A Database for Triticeae and Avena
II.4. A test for allelism of 32 induced six-rowed mutants.
Toshinori Fukuyama, Jiro Hayashi, Isamu Moriya and Ryuhei Takahashi.
The Ohara Institute for Agricultural Biology, Okayama University, Kurashiki
Dr. Tsuchiya obtained two six-rowed mutants, named "Kmut 27 and Kmut
213", from two-rowed cultivars, Svanhals and Hakata 2, respectively by
irradiating with X- and gamma ray. They are both somewhat different in
their appearance of head from the ordinary six-rowed forms. Kmut 27 is
less fertile in the upper and lower lateral spikelets with relatively short
awns, and Kmut 213 is characterized by underdeveloped lateral spikelets
only in the lower 1/4 of a head, and often by deformed rachilla.
The crosses between these two mutants and a six-rowed cultivar, Natsudaikon
Mugi, gave Fl plants with slightly pointed lateral lemmas, while the F1
plants of the crosses with their respective original two-rowed cultivars
developed round tipped laterals. Furthermore, the mutual cross between
these two mutants resulted in an F1 plant with a two-rowed head, and in
the F2, two-rowed and non-two-rowed plants occurred in a 9:7 ratio (Table
1). These facts suggest that the six-rowed characters in these two mutants
are controlled by two different recessive genes which are independent of
each other. This view may be supported by another fact that the "six-rowed"
character of Kmut 213 is independently inherited of the gene s and
r on chromosome 7 (Table 2), as Kmut 27 has already been known to
involve v2 on chromosome 7 (Takahashi and Hayashi, 1971). A gene
symbol v3 is then assigned to the six-rowed character of Kmut 213.
Table 1. Segregation of two-rowed and non-two-rowed
plants in F2 of a Kmut 213 X Kmut 27 cross.
Table 2. Interrelationships between "six-rowed"
and smooth awn, or short-haired rachilla in F2 of the cross of Kmut 213
with "439", a two-rowed, Syrian local form.
Since a total of 30 other "six-rowed" induced mutants were kindly provided
by the courtesy of Dr. A. Möes in Belgium, Dr. E. Pollhamer in Hungary
and Dr. F. Scholz in Germany, they were all subjected to the allelic test
by crossing with two mutants, Kmut 27 and 213, a six-rowed variety, Natsudaikon
Mugi, and their two-rowed parents. Also, a large number of diallelic crosses
were made among these new mutants. The shape, size, fertility and awn development
of the lateral spikelets of the resultant F1 plants were compared with
those of the parental strains or varieties. From the results, at least
three types could be classified. The first type, which gave normal six-rowed
plants in Fl of the cross with Natsudaikon Mugi, amounted to 23 out of
30 mutants tested. Seven of them, however, had somewhat more elongated
pedicels and shorter awn than the other mutants in this group, constituting
a subgroup of type 1. Four other mutants behaved almost the same as Kmut
213 and were classified as the second type. The remaining 3 mutants constitute
the third group which resemble closely the first group in appearance, though
somewhat shorter in lateral awn, but their genetic behavior was different
from either of the types 1 or 2: All of them gave F1 plants with intermedium-like
heads from the cross of Natsudaikon Mugi, and the crosses with Kmut 27
and Kmut 213 gave F1 with normal two-rowed head. A gene symbol v4
may be given to these new six-rowed mutants. No mutant allelic to v2
in Kmut 27 (class 4) was found among these 30 mutants.
In conclusion, 32 "six-rowed" mutants including Kmut 27 and Kmut 213,
were classified into the following four groups and a subgroup.
1. Ordinary six-rowed type controlled by v on chromosome 2, with
a subgroup with v'.
2. "Kmut 213" type controlled by v3.
3. The third type controlled by v4.
4. "Kmut 27" type controlled by v2 on chromosome 7.
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