Germplasm Enhancement of Maize

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GEM - 2002 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.


Inbred Line Development and Hybrid Evaluation in GEM Breeding Crosses

James A. Hawk and Tecle Weldekidan

Department of Plant and Soil Sciences, University of Delaware


To develop inbred lines from GEM breeding crosses with good per se and testcross performance, resistance to abiotic and biotic factors, and adaptation to the Mid-Atlantic and Corn Belt regions.

Materials and methods

Four hundred fifty-six S1 families, derived from six Stiff Stalk and seven non-Stiff Stalk GEM breeding crosses, were self-pollinated. S2 ears were harvested from selected S1 families based on agronomic and disease evaluations. Selfing was also initiated on 17 new Stiff Stalk and 10 non-Stiff Stalk GEM breeding crosses. S1 ears were harvested from selected plants based on plant height, ear placement, maturity, grain drydown, grain quality, standability, and disease and European corn borer resistance. Yield trials were conducted on 15 DKXL212:N11a inbreds crossed to multiple testers (42 entries plus 3 commercial checks) at seven locations (Georgetown, DE; Hurlock, MD; Ames, IA; Poseyville, FT Branch, MT Vernon, and Whiteland, IN) with 10 reps. We evaluated seven DKXL212:N11a inbreds for gray leaf spot resistance in a replicated test at Georgetown, DE and in a non-replicated observation trial at Blacksburg, VA.


One hundred sixty-two S2 ears were selected from 108 of the 201 Stiff Stalk S1 families evaluated, and 188 S2 ears were selected from 126 of the 255 non-Stiff Stalk S1 families (Table 1). A higher percentage of selections were made from the following breeding crosses: CUBA164:S1511b, DK212T:S0610, DK212T:S0620, DK212T:N11a10, DK888:N11a08b, DK888:N11a08e, and DK888:N11a17.

Based on per se evaluations for plant height and maturity, selections were made in 15 of the 17 new Stiff Stalk and six of the 10 non-Stiff Stalk breeding crosses (Table 2). We were not able to pollinate the MDI022:S21 breeding cross due to its extreme plant height and late flowering. Three hundred sixty-seven Stiff Stalk S1 ears and 197 non-Stiff Stalk S1 ears were selected based on grain quality, grain texture, ear size, maturity, insect and disease resistance, and other agronomic traits. 

The top 25 entries in the DKXL212:N11a yield trial are listed in Table 3. DE4(DKXL212:N11a365-1-1-2-1-1), DKXL212:N11a-197-1-1-1-1, and DKXL212N11a-2-1-1 yielded well on at least two of the three testers with yields not significantly different from the commercial check mean. 

In the DE gray leaf spot evaluation, DE3 rated intermediate (3.0) and DE4 resistant (1.0) compared to the susceptible check B73Ht (5.0) and the resistant check Mo17Ht (1.7) on a (1-5 scale with 1 most resistant). These lines performed similarly at the VA observation plot. Hybrid observations at VA indicate that DE4 transmits gray leaf spot resistance in hybrid combination and had similar resistance to the resistant hybrid check. We observed premature death on DE4 at the Georgetown location that may be related to root rot symptoms.

Conclusions and Future Outlook

Based on the yield results and per se evaluations, inbred lines DE4 and DKXL212:N11a-197-1-1-1-1 may have potential for improving both agronomic and disease performance. The 162 Stiff Stalk and 188 non-Stiff Stalk S2’s will be testcrossed in 2002-3 winter isolation blocks, and hybrid evaluations will be conducted Summer 2003.


We thank the following cooperators for their assistance in conducting trials: USDA-GEM (Iowa State University), Holden Foundation Seeds, Inc., Pioneer Hi-Bred Int. Inc., and Mycogen. We also thank Erik Stromberg, Department of Plant Pathology, Physiology, and Weed Science, VPI & State University; Blacksburg, VA for conducting the gray leaf spot test.

