I.4 Proposals Concerning Genetic and Cytological Symbolization and Maintenance of World Collections of Seed Stocks of Barley
Dr. D. W. (Scotty) Robertson died November 1, 1969. At the time of his death, Dr. Robertson was serving the North American Barley Research Workers Conference as coordinator for genetic linkage studies in barley. His responsibilities included assigning gene symbols and maintaining seed stocks of mutants that had been assigned symbols. Dr. Robertson was also serving the International Barley Genetics Symposium as overall coordinator for genetic linkage studies, as chairman of the committee for assigning gene symbols, as coordinator for chromosome 4, and as chairman of the editorial committee of the Barley Genetics Newsletter.
On August 10 and 11, 1970, C. R. Burnham, R. F. Eslick, T. E. Haus, J. G. Moseman, R. A. Nilan, R. T. Ramage, T. Tsuchiya, and G. A. Wiebe met at Aberdeen, Idaho. Genetic and cytological nomenclature and symbolization, maintenance of world collections of genetic and cytological seed stocks, duties and responsibilities of coordinators, the Barley Genetics Newsletter, and related subjects were discussed. The group decided to present proposals resulting from their discussions to the readers of the Barley Genetics Newsletter with the expectation that interested readers will offer suggestions to the international committee for assigning gene symbols and that the international committee will formulate and adopt amicable systems of gene nomenclature and symbolization and procedures for maintaining genetic and cytological seed stocks. The international committee for assigning gene symbols, appointed at the Second International Barley Genetics Symposium, Pullman, Washington, July 6-11, 1969, has the following members: Dr. D. W. Robertson (chairman), Dr. A. Hagberg, Dr. J. G. Moseman, Dr. D. von Wettstein, Dr. G. W. R. Walker, and Dr. G. A. Wiebe.
In preparing their proposals, the group that met at Aberdeen, Idaho on August 10 and 11, 1970 considered the following documents: "Rules for Nomenclature and Symbolization of Genes" recommended by the National Committee of Genetics and the National Committee of Plant and Animal Breeding, Science Council of Japan, 1952; "Recommended Rules for Symbolization" reported by the International Committee on Genetic Symbols and Nomenclature, 1957; "A Proposed System of Symbols for the Collection of Barley Mutants at Svalov" by A. Gustafsson, A. Hagberg, U. Lundqvist, and G. Persson reported in Hereditas 62:409-414, 1969; and the report of the committee on genetic marker stocks and gene symbols given by D. W. Robertson and D. von Wettstein at the Second International Barley Genetics Symposium, Pullman, Washington, July 6-11, 1969.
The following proposals are submitted for consideration:
(1) There should be a complete revision
of barley gene nomenclature and symbolization. At the present time,
two systems of symbolization are in use: (1) the classical map genes that
are designated with one, two, or occasionally, three letter symbols based
on description usually in English, but occasionally in other languages
and making free use of subscripts and superscripts; (2) large groups of
polymeric genes containing many allelic members that have been identified
following exposure to various mutagenic agents and that are designated
with three letter symbols based on Latin with an additional letter designating
loci and with a number designating alleles or mutational events. The two
systems should be revised and standardized taking into account that the
revised system should: be easily adapted to computer use; be designed for
ease of learning by students; insofar as possible, be consistent with usage
in related crops, such as wheat, oats, and maize; when there is little
conflict, retain historical usage; and provide for periodic revision as
progress of genetics makes the system meaningless or misleading.
(2) The "Recommended Rules for Symbolization" reported by the International Committee on Genetic Symbols and Nomenclature, 1957, along with amendments applying to barley and incorporating the principles expressed in (1) above should be used for barley gene nomenclature and symbolization. The following is a list of the "Recommended Rules for Symbolization" followed by proposed amendments and comments where applicable to barley.
1. In naming hereditary factors, the use of languages of higher internationality should be given preference. PROPOSAL: English should be considered as a language of higher internationality.
2. Symbols of hereditary factors, derived from their original names, should be written in Roman letters of distinctive type, preferably in italics, and be as short as possible. PROPOSAL: The original name should be as descriptive as possible of the primary effect of the hereditary factor. Symbolization should be as short as possible, beginning with the use of single letters, then double letters, triple letters, etc.
3. Whenever unambiguous, the name and symbol of a dominant begin with a capital letter and those of a recessive with a small letter. PROPOSAL: In deciding if a new hereditary factor should be designated as a dominant or a recessive, the genotype of the variety in which the mutant occurred should be the determinant. For genes that exhibit incomplete dominance, the capital letter symbol should be used to designate the phenotype of the original variety in which the mutant was found.
