1. Inheritance of variegated plant Bv in maize.

 

In 1939 (Genetics 24:109) we reported a case of a plant that developed fine streaks of color after B pollen was treated with ultra-violet light and applied to lg gl2b v4 plants. Treatment of the pollen was made by Dr. L.J. Stadler who first observed the abnormal plant. Cytological examination showed no chromosomal irregularities. Further genetic tests have indicated that this variegation is caused by a variegated B allele which has been designated Bv. Linkage relations of Bv with gl2 and v4 are approximately the same as with B.

 

Segregates of Bvb plants produce only two types Bv and b with an occasional back mutation from Bv to B. Progenies studied were not set up to detect changes from Bv to b. Three point backcross linkage tests gave the following results:

 

Progeny

 

48:610

%

48:608

%

48:607

 

 

 

 

 

 

(F2 not backcross)

Parental

+++

51

 

47

 

88

Combinations

gl2bv4

32

 

30

 

10

Recombinations

 

83

 

77

 

98

 

 

 

 

 

 

 

Region 1

+bv4

25

 

20

 

19

 

gl++

12

 

12

 

5

 

 

37

20.9 (19)*

32

19.2 (19)*

24

Region 2

++v4

23

 

18

 

21

 

gl b+

29

 

31

 

14

 

 

52

29.3 (21)

49

29.3 (21)

35

Region 1 & 2

+b+

3

 

6

 

12

 

gl+v

2

 

3

 

1

 

 

5

2.8

9

5.4

13

Solid B

 

0

 

0

 

3

 

 

 

 

 

 

 

Total

 

177

 

167

 

170

 

Characters analyzed separately

 

+

102

 

91

 

gl

75

42.4

76

45.6

+=Bv

88

 

80

 

b

89

50.3

87

52.1

+

95

 

96

 

v4

82

46.3

71

42.5

 

*Numbers in parenthesis refer to crossover percentage in Cornell Memoir 180.

 

The crossover percentages correspond fairly close to those listed in Emerson, Beadle and Fraser (Cornell Memoir 180). They are considered to be in agreement when it is thought there was either perhaps sone misclassification or differential mortality of v4 and gl plants before classification. Plants were classified in the seedling stage and gl+, gl v4, ++, and +v4 plants were marked with different colored stakes that were present when the plants were classified for Bv and b in August. It will be noted the proportions of B and b plants approximate the expected proportions rather closely.

 

The fact that the linkage values of Bv correspond closely to B, also the fact that only the B and b plants occur (as a rule) in segregating populations, lead us to the conclusion that it is the B allele itself causing the variegation and not another gene causing B to mutate.

 

Occasionally Bv plants produce large sectors that are entirely purple, sometimes including a tassel branch. Pollen from such sectors applied to b plants produces mostly variegated plants, about the same proportion as pollen taken from a variegated sector. (Most of the data on the Bv inheritance are in the files at the Connecticut Experiment Station. They will be assembled and published soon.