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Silage Evaluation of Topcrosses with Advanced Lines from GEM Breeding Crosses


James G. Coors

Department of Agronomy, University of Wisconsin

Overview:  Approximately 8% (2,500,000 ha) of all corn harvested in the USA is harvested as silage that is fed to ruminants. Most of the silage corn is grown in the northern Corn Belt and the northeastern U.S., where the percentage silage can be as high as 50%. New hybrids are now routinely screened for silage potential in several states including Wisconsin, Michigan, and New York because the quality differences among hybrids can have economic consequences for milk and beef production. Animal rations must be properly balanced, and nutritional composition has become an important factor for farmers when choosing which hybrids to plant. Unfortunately, the range in nutritional value among conventional hybrids is narrow, due to the fact that, until recently, conventional hybrids have been selected primarily for grain yield. The GEM project has potential for bringing new germplasm into the Corn Belt with excellent grain and silage yield, as well as improved nutritive value.

The UW corn breeding program has been an active cooperator with the GEM project since 1995, and our objective was initially to determine if any of the GEM germplasms would contribute to the development of high-yielding and high-nutritive value silage hybrids. We started with the evaluation of a number of temperate breeding populations in per se evaluations. In 1998, we adopted a different strategy, which we have continued to the present. We now routinely evaluate silage potential of elite GEM topcrosses with high grain yield and suitable maturity (< 120RM). These hybrids are chosen annually based on excellent grain yield in GEM evaluations conducted in previous years throughout the U.S. Corn Belt. If any of these topcrosses have high dry matter yield and good nutritional quality in our UW trials, the respective GEM parent or breeding population is included in the UW inbred development nursery for further inbreeding and selection.

Recent Activities:  Based on results obtained in 2001 (see 2001 GEM public summary reports), two GEM trials, GEM A and GEM B, were conducted in 2002. The GEM A trial consisted of the ongoing silage evaluation of elite GEM topcrosses that were identified in the past year as having high grain yield and suitable maturity for Wisconsin. There were 26 entries in GEM A involving breeding populations or early-generation GEM inbreds topcrossed to LH185, LH198, and LH283. The GEM B trial consisted of 61 GEM inbreds topcrossed to HC33, LH185, LH198, LH279, LH287, and LH295. The inbreds involved in the GEM B trial were developed by the UW silage breeding program and were chosen based on topcross silage evaluations in previous years.

Both trials were planted at two WI locations, Madison (May 7) and Arlington (May 16), with three replications at each location. The average planting densities were 29,359 plants/acre (GEM A) and 28, 227 plants/acre (GEM B). Dry conditions prevailed until mid July, but the Madison trial was in good shape by harvest on September 25. Arlington was damaged slightly by drought and the Arlington trial also experienced some root lodging, but the plots were in good enough condition to harvest on October 8. Harvest dates at Madison and Arlington were delayed beyond the optimum dry matter of 30-40% because of weather and equipment difficulties. Therefore, the average dry matter at harvest was high (47.3% for GEMA and 49.5% for GEMB).

Nutritional evaluations included assessment of neutral detergent fiber (NDF), in vitro true digestibility (IVD), in vitro NDF digestibility (IVNDFD), crude protein (CP), and starch concentration. Based on these values, milk/ton of forage and milk/acre will be estimated based on the MILK2000 equations ( developed by the UW Agronomy and Dairy Science Departments. MILK2000 uses forage composition (NDF, IVD, IVNDFD, CP, and starch) to estimate potential milk production per ton of forage. Forage yield is then used to estimate potential milk per acre.

GEM A highlights. As seen in table 1, seven testcrosses (indicated in bold) showed potential based on the milk/acre evaluations, which were all greater than 31,500 lbs/acre. Most of this production was due to high forage yield. However, one testcross, BR52051:N04-75-1 x LH198, also had excellent quality (low NDF, high IVD, and high milk/ton).

GEM B highlights. Six testcrosses were notable in the GEM B trial (table 2). Most of these had high production potential based on milk/acre. Three had excellent quality as well based on their low NDF, high IVD, and high milk/ton (SCRO1:N1310-398-1-B-21 x HC33, AR17026:N1019-65008-2-3-1 x HC33, and CUBA164:S1517-01113 x LH287).

