Germplasm Enhancement of Maize

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Javier Betrán
Martin Bohn
Mark Campbell
Marcelo Carena
James Coors
Jim Hawk
Manjit Kang
Richard Pratt
Margaret Smith
Dennis West
Bruce Hibbard
Wenwei Xu

GEM - 2003 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.

Aflatoxin evaluation of GEM advanced lines with different fatty acid content

F. Javier Betrán

Texas A&M University

Pre-harvest aflatoxin contamination is one of the main limiting factors for corn production in the South. Development of stress-tolerant corn and resistance to aflatoxin would add $50 million to Texas corn value annually, increasing food safety and allowing profitable production and marketing. Currently, there are not commercial hybrids fully resistant to aflatoxin contamination.


The objective of this project is to estimate the response to aflatoxin contamination of corn lines with different fatty acid content derived from GEM breeding crosses.


GEM derived lines with high linoleic and low oleic (DKB830:S11a17-35-B,  DKXL380:S08A12-24-B, BR52060:S0212-25-B, FS8B(T):N1802-35-1-B), and low linoleic and high oleic (CUBA164:S1511b-15-B, DKXL380:S08a12-12-B, DKB844:N11b17-21-B, AR16026:S1704-32-B) were evaluated for aflatoxin accumulation at Weslaco and College Station, TX during 2002, and at Weslaco during 2003 in trials with 4 replications under inoculation. Stress conditions were induced by limiting irrigation during and after flowering or by late planting.  Inoculation was conducted by placing A. flavus colonized corn kernels on the soil surface between treatment rows around mid-silk stage. The isolate was NRRL3357 and the inoculum was distributed at the rate of 1 kg (noncolonized dry seed equivalent) per 200 foot of row. At harvest, infected ears were husked, rated for insect injury and visible fungi colonization, dried, shelled, bulked and weighed. The whole kernel sample was ground with a mill and evaluated for AF. Quantification of AF was conducted with monoclonal antibody affinity columns and fluorescence determination (Vicam AflatestTM).


Significant differences among inbreds for aflatoxin content were observed at all locations. In year 2002, averages for aflatoxin were 90.3 ng g-1 at College Station and 630.8 ng g-1 at Weslaco (Table 1). CML176, Tx601, and CUBA164:S1511b-15-B were the less susceptible inbreds across locations in 2002. GEM lines DKXL380:S08A12-24-B and BR52060:S0212-25-B had low aflatoxin in Weslaco but high in College Station. In year 2003 aflatoxin average was 674.6 ng g-1 at Weslaco. As in 2002, resistant checks CML176 and Tx601y were the most resistant inbreds. The less susceptible GEM lines in 2003 were DKB844:N11b17-21-B and BR52060:S0212-25-B. On average, high oleic-low linoleic lines had less aflatoxin content than low oleic-high linoleic lines at each location and across locations. However, the range for aflatoxin among the low oleic–high linoleic lines was much greater than among the high oleic-low linoleic lines. Furthermore, the GEM lines with the lowest aflatoxin across locations were low oleic-high linoleic lines DKXL380:S08A12-24-B and BR52060:S0212-25-B. Therefore, with this reduce sample of inbreds non-conclusive differences were observed between high oleic-low linoleic and low oleic-high linoleic GEM lines. GEM derived lines with different fatty acid content reported here were more susceptible to aflatoxin than resistant checks.


Publications and Presentations:

Betran, F.J., T. Isakeit, G.N. Odvody, and K. Mayfield. 2003. Identification, development and characterization of corn germplasm to reduce aflatoxin contamination. Presentation at the Aflatoxin Elimination Workshop, Savannah, Georgia, October 13-15, 2003.

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Evaluation of Advanced GEM Lines for Multiple Insect Resistance and Fumonisin Concentration

Martin Bohn

University of Illinois, Urbana, Illinois

Project Description: The Western corn rootworm (WCR, Diabrotica virgifera virgifera LeConte) and the European corn borer (Ostrinia nubilalis Hb., ECB) are serious pests of maize in the U.S. causing estimated total costs of two billion U.S. dollars each year due to yield losses and control measures. As a result of insect feeding damage, secondary infections with other pathogens occur and reduce grain quality. Fusarium ear rots of corn, caused by Fusarium verticillioides, F. proliferatum, and F.  subglutinans are of great concern. These Fusarium species produce fumonisin, a mycotoxin, associated with severe animal and human health disorders.

