BGN 10: Segregation and linkage of genes on barley chromosome 3 in one cross-combination tested by chromosome-doubled monoploids and by F2-data BARLEY GENETICS NEWSLETTER, VOL. 10, II. RESEARCH NOTES
Linde-Laursen, pp. 42-44

II. 19. Segregation and linkage of genes on barley chromosome 3 in one cross-combination tested by chromosome-doubled monoploids and by F2-data.

Ib Linde-Laursen, Agricultural Research Department, Risø National Laboratory, DK-4000 Roskilde, Denmark. "R"

A line provided by Bodil Søgaard, Department of Physiology, the Carlsberg Laboratory, and carrying three normally segregating linked morphological marker genes, cer-zd67 (eceriferum), uz (semibrachytic), and cer-zn244 (eceriferum) (Søgaard, 1977), and one esterase gene, Est-f At (Hvid and Nielsen, 1977), on chromosome 3 and the alpha-amylase gene Amy-1 Ke on chromosome 6 (Nielsen and Frydenberg, 1974) was crossed with the Danish barley variety 'Tystofte Prentice' that carries genes Est-4 Su and Amy-1 Bi. Chromosome-doubled monoploids derived from female gametes of the F1-hybrids were produced by the bulbosum-method (Jensen, 1976) during two production cycles resulting in about the same number of monoploids. The segregations in the two cycles did not differ and are pooled.

Segregation of genes cer-zd67, uz, and cer-zn244 was scored among chromosome-doubled monoploids, F2-plants, and additional F2-plants progeny-tested by an average 20 F3-plants. However, F2-progenies non-segregating and segregating for the dominant allele of cer-zd67 were recorded together because of difficulties in distinguishing genotypes. Segregation of isoenzyme genes was recorded in monoploids only. Recombination frequencies were estimated by the method of maximum likelihood from the combined F2- and F3-data.

Segregation ratios of genes cer-zd67, uz, and cer-zn244 did not deviate significantly from 3:1 or 1:2:1 in F2 or in F2-progeny tests (cf. Table 1). The recombination frequencies showed cer-zd67, uz, and cer-zn244 to be linked in the given order (Table 2). The genes cer-zd67 and uz were more closely and uz and cer-zn244 less closely linked than previously reported (Søgaard, 1977).

Table 1. Segregation of genes cer-zd67, uz, and cer-zn244 among chromosome-doubled monoploids, F2-plants, and F2-progenies.

Table 2. Recombination frequencies + S.D.

In the monoploids segregation ratios of each of genes cer-zd67, uz, and cer-zn244 deviated significantly from the 1:1-ratios expected. In each case the deviation was caused by a deficiency of about 50 percent of plants with the recessive genotype (cf. Table 1). The segregation ratios of the esterase and alpha-amylase genes, respectively, did not deviate significantly from 1:1, the esterase genes showing a ratio of 68 (Est-4 At) to 71 (Est-4 Su) among monoploids and the alpha-amylase genes a ratio of 65 (Amy-1 Ke) to 74 (Amy-1 Bi). Because of the large deviations from 1:1 ratios of the single gene segregations of cer-zd67, uz, and cer-zn244, no estimations of recombination frequencies were carried out in this material. The isoenzyme genes segregated independently of each other and of the morphological marker genes.

Fl-material from the same cross-combination was used to produce both the chromosome-doubled monoploids and the F2-plants. Therefore, the deviating segregations in the monoploid material with reduced transmission of gametes with genes cer-zd67, uz, and cer-zn244 may be caused by the bulbosum technique of producing the doubled monoploids at one or several of the steps involved.

References:

Hvid, S. and G. Nlelsen. 1977. Esterase isoenzyme variants in barley. Hereditas 87:155-162.

Jensen, C. J. 1976. Barley monoploids and doubled monoploids: Techniques and experience. Barley Genetics III:316-345.

Nielsen, G. and 0. Frydenberg. 1974. Linkage between the loci Amy1 (alpha-amylase), o (orange lemma) and x (xantha seedling). BGN 4:53-54.

Søgaard, B. 1977. The localization of eceriferum loci in barley. V. Three point tests of genes on chromosome 1 and 3 in barley. Carlsberg Res. Commun. 42:67-75.

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