In our inbred breeding nursery in 2002, S5+ families were derived from breeding crosses UR13085:N0204, UR13085:N0207, AR17026:N1013, AR17026:N1019, SCRO1:N1310-398-1-B, CUBA164:S15-184-1-B, and CUBA117:S1520-156-1-B. Approximately 200 S3 families were derived from CUBA164:S1517. We also added three new sets of GEM inbred bulks to our inbred nursery in 2002, CHIS775:N1912-321-1-B-B, CH05015:N15-8-1-B-B, and DKXL370:N11a20-97-1.

Approximately 300 inbreds from CUBA164:S1517, CUBA164:S15-184-1-B, and CUBA117:S1520-156-1-B were planted in a crossing block with LH279 as the male pollinator. These topcrosses will be evaluated for silage potential in 2003.

Based on the GEM A and B evaluations in 2002, 15 inbred have been sent to the winter nursery for increase and additional testcrosses with LH198 and LH200. After one more year of testing, we should be able to determine whether any of these families are suitable for release.

For a complete nursery listing, see


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Developing Breeding Lines with Anthracnose Stalk Rot Resistance from Exotic Maize Germplasm

 Margaret Smith

Department of Plant Breeding, Cornell University


Anthracnose stalk rot (ASR), caused by Colletotrichum graminicola (Ces.) G.W. Wils., causes stalk rot problems and contributes to increased lodging in New York and throughout many U.S. maize-producing areas. The only economically feasible control of ASR is through resistant varieties and cultural practices that reduce disease incidence. Recent research has focused on exotic sources for improved ASR resistance, given the limited resistance available in temperate maize germplasm. This project aims to develop new maize inbreds with excellent resistance to ASR (derived from the tropical germplasm sources used) and good agronomic quality, yield potential, and temperate adaptation (derived from the proprietary temperate inbreds crossed to the exotic populations).

General Objective

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

Specific Objectives for Current Project Year

1) Increase seed of S6 (F7) lines that have shown promising levels of anthracnose stalk rot resistance.

2) Generate testcross seed of these lines with public and Holden’s testers for multi-location yield evaluation in 2003.

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, and were testcrossed. 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. Yield and resistance data were used to select S4 ears, which were grown out ear-to-row for inbreeding and selection for resistance, and testcrossed for yield evaluation at two or three New York locations in 2000. The same was done with S5 ears and their testcrosses in summer 2001. In summer 2002, S6 progenies were planted out ear-to-row for sib increase and crossing to both public and Holden’s testers. Testcross seed will be used for multi-location yield trials in 2003, to assess yield potential in combination with both elite commercial testers and with the public testers that have been used to date in this project.

Progress to Date

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 S5 families grown in 2001 and for the S5 plants from which S6 ears were selected are shown in Table 1. Ears were saved from only the more resistant families and the agronomically best plants within these families. Single plant selection for stalk rot resistance within families was not made at this point, assuming that alleles for resistance should be largely homozygous in S5 families. As a result, the standard deviation and range of values for individual S5 plant selections are higher than they have been in previous generations when individual plant selection was done. This variation likely reflects the inherent variability of the screening and rating technique, combined with the field variability that plagued our plots during the 2001 growing season. 

Yield data based on S5 testcross performance also was considered in selecting which families to maintain (see Table 2 for yield data on S5 testcrosses evaluated in 2001; bold indicates the entries derived from S5 families that were selected based on the combination of stalk rot resistance rating and testcross performance). Yield trial results were encouraging for some families, particularly those derived from GOQUEEN:N1603. Poorer performance in other families may be due in part to the public testers used, which will not give the highest potential combining ability or the best stalk and root quality. Testing in 2003 (presuming this work is funded) will include both public and Holden’s testers to evaluate the new inbreds in more competitive combinations.

Publications and Presentations

None for the current project year.

Summary of Accomplishments

The major accomplishment for this project to date is the development of advanced breeding lines (nearly finished inbreds) that are showing excellent resistance to anthracnose stalk rot. Resistance in the best of these materials is better than that available in currently released U.S. inbreds. Simultaneous selection for agronomic performance has identified the more promising fraction of these resistant selections, although only a few breeding lines appear to be competitive with current commercial hybrids in yield and standability. Finally, the process of anthracnose stalk rot inoculation and selection has contributed to new understanding of the appropriate basis for selection, by revealing that plants with little stalk rot in the inoculated internode likely represent partial escapes rather than truly resistant plants and should not be selected.