Objectives: The overall objective of this project is the development of maize varieties with host plant resistance against WCR and ECB as well as an improved Fusarium resistance as major components of an integrated pest management system. The specific objectives are to

  1. Evaluate GEM lines for their resistance against WCR as well as first and second generation ECB,

  2. Evaluate GEM lines for their resistance against Fusarium species,

  3. Determine the association between insect resistance and fumonisin concentration in GEM germplasm,

  4. Study the genetic basis of insect resistance in maize against both insect species by diallel crosses and testcrosses, and

  5. Initiate a recurrent selection program aimed to develop new maize lines with improved multiple insect resistant (MIR).

Material and Methods

Plant material: The main approach of this project is to screen in a first step advanced GEM material for its WCR, ECB, and Fusarium resistance. This germplasm comprises populations containing 25% exotic germplasm and inbred lines that were derived from these. In further steps, populations with 50% exotic germplasm and the exotic source populations (100% exotic germplasm) will be evaluated for resistances if the advanced germplasm does not show promising levels of resistance. Fifteen populations containing 25% percent exotic germplasm were selected, which combined resistance against WCR and ECB with acceptable agronomic performance by screening available GEM data sets (Table 1). In addition, ten lines derived form the non-Stiff Stalk population AR17056N2025 and five from the Stiff Stalk population CUBA117:S1520 S5 lines were selected.

Field experiments: Separate field trials were conducted to determine WCR and ECB resistance of inbreds and populations. Both experiments were conducted in adjacent fields at Urbana, Illinois. The experimental design was a generalized lattice design with four replications and two-row plots for the inbred experiment and four-row plots for the population experiment. Rows were 0.75m apart and 1.5m long. Ten to 12 plants were hand planted per row. All experiments were planted May 13, 2003.

Plants were manually infested with ECB larvae to ensure an even infestation level for all entries. The artificial infestation with first generation larvae (1ECB) was performed June 26 and 27, 2003. The artificial infestation with second generation larvae (2ECB) was performed July 24 and 25. The manual infestation was synchronized with the natural appearance of 1ECB and 2ECB moths to simulate natural infestation. For manual infestation, egg masses were applied directly into the plant whorl (1ECB) and into the axils of the first leaf above and below the ear (2ECB). About four egg masses per plant were applied two times at two consecutive days, accounting for about 180 larvae per plant and ECB generation. In the inbred experiment all plants within the first row of a plot were artificially infested with 1ECB egg masses, whereas the second row was infested with 2ECB larvae. In the population experiment 1ECB egg masses were applied to all plants in the first row and 2ECB egg masses to all plants in the third row. The following resistance traits were determined: (1) leaf damage ratings (LDR) using a 1-9 rating scale, as defined by Guthrie and Barry (1989), (2) stalk damage ratings (SDR) using a 1-9 rating scale, as described by Hudon and Chiang (1991), and (3) number of larvae per plant.  The WCR treatment was planted in a WCR trap crop area to ensure a high level of infestation. Damage to WCR larval root feeding was measured on five random plants per plot in the line experiment and on ten plants per plot in the population experiment. Root injury was assessed using the Iowa State 0-3 damage rating scale (root damage rating, RDR).


Western Corn Rootworm: The root damage ratings of all populations varied between 0.88 (DKXL212:N11a01) and 1.66 (UR13085:N0204) with a mean RDR of 1.41. No population was significantly less damaged by WCR larvae feeding than resistant check NGSDCRW1(S2)C4-15-2S2(S1) (Table 1). The inbreds showed RDRs ranging from 0.56 (CUBA117:S1520-153-1-B-B) to 1.73 (B73). Two inbred lines derived from stiff stalk population CUBA117:S1520 and two inbreds developed from non-stiff stalk population AR17056:N2025 showed significantly (P < 0.05) smaller RDRs than the resistant check.

European Corn Borer: For LDRs significant (P > 0.01) differences among populations as well as between inbreds were found. In the population experiment LDRs varied between 3.18 (UR13085:N0204) and 5.25 (CASH:N1410) and in the inbred experiment LDR values ranged from 2.73 (AR17056:N2025  Select # 2-B-B) to 7.62 (CUBA117:S1520-52-1-B-B). LDRs were determined for resistant inbreds B52, D06, and De811 in an experiment adjacent to the GEM germplasm screening using the same procedures and infestation dates as in the GEM study. The mean LDR for these resistant lines was 2.5 indicating that the screened GEM germplasm was mostly intermediately resistant to the first generation ECB larvae feeding. For all other ECB resistance traits differences between genotypes were not significant. 