4. Literal or numeral superscripts are used to represent the different members of an allelic series. PROPOSAL: All letters and numbers used in symbolization should be written on one line; no superscripts or subscripts should be used. This will avoid problems in programming computers to accomodate symbolization.
5. Standard or wild type alleles are designated by the gene symbols with a + as a superscript or by a + with the gene symbol as a superscript. In formulae, the + alone may be used. PROPOSAL: This rule will not be used in barley symbolization if the proposed amendment to rule 3 is followed.
6. Two or more genes having phenotypically similar effects are designated by a common basic symbol. Non-allelic loci (mimics, polymeric genes, etc.) are distinguished by an additional letter or Arabic numeral either on the same line after a hyphen or as a subscript. Alleles of independent mutational origin may be indicated by a superscript. PROPOSAL: It is proposed that subscripts and hyphens not be used in barley gene symbolization. In the case of polymeric genes, it is proposed that a letter or letters be used to designate the character, a number be used to designate a particular locus, and a letter or letters be used to designate an allele or mutational event at that particular locus. Alternation of letters and numbers written on the same line without hyphens or spaces will facilitate computer programming. (It is recognized that in typewritten or printed form, the letter l and the number 1 may cause some confusion. However, it is felt that such confusion will cause less annoyance than the use of spaces or hyphens.) Unsymbolized alleles or mutational events will be symbolized by a letter or letters representing the character, followed by two commas to reserve space for the locus number when determined, followed by a letter or letters representing the particular allele or mutational event. After appropriate allele testing the correct locus number will be placed between the commas and the commas will be dropped. An example of symbolization using the proposed system is ms2b where ms designates the character male sterility, 2 designates a particular locus for male sterility, and b designates a specific mutational event at the ms2 locus. In practical use the symbol ms will be used when speaking of male sterility in general (or if only one locus was known for the character), the symbol ms2 will be used when speaking of that particular locus, and the symbol ms2b will be used only when speaking of that particular allele or mutational event.
7. Inhibitors, suppressors, and enhancers are designated by the symbols I, Su and En, or by i, su, and en if they are recessive, followed by a hyphen and the symbol of the allele affected. PROPOSAL: It is proposed that a slash, (/), be used in place of a hyphen.
8. Whenever convenient, lethals should be designated by the letter l or L, and sterility and incompatibility genes by s or S. PROPOSAL: No proposed change.
9. Linkage groups and corresponding chromosomes are preferably designated by Arabic numeral. PROPOSAL: No proposed change.
10. The letters X and Y are recommended to designate sex chromosomes. PROPOSAL: No proposed change.
11. Genic formulae are written as fractions with the maternal alleles given first or above. Each fraction corresponds to a single linkage group. Different linkage groups written in numerical sequence are separated by semicolons. Symbols of unlocated genes are placed within parentheses at the end of the formula. In euploids and aneuploids, the gene symbols are repeated as many times as there are homologous loci. PROPOSAL: No proposed change.
12. Chromosomal aberrations should be indicated by the abbreviations: Df for deficiency, Dp for duplication, In for inversion, T for translocation, Tp for transposition. PROPOSAL: No proposed change.
13. The zygotic number of chromosomes is indicated by 2n, the gametic number by n and the basic number by x. PROPOSAL: No proposed change.
14. Symbols of extra-chromosomal factors should be enclosed within brackets
and precede the genic formula. PROPOSAL: It is proposed that extra-chromosomal
factors be designated by Ec/ followed by the genic formula.
(3) World collections of genetic and cytological
seed stocks should be maintained by coordinators appointed by the International
Committee for Genetic Svmbols and Nomenclature. Coordinators should
serve as custodians of viable seed stocks of all entries assigned to their
area of specialization. Any person desiring seed stocks need only write
to the coordinator concerned. For ease of handling, seed stocks in the
collection of mutants maintained at the Genetic Stock Center, Fort Collins,
Colorado,U.S.A., will be given Barley Genetic Stock numbers and be designated
BGS0001 to BGS9999. Other coordinators may, in the future, find it desirable
to assign stock numbers to their collections.
(4) The following procedure for requesting a symbol for a new mutant should be followed.
1. Submit to the chairman of the International Committee for Genetic Symbols and Nomenclature the following information and illustrations concerning the new mutant.
a. The name of the variety, hybrid selection, or stock in which the mutant originally occurred.
b. The source of the mutation (spontaneous origin, induction with a specific mutagenic agent, etc.)
c. Detailed description of the mutant phenotype including, where appropriate, morphological, physiological, and cytological details.
d. Inheritance data.
e. Photographs, slides, and/or line drawings illustrating the mutant phenotype. Color photographs and slides should be submitted with chlorophyll and other color mutants. Line drawings should be submitted where photographs do not adequately portray the mutant phenotype.
