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6. Symbols for loci and alleles controlling quantitative characters
6.1 Genes identified by segregational analysis: Symbols for loci and alleles controlling quantitative characters that are identified by segregational analysis should be in accord with the Recommended Rules for Gene Symbolization in Wheat.

6.2 Quantitative trait loci (QTLs): QTLs are loci controlling quantitative characters whose allelic classes do not exhibit discontinuous variation or dear segregational patterns. They are identified by association with one or more linked markers.

6.2.1 Basic symbol: The basic symbol for QTLs should be "Q".

6.2.2. Locus symbols: The "Q" should be followed by a trait designator, a period, a laboratory designator (see Section 5.6), a hyphen (-) and the symbol for the chromosome in which the QTL is located. The trait designator should consist of no more than four and preferably three letters, the first of which is capitalized. Different QTLs for the same trait that are identified in one chromosome should be assigned the same symbol except for the addition of a period and an Arabic numeral after the chromosome designation. All characters in the locus symbol should be italicized. For example, QYld.psr-7B. 1 and QYld.psr-7B.2 would designate two yield QTLs identified in chromosome 7B by the John Innes Centre. On a map of 7B, these could be abbreviated as QYld.psr.1 and QYld.psr.2.

6.2.3 Allele symbols: Alleles at QTL loci should be designated by a lower-case italic letter following the locus designation.

7. AFLP amplified fragment length polymorphism
A nomenclature proposal for AFLP loci has been received from Marc Zabeau at Keygene with the format 'XxyzAN1N2N3, where 'X' is the usual symbol for a DNA marker of unknown function; 'xyz' is the usual laboratory designator (e.g., kg for Keygene); A is a single upper-case letter denoting the rare-cutter enzyme used, e.g., P for PstI, etc.; N1 and N2 are two-digit numbers identifying standard one, two or three base-pair extensions (standard lists will be provided by Keygene); and N3 is a three-digit number corresponding to the molecular weight of the fragment.
The foregoing should be considered only as a proposal at this time as no AFLPs are listed in the catalogue. Comments regarding the proposal are welcomed and should be sent to the authors.

8. Guidelines for Nomenclature of Genes for Reaction to Pathogenic Diseases and Pest
1. All genes for resistance (low reaction) will be designated with a capital letter, even though they behave as recessive alleles. Moreover, the dominance of individual alleles may vary with the environment, the genetic background and the particular culture of the pathogen. Symbols for disease/pest-reaction genes are used by people of many disciplines, and since they are frequently communicated verbally, dominance relationships are not clear. Those alleles initially designated with a lower-case letter have tended to be miswritten with a capital. For example, the usually recessive resistance allele Sr17 was initially designated sr17 but its presentation in some reports was confusing.

2. Where no recombination occurs between genes conferring resistance to more than one pathogen, the gene(s) segment shall be designated separately for each disease; e.g. Pm1, Sr15 and Lr20.

3. Where recombination I>occurs between two closely linked factors for reaction to a pathogen, the recombined 'allele' may be designated as a combination of the separate alleles; e.g. the recombined 'allele' obtained by combining Lr14a and Lr14b was designated as Lr14ab. The decision as to whether a designation should be as a combination or as separate genes shall be at the discretion of particular workers. A maximum value of 1 crossover unit for designation as an 'allele' is suggested. Although the need to consider uniform symbolization of corresponding genes in pathogens is recognized, no recommendations are proposed.
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