Germplasm Enhancement of Maize
- 1996 Public Cooperator's Report
Grain Quality Characteristics Of Temperate Accession X Corn Belt Line Breeding Crosses
Ohio State University, Ohio Agricultural Research and Development Center
Average yield and harvest moisture values of the plot were 8.18 Mg/ha and 24.2%, respectively. One GEM entry, FS8A(S) displayed noticeably superior yield above that of the checks. Harvest moisture of the testcrosses was not too much higher than that of the checks indicating that the majority of the populations can be utilized for breeding at the latitude of northern Ohio. High levels of stalk lodging occurred in many of the testcrosses indicating that this is an undesirable trait that will have to be addressed in any breeding efforts. Several populations were observed to display unique value-added kernel physical and compositional characteristics. These data demonstrate that 50% temperate Latin American X Corn Belt populations will provide useful genetic variability for selection of new Corn Belt germplasm .
The objectives of this test were to determine the yield and agronomic performance, and grain physical and compositional characteristics of the testcrosses in standard 2-row plots typically used in performance evaluations. Hand harvested ear samples were also taken from 4-row plots to examine the possible influence of pollen contamination in 2-row plots and to provide whole ear samples for passport data on ear, kernel, and cob characteristics. These tests will assist the selection of the most promising populations for the improvement of value-added compositional and physical traits among those accessions with the best agronomic potential.
Twenty-nine temperate accession X Corn Belt crosses plus two checks were planted near Wooster, Ohio on 16 May 1995 in a replicated random complete block design with 4 replications according to standard agronomic practices. Plots were machine harvested on 20 November 1995 and grain samples were dried in a low temperature, forced air drying oven. Ear samples were also harvested from the inner 2 rows or all entries planted in 4-row plots at a nearby location. Ears were low temperature dried and ear samples were individually hand-shelled. Compositional traits were measured using a Tecator 1225 Whole-Grain Analyzer with calibration MA00004, provided by the manufacturer. Protein and oil values are presented on a dry wt. 0% moisture basis. Data were analyzed using SAS PROC GLM procedures.
A high level of stalk lodging (72% average) occurred in the 2-row plot. Average yield and harvest moisture values of the plot were 8.18 MG/Ha and 24.2%, respectively. The average yield value was below that of the checks; however, one GEM entry, FS8A(S), displayed noticeably superior yield above that of the checks (11. 43 MG/H). Several other GEM entries were not statistically different for yield in comparison with the check hybrids. The average harvest moisture value was 2 points above that of the checks. A reasonable level, indicating that the maturity of these materials is suitable for cultivation at the latitude of northern Ohio. The average protein concentration of the testcrosses was 1.5% points above that of the check average. Several GEM testcrosses displayed total protein concentrations fully 2 points or more above that of the checks. The highest protein concentration was 10.9% of ARZM 13035 11SS#.The average oil concentration of the GEM testcrosses was nearly one-half point higher than that of the checks. Testcross ARZM 16035 2 SS displayed the highest oil content, 5.3%.Average test weight of the testcrosses was slightly below that of the checks (due likely to somewhat higher harvest moisture values). The testcross ARZM 16021 9 SS had a test weight value of 63.9, characteristic of South American flint corn. Compositional data from grain samples harvested from the 4-row plots were largely in agreement of those from the 2-row plots, suggesting that pollen contamination from adjacent entries does not contribute large variation to the samples of a given plot. This is not unexpected because of the genetic diversity represented within each testcrosses. Examination of ear, kernel, and cob characteristics revealed FS8B(T) 18nss to have longer ears that other testcrosses or the checks. Most entries had between 14 and 16 kernel rows and red cobs. Two entries, ARZM 16035 2Ss and ARZM 16026 17SS had only white cobs, and two other entries had a mixture predominated by white cobs. Most samples had yellow endosperm color, although mixtures of kernel colors were also noted.
Evaluation of Maize for Resistance to Corn Rootworm Larvae
Iowa State University
Fifty-seven germplasms of maize, which included 23 tropical accessions, 27 temperate accessions, and 7 commercial tropical hybrids, were evaluated at three locations in both 1995 and 1996 for the traits of root damage, root size, secondary root development, root-pull resistance, and plant lodging. Eight 50% crosses and eight 25% crosses were tested in 1996.Highly significant differences existed among germplasms for all characters measured except root damage in 1996.There were no significant differences in 50% and 25% crosses for all traits. Crosses showed higher mean values for root size, root-pull resistance and lower values for root lodging than the mean values of tested germplasms in the same environment.
