II.9. Significance of erectoides mutants for practical breeding purposes.*
J. Grunewaldt. Max-PlanckInstitut für Züchtungs-forschung, 5 Köln 30, BRD, Germany.
*Financed by G.S.F. Müchen, and subcontracts between the Association
EURATOM/ITAL - Max-Planck-Institut Köln, and ERATOM/ITAL - G.S.F.
Muchen.
Only very few cases are known, where erectoides mutants could be used directly as new varieties. Pallas barley is one of them. Also another possibility, namely their utilization as cross parents, yielded in only a few cases varieties, as for example Midas and Hellas. The question, why breeders apparently have not paid more attention to the short, stiff straw of most ert mutants for the improvement of lodging resistance, can easily be answered. The pronounced pleiotropic effect of ert factors results in a complex of changes, desired (e.g. short culm) as well as undesired ones (e.g. dense ear, bad tillering, reduced fertility etc.). True pleiotropic complexes are thought to be unchangeable, but Hesemann and Gaul (1967) stressed the possibility of obtaining this by integration of the ert factor into a new genetic background.
To work out a practicable method on this basis, eleven barleys out of the world collection have been crossed with the erectoides mutant ert 16, a mutant from Haisa II, which is not yet localized. Following a special method of selection (Grunewaldt 1970), plants being homozygous for the ert factor could be selected in F2 generation.
The total variability for culm and spike-internode length in segregating mutant types is recorded in Table 1 together with the respective parents. In all cross combinations plants with shorter culms than ert 16 were found, with the extreme of only 24 cm reached in the combination ert 16 x Bulchi Gofa. This is only about 50% of length of the shortest ert 16 plant. The few longer culmed individuals were not found to be true breeding. With regard to spike-internode length, some combinations segregated for denser plants than in the pure mutant line, whereas others contained considerably laxer ones.
Table 1. Variability of culm and spike-internode length of the cross
The modification of ert characters has been independent of each other. Thus very short mutant types with very lax ears, and tall ones with dense spikes appeared. These individual "modified" mutants can be selected for true breeding, and types are available, combining the desired short mutant culm with a normal lax ear.
To predict the quality of segregating mutants, one can conclude, that no modified mutant will have longer culms than ert 16, and no one will reach the spike-internode length mean of the lax cross parent involved. There will be a gap between the laxest modified mutant and the cross-parent mean of 0.1 to 0.6 mm. This indicates that only relatively lax cross parents should be used to obtain a sufficient lax spike-internode length. The extremes of modified mutants are comparable with plants obtained by Persson and Hagberg (1969) after combination of two and more ert factors. Investigations have been set up to test if this phenotypic parallel has a common genetic basis.
References:
Grunewaldt, J. 1970. Die unabhängige Variation von Teilmerkmalen
des erectoides - Merkmalskomplexes einer Gerstenmutante in ver--ändertem
genetischen Hintergrund. Diss. TU Hannover, G.S.F. Bericht BT 50, 1971.
Hesemann, C. U. and H. Gaul. 1967. Züchterische Bedeutung von Gross-mutationen II. Beispiel für die unabhängige Variation von Teilmerkmalen einer Sommergersten-Mutante im veränderten genetischen Hintergrund. Z. Pflanzenzüchtg. 58:1-14.
Persson, G. and A. Hagberg. 1969. Induced variation in a quantitative character in barley. Morphology and cytogenetics of erectoides mutants. Hereditas 61:115-178.
