A Database for Triticeae and Avena
II. 25. A vegetative dwarf mutant in barley.
D. E. Falk and K. J. Kasha, Crop Science Department, University of Guelph,
Guelph, Ontario, Canada N1G 2W1. "R"
A vegetative, gibberellic acid sensitive dwarf mutant has been obtained
as a segregant in an M2 progeny of gamma irradiated Perth barley (CI15624).
The mutant plants have very short coleoptiles and short, wide, thickened
leaves. The internodes completely fail to elongate and so the plants remain
vegetative and tiller profusely. They are easily propagated by separating
the tillers at the crown. Some plants have remained entirely rosette for
well over a year.
Heterozygous, phenotypically normal, plants from the original M2 family,
and F2 families from crosses with the mutant have given 3 normal: 1 dwarf
segregation ratios; indicating that the dwarf is under the control of a
single, recessive gene. Tests have shown the dwarf plants to respond to
1 ppm foliar applied GA3 (0.5 ml) by some internode elongation. A single
foliar application (0.5 ml) of 1000 ppm GA3 was sufficient to produce a
nearly normal plant which set some seeds (Table 1).
Table 1. Response of cloned dwf dwf barley
plants to differing concentrations of exogenously applied GA3 (0.5 ml).
In further studies with gibberellic acid, from 0 to 4 weekly foliar
applications (0.5 ml) of 75 ppm GA3 were made to 60 cloned dwarf plants.
Twelve plants received each of the 5 treatments. Normal, untreated Perth
barley was grown as the check. Heights of plants were measured to the collar
of the flag leaf of the main culm 4 weeks after the last treatment was
applied to each group (Table 2). The 0, 1 and 4 spray application treatments
were statistically different from each other and from the 2 and 3 spray
treatments. The 2 and 3 spray treatments were not statistically different
from each other, based on the heights of the treated plants. There was
no difference between the height of the dwarf plants which received 4 GA3
treatments and that of normal, untreated Perth barley.
Table 2. Response of cloned dwf dwf barley
plants to weekly applications (0.5 ml) of 75 ppm GA3.
Plants which received 1, 2 or 3 GA3 treatments characteristically had
several elongated basal internodes and then much shorter internodes at
the apex where the plants "run out" of gibberellic acid and internode elongation
ceased (Figure 1). Some plants which received 3 spray treatments and all
the plants in the 4 spray group produced emerged spikes. Only the plants
in the 4 spray group produced seed. From 1 to 12 seeds were produced in
each of the spikes of the plants in the 4 spray treatment. Plants grown
from these seeds were all phenotypically dwarf although some carryover
of GA3 was apparent in the coleoptile lengths (Table 3). The seedlings
were completely vegetative and rosette. The coleoptiles of the M3 dwarfs
from dwf Dwf M2 plants were approximately 1/2 the length of their
phenotypically normal siblings (Table 3).
Figure 1. Comparison of whole plants and single
tillers of dwf dwf plants receiving 0, 1 and 4 weekly applications of 75
Table 3. Coleoptile lengths of M3 progeny of dwf
dwf, Dwf Dwf and dwf Dwf M2 plants (No GA3 applied).
This dwarf mutant is capable of using exogenously applied GA3 to give
nearly normal growth. These plants may be useful as bioassay material for
gibberellins, or they may be useful in the study ofgibberellin synthesis
and utilization in barley.
BGN 12 toc
BGN Main Index