10. Pollen size inheritance and correlation with combining ability.

 

Twenty‑three F8 inbreds selected from 3 different single crosses (according to the scheme AxB, BxC, AxC) and the original parental inbreds were analyzed for pollen size. Twenty‑five pollen grains per plant and 6 plants per inbred were studied (except in lines 1, 6, 8, 9, and 25 with only 4, 4, 5, 2, and 5 plants respectively.

 

All the F8 inbreds resulted from random selection in F2 and F3. After F3, selection was applied with the intention of keeping representative samples of the total segregation from each cross (for plant characters).

 

The means for each inbred and the significance of differences between inbreds are:

           

 

Group from P1 x P2

Group from P1 x P3

Inbred no.

2 3 4 5 6 7

10 11 12 13 14

Ave. short x long diameter*

100 110 119 114 111 115

102 107 105 98 110

F=17.98 s = 3.909

C.V. = 3.64

L.S.D. = 4.514

P = 0.05

 

*This product is proportional to the area of an ellipse with these diameters

 

Number of significant differences in group

P1 P2

-12/15 = 80%

"

P1 P3

-7/10 = 70%

"

P1 P2 and P1 P3

-22/30 = 73%

 

Total

41/55 = 74%

 

The average pollen size of the parents and that of the inbreds selected from crosses between them and also the test cross yields for each are:

 

 

Pollen large diameter x short diameter

Order of pollen size and yield

Test‑cross yield production

P1

100

3rd

53.2

P2

115

1st

62.5

P3

113

2nd

57.1

 

 

 

Larger Diameter

Test‑crosses yield in Bu./acre

Low x high average

P1 P2

69.50±.52

57.85

"

F8 from P1 x P2

70.15±.32

57.90

Low x med. "

P1 P3

68.66±.52

55.10

x

F8 from P1 x P3

68.13±.32

56.80

High x med. "

P2 P3

70.41±.28

59.80

"

F8 from P2 x P3

70.48±.33

57.80

 

The correlation coefficients between pollen size and test‑cross yields are:

 

 

Inbreds from

Inbreds from

Inbreds from

Total

 

P1 x P2

P1 x P3

P2 x P3

 

r value

+.94*

+.23

+.11

+.24

Probability to be by chance

.01

.6‑.5

.05

.10‑.05

 

*Pollen size was expressed as the product of diameters. Very little difference was found when average diametor was used.

 

For the total the r value approaches significance but not very important. There seems to be sane relation between pollen size and yield of test‑crosses, possibly high for inbreds selected from some crosses, not for others.

 

When combining ability was expressed as a performance index, which attempts to correct the yields for the relation between maturity and yield, no significant correlation was found.

 

Further studies are in progress, and crosses between these lines will be studied.

 

We wish to express our deep gratitude to Drs. Hayes, Rinke and Pinnell for the inbreds and the data on cambining ability, and for advice, suggestions and discussions.

 

Josˇ L. Blanco (and M.L. Blanco)

(Now at Galicia, Spain)