Rootworm resistance, as expressed and measured in the field, appeared to be mainly tolerance. The germplasms that responded best to corn rootworm infestation were: Guatemala209 (PI498583), PE11 (PI583912), CHIS775 (PI576258), CHIS740 (PI583890), BRA051403 (PI583911), BRA052051 (PI583917), BRA052060 (PI583918), FS8A(S) (PI536619), FS8B(S) (PI536621), FS8A(T) (PI536620), FS8B(T) (PI536622), and DK212T.
The root characteristics measured appear to be relatively stable over environments and would be suitable for evaluating maize germplasms for tolerance to corn rootworm.
Summary - Topcross Trial
Louisiana State University
Nineteen tropical maize accessions top-crossed to two temperate hybrids and four checks (a total of 42 entries) were evaluated in 1996 in a randomized complete-block design (two replications) at Baton Rouge, LA (Planting date: May 6 and harvest date: Sept. 13, 1996). Grain yield [YIELD], harvest grain moisture [MOIST], test weight [TSTWT], and midsilk [SILK] data were recorded. Values represent mean of two replications for most entries, however, a few plots in one block were damaged due to a wet spot in the field.
[DK212T] and [DK888] top-crossed with [FR615 x FR697], and [SCR Gp3] top-crossed with [FR992 x FR1064] out-yielded all four checks and other entries. The test mean was 118.1 bushels/acre (CV=13.2%), whereas the YIELD means of the top three entries were 154.2, 149.6, and 149.5 bushels/acre. [SCR Gp3] testcrossed with [FR992 x FR1064] produced the highest [TSTWT] in the test (60.2 Lbs/bushel). SILK dates ranged from June 27 to July 1 (mean=June 29). MOIST ranged from 14.2 to 18% (mean=16%).
A second-year evaluation of these entries is planned to detect an influence of environment on the traits examined.
Silage Potential of Temperate Maize Populations
Department of Agronomy, Univ. of Wisconsin
In 1996, the UW GEM project completed the analysis of 29 breeding populations (50% exotics) for silage nutritive value started in 1995. Several of the populations were not adapted to conditions in Wisconsin based on maturity. We therefore decided to resample the following 11 populations in 1996: AR16021:S9, AR16035:S19, AR17026:N10, AR17056:S12, CH05015:N15, UR10001:N17, UR13085:S19, UR13085:N2, AR01150:N4, CH04030:S9, and GOQUEEN:N16. These populations and 21 related 25% exotic populations were reanalyzed in Wisconsin during 1996 for stover neutral detergent fiber, acid detergent fiber, lignin, protein, in vitro dry matter digestibility, and cell wall digestibility. Of the 11 selected populations, one in particular, UR10001:N17, had notably higher nutritive value in 1995, particularly on a stover basis. It had low NDF, ADF, and lignin concentrations, and high protein. On a whole-plant basis, most quality components were average, however protein was again relatively high. The protein concentration in adapted U.S. hybrids averages approximately 7% for stover and 8% for whole plants. Among the more adapted selected populations, UR10001:N17, had markedly higher protein concentrations on both a stover and whole-plant basis. Its low NDF, ADF, and lignin concentrations also indicate that it may have high intake potential.
UW GEM Project - Improving Silage Quality of Temperate Maize Germplasm
Department of Agronomy, Univ. of Wisconsin
In 1996, the UW GEM project conducted the second year of analysis of 22 breeding populations for their silage nutritive value. These populations were evaluated at two locations, Madison and Arlington, WI using one-row plots with three replications/location. Ears were removed from one row, which was then harvested as stover alone. Samples were collected for dry matter determination and laboratory analyses. Samples will be analyzed this upcoming spring for stover neutral detergent fiber, acid detergent fiber, lignin, protein, in vitro dry matter digestibility, and cell wall digestibility. We also selfed approximately 100 plants in each family so that we will have at least 100 S1 families for stover evaluations and testcrossing in 1997.