Conclusions and future activities

These results confirm that base populations AR17056:N2025 and CUBA117:S1520 are possible sources for WCR resistance. Four inbreds derived from these populations showed significantly lower RDRs than the resistant check. The experiment will be repeated in 2004 to substantiate these finding. Based on these preliminary results a diallel will be formed in our winter nursery 2003 in Hawaii using these GEM lines together with other known sources of WCR resistance (e.g., B64, see Table 1). This diallel will allow the estimation of quantitative genetic parameters and the future exploitation of combined information from multiple crosses for QTL identification. All maize germplasm that was identified to be significantly less susceptible to WCR larvae feeding than the resistant check in the GEM study and in additional screening experiments conducted across three environments in summer season 2003 will be planted in isolation to form a new breeding population in summer season 2004.

For the 2003 GEM germplasm screening, populations were selected first based on their level of WCR resistance. From this set, populations with improved resistance against the first and the second ECB generation were selected. Even though, the screened material was highly selected, correlations between WCR and ECB resistance traits were mostly negative. Therefore, further GEM germplasm will be screened for improved resistance against ECB larvae feeding independent of its WCR resistance. In addition to the evaluation experiments, all evaluated populations were increased in the Urbana 2003 maize summer nursery. Per population, the 12 earliest plants were selfed to initiate the development of new inbred lines.


Guthrie, W.D., and B.D. Barry. 1989. Methodologies used for screening and determining resistance in maize to the European corn borer. pp. 122-129. In CIMMYT. Toward insect resistant maize for the third world. Proc. Int. Symp. Methodologies for developing host plant resistance to maize insects. El Batan, CIMMYT, Mexico. CIMMYT, Int., CIMMYT, Mexico.

Hudon, M., and M.S. Chiang. 1991. Evaluation of resistance of maize germplasm to univoltine European corn borer Ostrinia nubilalis (Hübner) and relationship with maize maturity in Quebec. Maydica 36:69-74.


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GEM report 2003 at ASTA meeting in Chicago

Mark Campbell, Nathan Polaske and Scott Hilton

Truman State University, Kirksville, Missouri

Amylomaize starch is required as raw material for a number of specialty food and non-food uses.   The focus of the breeding program at Truman State University has been towards the development of high-amylose corn using GEM germplasm as a source of modifying genes that work with the recessive amylose-extender (ae) allele to elevate starch amylose to 70% or greater.  In addition, development of amylomaize VII germplasm using GEM materials may potentially increase the existing diversity for this class of specialty grain and serve as an important source of genes for improving other agronomic traits.    The diagram (Figure 1) shows the basic approach used at Truman State University.  The four main objectives shown include:  identification and development of inbreds possessing modifying genes that work with the ae allele (ae normally results in starch having only around 55% amylose) to raise amylose levels to 70% or greater (A.K.A. amylomaize VII corn), introgression of GEM germplasm previously selected for yield into amylomaize VII germplasm  development and evaluation of test hybrids using proprietary amylomaize VII testers and, development of analytical techniques to improve identification of desirable starch properties such as starch amylose and starch content.. 


Figure 1.  Flow diagram showing the four main objectives towards the development of amylomaize experimental hybrids.


Amylose data from the most advanced inbreds developed from objective    are shown in Table 1.  The grain samples were produced in the 2002 summer breeding nursery near Kirksville, Missouri and represent the continued inbreeding and selection for Amylomaize VII types starches that are currently in the F7 or F6 generations.  It can be seen that a large number of these consistently possess amylomaize VII-type starch.   Although other plant introductions (e.g. Zia Pueblo and Cochiti Pueblo) also proved to be sources of modifying genes for developing amylomaize VII starch, inbreeding was discontinued since they did not hold up to inbreeding nearly as well as did the GUAT209:S13 derived lines.  These lines were further increased in the 2003 nursery and will be subjected to additional amylose testing this winter.  Selected lines from these materials will continue to serve as the source of amylomaize modifiers for use in objective .


Introgression of GEM germplasm into Truman amylomaize VII materials was begun in 2001.  This was done by having obtained a number of GEM lines from Dr. Linda Pollak that were previously selected for yield and having crossed them to several Truman amylomaize VII type lines.  The material was advanced in a winter nursery, mutant ae kernels were selected from segregating F2 ears and the seed was used to produce homozygous F3 ears in 2002 that were then evaluated for amylose content as shown in Table 2.  It can be seen that a number of F3 ears were recovered possessing amylomaize VII-type starch.


