Germplasm Enhancement of Maize

What's New | GEM Project | Yield Trials | Laboratory | Field Day | Documents | Annual Reports | Presentations | Publications | Linkage


Javier Betrán
L.L. Darrah
Jim Hawk
Bruce Hibbard
Robert Lambert
Gary Munkvold
Richard Pratt
Jerry Sell
Margaret Smith
Dennis West
James Coors
Wenwei Xu
Mark Campbell

GEM - 1999 Public Cooperator's Report

NOTE: The information in this report is shared cooperatively. The data are not published, but are presented with the understanding that they will not be used in publications without specific consent of the public cooperator.

Please notice that we didn't include the tables in each GEM public cooperator's report because of the size of the file. If you need the data, you can download them by clicking on the zipped file on the previous page or contact the webmaster for help.

 

Develop Food-grade GEM Lines with Superior Grain Quality And Resistance to Biotic and Abiotic Stress 

Javier Betrán

Texas A&M University

In 1998 we evaluated 100 GEM exotic breeding crosses at 5 locations and 258 GEM topcrosses at 2 locations in Texas. As result of all these evaluations we selected 19 GEM exotic breeding crosses. These crosses have been reevaluated during the1999 season in 3 Texas locations. At the same time these breeding crosses have been selfed in our summer nursery at College Station for further advance and selection. Bulks of derived lines from GEM breeding crosses were advanced and selected in our summer nursery. These derived lines were selected according with results from 1998 testcross evaluations and provided by Dr. Major Goodman (NCSU). Topcrosses of these derived lines have been evaluated during 1999 across 4 locations in Texas. Both selected breeding crosses and derived lines will be advanced in our winter nursery at Florida during winter 99. The derived lines will be testcrossed with testers from the opposite heterotic group for evaluations in Texas during year 2000. In addition, we have advanced and selected new GEM breeding crosses with potential to have aflatoxin resistance, and new derived lines with superior grain quality (energy dense, low linolenic, and high oleic). 

Back to Top

Evaluate Topcrosses of S1 lines of UR13085:S1912 (Best Combination of Good Rind Penetrometer Resistance and Vertical Root Pulling Resistance in 1997 Evaluations) to Mo17 Syn(H14)C4 and CarPop(ES)C5

L. L. Darrah

ARS-USDA at the University of Missouri

Results from evaluating 10 random S1 progeny from 13 GEM populations in 1977 showed that UR13085:S1912 had the best combination of good rind penetrometer resistance and vertical root pulling resistance. UR13085 is of the Cateto Sulino race, characterized very broadly as "tropical flint" or "Caribbean flint" and having orange, hard, flinty kernels. One-hundred-twenty S1 progenies were used for testcrossing to two testers in 1998. Testcrosses were made to Mo17 Synthetic(H14)C4 and CarPop(E5)C5. The former is a yellow synthetic made up from various commercial versions of Mo17, and the latter is a population originating with Everett Gerrish, formerly of Cargill Hybrid Seeds, which has a large component of tropical dent Tuxpeno.

For 1999, we had 90 testcrosses of UR13085:S1912 S1 to CarPop(E5)C5 and 70 testcrosses to Mo17 Synthetic(H14)C4 for evaluation. Three replications of each set of testcrosses were planted at Columbia, Novelty, and Tipton, MO. Protracted drought beginning in June resulted in discarding the Novelty and Tipton locations (30 bu/a yield when plots were gleaned off at Tipton). At Columbia, yields averaged 84 bu/a for the CarPop(E5)C5 testcrosses (range 52bu/a to 129 bu/a for Pioneer Brand 3394) and 92 bu/a for the Mo17 Synthetic(H14)C4 testcrosses (range 62 bu/a to 138 bu/a for Pioneer Brand 3394). For 2000, we need to grow an additional two locations of the testcrosses to obtain sufficient data for selection of the best performing families. 

Nineteen lines from ARO1150:N04 were advanced from S2 to S3, and these will be testcrossed in 2000 to MoSCSSS(R19)C4 for field evaluation in 2001.

