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.
Jos� L. Blanco (and M.L. Blanco)
(Now at Galicia, Spain)