BGN 19: Coordinator's Report: Chromosome 6

Coordinator's Report: Chromosome 6

Duane E. Falk
Crop Science Department
University of Guelph
Guelph, Ontario, Canada N1G 2WI


An updating of the map of chromosome 6 gives the male sterile gene located in the short arm its distinct locus identification of msg36bk as it has been shown to be non-allelic with the 35 previously determined loci (Franckowiak and Hockett, 1987). Chromosome 6 has a second male sterile locus msg6cf located very near the centromere and the marker gene orange lemma (o).

Fig. 1. The barley chromosome 5 linkage map with the best fit to all available linkage data. The map positions are given in centimorgans (cM). The order and positions of closely linked loci may not be definitive. The position of the centromere is probably slightly above that of locus fs2.

The gene Jmlh has been placed on chromosome 6 by trisomic analysis (Hayashi and Heta, 1985), although its position relative to other marker loci has not been determined.

A ditelotetrasomic has been reported for the short arm of chromosome 6 (Wang and Tsuchiya, 1988) which gives 23% ditelotetrasomics in the selfed progeny, making it relatively easy to maintain and giving the possibility of male transmission of the n + 1t gametes. This type of stock is particularly useful in localizing male sterile mutants.

Makino (1988) has used the presowing selection of male sterile plants based on the linkage sex1 and msg6 on chromosome 6 (see Falk and Kasha, 1982) to give large amounts of crossed seed between an irradiated female line (sex1 msg6) and multiple marker stocks of selected chromosomes (other than 6). By looking for deviations from the expected frequencies of recombinants, lines with both paracentric and pericentric inversions can be detected.

A single crossover plant was located in an F3 progeny of the cross sex1-msg6 / o-gs4 by the author in 1988. The crossover plant was glossy sheath (gs4gs4) but white lemma (O), male fertile (Msg6-) and had all j6 plump seed (Sex1Sex1). The F4 progeny grown from this plant indicate that sex1 and gs4 are probably very close and on the opposite side of the o locus from the msg6 locus. The positions of gs4 and sex1 relative to o cannot be determined in this particular line.

Male sterile plants from the new stock are being crossed with sex1, ant13, and uc2 stocks in an effort to more clearly define the gene order near the centromere of chromosome 6.

References:

Falk, D.E., and K.J. Kasha. 1982. Registration of a shrunken endosperm, male-sterile germplasm to facilitate hybridization in barley. Crop Sci. 22:450.

Franckowiak, J.D., and E.A. Hockett. 1987. Allelism tests for the genetic male sterile msg,,bk. BGN 17:77-78.

Hayashi, J., and H. Heta. 1985. Association of a mildew resistance gene Jmlh in Hanna 906 with chromosome 6. BGN 15:46-47.

Makino, T. 1987. An effective method of developing inversions on a specific chromosome.BGN 17:103-104.

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


table of contents | BGN main index