Back to Top

Evaluation of GEM Breeding Cross DKXL212:N11a S3 Lines for Disease and European Corn Borer Resistance and Agronomic Performance

James A. Hawk and Teclemariam Weldekidan

Department of Plant and Soil Sciences, University of Delaware

We self-pollinated and evaluated 87 S3 families from the DKXL212:N11a population for disease and European corn borer resistance and agronomic performance in the 1999 Summer nursery at Newark, DE. There was a heavy natural infestation of European corn borer and high incidence of Stewart’s bacterial wilt and Southern corn leaf blight. A Fall tropical storm resulted in heavy root and stalk lodging. In general, lines from this population are taller, later flowering and have tight husks and good grain quality. Root strength in this population was adequate with about two-third of the lines with no root lodging. We selected 54 S4 ears from 35 S3 selected families based on pest resistance and agronomic performance including low ear placement, short plant height, early flowering and rapid dry down. We also observed segregation for the lazy plant phenotype in two S3 lines derived from the same S2 family. The 54 S4 ears are being advanced in a winter nursery and will be evaluated in testcross hybrids on LH198 in Summer 2000.

Back to Top

Evaluation of 50% Exotic GEM Breeding Crosses for Western 
Corn Rootworm
and European Corn Borer Resistance

Bruce E. Hibbard, Vincent A. Smith, and Arnulfo Q. Antonio

USDA-ARS at University of Missouri

In 1999, we evaluated 114 available 50% exotic GEM breeding crosses plus checks for resistance to western corn rootworm (WCR) larvae and European corn borer (ECB). The WCR trial was conducted in a randomized complete block design with three replicates. Each plot was manually infested with 1,200 western corn rootworm eggs per 30.5 cm. At the time of maximum damage, four roots selected from each of the three replicates were washed of all soil and evaluated for corn rootworm feeding damage using the nodal injury scale (value represents the number of nodes eaten by WCR). First and second generation ECB screening was conducted by infesting ~140 larvae on the first six and last six plants in one 7.6 m row at 10-leaf stage and anthesis, respectively. At the time of maximum damage for first generation, plants were rated using Guthrie's 1-9 ECB rating scale (1=no damage, 9=severely damaged). Second generation ECB damage was rated by counting the number of tunnels and measuring the length of tunneling near the end of the growing season.

Although no significant differences were found between germplasm lines in the rootworm evaluation (n=3), all but one line were nominally less damaged than the susceptible control, B37×H84, and twenty-two lines were nominally less damaged than the resistant control, NGSDCRW1(C4)S2. All rootworm infestations in 1999 resulted in extremely high damage. The least damaged line in 1999 evaluation of 50% exotic materials, FS8B(S):S03, had root pruning on an average of less than two roots, while root pruning on the susceptible check, resulted in nearly two full nodes of roots being destroyed. All entries had a first generation ECB rating of five or less, indicating at least some resistance to leaf feeding. Sixteen lines had a rating of 2, indicating strong resistance. Average tunnel length for second generation ECB did not exceed three inches, even for the most susceptible lines, indicating a poor infestation of second generation ECB. For accurate ratings, second generation ECB experiments should be repeated.

Back to Top

Development of Corn Lines from GEM Germplasm with Improved Multiple 
Disease Resistance, Starch Content and Grain Yield

Robert Lambert

University of Illinois

One-hundred and fifty-four S4 families of BR5101 were grown in the nursery and infected with spores of the major multiple leaf and stalk rot diseases. They were grown at 28,000 less of infected leaf area and a stalk rot rating of 1 or less in early Sept. were saved. A total of 124 S4 families were harvested and assayed for starch concentration (using NIT). Thirty-three S4 families were saved with starch values in the range of 69 to 73%. These families were sent to a winter nursery for crossing to a tester (Monsanto Global Seeds) and will be tested at four locations in 2000. This population was also crossed to a B73 tester as S2 lines and tested at four locations in 1999, at Urbana, Clinton, Gibson City and Frankfort, IN. All data has been analyzed but Clinton IL location has very high winds with root lodging ranging from 100% to 0.0%. Fifteen of 50 hybrids has root lodging of 10% or less. Yields ranged from 160 to 75 bushels/ac. Yields at Gibson City ranged from 174 to 100 bu/ac and at Frankfort, IN from 160 to 75 bu/ac. The Urbana location is not analyzed yet and also samples were saved to assay for starch content. 

