Progress of RFLP-map construction in winter barley

A. Graner1, E. Bauer1, A. Kellermann1, S. Kirchner1, J.K. Muraya1, A. Jahoor2, G. Wenzel1,2 1Institute for Resistance Genetics, D-85461 Griinbach
2Institute for Agronomy and Plant Breeding, D-85354 Freising-Weihenstephan

Since the initial presentation of an integrated barley map composed of two progenies (Vada/H.spont. interspecific; Igri/Franka intraspecific)(Graner et. al. 1991) we have been focussing our efforts on the refinement of the intraspecific Igri/Franka map because both cultivars represent adapted winter barley germplasm, which segregates for agronomic traits such as resistance to barley yellow mosaic virus, and a population of Fl-anther derived doubled haploid lines had been produced from this cross (Foroughi-Wehr and Friedt, 1984). Major goals pertaining to this map are

  1. reduction of the average marker distance,
  2. to provide a set of mapped markers, which detect polymorphisms in adapted winter barley germplasm,
  3. to increase the compatibility with other maps, notably with the NABGMP Steptoe/Morex map by establishing a common denominator of both anonymous and known function probes (Table 1).
In its present state the map contains 374 markers, which detect 273 loci. The difference between both figures is due to the occurrence of markers clustering to one locus, especially in the centromeric region of each chromosome (Fig. 1). Because of a stringent selection of single or low copy markers and a low level of polymorphism between the parents (ca. 25 % with six restriction enzymes) this cluster effect has not been counterbalanced by the detection of duplicated loci. Given a total map length of 1433 cM, the average distance between any two loci is presently 5.2 cM.

A comparison of the Igri/Franka with the Steptoe/Morex and the Vada/H.spont. maps reveals that marker coverage of telomeric portions is fairly complete, except for the long arm of chromosome 4 (4H). Here a segment of about 20 cM still escapes detection. There are still two interstitial gaps larger than 30 % recombination. One is located on the long arm of chromosome 2 (2H). Based on comparison to the Vada/H.spont. and the S/M maps its estimated size is between 55 and 68 cM. The second gap is located on the short arm of chromosome 3 (3H). Here, inter-map comparison results in an estimated size of this gap between 17.6 cM (Vada/H.spont.) and 32.7 cM (S/M). Because it is likely that the respective chromosome regions of Igri and Franka share a high degree of identity by descent, it will become increasingly difficult and expensive to fill these and smaller gaps by saturation mapping. Therefore, the integration of two maps, which have been constructed in different genetic backgrounds seems to be by far more economic to achieve an even marker coverage.

Table la: anonymous probes on the Igri/Franka map

Table 1b: known function probes on the Igri/Franka map

Figure 1: Barley RFLP map derived from an Flanther derived progeny comprising 71 doubled haploid lines. Chromosomes are oriented with the short arm on top. Locus designations are preliminary and might be subject to change according to the upcoming recommendations of the Barley Molecular Probe committee. Framed probes represent reference points to the NABGMP Steptoe/Morex map. % recombination values were converted into map distances by Kosambi transformation.
IxF chromosome 1 (7H) IxF chromosome 2 (2H)
IxF chromosome 3 (3H) IxF chromosome 4 (4H)
IxF chromosome 5 (1H) IxF chromosome 6 (6H)
IxF chromosome 7 (5H)

References:

Foroughi-Wehr, B., Friedt, W. 1984. Rapid production of recombinant barley yellow mosaic resistant Hordeum vulgare lines by anther culture. Theor.- Appl. Genet. 67:377-382

Graner, A., Jahoor, A., Schondelmaier, J., Siedler, H., Pillen, K., Fischbeck, G., Wenzel, G., Herrmann, RG. 1991. Construction of an RFLP map in barley. Theor. Appl. Genet. 83:250-256

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