Crosses were made between selected F3 lines derived from Objective  onto two proprietary amylomaize VII testers representing the two main heterotic groups.   Yield trials and grain analysis will be conducted during the summer of 2004 in Iowa and Northern Missouri.  The amount of seed available for crosses is shown in Table 3.


Development of analytical techniques to improve the identification of desirable starch properties in GEM high-amylose germplasm. 

A.  Polorimetric Starch Quantification

As mentioned in last year’s work plan, one of our goals was to collect starch quantity data.  Typically starch content values are lower with many of the starch mutants, so it stands to reason that we should monitor starch levels during development of germplasm. 

Starch content and amylose data from F3 ears developed from Objective  are shown in Table 4.  Starch values varied widely and did not appear to be correlated with amylose content within this set of materials test.


B.     Use of Differential Scanning Calorimetry as a rapid and automated alternative to determining amylose within GEM germplasm segregating for high-amylose modifiers.

With this method, a 2% solution of L-α- Lysophosphatidylcholine is added, then placed in the DSC instrument, heated to 125oC to gelatinize and held for 2 minutes.  This is  followed by a slow cooling phase (10oC per minute) in which the LPC forms a complex with the amylose.  This crystallization results in an exothermic peak that is directly proportional to the percent amylose in the sample (Figure 2A).  A number of F3 samples from Objective  were analyzed using both the DSC method and the colorimetric iodine-binding method.  Values were compared revealing a correlation ( r ) of 0.83 (Figure 2B).


C.   Use of Proton-NMR for determining amylose content of ground (unpurified starch) corn samples using high amylose GEM amylomaize V and amylomaize VII germplasm.

An initial study was conducted using a waxy corn sample and GEM materials containing either  55, or 70 percent starch amylose.  All of this corn was dry ground in the coffee grinder.  Then we added 10mL of D2O, vortexed, and centrifuged.  The supernatant liquid was pipetted into the NMR tube and run at 70 degrees Celsius and spectra were collected as shown in Figure 3A.  Peak integrations of 1-4 and 1-6 bonds where determined and values compared to known amylose values are shown in Figure 3B.


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EarlyGEM’: Incorporating GEM Elite Lines in Early Maize

M. J. Carena

Department of Plant Sciences, North Dakota State University

Maize Breeding Program

Current personnel:

M. J. Carena                                        Project Leader
Duane Wanner                                     Research Specialist
Fernanda Boato da Silva (Brasil)          Visiting Scientist
Clarissa Barata (Brasil)                         Graduate Research Assistant (MS student)
Alyson Hyrkas (USA)                          Graduate Research Assistant (MS student)
Min Hu (China)                                    Graduate Research Assistant (Ph.D. student)
McDonald Jumbo (Malawi)                  Graduate Research Assistant (MS student)
Marcelo Melani (Argentina)                  Graduate Research Assistant (MS/Ph.D. student)
Juan Osorno (Colombia)                      Graduate Research Assistant (Ph.D. student)
Bahadir Sezegen (Turkey)                    Graduate Research Assistant (MS student)


The importance of early maize for grain in the northern Corn Belt has increased significantly in the past years. Maize has become the top third commodity based on cash receipts in North Dakota. Maize production is at a record high 130 million bushels and state grain yield has increased an average of 5.3% (4.8 Bu/A) per year for the period from 1997 to 2003. Harvested acreage for the state also increased from 590,000 to 1,300,000 acres during the same period. An important fact, however, is that ND maize producers still need to be looking at low risk hybrids for this area meaning early enough hybrids for their region having equal or better potential than late maturing ones.

The goal of NDSU maize-breeding program is to conduct research in maize breeding for the northern Corn Belt emphasizing germplasm adaptation and improvement, inbred line development, and hybrid testing. Specific objectives include:

  1. Identify elite exotic genetic materials for adaptation

  2. Maximize genetic improvement of maize germplasm adapted to North Dakota

  3. Develop improved maize inbred lines and varieties for the northern Corn Belt

  4. Coordinate hybrid maize performance testing trials

  5. Assess the potential of maize diversification

  6. Educate plant breeders

The breeding program works towards releasing inbred lines that are competitive in performance, drying costs (maturity), lodging resistance, and quality to those of the industry. Our broad-based germplasm has provided new inbred lines that can be successfully classified in more than one heterotic group.                                                                          

The maize-breeding program at NDSU has been an official public cooperator with the GEM project since 2001. Our cooperation started in 2000 when we decided to evaluate the first released GEM lines for adaptation to the northern Corn Belt. This initiative was selected for funding in 2003. Our research will evaluate the usefulness of GEM material in the northern Corn Belt. We have defined ‘EarlyGEM’ as the long-term and continuous effort to incorporate GEM elite germplasm into the northern Corn Belt (Carena, 2002).

