Pisum Genetics      Volume 27  1995                Research Reports          page 22

Linkage of gene chi-33 on linkage group VI

Swiecicki, W.K.                             Institute of Plant Genetics, Polish Academy of Sciences

and Kruszka, K.                                                      Strzeszynska 34, Poznan 60-479, Poland

The spontaneous chlorotica mutation chi-33 (Wt11019) shows clear expression at the seedling stage except under greenhouse conditions (1). A preliminary linkage test (1) indicated significant linkage between chi-33 and linkage group VI marker Pl (29 cM) but linkage with wlo on this chromosome was not significant.

To locate chi-33 more precisely, we crossed Wt11019 with tester line Wt11777 which carries four group VI markers Pl, Arg, wlo and art-1. In the F2, chi-33 and the four markers all showed normal monohybrid segregation (Table 1). Dihybrid segregation analyses (Table 1) provided strong evidence of linkage between chi-33 and markers Arg (P<0.0001, 13.6 cM) and Pl (P<0.0001, 16.7 cM) but only weak evidence of linkage between chi-33 and markers wlo (P<0.01, cM 25.4) and art-1 (P<0.05, 29.7 cM). Together with the previous data (1), these results indicate chi-33 is located in the linkage group VI and closer to Pl than wlo. The data in Table 1 suggest the following arrangement of loci:

                                        

 

Table 1. Monohybrid (a) and dihybrid (b) segregation in the F2 population of the cross
K. 1317 = Wt 11019 (chi-33, arg, pl, Art-1, Wlo) x Wt 11777 (Chi-33, Arg, Pl, art-1, wlo).

(a)

Phenotype*

Chi-sq. (3:1)

Locus

D

R

Total

Chi-33

100

30

130

0.26

Arg

98

32

130

0.01

Pl

96

31

127

0.02

Art-1

102

27

129

1.14

Wlo

96

34

130

0.09

(b)

Phenotype*

Joint Chi-sq.

Recomb fract.

SE

Loci

DD

DR

RD

RR

Total

Chi-33/Arg

91

9

7

23

130

56.9

13.6

3.2

Chi-33/Pl

88

11

8

20

127

43.0

16.7

3.7

Arg/Pl

95

2

1

29

127

111.1

2.3

1.3

Chi-33/Art-1

75

25

27

2

129

4.4

29.7

7.9

Chi-33/Wlo

68

32

28

2

130

7.7

25.4

8.1

*D = homozygous dominant + heterozygous; R = homozygous recessive

1. Apisitwanich, S. and Swiecicki, W.K. 1993. Pisum Genetics 25:17.

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