Doubled haploid (DH) lines derived from Fl gametes between different genotypes are frequently used for genetical analysis. In barley, several series of DH lines have been produced from different cross combinations by the bulbosum method. For RFLP and RAPD analyses, it is important to show the Mendelian segregation at each locus in the DH lines, without any distortion.
As shown in Table 1, distorted segregation at Est5 locus for esterase isozyme on the short arm of chromosome 1 was observed in a series of Canadian DH lines derived from 'Leger' x 'CI 9831', although no segregation distortion could be detected at four loci: v for six-rowed spike, r for smooth awn, Re2 for purple lemma, and Est1 for esterase (Choo et al. 1992). The segregation distortion at the Est5 locus also occurred in a different series of Japanese DH lines derived from 'Kanto Nakate Gold' x 'Moho Golden'. However, in North American DH lines of 'Steptoe' x 'Morexl, no segregation distortion at the locus could be found (Kleinhofs et al. 1993).
Further, segregation of isozyme alleles at the Est5 locus was examined in F2 seedlings of two cross combinations shown the significant distortion. Table 2 shows no segregation distortion at the Est5 locus in the two F2 populations.
From these results, it is clear that the segregation distortion at the Est5 locus occurs only in the DH lines derived from some specific crosses, and that the distortion cannot be detected in F2 populations of the same crosses. The distortion in DH lines may be caused by difference in crossability between H. hulhosum and cultivated barley, and a locus for the crossablity may be linked with the Est5 locus.
Choo,T.M., K.M. Ho, T. Konishi, and R-A- Martin. 1992. Tests for randomness among doubled-haploid lines derived by the bulbosum method in barley Hordeum vulgare L. SABRAO Jour. 24:87-92.
Kleinhofs,A., A. Kilian, M.A. Saghai Maroof, R.M. Biyashev, P. Hayes, F.Q. Chen, N. Lapitan, A. Fenwick, T.K. Blake, V. Kanazin, E. Ananiev, L. Dahleen, D. Kudrna, J. Bollinger, S.J. Knapp, B. Liu, M. Sorrells, M. Heun, J.D. Franckowiak, D. Hoffman, R. Skadsen, and B.J. Steffenson. 1993. A molecular, isozyme and morphological map of the barley (Hordeum vulgare) genome. Theor. Appl. Genet. 86:705-712.