2. Submit a suggested symbol and justification for its use in accordance with recommended rules of symbolization.
3. Send seed samples (50 kernels or more) of the mutant and the variety in which it occurred to the Genetic Stock Center, Department of Agronomy, Colorado State University, Fort Collins, Colorado 80521, U.S.A. (Attention: Dr. T. Tsuchiya). A symbol will not be assigned until receipt of viable seed of the mutant.
4. At the time of assignment of a gene symbol, the mutant stock will be assigned a Barley Genetic Stock (BGS) number.
5. After results of data regarding a new gene are published, two copies
of the reprints are to be sent to the Genetic Stock Center.
(5) A complete description of all mutants
that have been assigned gene symbols should be published in the Barley
Genetics Newsletter. Descriptions submitted with applications for new
gene symbols should be published annually. Descriptions for mutants that
are already symbolized should include any previous symbolization and appropriate
references. It is suggested that: descriptions of genes that have been
associated with chromosomes be prepared by the chromosome coordinators;
descriptions of genes in special collections (male steriles, erectoids,
disease resistance, eceriferum, etc.) be prepared by the special gene coordinators;
descriptions of designated genes not associated with chromosomes and not
included in special collections be prepared by volunteers. At the time
of publication of the descriptions, seed stocks of the gene will be given
a Barley Genetic Stock number.
(6) Lists of seed stocks in the various
world collections of chromosome variations (autotetraploids, inversions,
translocations and balanced tertiary trisomics. trisomics and aneuploid
stocks) should be published in the first issue of the Barley Genetics Newsletter.
Lists of new entries added to the world collections should be published
in the Barley Genetics Newsletter annually.
(7) The following symbolization should be
used to designate individual translocated chromosomes in translocations
and balanced tertiary trisomics. A translocated chromosome should be
symbolized by a capital T to designate a translocated chromosome, followed
by the number of the chromosome furnishing the centromere-bearing segment,
followed by the number of chromosome furnishing the translocated segment,
followed by the letter representing the particular translocation from which
the chromosome was derived. As an example, the translocation T1-2a has
two translocated chromosomes: chromosome T12a which has a centromere-bearing
segment of chromosome 1 combined with a translocated segment of chromosome
2 and chromosome T21a which has a centromere-bearing segment of chromosome
2 combined with a translocated segment of chromosome 1. As another example,
the balanced tertiary trisomic 51b ms1 has an extra chromosome T51b
(which has a centromere-bearing segment of chromosome 5 combined with a
translocated segment of chromosome 1) derived from the translocation T1-5b.
The recessive ms1 allele is carried on the two normal number 5 chromosomes
and the Ms1 allele is carried on the extra T51b chromosome.
(8) Map positions of gene and chromosome
markers should be designated in the following manner: The maps of each
arm of each chromosome will have the centromere representing the beginning
of each map. The centromere shall represent map position 0. Map position
will be described as: the number of recombination units from the centromere,
the arm in which the marker is located (S - short and L - long), and the
number of the chromosome involved. Examples are: the map position of a
marker located 10 recombination units from the centromere in the short
arm of chromosome 1 will be designated as lOS1; the map position of a marker
located 20 recombination units from the centromere in the long arm of chromosome
3 will be designated as 20L3. (T. Tsuchiya, using telocentric trisomics,
and R. T. Ramage, using translocation and balanced tertiary trisomics,
have volunteered to do the necessary work to locate the centromeres in
the linkage maps or to get someone else to do it.)
(9) Coordinators should be appointed for the various chromosomes, for special gene collections and for various chromosomal variations and their duties and responsibilities should be:
1. Maintain current information concerning their area and serve as a source of information concerning that area.
2. Prepare an annual report for the Barley Genetics Newsletter.
3. Maintain world collections of seed stocks. Chromosome coordinators should keep a stock of at least one allele of every locus of their chromosome. Special coordinators of large groups of polymeric genes should maintain all alleles of their group.
4. Perform, or encourage and support others to perform, special work necessary to the advancement of barley genetics. Examples of special work would be: the translocation and balanced tertiary trisomic coordinator should determine cytological breakpoints for all translocations in the world collection and should establish balanced tertiary trisomics for lethal genes and genes of low vigor that are needed extensively in linkage study; chromosome coordinators should develop, or encourage others to develop, multiple marker stocks, backcross genes into more desirable backgrounds, produce stocks combining new genes with a male sterile gene (to facilitate future allele testing), etc.
5. If a coordinator feels that he cannot meet these and other special duties and responsibilities as they develop, he should notify the international committee (see page 1) so that another coordinator can be appointed.