There were 100 S1 families of DREP 150 planted in nursery (estimated 2400 plants) that ranged in starch values from 73 to 68%. Plants were again selected (as above) for multiple disease resistance. A total of 150 plants were saved and the S2 seed assayed for starch content. The highest 48 ears were saved and sent to a winter nursery for crossing the starch value for the 48 ears ranged from 69 to 74%. Plans are to grow the two testcross exp. in 2000 each at four locations. Also the lines from the two populations will be planted and selected again for multiple disease resistance and starch content. Also crosses of lines between the two populations will also be made for testing in 2001.

Back to Top

Fusarium ear rot resistance screening of GEM germplasm

Gary Munkvold

Dept. of Plant Pathology, Iowa State University

Currently the resistance of corn hybrids to ear rot diseases caused by Fusarium species is not adequate. There is a need for new sources of resistance. Additionally, exotic germplasm being developed for incorporation into U.S. commercial hybrids must be evaluated for susceptibility to these ear rot diseases. We are addressing this problem by evaluating exotic germplasm for resistance to Fusarium and Gibberella ear rots. Ear rot diseases cause losses in yield and quality in the U.S. corn crop on an annual basis. Mycotoxins produced by the pathogenic fungi cause losses in livestock production and are a potential threat to human health when they are found in human foodstuffs prepared from corn. Mycotoxins can also present an obstacle to the marketing and export of corn grain. We characterized the relative susceptibility to Fusarium ear rots of lines being developed for incorporation into U.S. commercial hybrids. This information is essential for the incorporation of this germplasm into commercial maize production. We demonstrated that fumonisin concentrations in inoculated ears were closely correlated with visual disease ratings. This knowledge can greatly increase the cost-effectiveness of evaluating corn germplasm for susceptibility/resistance to Fusarium ear rot. We will characterize the relative susceptibility to Fusarium ear rots of advanced lines being developed for incorporation into U.S. commercial hybrids. The information has been transferred to major U.S. seed companies. Inbreds developed in the GEM project are now available to seed companies. They will facilitate the development of new commercial corn hybrids, which may be available to farmers during the next 2-3 years.

Back to Top

Introgression of Grain Quality Traits from GEM Germplasm into Corn Belt Maize

Richard C. Pratt

The Ohio State University

GEM FS8A(S):S09 S2 testcrosses to LH185 were grown in unreplicated trials at two locations in Ohio. One set of testcrosses was derived from selections made in Iowa by Dr. Pollak’s team, and one set of testcrosses was derived from selections among the same 441 S1 progenies by Dr. Pratt’s team in Ohio. The Iowa selected testcrosses were grown at the OARDC Western Branch and the Ohio selected testcrosses were grown at the OARDC Northwest Branch.

The Western Branch site experienced considerable drought stress. The Northwest Branch site experienced some drought stress but yields were excellent. Stalk lodging was minimal at both locations. The testcrosses yielded selections at approximately the 10% level that were highly competitive with the commercial hybrids entered as replicated checks in the tests. Grain quality testing is in progress.

GEM FS8A(S):S09 S2 Testcrosses to LH185 LP Selections Grown at OARDC Western Branch.

FINAL

STAND

%

%

YIELD

pl/ha

H20

LODGED

Mg/ha

All GEM FS8(A) Testcrosses to LH185 (n=74)

66443

13.4

1%

7.1 +/- 1.2

Top 11% GEM FS8(A) Testcrosses to LH185 (n=9)

66443

13.7

2%

8.9 +/- 0.4

Commercial Check Averages (n=7)

66443

12.8

1%

8.0 +/- 1.1

GEM FS8A(S):S09 S2 Testcrosses to LH185 RP Selections Grown at OARDC Northwest Branch.