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Grain Yield, Drought Tolerance, and Corn Earworm Resistance of GEM Breeding Crosses

Wenwei Xu

Texas A&M University Agric. Res. and Ext. Center, Lubbock, Texas


To characterize the yield potential, drought tolerance, and corn earworm resistance of 71 GEM breeding crosses and to select the best germplasm for developing drought tolerant and CEW resistant inbred lines.

Materials and Methods

Seventy-one GEM breeding crosses and three checks (B73xMo17, Pioneer hybrids 34K77 and 3223) were grown under three water treatments in Lubbock in 2002. Of the 71 crosses, 44 had 25% tropical background while 27 had 50% tropical background. Seeds were planted on April 18. Under each water treatment, the experiment used a randomized complete block design with three replications. Each plot consisted of one 15 foot-long row planted 40 inch apart. The stand was thinned to 26 plants per row (22,646 plants/a). Three water treatments-well-irrigation and two severe drought stresses (Stress 1 and Stress 2) were in the same field. During the season, a total of 16.4, 5.2, and 7.0 acre-inch irrigation water were respectively applied through a subsurface drip irrigation system to the well-irrigation, Stress 1 and Stress 2. Stress 1 was originally designed to receive 50% irrigation water of the well-irrigated block from June 21 throughout the season. Due to heavy rain in June, irrigation was withheld from June 24 to July 28. Watering was restored on July 29 and 0.54 acre-inch water was applied from July 29 to August 14. In Stress 2, irrigation was withheld from June 20 to July 29 and 2.66 acre-inch water was applied from July 29 to August 14. On July 18, 0.30 acre-inch water was applied in Stress 2 to slow down the progress of drought stress. Total precipitation from January to August was 8.58 inches. In both Stress 1 and Stress 2, soil drought stress occurred when most genotypes were at tasseling stage. Ten days after flowering, drought stress became severer. Plants in Stress 1 experienced more severe drought stress than those in Stress 2.

Results and Discussion

Maturity, plant height, CEW resistance, mold, and yield under well irrigation

Maturity: There were significant genotypic differences for days to anthesis and silking. The average days from planting to pollen shedding ranged from 66 (AR13026:N08a) to 83 (BG070404:D27 and CHIS462:N08a) with a mean of 73 days. Six genotypes flowered significantly later than P3223 (RM=116 days): BG070404:D27, BR51675:D27, CHIS462:N08a, CUBA164:D27, CUBA84:D27, and PRICGP3:N12. None of the GEM crosses flowered significantly earlier than P34K77 (RM=107 days).

Plant height: Plant height ranged from 180 (UR01089:N2225) to 294 cm (CUBA84:D27) with a mean of 221 cm. Ten crosses were much taller than Pioneer 3223 (223 cm): BG07404:D27, BR5150:N11a, BR51675:D27, CHIS462:N08a, CUBA164:D27, CUBA84:D27, PASCO14: N04, PRICGP3:N12, and SCRO1:N13.

Corn earworm (CEW) resistance: The CEW penetration, an indicator of CEW resistance and measured by CEW ear penetration from ear tip toward the ear base over ten ears per replication, ranged from 4.0 to 11.3 cm with a mean of 7.5 cm. All three check hybrids (B73xMo17, P34K77 and P3223) had average CEW ear penetration. Nine crosses had a significantly lower CEW ear penetration than the average (7.5 cm), including BG070404:D27 (4.0 cm), DK888:N11a (4.2 cm), BR51501:N11a (4.6 cm), ANTIG03:N12 (4.8 cm), CUBA84:D27 (5.0), DKXL380:N11a (5.1 cm), BR51675:D27 (5.2 cm), DK212T:N11a (5.2 cm), and ANTIG01:N16 (5.4 cm). 

