28 PNL Volume 19 1987 RESEARCH REPORTS
LOW PENETRANCE AND VARYING EXPRESSIVITY IN A CHLORAMPHENICOL-
INDUCED PEA MUTANT
Loennig, W.-E. Max-Planck-Institut fur Zuchtungsforschung
Federal Republic of Germany
In 1985 (1) I described a chloramphenicol-induced chlorophyll
mutant of the pea. During 1985 and 1986 thirty-eight families
comprising 1161 plants were derived from M3 plants of this
asymmetric chlorophyll mutant to ascertain penetrance and expres-
sivity of the mutant feature.
Table 1 gives the penetrance of the character in 15 plant
families grown in 1985. 
Table 1. Penetrance of mutant feature (1985): All the mother
plants from which these families were derived had
clearly shown the chlorophyll defect.
Family no.
Plants without
chlorophyll defect
Plants with
chlorophyll defect
1
31
-
2
23
1
3
8
-
4
12
-
5
21
1
6
14
-
7
17
1
8
10
-
9
7
7
10
7
3
11
4
1
12
6
3
13
10
3
14
7
1
15
9
1
22
Table 1 shows that only 12 out of 208 descendents (=10.5%)
showed the feature. To further investigate the problem, 15 fami-
lies derived from plants of Table 1 showing the feature and 11
familes not showing the feature were investigated in 1986 (Tables
2a and 2b) .
PNL Volume 19 1987 RESEARCH REPORTS 29
Table 2a. Penetrance of mutant feature in familes derived from
plants enumerated in Table 1: All the mother plants
had shown the feature.
1986-
Family no.
Derived
from 1985-
Family no.
Plants without
chlorophyll defect
Plants with
chlorophyll defect
1
7
21
-
2
9
9
3
3
9
17
1
4
9
46
8
5
9
33
11
6
9
9
2
7
9
71
1
8
9
46
3
9
12
64
12
10
13
45
5
11
13
39
3
12
13
43
443
4
53
Table 2b. Penetrance of chlorophyll defect: None of the mother
plants had shown the feature.
1986-
Family no.
Derived
from 1985-
Family no.
Plants without
chlorophyll defect
Plants with
chlorophyll defect
1
7
69
I
2
7
40
-
3
7
33
-
4
7
32
1
5
9
81
3
6
9
23
4
7
9
52
-
8
9
26
1
9
9
33
8
10
9
30
-
11
14

16

435
2
22
Thus 53 out of 496 plants manifested the mutant feature in
1986 (11.96%, a percentage similar to that of the preceding year).
Table 2b shows the results of the 11 families derived from mother
plants not showing the mutant feature. In this case, 7 out of 11
mother plants not showing the mutant character revealed it in
their descendents. However, the overall penetrance was only about
30
PNL Volume 19 1987 RESEARCH REPORTS
half of that (4.8%) of the descendents of the mother plants which
had clearly shown the defect. Further investigations are required
to determine whether the chlorophyll defect is gradually declining
and is already lost in some descendents.
Expressivity: Expressivity varied greatly. In some plants
the chlorophyll defect was already visible in the seedling stage;
in the majority of the cases the defect was discerned in the
leaves beginning about the 10th to the 12th node of the plants;
and in still other individuals only the terminal leaves of the
plant showed the feature.
Crosses: Reciprocal crosses with the mother line , 'Dippes
Gelbe Viktoria' (DGV), have been carried out. In none of the
cases in which DGV was the female was the feature evident (13 F1
and the 11 F2 families derived from them). In the four F1
plants derived from the reciprocal cross there was one plant with
the chlorophyll defect. However, because of the low penetrance of
the mutant feature, contaminations cannot be excluded at present
so that these crosses have to be repeated.
1. Loenning, W.-E. 1985. PNL 17:50-51.
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