and selected F3 progeny lines (Click here)
Two dwarfing mutants differing in their response to exogenously applied gibberellic acid (GA3) were genetically analyzed by Börner and Korzun (1996). Further information about the origin of both lines were obtained by A. E. Martinez, INTA Castelar, Argentina. Based on this information and Boother (1989) 'Hv287' and 'Hv288' were produced by backcrossing (twice) of 'M.C. 90' (or GA-ins), induced by X-ray treatment and 'M.C. 96' (or GA-less) induced by EMS treatment on to the cultivar 'Triumph'. Both mutants were derived from 'M.C. 20'. 'M.C.' is an abbreviation for 'Mutante de Cebada' (i.e. barley mutant) but not for 'Monte Cristo', as interpreted earlier.
A cross was initiated between 'Hv287' and 'Hv288' with the aim to establish homozygous double mutants. The identification of such genotypes is only possible by applying a GA seedlings test (Börner 1996) for F3 progenies. The results of the GA tests are given in figure 1. The two examples 'Line 4' and 'Line 67' could be identified as homozygous single mutants, corresponding to the parents 'Hv288' and 'Hv287', respectively. A few F3-lines, however, (e.g. 'Line 63') were classified to be homozygous double mutants. As could be seen in the control variant pattern (without GA3) these genotypes are characterized by low seedlings lengths comparable to 'Hv288' and probably due to low endogenous GA contents (GA-less mutant). After GA treatment, however, the seedlings lengths are comparable to those of the GA insensitive mutant 'Hv287' but did not reach the level of 'Hv288'.
Fig. 1. GA response patterns of 'Hv288', 'Hv287'
(Click here) and selected F3 progeny lines (Click here)
The combination of both GA sensitive and GA insensitive mutant loci in one line should provide an interesting material for physiologists studying the role of plant hormones. Limited amounts of seeds for research purposes are available from the authors.
References
Börner, A. 1996. GA response in semidwarf barley. BGN 25: 24-26.
Börner, A., Korzun, V. 1996. Genetical studies of two barley mutants differing in their GA response. BGN 25: 27-29.
Boother, G. M. 1989. Gibberellins and genetic control of shoot growth in barley. Ph.D. thesis, University of Bristol.