PNL Volume 12
1980
RESEARCH REPORTS
DIGENIC SEGREGATION FOR CHLOROPHYLL MUTANT IN PISUM
Ezhova, T. A. and S. A. Gostimski
Moscow State University, USSR
After irradiating (200 rads) pea seeds with fast neutrons we have isolated
a lethal chlorina-mutant with blocked photosystem 1. All the families which
segregated chlorina mutants could be divided into two distinct groups (Table 1).
Families in the first group produced green and mutant plants according to
a 3:1 monohybrid segregation (families 1,2,3,4,6,8,11,12,13,14). Families
in the second group segregated according to a ratio of 15 green plants to
1 mutant (families 5,7,9,10,15,16).
Evidently some green plants were heterozygous for two genes whereas others
were heterozygous for a single gene. This was supported by the fact that the
families which initially segregated monogenically did so again in subsequent
generations. From the families which segregated in a 15:1 ratio, some segre-
gated chlorina mutants in a 3:1 ratio and some in a 15:1 ratio.
The chlorina phenotype reported here thus appears to result from the action
of two duplicate recessive genes.
Table 1. Segregation for an induced chlorina mutant in 16 different i'amiles,
Number or plants
2
2
Family no.
Normal
Mutant
Total no.
X (3:1)
X (15:1)
1
59
13
72
1.85
17.13***
2
69
16
85
1.73
22.93***
3
90
22
112
1.71
34.29***
4
72
25
97
0.03
63.10***
5
40
2
42
9.18**
0. 16
6
22
7
29
0.01
17.84***
7
42
1
43
11.79.***
1.13
8
28
14
42
1.56
52.58***
9
50
1
51
14.44***
1.60
10
51
2
53
12.74***
0.56
11
30
15
45
1.67
56.33***
12
58
12
70
2.31
14.18***
13
55
24
79
1.22
78.50***
14
69
22
91
0.00
49.91***
15
48
1
49
13.78***
1.48
16
44
2
46
10.46**
0.28
827
176
1003
84.48***
412.00***
Differences between observed and theoretical segregations are significant
*P>0.95; **P>0.99; ***P>0.999. f=16 f = l6