Grain molds: The average percentage of molded kernels (mold) was 5.5% ranging from 2.7% to 11.7%. The molds in AR01150:N0406, AR13026:N08a, AR17026:N1013, BARBGP2:N08a12, CASH:N1407, DKB844:N11b17, DREP150:N2011d, and GOQUEEN:N16 were significantly higher than the average. Molds were highly correlated with CEW penetration (r=0.68**). None of the 74 entries had molds significantly below the test mean.

Ear length: The ear length ranged from 15.7 to 22.3 cm with a mean of 19.1 cm. The ears of 11 breeding crosses BR51403:N16, BR51675:N0620, BR52051:N04, CH05015LN1204, CML329:N18, GOGUEEN:N16, GUAD05:N06, PRICGP3:N1211c, PRICGP3:N1218, SCRO1:N13, and SCRO1:N1318 were significantly longer than three checks and test mean.

Yield: The average yield was 106.9 bu/a ranging from 43.8 (BARBGP2:N08a12) to 172.2 bu/a (P3223). Three check hybrids P3223, P34K77, and B73xMo17 were ranked as 1, 6, and 58 respectively. Top 10 yielding GEM breeding crosses were ANTIG01:N12, PRICGP:N1218, ANTIG01:N16, BR51403:N16, CUBA84:D27, UR11002:N0308b, CUBA164:D27, SCRO1:N13, and ANTIGO03:N1216. These crosses yielded 134.3 to 152.5 bu/a.

Yield and Stay Green Under Severe Drought Stress (Stress 1):

Yield: The average yield was 39.6 bu/a ranging from 9.3 (CHIS462:N08a) to 72.0 bu/a (AR16026:N12). Top 10 yielding entries include AR16026:N12 (72.0), UR11002:N0308b (70.9), BR51675:N0620 (68.3), P3223 (66.1), UR13010:N06 (63.3), P34K77 (63.2), CH05015:N1204 (59.7), CUBA110:N1712 (57.8), CH04030:N0306 (56.9), and DKB830:N11b20 (56.5). 

Stay green trait: Stay green was scored on August 5 and August 10. The average stay green rating over two rating dates ranged from 2.6 (CUBA84:D27) to 4.6 (B73xMo17) with a mean of 3.8. Fourteen GEM breeding crosses had stay green rating below 3.4, significantly lower than the average and of course three checks.

Yield and Stay Green Under Severe Drought Stress (Stress 2): 

Yield: The average yield was 44.2 bu/a ranging from 25.8 (AR17056:N13) to 92.8 bu/a (P3223). Top 10 yielding entries include P3223, AR16026:N12, UR11002:N0308b, ANTIG03:N1216, ANTIG03:N12, P34K77, SCROP3:N1411a, DKB830:N11b20, ANTIG01:N16, and GUAD05:N06. Their yields were between 61.7 to 92.8 bu/a.

Stay green trait: The average stay green rating over August 5 and August 10 was 3.1 ranging from 2.0 (CHIS462:N08a) to 4.3 (AR17026:N1013).  Fifteen entries including P3223 had a rating significantly below the test mean. 


The detailed data are available from the GEM coordinator. Based on the results of three water treatments, we identified top 15 GEM breeding crosses that showed good yield potential, earworm resistance, stay green rating, grain mold resistance, long ear, early maturity, tall plant, upright leaves, or good husk coverage or a combination of these characters (Table 1). The top 15 crosses are ANTIG03:N12, UR11002:N0308b, AR16026:N12, ANTIG01:N16, BG070404:D27, PRICGP3:N1218, CUBA84:D27, CUBA164:D27, ANTIG03:N1216, CH05015:N1204, PRICGP3:N1211c, BR51501:N11a, BR51403:N16, BR51675:N0620, and GUAD05:N06. The top ranking cross ANTIG03:N12 yielded well under irrigated and drought stressed conditions, and had good CEW resistance, low grain mold, good stay green trait, upright leaves, and good husk coverage.