Evaluation of US GEM Project Germplasm for Leaf Blights and Rind Puncture Resistance
University of Illinois
The objective of this project was to evaluate a number of GEM accessions for leaf blight and rind puncture resistance. A detailed report of the results from 1995 was provided last year. This year, we evaluated available 50 and 75% GEM crosses for flowering date, overall disease reaction when inoculated with a mixture of leaf blights, rust reaction from a natural infection, and individual reactions to Northern and Southern leaf blights. Detailed data will be incorporated into the GEM data base. A number of these crosses showed excellent disease resistance. Particularly noteworthy were DK888:N11a and DK888:N11a12.In general, reaction of the 50 and 75% versions of the same population had similar disease reaction scores. These results should be useful in identifying sources of disease resistance from the GEM materials.
Evaluation of Tropical Accessions as Sources of Genes to Improve a Corn Belt Hybrid
University of Illinois
This is the report of the first year's work on a three year project. Thegeneral objective is to identify tropical accessions with the most promise for improving corn belt hybrids for grain yield and disease resistance. As part of this objective, a specific objective is to determine the effectiveness of Dudley's method of identifying parents for discriminating among populations when the populations have been crossed to a common parent. Work in 1996 consisted of crossing each of the available tropical x B73 and tropical x Mo17 crosses to LH185 and FR1064.Attempts were made to obtain 100 pollinations per cross. Of the populations crossed to the inbreds, 14 were tropical x B73, 18 were tropical x Mo17, and 11 were temperate accessions selected from the 1995 evaluation for stalk strength as having good penetrometer resistance. Of the population x B73 or Mo17 crosses, 7 were the same tropical populations crossed to both B73 and Mo17.The crosses produced in 1996 will be grown in yield and disease trials along with the hybrid LH185 x FR1064 and the inbreds LH185 and FR1064 in 1997 and 1998.Because we have populations crossed to both B73 and Mo17, the ability of Dudley's method to identify sources of favorable alleles when only half the genome consists of the population being evaluated can be determined. In addition, any differences between B73 and Mo17 in reducing discrimination between populations can be evaluated.
Fusarium Ear Rot Resistance Screening of GEM Germplasm
Dept. of Plant Pathology, Iowa State University
Forty-five entries from the GEM collection were screened at a single location for resistance to ear rot diseases caused by Fusarium moniliforme [FUS] and Fusarium graminearum [GIB]. Fourteen entries were temperate accessions, one was a semi-tropical accession, ten were temperate crosses (50%) with public lines (B73 or Mo17), and 20 were temperate crosses (50%) with proprietary lines. Susceptible and resistant commercial hybrid checks were included, as were inbreds B73 and Mo17. The two pathogens were inoculated in separate plots; F. graminearum [GIB] inoculations were performed by the silk-channel method, while F. moniliforme [FUS] inoculations were performed with a pin-bar inoculator. All plants in 17-ft rows were inoculated. Early season flooding reduced plant stands, so that the number of plants per row varied from 0-24. On days without precipitation for six weeks after the first inoculations, approximately 5 mm of overhead irrigation was applied to the plots to maintain humidity. Disease was rated according to a 1-7 scale, in which 1= no symptoms and 7= >75% of the ear showing symptoms. [GIB] inoculations were successful, and mean ratings ranged from 2.0 to 5.2. Four accessions, [UR01089], [UR05017], [UR13088], and [AR16035], and their crosses had mean ratings <= 3.0. Five other crosses also had ratings below 3.0, but their corresponding accessions had poorer ratings. Accessions [CASH] and [CH04030] had ratings =3.0. [FUS] inoculations were not successful; the pin-bar failed to penetrate husktissue on most entries, and symptoms did not develop. Nearly all entries received a mean rating near 2.0 (1-3% of kernels with symptoms). In summary, possible [GIB] resistance has been identified in four accessions, and the [FUS] inoculation method needs to be modified.
Anthracnose Stalk Rot Resistance from Exotic Maize Germplasm
Margaret E. Smith and Laraine Ericson
Cornell University, Ithaca, N.Y.
Thirty populations (50% exotic : 50% temperate) were screened for anthracnose stalk rot resistance in 1995.The five populations showing the most resistance according to mean resistance ratings [FS8B(T):N1802, CH04030: S0906, AR01150:N0406, CASH:N1403, and GOQUEEN:N1603] were chosen for breeding work that was initiated in 1996.For each population, the 25% exotic:75% temperate testcrosses derived from that population were evaluated in yield trials including standard commercial checks, with three replications per location grown at three long-season New York locations. Since we are still trying to finish harvesting yield trials, data is not yet available for these evaluations. As soon as possible, this data will be submitted to add to the GEM database.
