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obvious from these data: (1) apparently earto-row
selection was slightly more effective
than was stratified mass selection in both populations
at. both plant population levels, and
(2) for the Composite Chalqueno 61, either
method of selection was more effective at the
43,000 plant rate, than at the 63,000 planting
rate.
Although it is readily apparent that both
of the methods of selection compared in this
project were effective in increasing yield,
earlier investigators ha'(e reported certain undesirable
side effects when selection is based
principally on the basis of yield. Data from
this study, bearing on this question, are summarized
in Table 16.
These data indicate that, in addition to
yield, the corns have been improved in respect
to ear rots (the percentage of rotted ears decreased
with either method in both populations).
Also, improved were the characters
tillers-with ears and ears-per-plant, both of
which are, in part, another measure of yield.
Both methods of selection, however, as
practiced in these studies, resulted in an increase
in days-to-flower, ear height and lodging.
In most cases, the plant breeder would
consider such changes as undesirable.
As reported here last year, studies are underway
to determine whether manipulation of
the environment under which the selection is
practiced could reduce the magnitude of these
undersirable indirect responses.
TABLE 16. Percen t changes in various characters in two populations as effected by stratified ma••
selection and ear-to-row selection for yield.
I
..
e c
-u
._ 0
Method. ,..-
Character In % of orlglna' population
u
Population of ¥
Days to Tillers Ear Ears/ Rotten
Selection 1 ~;X Yield
Lodging
0 ... Flower with ears Height Plant Ears
Z 0
Composite Chalque;;o 61 Mass 5 + 22.1 +6 + 3.6 + 12 + 14 + 13 - 4.7
Ear-tOorow 4 + 24.5 +6 +2.9 + 13 +13 + 14 - 6.0
Mexico Group 10 Mass 5 + 21.5 +6 + 9.7 + 6 + 2 + 24 - 4.1
Ear·tOorow 4 + 22.2 +4 + 5.0 + 4 + 2 + 12 - 1.6
Final cycle of selection compared to hybrid controls.
TABLE 17. Yields of Dry Ear Corn and other agronomic traits comparing Stratified Ma•• Selection
by weight (W) versus prolificacy (P) in Composite II Celaya and Puebla Group I. Three year average.
(1967, 1968, 1969). 20 replications per year. EI Roque, Guanajuato, Mexico.
Population Cycle Method
Ylerd Ears/l00 Tillers/I00 % Ear Height Days to
tons/ha Plants Planu Lodging ( meters) Flo_r
Composite
Ceraya II 0 6.1 96 21 12 2.03 81
W 6.3 97 25 10 1.99 82
P 6.4 97 18 9 2.03 82
2 W 7.0 111 39 16 2.09 84
P 6.9 108 34 13 2.10 84
3 W 7.2 110 43 15 2.13 84
P 7.3 118 48 16 2.14 85
Puebla
Gpo. I 0 6.2 98 26 48 2.28 87
W 7.5 112 36 40 2.31 86
P 7.1 111 40 38 2.22 86
2 W 8.2 125 55 42 2.29 87
P 7.8 115 39 39 2.28 87
H·366
Control 7.4 114 7 13 2.29 88
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