Strains of field corn resistant to the survival of the European corn borer. Page: 3
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STRAINS OF CORN RESISTANT TO EUROPEAN CORN BORER 3
occurred with reference, respectively, to the age of the borers and
their location in the plants. The plant characters associated with
borer resistance were also considered.8
In 1938 tests were conducted with over 200 top-cross strains, including
an early group of segregating and advanced lines top crossed
with the Waugh variety, a later group of lines top crossed with the
Krug variety, one lot of lines top crossed with the Western Plowman
variety and another lot top crossed with Iowa synthetic hybrid 8037.
More than 100 single-cross and top-cross strains were tested in 1939.
The performance of the strains tested during the 10-year period has
been used as a basis for this bulletin.
Inbred lines were first tested as such in 1935, and similar tests
were made each year thereafter. Lines that showed promise as inbreds
were later tested in single-cross combinations.
EXPERIMENTAL PROCEDURE AND METHODS OF ANALYSIS
The possibility of finding .inadequate samples of borers resulting
from natural infestation and the necessity of counting the eggs laid
naturally were obviated by placing on t plplants by hand eggs produced
by moths confined in laboratory cages. In appraising the
borer resistance of the strains, their stage of maturity at time of
hatching of the eggs and differences due to sampling errors were considered,
and it is believed that the large numbers of eggs placed on:
the plants by hand subordinated any possible effect of the differences
in natural oviposition among the strains. Furthermore, the use of
check plots showed repeatedlythat the ranking of the strains based
on infestations induced largely by hand was not materially different,
from the ranking resulting from infestations produced wholly by the
moths in nature.
The strains were planted in several blocks, or replications.. Each
strain was assigned at random to one plot within each block. The
corn was planted in hills 42 inches apart each ways with six kernels to
the hill and thinned later to three plants. The number of hills per.
plot and the number of replicated plots varied among the experiments.
All the plots within one or more blocks were planted on the.
same day, and the plants were infested with egg masses on the same
dates as described in an earlier paper. An endeavor was made each
year to complete the manual infestations before the availability of
the tassel buds made them a factor in borer survival... Each plant
was marked with a tag showing the date of silking and was later dissected
so that the mature or nearly mature borers present cold be
counted before the migration of some of the full-fed borers away
from the plant.
The experiments of 1938 and 1939 are given as examples of the
procedure followed in testing large numbers of strains and for analyzing
the data from them, the methods here presented being those
finally adopted as the most efficient for the purpose. The strains
were planted i 2-hill plots of 6 plants each randomized within each
of 6 or 7 replication blocks per plan ng. n 1938 the hybrids were
F PAi, L H. m BIVAL WIRnmT, AD LOCAMOW OF rUIlUA COBw BoBn LATA3 U mIK a O1 a0
OISTANT AND voCZpPTILm rn1LD CO"a. (To b submitted fo pubication.]
o PATCH, L. H.. and Pzmcs, L. L. LABORATORY PRODUCTMN or CLWTaM oF BXKoFRAH OORN BOaB1
*oos roB UVs mN BAND INFrTAmION Or COIN. JoUr. Econ. Ent. 2: 19-20, illus. 1983.
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Patch, L. H.; Holbert, J. R. & Everly, R. T. Strains of field corn resistant to the survival of the European corn borer., book, May 1942; Washington D.C.. (digital.library.unt.edu/ark:/67531/metadc3504/m1/3/: accessed February 23, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.