Coordinator's report: Chromosome 2
J.D. Franckowiak
Department of Plant Sciences, North Dakota State University
Fargo, ND 58105, USA.

Takeda and Zhang (1995) mapped a dominant gene for a positive response to phenol, Phr, in the long arm of chromosome 2 between the v (six-rowed spike) and the li (liguleless) loci. Recombination estimates are 24.7 ± 2.6 for v to Phr and 22.2 ± 4.7 for Phr to li. The 51 of 9,242 Hordeum vulgare accessions, which had no visual reaction to a 1% phenol solution, were collected at sites from Spain to Korea. Accessions with no phenol reaction were collected primarily from the Middle East, and the rest were from countries along the so-called "Silk Road".

One of three components necessary for rapid cell death in response to Erysiphe graminis f. sp. hordei infection was mapped in chromosome 2 (Freialdenhoven et al., 1994). The gene Nar-1 is needed for the necrotic response to powdery mildew associated with the Mla.12 gene for resistance. The recessive allele at the Nar-1 locus causes a susceptible response even when the Mla.12 and Nar-2 genes are present. The locus symbol Nar, however, has been used previously for a series of genes controlling nitrate reductase (Kleinhofs, 1992; Wettstein-Knowles, 1992).

Giese et al. (1993) mapped the Ml(La) or Laevigatum gene for powdery mildew resistance in chromosome 2 using RFLP markers.

Schreiber (1993) used the close linkage between the v1 (six-rowed spike 1) and Lk (awnless) loci to demonstrate that "gene conversion" is possible in F1 hybrids of barley. The occurrence of "gene conversion" is low, but Schreiber demonstrated that only one of the two adjacent loci was homozygous in the F2 progeny from aberrant spikes.

Genome mapping projects have associated many quantitative trait loci (QTL) with chromosome 2. Several of the QTLs may be associated in the future with simply inherited genes. Backes et al. (1994) found that a large component for the low reaction to Rhynchosporium secali in chromosome 2 of 'Igri'. Han et al. (1994) placed QTLs with large effects on kernel weight, kernel plumpness, grain protein, diastatic power, and alpha-amylase in chromosome 2. Hayes and Iyamabo (1994) associated major effects on heading date and plant height was with chromosome 2S of 'Steptoe'. At some locations, a significant yield effect was associated also with this same region. These responses may be associated with the Ea1 gene for photoperiod sensitivity is present in chromosome 2S of Steptoe (Franckowiak, 1995). The Ea1 gene from Igri was mapped to the same region of chromosome 2S by Laurie et al. (1994), but the gene symbol Ppd-H1 is used in their report.

Isozyme loci reported to be associated with chromosome 2 are listed in Table 1.

The recessive allele at the wst7 (white streak 7) locus in chromosome 2L (Franckowiak, 1995) was tested for allelism using accessions from the Genetic Stocks of Barley held at USDA-ARS National Small Grains Germplasm Research Facility, Aberdeen, Idaho. Because the original of the wst7 or wst,,k gene used in development of the Multiple Recessive Marker Stocks is unknown (Wolfe and Franckowiak, 1990), several sources of similar genes were check as possible alleles. Crosses to stocks B21-7 and T35-26, identified as having the ribbon grass gene, produced positive results (Franckowiak, unpubl.) Thus, the white streak 7 (wst7) locus should be called the ribbon grass locus and the gene symbol rb should be used. Several previous reviews of barley genes have placed the rb locus in chromosome 4.

References:

Backes, G., G. Fischbeck, A. Graner, and A. Jahoor. 1994. Localisation of agronomically important traits in barley (Hordeum vulgare L.) by means of RFLP marker. BGN 23:60-64.

Franckowiak, J.D. 1995. Coordinator's report: Chromosome 2. BGN 24:132-138.

Freialdenhoven, A., B. Scherag, K. Hollricher, D.B. Collinge, H. Thordal- Christensen, and P. Schulze-Lefert. 1994. Nar-1 and Nar-2, two loci required for Mla12-specified race-specific resistance to powdery mildew in barley. Plant Cell 6:983-994.

Giese, H., A.G. Holm-Jensen, H.P. Jensen, and J. Jensen. 1993. Localization of the Laevigatum powdery mildew resistance gene to barley chromosome 2 by the use of RFLP markers. Theor. Appl. Genet. 85:897-900.