Recent Activities Related to GEM Project:

The maize-breeding program at North Dakota State University has screened 152 GEM (A, B, and C) released lines for fifteen adaptation traits in 2001. The most adapted (based on agronomic data in Fargo, ND) and top yielding genotypes (based on GEM data accumulated during 1999, 2000, and 2001) were selected and crossed to North Dakota inbred lines ND2000 (released in 2002) and ND99-16 (unreleased) in 2002. Stiff Stalk donors (CUBA117:S1520-388-1-B or GEM3 in our designation, CHIS775:S1911b-B-B or GEM13, CUBA117:S15-372-1 or GEM12, and AR16026:S17-66-1-B or GEM21) were identified for backcrossing. B73 was included as check in backcrosses to elite early lines. Sixty-two rows were planted in 2003 breeding nursery in order to produce BC1 populations. F1s were planted side by side with the recurrent parent (early line). Adaptation traits have been considered within F1 rows. We have discarded later-flowering plants and harvested each BC1 plant from each cross separately. ND99-16 crosses were discarded since their F1s were at least 5 days later than F1s involving ND2000. Other F1s were discarded based on agronomic deficiencies (poor stands, low seedling vigor under cold stress, drought stress, lodging, insect and disease susceptibility, height, and relative maturity). GEM3 x ND2000 has shown good adaptation, provided relatively tall plants, had few plants with root lodging, and flowered 65 days after planting (typical under ND conditions). GEM13 x ND2000 showed good adaptation based upon its height and flowering time (67 days after planting). However, F1 plants were not uniform and seedling vigor was below average. GEM12 was discarded based on poor agronomic traits in the hybrids. GEM21 flowered 65 days after planting and showed few plants with stalk lodging. B73 x ND2000 hybrids (made of lines expected to fit within the same heterotic group) flowered 65 days after planting and has shown very good adaptation.

Plans for 2004-06:

Sixty seeds from each BC1 will be planted in 23-foot rows in 2004. No BC2 populations will be produced. We will self-pollinate intermediate and earliest plants. Rows will be checked for uniformity and plants with below average agronomic characteristics will be discarded. At least 100 BC1:S1 lines will be crossed to a popular commercial sister-line tester. Testcrosses will be evaluated for grain yield, grain moisture, root lodging, stalk lodging, test weight, and days to flowering at 6 ND environments.

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Development of Inbreds, Hybrids, and Enhanced GEM Breeding Populations with Superior Silage Yield and Nutritional Value

James G. Coors, Dustin T. Eilert, Patrick J. Flannery

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. 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.

As in the past, in 2003 we continued to evaluate silage yield and nutritive value of the most productive GEM topcrosses identified in grain yield evaluations conducted over the past several years by the GEM project. 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.

In 2003, we launched a new breeding effort for GEM breeding populations CUBA164:S1517, CUBA164:S15, and CUBA117:S1520. Superior inbred families identified in the topcross evaluation of these materials will be recombined to reconstitute an improved breeding population (tentatively designated the GEM Quality Synthetic, GQS). The superior families will also be further inbred and crossed to several non-Stiff Stalk tester inbreds to identify inbreds suitable for release. We will continue breeding with the GQS synthetic using the same S2-topcross system used for the Wisconsin Quality Synthetic (WQS). WQS has undergone two cycles of S2-topcross selection using B73-related tester inbreds. Since GQS will be approximately 75% Stiff Stalk Synthetic, inbreds from the two sources may well produce silage hybrids with high forage yield as well as superior nutritional quality.

Recent Activities:  Based on results obtained in 2002 (see 2002 GEM public summary reports), two GEM trials, GEM A and GEM B, were conducted in 2003, and all data has been analyzed and summarized herein. We also evaluated the S2+ topcrosses from Cuba breeding populations, and forage yield data is available for review. Forage quality analyses for the Cuba breeding populations will be completed in December.

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 (<120RM) for Wisconsin. There were 36 entries in GEM A involving breeding populations or early-generation GEM inbreds topcrossed to HC33, LH185, LH198, LH247, and LH283. The GEM B trial consisted of 13 GEM inbreds topcrossed to HC33. 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. The CUBA trial included a total of 169 topcrosses to LH279. The source populations were  CUBA164:S1517 (114 S2 topcrosses), CUBA164:S15 (15 S5 topcrosses), and Cuba117:S1520 (40 S4 topcrosses).

