II.21. Studies of the pleiotropic character complexes in erectoides mutants.
Y. Lind and H. Gaul. Department of Plant Genetics of the Gesellschaft für Strahlenund Umweltforschung mbH, 8059 Grünbach 1 üb. Erding/ Obb., FRG.
In 1972 we have initiated a program to further investigate the pleiotropic character complexes. Such complexes are known to occur in erectoides mutants. In previous studies we had shown that it is possible to separate desired features from undesired ones, even though both were controlled by the same gene (Gaul, H., F. Grunewaldt and C. U. Hesemann, 1968; Gaul, H. and J. Grunewaldt, 1970; Grunewaldt, J., 1970; Hesemann, C. U. and H. Gaul, 1967).
The mutants used in our present studies are ert-a19, ert-a38, ert-c48, ert-c82, ert-g24, ert-g80 and ert-g84. They were described by Persson and Hagberg (1969) and Persson (1969). Each erectoides mutant was crossed with the varieties "Union", "Eli", "Hanna", and the mutant "lo 8". Additionally, backcrosses were made with their mutual mother variety "Bonus". The characters analyzed are culm length and spike-internode length. Allelic, as well as non-allelic erectoides mutants differ in both features from each other, from the three varieties and from the mutant lo 8. In addition, these four barley types have also different character expressions. The deviation degree of the characters, both in the mutants and in the varieties, can be seen in Table 1.
Beginning with the F2 generation, we shall select plants showing an independent variation of both characters. We call such plants "modified mutants". Their frequency will be measured in each F2 generation.
Three main problems are to be studied:
(1) Which is the part played by the genotype in separating pleiotropic characters of the mutants that are phenotypically either similar or different?
(2) Is there any correlation between the difference in character expression in the cross parents and the frequency of modified mutants?
(3) What is the best method to be used for the selection of as many modified mutants as possible?
All the F1 generations were grown and analyzed in 1973, except the crosses with ert-g24, ert-g80, and Hanna which have not yet yielded F1 plants. Each generation comprises 50 plants. In all combination-crosses and in all backcrosses culm length of the mutants was inherited recessively. The F1 plants did not differ significantly from the varieties and the mutant lo 8 (Table 2).
Spike-internode length and culm length were inherited independently. In all crosses with allelic mutants, spike-internode length had the same mode of inheritance, irrespective of the morphological differences of plants.
However, differences could be noticed in the F1 plants when non-allelic mutants were used in crosses. The hybrids of such mutants had different spike-internode lengths, whereas their parents had a similar culm- and spike-internode length. The mode of inheritance of the characters in the mutants can be seen in Table 2. At the 0.01 level all F1 plants differed significantly from the erectoides mutants as regards their culm length and spike-internode length. Therefore, only differences between the mean values of the characters in the F1 generation and those of the cross parents Bonus, Union, Eli and lo 8 are presented in this Table.
Table 2. Comparison of the mean values of culm length and spike-internode length.
The results of the analysis of the F1 generations lead to the conclusion that the mode of inheritance is not determined by the morphological similarity or difference of the erectoides mutants. The mode of inheritance of mutant characters, i.e. recessive or intermediate, depends entirely on the mutants being allelic or non-allelic.
The four varieties and the mutant lo 8, the genotypes of which are unknown, have a pronounced and diverse influence on the phenotype of the F1 plants.
References:
Gaul, H., J. Grunewaldt and C. U. Hesemann. 1968. Variation of character expression of barley mutants in a changed genetic background. Mutations in Plant Breeding II, IAEA, Vienna, 77-95.
Gaul, H., and S. Grunewaldt. 1970. Independent variation of culm length and spike-internode length of a barley-erectoides mutant in a changed genetic background. Barley Genetics II, 106-118.
Grunewaldt, S. 1970. Die unabhängige Variation von Teilmerkmalen des erectoides- Merkmalskomplexes einer Gerstennutante in verändertem genetischen Hintergrund. Diss. TU Hannover, G.S.F. Bericht BT 50, 1971.
Hesemann, C. U., and H. Gaul. 1967. Züchterische Bedeutung von Grossmutationen. II. Beispiel für die unabhängige Variation von Teilmerkmalen einer Sommergersten-Mutante im veranderten genetischen Hintergrund. Z. Pflanzenzücht. 58: 1-14.
Persson, G. 1969. Genetic analysis of a quantitative character, ear internode length, in barley. Berlingska Boktryckeriet, Lund, 1-26.
Persson, G. and A. Hagberg. 1969. Induced variation in a quantitative character in barley. Morphology and cytogenetics of erectoides mutants. Hereditas 61:115-178.