For each of the five populations selected for this breeding project, one of the 25% exotic:75% temperate derivatives was chosen to initiate inbred development. Five hundred plants per population were grown in the breeding nursery. One hundred plants were selected (based on early flowering, good nick, and good plant type) and self-pollinated. At harvest, S1 ears from the 50 plants per population with the best standability and ear quality were harvested. These progenies will be grown out ear-to-row in 1996, self pollinated, inoculated with the causal organism of anthracnose stalk rot, and selected to continue inbred development.
Evaluation of 50% Corn Belt:50% LAMP and 75% Corn Belt:25% LAMP Accessions for Drought Resistance
University of Delaware
We evaluated 38 GEM entries (25% tropical) using two testers (Tests 96132 & 96133) for yield, agronomic performance, and per se resistance to Stewart's bacterial wilt. The 38 GEM entries and 7 commercial hybrid checks were evaluated in a RCBD design at three DE locations, with one replication/location. Rainfall was plentiful throughout the growing season and did not permit an adequate evaluation for ASI (anthesis silking interval). Entry 15 (BR5150:Nl 1 12), the most outstanding accession, performed well across all three locations on both testers and was highly resistant to Stewart's wilt. This hybrid ranked 9th and 4th in the pooled analysis for the 96132 and 96133 tests, respectively. Other entries with good yield, agronomic, and Stewarts wilt resistance are entry I I (DREP I 50:N2012), 12 (CHIS775:Nl 912) and 30 (DK-XL370:Nl 120).Most entries had adequate levels of resistance to Stewart's wilt, but CUBA I I O:N 1 71 1 C and SCROGP3:NI413 had over 18% infected plants which was comparable to B73.
We also evaluated 38 GEM entries (50% tropical) and 7 commercial checks in a Southern Regional Test at the same three DE locations with one rep/location. The top yielding entries with good agronomic performance were derived from DeKalb tropical hybrids: entries 17 and (DKXL212), 31 (DK212T), 34 (DK B844).Entry 22 (Tuson GUA209) yielded well but had more stalk lodging than these other entries.
1996 Evaluations of GEM Accessions and GEM Derivatives for Corn Rootworm Damage
Bruce E. Hibbard and B. Dean Barry
USDA-ARS, Plant Genetics Research Unit, Columbia, MO
In 1995, we evaluated all available original GEM accessions for resistance to western corn rootworm larvae [RTWORM]. In 1996, we reevaluated the best 21 original accessions from 1995, we evaluated all available crosses of these 21 accessions and elite materials, and we evaluated selfs that we generated from our 1995 maize nursery of the 21 selected accessions. All three experiments were in a randomized complete block design with 3 replicates. Each plot was manually infested with 1,200 western corn rootworm eggs per 30.5 cm. At the time of maximum damage, five roots selected from each of the three replicates were washed of all soil and evaluated for corn rootworm feeding damage using a 1-6 scale [1=no damage, 2=feeding scars evident, 3=one or more roots eaten to within 1.5 inches of the stalk, 4=one node of roots completely destroyed, 5=2 nodes of roots completely destroyed, 6=3 nodes of roots completely destroyed].
Significant differences were found between germplasms in all three experiments for susceptibility to corn rootworm feeding damage. In our reevaluation of the original accessions, 4 accessions were significantly less damaged than the susceptible check B37xH84, but none were significantly less damaged than the susceptible check B73xMo17, and no accession was even nominally less damaged than the resistant check, NGSDCRW1.In our evaluation of the GEM crosses, 56 accessions were significantly less damaged than the susceptible check B37xH84, and 1 accession, CUBA 164:S1517, was nominally less damaged than our resistant check, NGSDCRW1, however, none were significantly less damaged than the susceptible check B73xMo17.In our field evaluation of selfs that we generated from our 1995 selected GEM accessions, 10 of 18 lines were significantly less damaged than the susceptible check, B37xH84 and two of these (PI 493039 E2 and PI583911 E1) were nominally less damaged than the resistant check NGSDCRW1 (the selfs chosen for field evaluation had been selected from greenhouse trials). No strong resistance to corn rootworm damage has been identified from the GEM materials, but some accessions are much less susceptible than others.