FINAL

STAND

%

%

YIELD

pl/ha

H20

LODGED

Mg/ha

All GEM FS8(A) Testcrosses to LH185 (n=92)

66443

14.0

3%

13.6 +/- 1.1

Top 10% GEM FS8(A) Testcrosses to LH185 (n=9)

66443

13.6

2%

15.4 +/- 0.3

Commercial Check Averages (n=7)

66443

12.9

5%

14.6 +/- 0.8

Back to Top

Nutritive Value of Experimental Varieties of Corn for Broiler Chickens

Jerry Sell

Iowa State University

General Objective: To determine the nutritional value for broiler chickens of two experimental corns and their F2 hybrid.

The project was done in two parts. The experiment of Part A was designed to determine the nitrogen-corrected metabolizable energy value (MEn) for broiler chickens of four experimental varieties of corn. The feeding value of the varieties of corn was assessed in Part B.

Four experimental varieties of corn were evaluated, and an unidentified batch of corn obtained commercially was included for comparison. The identities and amounts of the experimental corns available for the research are shown in Table 1. Quantities of Gem 1 and Gem 3 corns (10.39 and 14.89 kg, respectively) were small and limited the number of chickens that could be used and limited the duration of the experiments. 

The experimental corns were supplied in whole kernel form. In preparation for diet mixing, the corns were passed through a roller mill to obtain particle sizes satisfactory for inclusion in feeds of broiler chickens.

Experimental Procedure, Part A:: To determine the MEn value of the corns, 200 1-day-old, male broiler chicks were obtained from a commercial hatchery. Chicks were housed in Petersime brooder batteries and all were fed a corn-soybean based broiler starter diet for 6 days. Feed and water were provided for ad libidium consumption. When the chicks were 7 days old, they were weighed individually. Five chicks were allotted to each of 24 experimental pens so that the average weights of all pens of chicks were similar. The experimental pens were designed to facilitate collection of excreta for use in the determination of MEn. Each of six dietary treatments was assigned randomly to four pens of chicks, starting when the chicks were 7 days old. Glucose was used at 30% of a basal diet to serve as a reference source in the calculations of the MEn values of the corn varieties. The five test diets were obtained by substituting each of the different corns (Gem 1, 2, 3, and 4, and a commercial corn) for all of the glucose of the basal diet on an equal weight basis. The composition of the basal diet is presented in Table 2. All diets were formulated to meet or slightly exceed the nutrient concentrations recommended by the National Research Council (1994). Celite was included in all diets at 0.7% to serve as an indigestible marker (acid-insoluble ash) to facilitate calculation of dietary MEn.

The experimental diets were fed for six days, and, on Days 5 and 6, excreta were collected from each experimental pen. Excreta and samples of diets were freeze-dried in preparation for analysis. Dried samples were analyzed for gross energy, nitrogen, and acid-insoluble ash. Data obtained from these analyses were used to calculate the MEn of each diet according to the procedure described by Hill and Anderson (1958). The MEn value of each diet and the known MEn value of glucose (3,640 kcal/kg) then were used as described by Hill and Anderson (1958) to estimate the MEn of each variety of corn.

Results of Part A: The estimated MEn values, expressed on an “as is basis”, and the crude protein, fat, starch, and dry matter content of the varieties of corn are shown in Table 3. The MEn value of the Commercial corn was within an expected range on the basis of reference values in the literature and results of previous research in our laboratory. The MEn values of the experimental varieties, however, were relatively low, especially those of Gem 3 and Gem 4 corns. Reasons for the relatively low MEn of the experimental corns are not evident. The experimental varieties contained greater concentrations of protein than the Commercial corn and thus, may have contained less starch. The fat concentrations of the experimental corns were within a range usually found in commercial corns. Varieties Gem 3 and Gem 4 had the lowest concentration of starch and this may have contributed to their relatively low MEn, compared with Gem 1 and Gem 2.

Experimental Procedure, Part B:: Two-hundred-fifty male broiler chickens were obtained at 1 day of age from a commercial hatchery. Chicks were placed in floor pens equipped for brooding and rearing. All chicks were fed a corn-soybean meal based starter diet until 7 days of age. Then, the chicks were weighed individually, and five chicks were placed in each of twenty-five floor pens so that average weights of the pens of chicks were similar. Each of five dietary treatments was assigned to five pens of chicks.

