64
PNL Volume 19
1987
RESEARCH REPORTS
GENETIC STUDIES OF SEMID0M1NANT MUTATIONS IN PEA
Sidorova, K. K.
and L. P. Uzhintseva
Institute of Cytology and Genetics
Siberian Division, Academy of Sciences
Novosibirsk, USSR
Mutants with dominant or semidominant inheritance occur very
rarely among the diverse mutants induced in pea; most mutations
are recessive. For this reason, each dominant or semidominant
mutation is of theoretical interest. Two mutants with semidomi-
nant inheritance were induced in a line derived from the variety
'Torsdag'. Mutant N 5 with compact stem was induced by irradia-
tion with gamma-rays; mutant N 66, which is short and branchy, was
induced using ethylene imine (Table 1).
Distinct differences in morphology were evident between the
mutants and heterozygotes for the mutations and the original line
(Table 2).
Seed productivity was lower in the mutants than in the origi-
nal line. Specifically, in Torsdag the number of pods per plant
was 15.6, seed number was 54.6 and seed mass was 11.4g; the res-
pective values for Mutant N 5 were 11.3, 41.0, and 6.0g; and for
mutant N 66 they were 10.9, 37.1, and 5.3g.
The frequency and spectra of natural and gamma-ray induced
changes and their inheritance were analyzed in the original and
semidominant mutant M12 lines (Table 3).
The frequency of natural mutations in the semi-dominant mu-
tant lines was found to be an order of magnitude higher than in
the original line. The same was observed in the experiment with
the recessive mutations. Of interest is the compact mutant N 5
with induced variability surpassing that of the original line.
The range of induced variability, as in the recessive mutants, was
smaller in the short, branching mutant N 66 than in the original
line.
Analysis of natural and induced variability in the mutant
M10-15 lines has a bearing on evolutionary aspects of the origin
of new plant forms.
PNL Volume 19 1987 RESEARCH REPORTS 65
Table 1. Observed and expected numbers of segregants in each of three
phenotypic classes in F2 from crosses of mutant x normal
(cv. 'Torsdag').
Cross
Segregation in F2
x2
P
Observed
Expected at a
1:2:1 ratio
Mutant 5 x Torsdag
34 :71 :40
36.2:72.5:36.2
0 .56
0.9 - 0.8
Tors dag x Mutant 5
32:56:36
31:62:31
1 .42
0.5 - 0.2
Mutant 66 x Torsdag
29:81:36
36.5:73.0:36.5
2.42
0.5 - 0.2
Torsdag x Mutant 66
21:41:21
20.8:41.5:20.8
0.01
1.0 - 0.9
Table 2. A morphological characterization of the original line, mutants,
and heterozygotes in pea.
Variety,
mutant, hybrid
Height
(cm)
Node
number J/
Average
internode
1 ength
(cm)
Stem
number
per
pi ant
Length/
width of
leafl ets
(cm)
Length/
width of
stipules
(cm)
Torsdag
77.3
18.1
4.3
1
5.4/2.8
5.8/4.0
Mutant 5
31.9*
17.3*
1.8*
1
3.9/1.8*
3.7/2.6*
Mut.5xTorsdag
51.3*
17.6
2.9*
1
4.7/2.2*
4.6/3.2*
Mutant 66
15.7*
12.5*
1.2*
3.3*
3.8/1.9*
3.8/2.4*
Mut.66xTorsdag
31 .8*
16.4*
1.9*
2.0*
4.5/2.5*
4.6/3.4 *
1/Measurements were made at the full flowering stage.
Table 3. Frequencies of natural and induced nutations in the original and
__semidominant mutant lines of pea.__
Original line
Mutant 5
Mutant 66
Control
Gamma-ray
treated
Control
Gamma-ray
treated
Cont rol
Gamma-ray
treated
Total number of families
241
221
221
199
195
161
Families with mutants (%)
0.4
7.2
4.1**
14.1*
3.6*
5.6**
Total number of plants
7993
4927
6141
3575
4457
2504
Mutants (%}
0.04
1.48
0.31***
2.40**
0.25***
0.48***
Number of mutation types
1
15
8
18
8
10
* - P=0.05; ** - P=0.01; *** - P=0.001 as compared with the original line
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