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Use of GEM Breeding Materials for the Development of  High-Amylose Maize Germplasm (2002 GEM Report)

Mark Campbell, Nathan Polaski, Amanda Wood, Meghana Kunkala, Derek Lahr

Truman State University, Division of Science

Overview and General Objective of the Project

In the US, around 50,000 acres of high-amylose corn are produced. This is processed by various wet-mills in order to produce high-amylose starch which has a number of food and industrial applications. High-amylose corn possesses starch having an amylose content of greater than 50% compared to normal starch (25% amylose). A number of discrete classifications of high-amylose corn exists based on their specific amylose content including Amylomaize V (50-60% amylose) and Amylomaize VII (70-80% amylose). The starch from high-amylose corn is used in the textile industry, in gum candies, production of biodegradable packaging material and as an adhesive in the manufacture of corrugated cardboard. There are a number of new applications of high-amylose starches especially because of its nuetracuetical value. Specifically it has a low glycemic index, it serves as dietary fiber and it can be used as a food coating to minimize fat uptake, and therefore caloric value, of fried foods.

High-amylose corn generally yields around 60% of that observed among normal hybrids. In addition, since the development of high amylose corn has been limited to a few breeding programs there is an expected yield lag compared to normal corn. It has been predicted that the volume of high-amylose corn may increase steadily in the near future because of the number of new applications that have emerged in the past decade and because of new applications currently being suggested. For these reasons, it would benefit the starch industry to expand the germplasm base for this specialty crop. The two primary benefits would be to 1) identify new sources of modifying genes that, together with the amylose-extender (ae) gene elevate starch amylose to 70% or greater and 2) to incorporate GEM germplasm in order to increase genetic diversity which may lay a better foundation for future improvements in yield and other desirable agronomic traits.

Specific Objectives and Results from 2002

A.  Inbred Line Development

For the past several years, a number of exotic populations obtained from the North Central Regional Plant Introduction Station and from GEM were crossed on to a corn-belt source of the amylose-extender (ae) mutation (OH43xH9 ae/ae). The material was advanced to the F2 and screened for amylose content by selecting materials having 70% amylose or greater. From this work, three sources of germplasm were found including the populations Zia Pueblo NRC 5357, Cochiti Peublo NRC 5298 and the GEM cross GUAT209:S13. These materials were self pollinated for a number of generations in order to develop inbred lines with a stable amylose content of 70 percent or greater. Inbred lines grown in 2001 which mostly represented the F5 generation of inbreeding were analyzed this past summer and are shown in Table I. In general a number of inbreds are displaying consistently high amylose levels. An exception would be for those lines derived from the Zia Pueblo and Cochiti Pueblo populations. These lines do not hold up well to inbreeding and in many cases sib-pollinations were made within families or among families in order to advance the seed. This may have resulted in the modifying genes not being well fixed in this material. Efforts were made to cross these onto superior GEM germplasm in order to preserve the high-amylose modifying genes as explained in the next section. 


B.  Initiation of a Backcross Program Using Selected GEM Lines from Public Cooperators

In order to develop germplasm having desirable high-amylose modifiers in a high yielding background an effort was made to begin a backcross into selected germplasm. During the summer of 2001 the following GEM lines were obtained from Dr. Linda Pollak (USDA/ARS, Ames, IA) to be used as recurrent lines since they represented the highest yielding material from this project at the time (Table II).

During the winter of 2001/2002 the material was advanced in a winter nursery in Puerto Rico where F1 ears (segregating F2 Kernels) were harvested. Mutant kernels were selected from these ears and planted in a summer breeding nursery during the 2002 growing season where plants were self-pollinated. Grain from three selected ears per row was analyzed for starch amylose and the data shown in Table III. From the data it appears that high-amylose modifiers were recovered and are segregating in many of the F2 ears from crosses with GEM lines. This indicates that further backcrossing in these GEM lines may be possibly successful.

Although the data are limited, the distribution of the amylose values from these crosses suggests that the inheritance of the modifying genes may be qualitative in nature and therefore governed by one or a few genes (Figure 1). This is because the distribution of amylose values appears to be bi-modal in which amylose values from samples generally are either grouped near 55% or near 70%. Future studies will be necessary to more completely describe the inheritance of these modifiers.