The group that met at Aberdeen, Idaho on August 10 and 11, 1970 examined the existing gene symbols with the intention of determining what problems are to be encountered in revising the system of gene nomenclature and symbolization. Suggestions are offered in three areas:
1. Many genes can be logically grouped and rules for nomenclature and symbolization established for the group. An example would be genes for disease and insect resistance. For this group of genes, it is proposed that, when not ambiguous or misleading, the symbol should consist of the first letter of the genus and the first letter of the species of the parasite. In the case of virus diseases, the symbol should be based on the common name of the virus. In some cases, it may be desirable, because of historical usage, to base symbolization on the common name of the parasite. The following is a list of symbols proposed for genes conditioning resistance to diseases and insects:
Ay vs. ay: Resistance vs. susceptibility to Aster
Yellows virus.
Eg vs. eg: Resistance vs. susceptibility to Erysiphe
graminis (powdery mildew).
Gb vs. gb: Resistance vs. susceptibility to greenbug
(Toxoptera graminium).
Ha vs. ha: Resistance vs. susceptibility to Heterodera
avenae (eelworm).
Hg vs. hg: Resistance vs. susceptibility to Helminthosporium
gramineum (stripe disease).
Hs vs. hs: Resistance vs. susceptibility to Helminthosporium
sorokinanum (spot blotch).
Ht vs. ht: Resistance vs. susceptibility to
Helminthosporium teres (net blotch).
Pg vs. pg: Resistance vs. susceptibility to
Puccinia graminis (stem rust).
Ph vs. ph: Resistance vs. susceptibility to Puccinia
hordei (leaf rust).
Ps vs. ps: Resistance vs. susceptibility to
Puccinia striformus (stripe rust).
Rs vs. rs: Resistance vs. susceptibility to
Rhynchosporium secalis (scald).
Sm vs. sm: Resistance vs. susceptibility to stripe mosaic virus.
Sp vs. sp: Resistance vs. susceptibility to
Septoria passerinii (leaf blotch).
Uh vs. uh : Resistance vs. susceptibility to Ustilago hordei
(covered smut).
Un vs. un: Resistance vs. susceptibility to Ustilago
nuda (loose smut).
Yd vs. yd: Resistance vs. susceptibility to
Yellow Dwarf virus.
2. Certain of the gene symbols currently being used should be retained because they are in agreement with the proposed system of symbolization or because of historical usage. The following is a list of symbols that should be retained in their present form.
B vs. b: Black vs. white lemma and pericarp.
Bl vs. bl: Blue vs. white aleurone.
Bt vs. bt: Brittle vs. non-brittle rachis.
Ddt vs. ddt: Susceptibility vs. resistance to DDT.
Ds vs. ds: Normal vs. desynaptic chromosomes.
Ga vs. ga: Presence vs. absence of gametophyte factor
K vs. k: Kapuze vs. non-kapuze (hooded vs. non-hooded
lemma).
Ms vs. ms: Male fertility vs. male sterility
N vs. n: Covered vs. naked kernels.
R vs. r: Rough vs. smooth awn.
S vs. s: Long vs. short rachilla hairs.
Sh vs. sh: Spring vs. winter growth habit.
Uc vs. uc: Normal vs. uniculm.
V vs. v: Row number in H. distichum vs. H.
vulgare (two-row vs. six-row)
3. A simplified system of naming and symbolizing mutants for plant pigments can be evolved. Such a system could start with seedling pigmentation and be extended to other parts of the barley plant. The following system of symbolization of seedling pigmentation is suggested:
A vs. a: Green vs. albino seedlings (lethal).
Y vs. y: Green vs. yellow seedlings (lethal).
Av vs. av: Green vs. albino virescent seedlings.
Yv vs. yv: Green vs. yellow virescent seedlings.
As vs. as: Green vs. albino stripe seedlings.
Ys vs. ys: Green vs. yellow stripe seedlings.
Az vs. az: Green vs. albino zoned seedlings.
Yz vs. yz: Green vs. yellow zoned seedlings.
Lg vs. lg: Green vs. light green seedlings.
Yg vs. yg: Green vs. yellow green seedlings.
Mutants for seedling pigmentation that do not readily fit into one of the above categories could be placed in the one that most closely fits without disrupting the general system. The symbols suggested for the three areas discussed could all be extended to account for polymeric genes and/or multiple alleles. Examples are: Rs1, Rs2, Rs3, and Rs4 for resistance to Rhynchosporium secalis (scald); Kle for the allele for elevated hoods; and, as a hypothetical example, as2c, for a specific mutational event at a particular locus for an albino stripe seedling.