A Database for Triticeae and Avena
II. 16. Forward and back mutations at the ligule-less (li)
locus of barley.
T. Konishi. The Ohara Institute for Agricultural Biology, Okayama University,
Kurashiki, 710 Japan.
In barley dormant seeds, cells in the shoot apical meristem stay in
the G1 stage, and the first DNA synthesis takes place with a partial synchronization
after soaking of seeds (Tatara and Yamaguchi 1973). Therefore, mutagen
treatments for a short period at different stages of interphase will be
useful for achieving some specificity in the type of mutations (Yamaguchi
et al. 1975). The present investigation was undertaken to induce forward
and back mutations at li locus by mutagen treatments at different
stages of cell cycle in barley embryos.
Table 1. Ligule-less and chlorophyll mutations by
EMS treatments (300 mM, 1 hour) after different durations of presoaking
As to forward mutation, two series of experiments were conducted in
different years to obtain li mutants from a six-rowed naked cultivar,
Akashinriki, with normal ligules and auricles. The procedures of the two
experiments were the same, but different in the duration of soaking. The
seeds were prepared to be as uniform as possible in size (2.5 - 2.8 mm
in thickness) and water content (12%), and they were soaked in distilled
water during different times as shown in Table 1. After presoaking, the
seeds were treated in 300 mM EMS solution for one hour, and washed in running
water for 8 hours. These treatments were made at the same temperature of
20°C. M1 plants were grown in a greenhouse for preventing outcrossing
with other genotypic pollens, and one spike from each of the M1 plants
was harvested. Thirty progenies per M1 spike were raised in a nursery,
and the appearance of li mutants was examined at M2 seedling stages.
According to Table 1, four li mutants appeared in an M1 spike progeny
of 15-hour presoaked plot of the first experiment, and two li mutants
were observed in another progeny in 16-hour presoaked plot of the second
Table 2. Reverse mutation at li locus by EMS treatments
(300 mM, 1 hour) after different durations of presoaking at 20°C.
For the study of the reverse mutation to the normal phenotype with well-developed
ligules and auricles, a li strain, Akashin li-1, derived from the
original Akashinriki by EMS treatments was used. The li strain is
isogenic to the normal variety except for the li locus, and known
to be spontaneously revertible to the normal type with a low frequency
(Konishi 1975). The seeds were treated with either EMS or BUdR using the
same procedures as those mentioned in the previous experiments. Table 2
shows us that EMS treatment after 16-hour presoaking gave more than one
revertant per M1 spike progeny, simply called here "multiple" event, which
was thought to be the induced mutant. However, in the other treated plots
and also in the control, there were found only single, not multiple, events
which were produced by spontaneous reversions at li locus.
Table 3 indicates the result of BUdR treatments of the li strain,
Akashin li-1. In this experiment, a multiple event with 4 revertants in
an M1 spike progeny was also induced in 16-hour presoaked plot.
Table 3. Reverse mutation at li locus by
BUdR treatments (2 mM, 1 hour) after different durations of presoaking
On the other hand, the highest frequency of chlorophyll mutations was
found in the same 18-hour presoaked plot in each of these four experiments.
These results suggest to us that DNA synthesis may begin at or near
li locus of chromosome 2, and become maximum in 18 hours after the
beginning of presoaking of seeds.
Konishi, T. 1975. Reverse mutation at the ligule-less locus (li)
of barley. Barley Genetics Newsletter 5:21-23.
Tatara, A. and H. Yamaguchi. 1973. Timing of nucleic acid syntheses
and mitosis in the first leaf meristem of germinating barley seed. Japan.
J. Breed. 23:15-24.
Yamaguchi, H., S. Tano, A. Tatara, S. Hirai, K. Hasegawa and M. Hiraki.
1974. Mutations induced in germinating barley seeds by diethyl sulphate
treatment at the interphase. "Polypoidy and Induced Mutations in Plant
Breeding," IAEA, Vienna 1974:395-399.
BGN 10 toc
BGN Main Index