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OSU Report – GEM Annual Cooperators Meeting

Rich Pratt

Ohio State University-Ohio Agricultural Research Development Center, Wooster, OH

The breeding line (OSU 43-2) was approved for release by the Director of the OARDC, OSU on March 24, 2002. Breeder’s seed was increased by controlled full-sib pollination of the S3 in the 2002 OSU nursery. Seed from over 100 ears was bulked to form the seed lot for distribution. 

It has been released to GEM cooperators as GEMS-0002 following the GEM protocol. 

The line was selected from the GEM FS8(A)S:S09 population. The genetic composition of the population is estimated to be approximately 50% BSSS related, 21% tropical, 18% southeastern U.S., and 11% diverse Corn Belt (with a high proportion of inbred C103A). The breeding program was conducted through a collaborative effort between OSU/OARDC, the USDA-ARS maize research group at ISU, Golden Harvest Seeds, Inc., and through in-kind support provided by other private sector cooperators. 

Mid-silk date of the GEMS-0002 is approximately one week earlier than that of B73 in Ohio, and it produces moderate amounts of pollen. Plant height is quite moderate (avg = 133.2 cm) and ear placement is slightly below mid-plant height (avg ear height = 55.8 cm). Cob color is white and ears generally display 12 kernel rows (average 12.5, range 10-16). Ear width is approximately 3.8 cm (range 3.5 to 4.4 cm). Ear length is approximately 13.2 cm (range 11 to 15 cm). Kernels of GEMS-0002 are yellow to yellow-orange in color and are slightly dented to flinty and have a 100 kernel wt. of 21.7 g. Grain protein composition is somewhat elevated (approx. 2 to 2.5 points above B73) and average density is 1.35 g/cc. The line has not been exposed to high levels of foliar or stalk-rotting diseases and definitive information concerning its susceptibility to pests and diseases is unknown. Testcross performance of OSU 43-2 (GEMS-0002) was presented in last year’s annual report. 

GEMS-002 is intended as a breeding resource for the improvement and diversification of elite, non-‘Lancaster Sure-Crop’ related inbreds. The line is unique in that it has a relatively high proportion of tropical germplasm yet is able to impart earliness to hybrids. It has potential as a source of germplasm in breeding programs throughout much of the U.S. Corn Belt. It is recommended that it be introduced into breeding programs by crossing with elite inbreds followed by modified pedigree selection. Using this method, it is anticipated the agronomic characteristics can still be improved since only one cycle of selection has been practiced.

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Breeding Maize Lines with Exotic Germplasm

Dennis West

Plant Sciences and Landscape Systems, University of Tennessee, Knoxville


Develop new parental maize lines with desirable milling and grain quality characteristics from GEM populations.


Incorporation of  genes from exotic germplasm populations for selection has the potential to produce new maize lines that exceed the performance of those currently available for characters such as grain quality components (milling traits, carbohydrate, protein, and oil) and stress tolerance.


1)  Outstanding new lines from GEM accessions were identified from yield trials in 2002.
2)  Crosses between 24 GEM accessions and adapted germplasm were advanced by self-pollination and selection in 427 nursery rows.

Research Approach

Evaluate maize lines from GEM accessions in topcross yield trials in Tennessee. Select superior lines/populations from topcross trials and cross these with elite adapted lines. Self-pollinate and select in segregating populations of crosses between GEM and adapted lines.


In 2002, 883 experimental hybrids were evaluated in 15 yield trials in Tennessee. 

These hybrids were crosses between GEM lines and adapted germplasm. Results from this single replicate trial at Knoxville, TN are shown in table 1. Several experimental hybrids were competitive with commercial check hybrids included in these trials. An experimental hybrid in trial Wj9 yielded 50 bu/a more than the average of 8 check hybrids, and a testcross in trial W89 produced 47 bu/a more than the check average. The best lines from these GEM accessions will be selected for further testing and incorporation into value-added breeding for new parental lines. Inbreeding and selection was continued in populations resulting from crosses between GEM lines identified in previous trials. 

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Contact us | Home | USDA | ARS | NCRPIS | ISU | Corn Breeding | January 19, 2006