Variability for Resistance to Aspergillus flavus and Maize Weevil Feeding
Department of Agronomy, Louisiana Agricultural Experiment Station
Sixty-one tropical x temperate crosses were evaluated in a randomized complete-block design at Baton Rouge, LA in 1995. Ten ears/plot were inoculated with Aspergillus flavus [ASPER] 15 days post-midsilk with the needle-in-silk-channel technique. After harvest, a sample of 156 kernels/plot was evaluated for percent kernel infection by incubating kernels in the laboratory. Non-preference by (resistance) Maize Weevil [WEEVIL] was determined by subjecting 100 g grain samples to free-choice weevil feeding for 100 days.
Analyses revealed significant differences among crosses for both percent kernel infection (CV=26%) and weevil non-preference/preference (CV=7.3%).The mean percent kernel infection was 33.8% ± 12.6 and mean non-preference (weight of grain not consumed by weevils) was 86.1 g ± 8.4.The crosses with the lowest percent kernel infection (10.6 to 18.4%) were [ARZM 17026 x SS (16)], [XL370A x nSS#1(11)], [ARZM 13026 x SS(15)], and [URZM 13085 x SS(19)].Non-preference by the Maize Weevil (grain weight= or > 90 g) was detected in 15 crosses, with [DOM REP 150 x nSS(20)], [CUBA 110], [ARZM 13035 x SS#2(11)], [DK212T x nSS#1(11)], and [FS8B(T) x nSS(18)] being the top five crosses. The least non-preference was detected in [ARZM 03056 x nSS(9)] and [BVI 155 x SS(20)] (<74 g grain weight).
Yield [YIELD] was recorded as grain weight/ear. [DK212T x nSS#1(11)] and [BRA 051403 (PE001) x nSS(16)] yielded 148.2 and 147.2 g grain weight/ear. The lowest grain weight of 86.5 g/ear was recorded for [Golden Queen x nSS(16)]. The highest/day grain moisture loss (1.0%/day) during a 30-day post-midsilk and harvest period was recorded for [ARZM 17026x nSS(10)].
VARIATION IN VALUE-ADDED PROPERTIES OF GEM MATERIAL
L.A. Johnson and S. Singh
Center for Crops Utilization Research, Iowa State University
Fifty-three Latin American (LA) accessions, two commercial dent corn hybrids and two inbred were evaluated for their compositions, physical properties, wet-milling characteristics and functional properties of starches recovered to determine unique trait, which could be introduced in plant breeding program to develop hybrids with improved millability.
Kernels of the LA accessions had a wide range in starch content (70.9 to 75.1 % versus 73.3% for commercial dent hybrids). On average, protein (9.9%) and oil (4.8%) contents were higher in the LA accessions than in commercial dent hybrids (8.4 and 4.0%, respectively).
Absolute densities were consistently higher for the LA accessions (1.32 versus 1.29 g/cc). Absolute density is highly correlated with protein content and kernel hardness, which makes LA accessions more suitable for dry milling.
The wet-milling properties of the LA accessions were not nearly as good as the commercial dent corn hybrids (starch yields averaged 54.4% for the LA accessions versus 64.8% db for the commercial dent hybrids). Gluten yields were much greater for the LA accessions than for the commercial dent hybrid, due to starch in the gluten fraction increasing starch loss and reducing the protein content of the gluten. Occasionally, high fiber yields were also obtained for the LA accessions indicating that the starch did not separate well from the fiber.
On average, starches from LA accessions gelatinized at lower temperatures (70.0 versus 71.3'C) and over narrower ranges (7.9 versus 10.5'C) than did the starches from the commercial dent hybrids. On average, heats of gelatinization were similar for starches from the LA accessions and commercial dent hybrids.
SINGH, S.K., L.A. JOHNSON, L.M. POLLAK, S.R. FOX, and T.B. BAILEY. 1996.Comparison of laboratory and pilot-plant corn wet-milling procedures. Cereal Chem. (Accepted: October 30, 1996).
VARIATION IN VALUE-ADDED PROPERTIES OF GEM MATERIAL
L.A. Johnson and S. Singh
Center for Crops Utilization Research, Iowa State University
Ten accessions were selected for value-added traits from the 53 original GEM selections and were crossed with two dent corn inbreds (B73 and Mol7).The selected accessions had wide variations in physical, compositional and value-added properties so that heritabilities of these traits could be studied.
In all crosses, the Fl generation had lower starch contents and higher protein contents than either parent. The Fl crosses averaged 3.81 and 4.39 percentage points less in starch content than the averages of the two parents when crossed with Mol7 and B73, respectively. The Fl crosses averaged 3.24 and 3.79 percentage points higher in protein content than the averages of the two parents when crossed with Mol 7 and B73, respectively. Fat contents did not significantly vary from the averages of the parents.
