BGN 19: Coordinator's Report: Chromosome 7

Coordinator's Report: Chromosome 7

George Fedak
Plant Research Centre
Research Branch
Agriculture Canada, Ottawa.


Acrotrisomic 7S7L (containing the entire short arm of chromosome 7 plus 27.6% of the proximal portion of the long arm) was used to verify the arm location of five marker genes. Based on F2 segregation ratios four of the alleles, nld, va, fs, and r, were located on the deficient segment of the long arm while the S locus was probably located on the proximal portion of that arm (Riley and Tsuchiya, 1988).

The pollen fertility and seed set in selfed ditelotetrasomic 7S was 92.6% and 70.8%, respectively. Progenies of selfed ditelotetrasomic 7S consisted of 27.1% plants with two telos and 50.0% with a single telo (Wang and Tsuchiya, 1988).

The nar2 locus that codes for a protein involved in molybdenum cofactor function in nitrate reductase was mapped to chromosome 7 at a position 8.4 ± 2.1 and 23.0 ± 4.6 map units from the nld and mt2 loci, respectively (Melzer et al., 1988). The arm location was not specified but the locus was likely located in the centromeric region.

A locus multinoded dwarf (mnd)* was located on the long arm of chromosome 7 with recombination values with r and tg of 39.00 + 4.76% and 30.57 + 6.59%, respectively (Prasad and Toner, 1988).

The locus glo-b for globe shaped grains had previously been located on chromosome 7 with five mutants designated glo-b1 to glo-b5 that were either allelic or closely linked to that locus. Two additional mutants designated glo-e1 and glo-e2 that were either allelic or closely linked but independent of the _qlo-b locus have recently been reported (Hauser et al., 1988). In terms of structural rearrangements of chromosome 7, Konishi and Linde Laursen (1988) reported that a strain of H. spontaneum had both a spontaneous reciprocal translocation between the long arm of chromosome 7 and short arm of chromosome 3 plus a paracentric inversion in the short arm of chromosome 7. The latter rearrangement results in a chromosome 7 with two tandenly arranged secondary constrictions.


*Editor's note: This gene is not the same mnd gene as described by Nilan (1964) and located on chromosome 2S.

References:

Hauser, J., A. Jahoor, and G. Fischbeck. 1988. Localization of induced mutants for globe shaped grains. BGN 18:54-58.

Konishi, T., and 1. Linde-Luarsen. 1988. Spontaneous chromosome rearrangements in cultivated and wild barleys. Theor. Appl. Genet. 75:237-243.

Melzer, J.M., A. Kleinhofs, D.A. Kudrna, R.L. Warner, and T.K. Blake. 1988. Genetic mapping of the barley nitrate reductase-deficient nar1 and nar2 loci. Theor. Appl. Genet. 75:767-771.

Prasad, G., and S.B. Toner. 1988. Linkage of two mutant genes for multinoded character with marker loci on barley chromsomes 5 and 7. 18:46-48.

Riley, R., and T. Tsuchiya. 1988. Acrotrisomic analysis of five genes for chromosome 7 in barley. BGN 18:14-15.

Wang, S., and T. Tsuchiya. 1988. The pollen fertility, seed set and transmission rate of ditelotetrasomic 6S and 7S in barley. BGN 18:17-18.


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