Adaptation of CIMMYT's High Protein

 Quality Corn Varieties to Puerto Rico

 C. Cardona L. Wessel-Beaver P. R. Hepperly
 College of Agricultural Sciences
 Mayaguez, Puerto Rico


 Six modified endosperm opaque-2 corn varieties from
CIMMYT were evaluated at Lajas and Isabela, Puerto Rico in
1983. Two Puerto Rican varieites, Mayorbela and Diente de
Caballo, were used as checks. Opaque-2 (o2) corn normally
has soft endospoerms, while modified varieties approach the
appearance of normal corn. The subplots of each variety were a
check, benomyl treatment, and Fusarium moniliforme silk in-
oculation. Traits measured included incidence of seedborne
fungi, plant and ear heights, visual ear infection, ear lengths
and diameter, yield and 500 kernel weight, and modification.
Yields and modification of the CIMMYT varieties were similar


to that of the traditional (non o2) varieties. F. moniliforme
was found to be the most important seedborne fungus. The
inoculation technique was found to increase incidence of F.
monoliforme and should be useful for evaluating large
numbers of families in a selection program. Improvement of
yield and adaptability of CIMMYT's materials is needed for
viable commercial production of these varieties. On the basis
of this evaluation, S1 recurrent selection has begun in two
modified o2 varieties.
Keywords: Zea mays L., maize, opaque-2, modified
opaque-2, Fusarium monoliforme.


 Since the discovery of opaque-2 (o2) endosperm mutant by
Mertz et al. (1964), many directions of research have been tried in
order to efficiently utilize the gene's ability to increase lysine and
tryptophan levels, thus improving corn protein quality. Early on,
some researchers were discouraged by undesirable characteristics
such as lower grain yield, poor consumer acceptance, and suscep-
tibility to machine harvest damage, insects and ear rots (Diaz,
1972; Gulya et al., 1979; Lambert et al., 1969; Pinstrup-
Anderson, 1971; and Warren, 1978). Since the 1970's much work
has been directed towards the use of genetic modifiers that improve
the endosperm texture of o2 corn, giving it a more normal ap-
pearance and hardness. CIMMYT (Centro Internacional de Mejora-
miento de Maiz y Trigo) has used this approach to develop its
"quality protein maize" (QPM) populations (Vasal et al., 1980).
 Although once a widely grown crop, very little corn is presently
grown in Puerto Rico. Nevertheless, large quantities of corn are
imported as feed for the livestock, pork, and poultry industries
(Puerto Rico Department of Agriculture, 1979-80). Furthermore,
as fewer acres are planted to sugarcane, alternate crops and rota-
tions of crops must be considered. Local production of corn
varieties with improved protein quality could reduce the amount
of corn and protein supplements that are presently imported for
monogastric animals such as swine and poultry.
 The primary objective of this research was to compare the
adaptation of six modified endosperm o2 corn varieties to two
traditional varieties in Puerto Rico. Other objectives were to:
 1. Determine the susceptibility of modified o2 and tradi-
 tional varieties to ear infection by Fusarium moniliforme,
 comparing natural and artificial inoculation;
 2. Select the best modified o2 varieties for use in a S1 family
 recurrent selection program; and
 3. Determine which agronomic characteristics should be in-
 cluded in a selection program.

MATERIALS AND METHODS
 Six modified (hard and vitreous) endosperm o2 corn varieties
from CIMMYT, and two Puerto Rican varieties (Mayorbela and
Diente de Caballo) were evaluated in trials planted in March and
May 1983, in Lajas and Isabela, Puerto Rico, respectively. Diente
de Caballo is a tall, late, floury type, while Mayorbela is earlier
and shorter with a flint kernel type. A split plot design, with

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eight varieties arranged in a randomized complete block design
and three subtreatments, was used. The subplots were:
 1. A check not sprayed or inoculated;
 2. A treatment with the fungicide Benomyl, but
 uninoculated; and
 3. Artificial inoculation with Fusarium moniliforme.
The whole plots were randomized except for the normal varieties
which were either placed downwind from 02 varieties and/or
were surrounded by an o2 bulk to minimize normal contamina-
tion of the o2 varieties.
 The twelve row whole plots were divided into four rows per
subplot. Row length was 5.1 m with plants spaced 26 cm apart
(about 43,200 plants per hectare). Fertilizer was preplant incor-
porated at a rate of 56 kg ha-' of 15-5-10 with 175 kg ha-' of
nitrogen sidedressed at five weeks after planting in the form of
urea. Furadan (1.7 kg ha-' of actual ingredient) was preplant in-
corporated and insecticides (Lannate and Sevin) applied weekly
or biweekly as needed. Trials were irrigated as needed. Lasso and
Round-up were used for weed control. The center two rows (ex-
cluding end plants) in each subplot were hand harvested.
 At Lajas, the fungicide Benomyl was sprayed on the ears and
silks when the first varieties began to flower and ten days later. At
Isabela one application of Benomyl was used at ten days after first
flowering (when all varieties were flowering). Inoculation of F.
moniliforme was carried out by a modification of a technique us-
ed by Warren (1978). A suspension of spores was brushed onto
silks cut with a scissors to a length of about 2.5 cm. The silks were
then covered with a pollination shoot bag. In Lajas a total of 20
plants in two rows were inoculated at 10 and 20 days after first
flowering (the average of the two dates is used in this report). In
Isabela only one inoculation was made.
 Traits measured were days to 50% anthesis, plant and ear
height, ear length and diameter, number of moldy kernels, per-
cent of ear area damaged by insects (primarily ear worm), grain
yield, 500 kernel weight, percent endosperm modification,
degree of endosperm modification (reference 10 with technique
modified to a 0 to 5, opaque to normal, scale), percent germina-
tion and seedborne fungi.
 Data were subjected to analyses of variance separately and over
locations. Treatment means were compared using a protected
LSD (F-LSD) (Carmer and Swanson, 1971).


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