Absolute densities increased with increased protein content. Average test weights and 1 000 kernel weights increased when GEM accessions were crossed with Mol7, but decreased when crossed with B73.
Upon wet milling, average starch yield for the Fl generations was very close to the mid point of the GEM and B73 parents. The starch yields of the F 1 generation were much greater for Mol7 crosses. The starch yields for the GEM x Mol7 crosses often exceeded either parent. Several GEM x MO17 crosses had starch yields almost typical for commercial corn belt dent hybrids. These observations are surprising because the lower starch contents and higher protein contents would have suggested poor wet-milling properties. Contrary to popular belief, these results confirm our earlier observations that higher protein content does not always lead to poorer wet milling. In general, crossing GEM accessions with Mol7 gave better wet-milling properties than did crossing GEM accessions with B73, even though B73 has better wet milling properties than does Mol7.
Determining functional properties of recovered starches are underway and completed during the present project year.
Maize Plant Resistance to Fall Armyworm Larvae
Billy R. Wiseman
USDA-ARS, Tifton, GA
Eighteen plant introductions from the U.S. GEM Project, and four resistant and susceptible checks were evaluated for leaf-feeding resistance against the fall armyworm in a field at Tifton, GA. The experiment was arranged as a randomized complete block design with 5 replications. At the 8 leaf stage 2 applications of 20 fall armyworm larvae were placed in the whorl of 10 plants per plot in each replication on the same day. Whorl-leaves damaged by larval feeding were given a plot rating at 7 and 14 days after infestation (DAI) on a 0-9 rating scale where 0 = no damage and 9 = severe damage to the whorl. Mean ratings plus the standard error of the mean are presented below. At 7 DAI 8 PI's had a rating of less than 5; five were as resistant as the resistant check, FAW CC (C5) .At 14 DAI five lines were as resistant as the resistant check, two (PI 483816 and PI 483836) did not show any increase in damage from 7 days to 14 days.
Maize Plant Resistance to Corn Earworm Larvae
Billy R. Wiseman
USDA-ARS, Tifton, GA
Twenty-four maize plant introductions from the United States Germplasm-Maize Project, a resistant Zapalote Chico, a susceptible, Stowells' Evergreen sweet corn, check, a pinto bean diet, and a pinto bean diet plus celufil checks were evaluated at Tifton, GA for resistance against larvae of the corn earworm. The experiment was arranged as a randomized complete block design with 30 replications. Silks that had emerged two days from maize grown in the field were excised to the ear-tip, taken to the laboratory, oven dried at 411 C for 10 days, ground with a Cyclotec 1093 sample mill and mixed into pinto bean diets at 50 mg/ml diet. Diet- mixtures were dispensed into plastic cups and 1 neonate corn earworm was placed in each diet cup. Ten grams of fresh silks of each entry was analyzed for maysin content. Weight (mg) of larvae was recorded 8 days after infestation. Mean weight of larvae and pupae, development time of larvae plus the standard error of the mean are presented below. Silk-diets of 9 PI's produced larvae weighing less than 50 mg, and 7 PI's produced larvae with a mean weight equal to the weight of larvae produced on the silk diet of Zapalote Chico. Only one of the PI's (PI 516022) was equal in resistance to that of Zapalote Chico for development time of larvae. Five of the PI's produced pupae equal in weight to pupae for larvae fed Zapalote Chico silk-diet. PI 489361 had an unusually high maysin content, but did not produce the corresponding low weight of larvae. Three PT's, PI 467139, PI 492753, and PI 516022, had a very low silk-maysin content, yet silk-diets produced very small larvae. A significant (P 0.01) negative relationship (r' = -0.443, n = 32) was found between weight of larvae at 8 days and chlorogenic acid content of fresh silk. A non-significant (r = -0.268 n = 32) was found between weight of larvae and maysin content of fresh silk.
Evaluation of Germplasm Crosses for Aflatoxin
W. P. Williams and G. L. Windham
Corn Host Plant Resistance Research Unit, Miss. State, MS
Thirty germplasm crosses (50% exotic), known resistant and susceptible hybrids, and a commercial hybrid were evaluated for aflatoxin contamination at the Plant Science Farm, Mississippi State, MS. Seeds were planted on April 29 in single-row, 5.1 m plots and plants were thinned to 20 plants per plot. Ears were inoculated with Aspergillus flavus at 7 days after midsilk (50% of the plants in the plots had silks emerged) using the side needle technique (Zummo and Scott, Plant Dis. 73:313-316).
