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Quantitative Approach in
Improving Protein Quality
An attempt to improve protein quality
through a quantitative approach was initiated
in the Caribbean Composite and Puebla Gpo. 1
populations during 1969.
Several S1 lines were developed and each
population analyzed for protein and tryptophan
content. Families with high protein and tryptophan
values were submitted to individual
kernel analysis on a sample of 10 seeds per
family. Two seeds with the highest tryptophan
values per family were selected and their
embryos were grown in peatcups and later
transplanted to the field. Mean protein and
tryptophan values are given in Tables 8 and 9.
S1 lines in each population show wide
variation in values for protein and tryptophan.
This suggests the possibility of making improvement
in protein quantity and quality
through different selection schemes.
The plants from individual kernel analysis
in each of these populations will be intercrossed
to form high tryptophan composites
and a new set of S1 lines will again be derived
for the second cycle of selection.
TABLE 8. Protein and tryptophan analyses of S1
families in composite C (Caribbean Composite)
during the year 1969.
Identity
Number Protein ( %)
( % ) Tryptophan in
Protein
Sample
Composite C 500 9.54 0.40 0.038
Selected S,
Families 53 10.19 0.49 0.050
High Seeds
2/Family 80 10.37 0.052
Selection
Differenti~1 0.83 0.014
Selection (%) 8.7 37.8
Regression of % Tryptophan in protein on total
protoln b = - .03.
TABLE 9. Protein and tryptophan analysis of S1
families in Puebla Gpo. I during the year 1969.
MAIZE GERM PLASM COLLECTION,
DISTRIBUTION AND MAINTENANCE
CIMMYT corn materials have been observed
world-wide and the most useful introductions
have proven to be those from areas
with similar ecological conditions, inclUding
corresponding latitude and elevation above
sea level. For example, corns from the United
States spread readily to Europe, Chile, Argentina,
South Africa and like locations. In
parallel fashion, the varieties from Mexico,
Central America and the Caribbean moved to
central and northern Africa, Thailand, India,
the Philippines, South America, Australia and
to many islands throughout the tropics.
Clearly, combinations which would permit
superior yields over wider ecological ranges
would represent a big advance. As a move
in this research direction, heat-unit and daylength
responses are being studied to determine
the extent to which they are involved
in the adaptation of given varieties of maize.
Two pools of germ plasm have been established
by CIMMYT in a long range attempt to
provide materials for investigating some of the
determinants of varietal "adaptation". One of
these is called a "world composite". The
other includes germ plasm from all latitudes
in the western hemisphere, ranging from
Alaska to Argentina. It has had five generations
of mixing. If specific genetic factors for
day-length response exist in maize, they
should be included in these pools. Sampling
from these pools and systematic evaluation
by breeders at different points in the world
can provide useful information over a span of
several years.
Maize Germ Plasm Bank
At its maize germ plasm bank, CIMMYT
maintains a reservoir of the genetic variability
found in the species Zea mays L. Germ plasm
is collected, maintained and distributed to interested
breeders who, in turn, develop the
varieties needed by maize growers through
out the world.
Iclontity
Puebla Gpo. I
Selected S.
Families
High Seeds
2/Family
Selection
Differential
Selection (%)
N be Protoin ( % )
um r (Avera.)
200 10.24
32 10.70
57
( % ) Tryptophan in
Protein
Samplo
0.44 .045
0.53 .057
.064
.019
42.2
The Bank's activities in 1969 included:
Inventory: A complete inventory of the
4,655 maize populations stored under refrigeration
was finished in 1969. Inventory information
has been transferred to IBM cards and
a preliminary listing printed. This list includes
accession number, population name, racial
classification, location, crop year, and plot
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