The dietary treatments differed in the source of corn used as a major constituent. All diets were formulated to be isonitrogenous and adequate in essential amino acids by using the protein and amino acid concentrations determined by laboratory analysis. Thus, the percentages of the different varieties of corn in the diets differed slightly because of their varying protein content. The composition of diets tested in Part B is shown in Table 4. Because the determined MEn of the test corns were inordinately low, the MEn value of the Commercial corn (3,208 kcal/kg) was used for all corns to formulate the diets. This was done to minimize the effects of the use of markedly different concentrations of supplemental fat in the diets, which could have a compounding effect on the evaluation outcome. It was assumed that, if the MEn of the test corns were low, compared with the commercial corn, chicks fed diets containing the test corns would consume more feed per unit of weight gain. 

The supplies of two test corns (Gems 1 and 3) were small. Thus, the feeding trial was only 9 days in duration. Body weights of chicks were recorded at the start of the experiment and body weight and feed consumption data were recorded when chicks were 16 days old. Data were analyzed statistically by ANOVA to determine the effects of dietary treatments on the dependent variables. In instances of significance (P < 0.05), Duncan’s multiple range test was used to identify differences among the treatment means.

Results of Part B: Data presented in Table 5 show that broiler chickens fed the diet containing Gem 1 corn gained less weight and were lighter at the end of the 9-day experiment than those of chicks fed diets containing Gem 2 or Gem 4 corns. Amount of feed consumed per chick was greatest for chicks fed the diet containing Gem 2 corn and was least for chicks fed the Commercial corn diet. Other treatments resulted in intermediate amounts of feed consumed. Feed efficiency (feed-to-gain ratio) of chicks fed the diet based on Commercial corn was superior to that of all other treatment groups, except for the Gem 4 group. Poorest feed efficiency was observed for chicks fed the diet containing Gem 1 corn, although feed efficiency of this group did not differ significantly from that of chicks fed diets based on Gem 2 and Gem 3 corns.

Discussion:: Weight gains of broiler chicks fed diets containing the experimental corns were as good as and, in some instances better than gain of chicks fed a relatively low-protein Commercial corn, indicating that the protein supplied by the experimental corns was well utilized for growth. In general, feed efficiency was poorer for chicks fed diets containing experimental corns. This observation corresponded, in general, with the results of the MEn determination. The MEn of all experimental corns was less than that of the Commercial corn. Consequently, because the MEn value assigned the experimental corns for diet formulation purposes was the same as that of the Commercial corn, MEn of the diets based on experimental corns would have been less than that of the Commercial corn diet. Feed efficiency of chickens is usually inversely related to dietary MEn concentration. It should be noted, however, that the effect of the individual experimental corns on feed efficiency did not correspond well with the determined MEn value. For example, the MEn value of Gem 4 corn was no different statistically from that of Gem 1 corn, but feed efficiency of chicks fed the Gem 1 diet was inferior to that of chicks fed the Gem 4 diet. 

Overall, the data show that the greater protein content of the experimental corn could prove advantageous economically for use in feeds of broiler chickens because of a decrease in the amount of the major protein source (soybean meal) needed in diets containing these corns. Additional research should be done with larger supplies of the experimental corns to obtain more definitive information about their feeding value.

References:

Hill, F. W. and D. L. Anderson, 1958.Comparison of metabolizable energy and productive energy determinations with growing chicks. J. Nutr. 64:587-603.

National Research Council, 1994.Nutrient Requirements of Poultry.9th Rev. Ed., National Academy Press, Washington, DC.

Back to Top

Anthracnose Stalk Rot Resistance from Exotic Maize Germplasm

Margaret Smith

Department of Plant Breeding, Cornell University

General Objective:

To develop temperate-adapted maize inbreds with both anthracnose stalk rot resistance and good yield potential from GEM accessions.

Specific Objectives:

1) To continue selfing and selection for anthracnose stalk rot resistance in progenies from the 75% temperate: 25% exotic populations that have adequate testcross yield potential.

2) To evaluate testcross yield potential of the early generation inbred families and select those that are most promising for continued stalk rot selection.

