicative of one of the species carrying such modified haplomes. Further modifications may be indicated by superscripted numerals.

9. When a previously unrecognized basic haplome is identified, a symbol should be assigned to it in accordance with these rules.

10. A haplome symbol may be underlined to indicate the origin of the cytoplasm of an alloploid species.

11. From 1996 on, the haplome symbols designations presented here should have priority over subsequent proposals.

Proposed Addition to the Rules (no action has been taken on this proposal).

Any time the haplomic constitution of a taxon is determined, a herbarium specimen shall be prepared from a mature plant of the material used. This voucher specimen must be deposited in an internationally recognized herbarium. Publication of the haplomic constitution must include the code of this herbarium and sufficient additional information to enable the specimen concerned to be identified unequivocally.

Comment: Correct identification of the material used is essential if determinations of haplomic constitution are to be of value. Deposition of voucher material ensures that determinations can be verified at a later date and that, if the taxonomy of the group involved is changed, the haplomic information can be associated with the appropriate newly recognized or modified taxa.

A useful criterion for "internationally recognized herbarium" is listing in Index Herbariorum but the most critical aspect is that it should be a herbarium whose specimens are regularly consulted by taxonomists and one that is willing to loan specimens to other herbaria on request. Personal herbaria do not meet these criteria, nor do some research station herbaria.

Haplome Symbols