Ears were harvested 63 days after midsilk, dried at 38 C for 7 days, and machine shelled. Grain samples from each row were poured into a sample splitter twice to mix grain. Grain samples were ground using a Romer mill (Union, MO). Aflatoxin contamination in 50 g subsamples from each plot was determined using the Vicam Aflatest (Watertown, MA).
Most of the germplasm crosses had high levels of aflatoxin contamination.However, BR51501:Slla had numerically less aflatoxin contamination than the two resistant hybrids (Mp3l3E X Mp420 and Mp420 X Tx6ol).This germplasm cross and others such as BR52060:SO2 and BR52051:Sl7 may be potential sources of resistance to aflatoxin contamination due to A. flavus.
Evaluation of LAMP Line Crosses with Mol7 for Southwestern Corn Borer Leaf Feeding
W. Paul Williams and Frank M. Davis
Mississippi State, MS
Thirty-three LAMP line crosses with Mo 1 7 (50% exotic) were evaluated for resistance to leaf feeding by southwestern corn borer (Diatraea grandiosella) at Mississippi State in 1996.Plants were grown in 1-row plots (20 plants/row) in a randomized complete block design with two replications. The experiment was planted May IO and infested with 3 0 southwestern corn borer neonates per plant on June 11. Damage was visually rated on June 25 using a scale of 0 (no damage) to 9 (heavy damage).
None of the line x Mo 1 7 crosses performed as well as the resistant check (Mp7O4 x Mp7O7).All other entries, including Mp7O4 x Mo 1 7 (a cross between a known resistant line and Mol7),sustainedsubstantialdarnage.Some of the crosses between Antigua lines and Mol7, however, were equal to Mp7O4 x Mo17. These might be worth evaluating further as either lines or as 25% exotic crosses. Among those that might have potential are entries 14 (Antigua 1-44-1-1), 17 (Antigua 1-64-4-1), and 18 (Antigua 1-67-3-1).
Characterization of Physical and Compositional Grain Quality Characteristics of Temperate Accessions
The Ohio State University
One-hundred and thirteen temperate accession X Corn Belt testcrosses crosses plus two checks were planted near Wooster, Ohio in late May in a random complete block design with three replications according to standard agronomic practices- The two-row plots were mechanically harvested in November- Average yield and harvest moisture values of the testcrosses were 7.41 Mg/Ha and 30. 1%, respectively. One GF-M entry, LJRI3010-.NO613, displayed noticeably superior yield than the checks. Several other GEM entries were not statistically different than the check hybrids. Average stalk lodging of 36% was approximately half that of last year's test.
Grain samples were harvested and dried in a low temperature, forced air drying oven- Ear samples were also taken from all entries planted at another location and low temperature dried. Grain physical and compositional testing has been completed only for the mechanically harvested plot. AR 170561-SI2 had the highest protein content at I 1, 1% and two FSA derived testcrosses had the highest oil content at 4-8%. The density values AR 17056-S1216 and CHO4030:SO906 are considerably higher than those of the checks- Starch values were similar for most entries.
Reaction of U.S. GEM 25% Tropical Breeding Crosses to Cercospora Zeae-Maydis.
John E. Ayers and Melvin W. Johnson
Penn State University,
One hundred and one entries (25% tropical breeding crosses) were planted at a location near Oley, Pennsylvania (Berks County) with a history of gray leaf spot (GLS) caused by Cercospora zeae-maydis. Nine additional hybrids were added to complete a 10 × 11 lattice design. There were two replications. Due to wet soil conditions, planting was delayed until May 23.The experiment was planted with no prior tillage in a field that had been in continuous no-till corn production for several years. The growing season was characterized by above normal rainfall and below normal temperatures. The onset of GLS was delayed beyond the normal date expected for this region but because the crop was planted late, initial lesions appeared at about the normal stage of crop development; i.e., just past anthesis. Disease ratings were made on September 23 on a 0.5 to 5.0 scale where 0.5 equals few or no lesions and 5.0 equals plants prematurely dead. Additional agronomic characteristics were measured during the growing season and will be included in the data set. Statistical analyses have not been completed.
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