Materials and Methods: The results described herein represent the latest year of a multi-year inbred development effort. Results of 1995 per se evaluations were used to select five 75% temperate: 25% exotic populations with potential for anthracnose stalk rot resistance. Results of 1996 testcross yield evaluations of these populations were used to select the four with the best yield potential. For each of these four populations, 50 S1 ears were grown out ear-to-row in summer 1997. Eight plants per family were self-pollinated, injected with approximately 500,000 conidia/plant of Colletotrichum graminicola, and selected for anthracnose stalk rot resistance at harvest. In 1998, selected S2 ears were grown out ear-to-row for another cycle of inbreeding and selection for resistance, as well as for testcrossing. Selected S3 ears were grown out ear-to-row for inbreeding and selection for resistance in 1999, and testcrosses from the S2 families that gave rise to these selections were evaluated in yield trials in three New York locations.

Results: Populations selected based on per se anthracnose stalk rot resistance (evaluated in 1995) and testcross yield potential (evaluated in 1996) were FS8B(T):N1802, CH04030:S0906, AR01150:N0406, and GOQUEEN:N1603. Stalk rot resistance ratings for the 20 S2 families per population grown in 1998 and for the S2 plants from which S3 ears were selected are shown in Table 1. It should be noted that ears were saved from only the more resistant families as well as the best plants within these families in each population.

Means for anthracnose stalk rot rating (mean percent rotted tissue for the lower eight stalk internodes) for 20 S2 families per population and for the 12-20 plants from which S3 ears were selected, Aurora NY, 1998. 

Data from the summer 1999 inoculations and ratings on S3 progenies and from the yield trials of S2 testcrosses have been collected, but remain to be converted, analyzed, and summarized. Observations from the field suggest that levels of resistance have been maintained and/or improved, while days to flowering continue to be reduced gradually.

Back to Top

Cereal Breeding

Dennis West and David Kincer

University of Tennessee, Knoxville

COOPERATION: 957 yield test plots at Knoxville, TN were used to evaluate testcrosses of GEM germplasm. Data on yield, maturity, and lodging was forwarded to Raleigh, NC, to the coordinator for the southern region.

LOCAL ACTIVITY: 18 S2 lines provided by Dr. M. Goodman, NCSU, were selfed and crossed with elite Tennessee germplasm. These lines were identified in earlier trials as having potential to contribute useful genes to local germplasm.
 
 
Back to Top

Silage Evaluation of Topcrosses with Advanced Lines from GEM Breeding Crosses

James G. Coors

Department of Agronomy, University of Wisconsin

The purpose of our GEM research was to estimate silage yield and nutritive value of the most productive GEM topcrosses. Twenty-four elite GEM topcrosses involving hybrids having a maturity rating < 120RM were chosen based on excellent grain yield in previous GEM evaluations conducted in 1998 and earlier years. The 24 GEM topcrosses, along with four check hybrids, were planted in two Wisconsin locations (Madison and Arlington) with two replications at each location. Traits measured included forage yield at approximately 35% whole-plant dry matter (DM), neutral and acid detergent fiber (NDF, ADF), in vitro true dry matter digestibility (IVTD), in vitro digestibility of NDF (IVNDFD), and crude protein (CP). The trials went well with an average silage yield of 9.49 t/a. (See table below). High temperatures during the summer depressed silage quality somewhat from past years. 

Two GEM topcrosses in particular had both excellent yield and quality: CUBA164:S15-64-10 X LH185 and CUBA164:S15-184-1 X LH185. The former had the highest silage yield in the trial, which included check hybrid N4687, one of the highest yielding silage hybrids currently available in the north central region of the U.S. Furthermore, both GEM topcrosses had above average quality for all traits examined (low NDF, ADF, and high IVTD, IVNDFD, and protein). In particular, CUBA164:S15-64-10 X LH185 had excellent digestibility on both a whole-plant and fiber basis. Both topcrosses should continue to be evaluated for silage potential. If our results hold true in the future, these lines could be very useful for breeders in the northern Corn Belt.