Han, F., and S.E. Ullrich. 1994. Mapping of quantitative trait loci associated with malting quality in barley. BGN 23:84-97.

Hayes, P.M., and O. Iyamabo. 1994. Summary of QTL effects in the Steptoe X Morex population. BGN 23:98-143.

Kleinhofs, A. 1992. The NABGMP mapping progress report, spring 1992. BGN 21:38-48.

Kleinhofs, A., A. Kilian, and D. Kudrna. 1993. The NABGMP mapping progress report, spring 1993. BGN 22:27-41.

Laurie, D.A., N. Pratchett, J.H. Bezant, and J.W. Snape. 1994. Genetic analysis of a photoperiod response gene on the short arm of chromosome 2 (2H) of Hordeum vulgare (barley). Heredity 72:619-627.

Macaulay, M., D.A. Laurie, and B.P. Forster. 1994. Extraction and genetic control of two new water-soluble proteins of mature barley seed. Biochem. Genet. 32:137-144.

Mena, M., R. Sanchez-Monge, L. Gomez, G. Salcedo, and P. Carbonero. 1992. A major allergen associated with baker's asthma disease is a glycosylated monomeric inhibitor of insect alpha-amylase: cDNA cloning and chromosomal location of the gene. Plant Mol. Biol. Int. J. Mol. Biochem. Genet. 20: 451-458.

Schreiber, H. 1993. High non-reciprocal recombination in a barley cross. BGN 22:63-64.

Søgaard B., and P. von Wettstein-Knowles. 1987. Barley: genes and chromosomes. Carlsberg Res. Comm. 52:123-196.

Takeda, K., and C.L. Zhang. 1995. Inheritance and geographical distribution of a phenol reaction-less mutant in barley. BGN 24:32-34.

Wettstein-Knowles, P. von . 1992. Cloned and mapped genes: Current Status. p. 73-98. In P.R. Schewry. Barley: Genetics, Biochemistry, Molecular Biology and Biotechnology. CAB International, Wallingford, UK.

Wolfe, R.I., and J.D. Franckowiak. 1991. Multiple dominant and recessive genetic marker stocks in spring barley. BGN 20:117-121.

Table 1. A listing of biochemical genes associated with chromosome 2 as extracted from previous summaries of barley genes.

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Locus   Chr.  Locus name              References* 
symbol  loc.
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Adh8    2S    Alcohol dehydrogenase 8 Good et al., 1988 

Bmy2    2S    beta-amylase 2          Kreis et al. 1988 

Chs1A   2S    Chalcone synthase 1A    Rhode et al,, 1991 

Chs1B   2S    Chalcone synthase 1B    Rhode et al., 1987 

Cig6    2     Cold-induced gene 6     Dunn et al., 1991 

Crg3A   2L    Cold-regulated          Bartels et al., 1990 
              protein 3A

Gln2    2L    Glutamine synthetase,   Cannell et al., 1989
              chloroplastic 2 

His3C   2L    Histone 3C              Brandt, 1986 

Iam1    2     Inhibitor of            Mena et al., 1992 
              alpha-amylase 1

Idh2    2     Isocitrate              Brown and Munday, 1982 
              dehydrogenase 2

Isa1    2     Inhibitor of subtilisin Hejgaard et al., 1985 
              and alpha-amylase 1

Ndh4    2     NADH dehydrogenase 4    Nielsen and Johansen, 1986 

Pbq     2     Basic protein Q         Hejgaard and Bjorn, 1985 

Pcr1    2L    Prochlorate reductase 1 Apel et al., 1989 

Pox     2S    Path-induced peroxidase Dudler et al., 1991 

Prx2    2L    Leaf peroxidase 2       Bosch et al., 1986 

RbcS    2S    Ribulose biphosphate    Cannell et al. 1989 
              carboxylase small subunit

Rm5S1   2L    Ribosomal 5S RNA 1      Kolchinsky et al., 1990 

Sod1    2     Superoxide dismutase 1  König, 1988 

Wsp4    2     Water-soluble protein 4 Macaulay et al., 1994 
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* References are cited in listings of mapped barley genes,
published by Søgaard and Wettstein-Knowles (1987),
Wettstein-Knowles (1992), Kleinhofs (1992), and Kleinhofs et al.
(1993).