Coordinator's Report: Chromosome 4
Coordinator's Report: Chromosome 4
Brian P. Forster
Cell and Molecular Genetics Department, Scottish Crop Research Institute
Invergowrie, Dundee DD2 5DA, UK.

First the good news, several new genes have been mapped to chromosome 4 using various mapping populations and various methods including protein, isozymes, RFLP and microsatellite technologies. They include: Dhn6 - dehydrin, Adh4 - alcohol dehydrogenase, Pgk2A - cytosolic phosphoglycerate, Aco2 - aconitate hydratase, Hxk2 - hexokinase, and rubisco activase (Kasha et al., 1993; Kleinhofs et al., 1993; Becker and Heun, 1995). In addition the centromere has been placed between the ert-i and lg4 loci, this is based on telotrisomic data from Singh and Tsuchiya, 1974 (Franckowiak pers. commun.). The bad news is that two genes previously assigned to chromosome 4, cer-cqu (gs6, gs, gs8) and rb, have been removed from the map. Both are now known to be located on chromosome 2 and not on 4.

Several quantitative trait loci have been located on chromosome 4. These include: days to heading, days to maturity, plant height, reaction to net blotch and powdery mildew, grain size, total grain protein, wort-soluble protein, grain yield, alpha amylase activity and lodging (Hackett et al. 1992; Tinker et al. 1993; Han et al. 1993, Hayes et al. 1993).

Compared to the other barley chromosomes, 4 has the least number of mapped genes and genetic markers. A list of mapped genes is given below, but a more up to date list is currently being compiled for the `GrainGenes' data base (David E. Matthews, pers. commun.). Not all the genes listed below are included in Figure 1. The gene symbol for infertile intermedium has been changed from `I' to `i' as this gene is recessive. Also the eceriferum gene symbol cer-zh has been changed to gl, these two genes have been shown to be allelic and gl has precedence, (Lundqvist and von Wettstein, 1971). The map given in Figure 1 differs from that given in BGN 24 in that the zero position is given to z and not cer-j (z is genetically closer to the centromere. The erroneous genes, cer-cqu and rb have been deleted from the map. The mapping of the centromere (between ert-i and lg4) has revealed an inequality in both the number of genes mapped and the genetic length of the two arms of chromosome 4, with the short arm having about a quarter of the capacity of the long arm in both respects.

Mapped Genes

f9 - chlorina; i - infertile intermedium; v5 - six row; K - hooded; ert-i - erectoides; z - zebra striped leaf; lg4 - light green; f10 - chlorina seedling; N182 - reaction to Erysiphe graminis; ari-c - breviaristatum; lb2 - long weak internode, gl - eceriferum; Ml-g - reaction to Erysiphe graminis; cer-zg - eceriferum; br2 - brachytic dwarf; cer-j - eceriferum; min - semi-minute dwarf; Bl - white aleurone xenia; sid - single elongated internode dwarf; ml-o - reaction to Erysiphe graminis; Hs - hairy sheath; sh - spring habit; yh - yellow head; Bmy1 - beta-amylase; Wsp3 - water-soluble protein.

Aco -2 - aconitate hydratase; Adh4 - alcohol dehydrogenase; Dhn6 - dehydrin; Hxk2 - hexokinase; Pgk2A - cytosolic phosphglycerate kinase; rub - rubisco activase.

References :

Becker, J. and Heun, M. (1995). Barley microsatellites: allele variation and mapping. Plant Molecular Biology 27, 835-845.

Kasha, K.J., Kleinhofs, A. and the NABGMP (1993). Mapping the barley cross Harrington X TR306. Barley Genetics Newsletter 23, 65-69.

Kleinhofs, A., Kilian, A., Kundrna, D. and the NABGMP (1993). The NABGMP Steptoe x Morex mapping progress report. Barley Genetics Newsletter 23, 79-82

Hackett, C.A., Ellis, R.P., Forster, B.P., McNicol, J.W. and Macaulay, M. (1992). Statistical analysis of a linkage experiment in barley involving quantitative trait loci for height and ear-emergence time and two genetic markers on chromosome 4. Theoretical and Applied Genetics 85, 120-126.

Han, F. Ullrich, S.E. and the NABGMP (1993). Mapping of quantitative trait loci associated with malting quality in barley. Barley Genetics Newsletter 23, 84-97.

Hayes, P.M., Iyambo,O. and the NABGMP (1993). Summary of QTL effects in the Steptoe x Morex population. Barley Genetics Newsletter 23, 98-143.

Lundqvist, U and von Wettstein, D. (1971). Stock list for the eceriferum mutants. Barley Genetic Newsletter 1, 97-102.

Singh, R.J. and Tsuchiya, T. (1974). Further information on telotrisomic analysis in barley. Barley Genetics Newsletter 4, 66-69.

Tinker, N.A., Mather, D.E. and the NABGMP (1993). Main effects of quantitative trait loci in Harrington/TR306 two-row barley. Barley Genetics Newsletter 23, 72-78.


Total length: 136.0 cM

Figure 1. The gene map of chromosome 4.