Back to Top

Evaluation of GEM Germplasm for Drought Tolerance and Corn Earworm Resistance

Wenwei Xu, Tom Archer, and Lance Bradford

Texas A&M University System Agricultural Research and Extension Center, Lubbock, TX

Seventy–three GEM breeding crosses and four check hybrids (Pioneer hybrids 3223 and 34K77, B73 x Mo17, and CK4) were evaluated for yield and agronomic performance, pre-tassel drought tolerance, post-tassel drought tolerance, and corn earworm (CEW) resistance in four tests at Lubbock, Texas in 1999. Each test used a randomized complete block design with three replications. In full-irrigation test, CHIS775:S19, CML287:S18, CML287:S15, DKB830:S19, ANTIG01:S02, SCROGP3:N2017, and DREP150:N20 plus three checks (3223, 34K77, and CK4) were the top-ten yielding hybrids. In pre-tassel drought stress test, several GEM crosses had equal or better performance than Pioneer hybrids 3223 and 34K37 which are considered the most drought–tolerant commercial hybrids.GUAT209:N1925 and CML287:S15 had good pre-tassel drought stress tolerance and better stalks than the check hybrids. In the post-tassel drought stress, the yield of 25 GEM crosses (such as BR51501:S11a20, GUAT209:N1925, BVIR103:S0411a, and DKXL212:S09) had no significant difference from Pioneer hybrid 3223. 

A more detailed yield report is available from the GEM Coordinator (lmpollak@iastate.edu).

In CEW test, three crosses were significantly better than the mean of all 77 entries (7.9 cm) in resistance to CEW feeding: CUBA117:S15 (5.1 cm), GUAT209:N19 (5.1 cm), and BR51501:S11a (5.3 cm). Feeding damage below 5-cm is usually considered as an indication of CEW resistance. In addition, data on plant height, ear height, maturity, ASI, stalk lodging, stay green rating, grain mold and husk coverge were also presented. The identified GEM breeding crosses may provide new sources of genes to manage drought stress and economic insects. 

Corn earworm (CEW) feeding data from Lubbock, TX for the GEM breeding crosses. Data were collected from 10 ears in each replication over three replications.

Back to Top

Comparison of Methods for Amylose Screening Among ae Maize Starches with GEM and other Plant Introduction Backgrounds

Mark Campbell and Nurtay Abdubek

Division of Science, Truman State University, Kirksville, MO

Breeding for high-amylose corn starch requires a rapid analytical method for determining starch amylose so that generating chemistry values does not pose a major limitation in the volume of materials to be screened. Two recently described methods, one an iodine-based technique involving the solubilizing of starch from ground whole corn with DMSO and one based of near-infrared transmittance spectroscopy (NITS) were compared to an older iodine-based colorometric method using isolated starch. The materials evaluated consisted of many plant introductions and 98 experimental materials generated from the USDA Germplasm Enhancement of Maize (GEM) project. Crosses were made between this material and a corn-belt denthybrid (OH43 x H99) converted with the amylose-extender (ae) allele. F3 ears presumed to be homozygous for the ae allele were then evaluated in order to identify possible modifiers of ae conditioning high starch amylose. A core set consisting of 155 samples were selected form a total of 1006 ear samples which were all subjected to starch amylose analysis using the three methods. The NITS method showed poor correlation to the Williams method (r = 0.88) however NITS did appear to discriminate between sample having been converted to ae versus those having a normal or possibly segregating endosperm type. The DMSO-iodine method showed a much better correlation (r = 0.92) and appeared to better discriminate among samples having amylose values >65% from those at or near 55%. Results from this study suggest that NITS may be useful when a quick screening method is needed to discriminate mutant from non-mutant genotypes especially when visual identification is difficult. In addition, the Knutson method could be used to replace Williams when trying to identify high amylose levels among ae genotypes. Finally, this study revealed that exotic germplasm may be an important source of modifiers to the ae allele since values as high as 70% have were identified.

 

Back to Top

We are grateful to our Cooperators for their support!

 


Contact us Return to GEM homepage Link to USDA homepage Link to USDA-ARS homepage Link to NCRPIS homepage Link to ISU homepage Link to ISU Corn Breeding Project homepage Last time updated
Contact us | Home | USDA | ARS | NCRPIS | ISU | Corn Breeding | January 19, 2006