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PNL Volume 20
1988
RESEARCH REPORTS 9 |
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NEW CHLOROT1CA GENE (chi 32) IN CHROMOSOME
3 |
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Czerwinska, St. |
Plant Breeding Station, Wiatrowo, Poland |
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Physical mutagens were compared
in investigations on the influence of genotype x mutagen combinations on
the mutation spectrum in pea. Seeds of line Wt 3519 (cv. 'Porta') were
treated with three doses of fast neutrons from a cyclotron (200r, 350r.
500r) and from a reactor (170r, 290r, 400r) and with gamma rays from a
60Co source (4000r, 7000r, lOOOOr) . In the M2 generation
containing about 21,000 plants, 720 mutation cases were selected. Among
them about 30 percent were chlorophyll mutations. Most numerous was the
chlorotica type (72 mutation cases) . Some of them were phenotypically
similar to those described by Blixt (1) , but mutant Wt 15325, induced by
350r Nf, was distinguishable. Plants were characterized by a
yellow-green color affecting the whole plant (leaves, stem, tendrils, and
sepals) being more visible in later stages of plant development
.
The segregation in M2 family as
well as the results of the original tost cross showed Mendelian, recessive
inheritance: [Wt 15325 (mutant) x Wt 3519 (initial line)]=91:34 observed
(Chi-square=0.32); [Wt 3519 x Wt 15325]=130:40 observed (Chi-square=0.20)
.
There are 30 recessive genes of
the chlorotica type described earlier. So to prove novelty of a new
isolate a locus identity test cross should be performed. To shorten the
process, we conducted linkage tests with the hope that the results would
show the presence of a new gene. The mutant Wt 15325 was crossed with
tester lines for the seven chromosomes. In F2, undisturbed monohybrid
inheritance for most of gene markers was found; the populations also
confirmed the recessive nature of the chlorotica mutant (Table 1A)
. |
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Table 1. Phenotypic distribution in an F2 population segregating f o r chlorotica f r o m WL 1288 (testerline) x Wt 15325 mutant. |
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A. Monohybrid F. segregation |
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Locus
Chi B St M
A |
X
296 185 302 230 301 |
X
104
67 94 50 88 |
Total
400
252 396 280 389 |
Chi-square (3:1)
0.21
0.34
0.34
7.62*
1.17 |
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l. Joint segregation of chlorotica with b st M |
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Gene
pair
X Y
Chi-B
153
Chi-St 219
Chi-M 217
B-St
163 |
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xY
32 83 11 30 |
xy
13
18
41.
37
10 |
Total
252 396 278 252
232 |
Joint Chi-square
0.14ns
2.64ns
168.10**
49.57**
0.00ns |
Recomb.
fract. |
S.E. |
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8.5
23.1 |
1.8
3.1 |
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B-M |
141 |
26
55 |
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10
PNL Volume
20
1988 RESEARCH
REPORTS |
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There was no evidence of linkage
with markers on chromosomes 1,2,4,5,6,7. But deviations from independent
dihybrid segregation of the gene pair Chi-M were found with a CrO value of
8.5 (Table IB) . According to the present Pisum map there are no known
chlorotica genes in the M-segment of chromosome 3, although chi-6 and
chi-16 are known to reside elsewhere on the same chromosome. On these
grounds I propose the symbol chi-32 for the new gene of chlorotica type.
For final mapping we plan to confirm the above results in comparison to
two loci — using uni or preferably isozymic loci Lap-2,
Acp-3. |
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1. Blixt, S. 1972. Agri Hort. Genet. 30.
My cordial thanks are due to Dr.
W. K. Swiecicki and to K. Leraczyk for their help, encouragement, and use
of Station facilities. |
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***** |
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