All three trials were planted at two WI locations, Madison (May 16) and Arlington (June 2), with three replications at each location for GEMA and CUBA, and two replications at each location for GEMB. The average planting densities were 32,500 plants/acre (GEMA, GEMB) and 32,700 31,600 plants/acre (CUBA) at Madison, and 31,600 plants/acre (GEMA, GEMB) and 32,700 plants/acre (CUBA) at Arlington. Early season moisture was more than adequate. Excessive rainfall caused a delay in planting the Arlington location. Dry conditions during pollination and several weeks thereafter reduced yield potential at Madison, but the trial was in good shape by harvest (September 12 for GEMA and GEMB, and September 10 for CUBA). The Arlington trial was damaged slightly by drought and also experienced some root lodging. A killing frost occurred prior to harvest (October 5-6 for GEMA and GEMB, and October 9 for CUBA). The combination of drought stress at Madison and killing frost at Arlington led to high average dry matter at harvest (40-42% for GEMA and GEMB, 45-47% for CUBA).

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 were 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  Two topcrosses had predicted milk yields greater than 34,000 lbs/acre milk/acre (Table 1). Most of this potential was due to high forage yield, e.g., DK212T:N11a12-122-1 X HC33. However, one topcross, BR52051:N04-76-1 X LH198, also had excellent quality (low NDF, high IVD, high NDFD, and high milk/ton). Several of the entries in the GEMA trial were also evaluated in 2002 (see 2002 GEM public summary reports). Inbred bulks from BR52051:N04-76-1 and related lines were planted in the 2003 nursery for further selfing and topcrossing.

GEM B highlights  One topcross, AR17026:N1019-65008-2-3-2-1 X HC33, in the GEM B trial had high silage production potential based on milk/acre (Table 2). This topcross had high forage yield and average milk/ton. The low NDF value indicates that this topcross may have excellent intake potential. This topcross was also entered in the UW corn performance trials conducted by the UW Corn Extension program. In the southern zone (Arlington, Lancaster) late-maturity trial, AR17026:N1019-65008-2-3-2-1 X HC33 was statistically equivalent to the best hybrid in the trial for forage yield and milk/acre. This topcross is designated “JC11” in the report, which can be accessed via We will consider formal release of AR17026:N1019-65008-2-3-2-1 in the near future.

CUBA highlights  We have completed yield evaluations of 169 S2 topcrosses in the CUBA trial. Ninety-five topcrosses were selected for nutritional evaluation based on yield potential and root lodging. The entries listed in Table 3 represent the 20 highest-yielding topcrosses with root lodging scores < 4.0. Nutritional quality evaluations will be completed during December, 2003. For each topcross in the CUBA trial, S4+ inbreds are available for further inbreeding and crossing with inbreds from the WQS population next summer.

Nursery activities  In our inbred breeding nursery in 2003, S5+ families were derived from breeding crosses UR13085:N0204, AR17026:N1019, SCRO1:N1310-398-1-B, CUBA164:S15-184-1-B, CUBA164:S1517, CUBA117:S1520-156-1-B. S4 families were derived from several new sets of GEM inbred bulks from breeding crosses BR52051:N04, CHIS775:S1911b, CUBA164:S1517, CUBA164:S2012, and DKB844:S1601.

Approximately 85 inbreds from UR13085:N0204, AR17026:N1019, SCRO1:N1310-398-1-B, CHIS775:N1912-321-1-B-B, CHO5015:N15-8-1-B-B, and DKXL370:N11a20 were crossed with at least two inbred testers depending on maturity (HC33, LH198, LH227, and LH244). These topcrosses will be evaluated for silage potential in 2004.

For additional information, all activities of the UW silage breeding program, including nurseries and yield trials, are available through our web site (


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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


Identify GEM breeding crosses and lines with desirable agronomic characteristics, resistance to abiotic and biotic stresses, and high, consistent yield performance.

Materials and Methods:

One hundred seventy GEM breeding crosses were evaluated for adaptability, maturity, flowering synchrony, standability, plant and ear height, pest resistance, stay green, grain quality and drydown. Inbreeding was also initiated on ten new Stiff Stalk and five non-Stiff Stalk GEM breeding crosses. Three hundred twenty plants per population were selfed. S1 ears were harvested from selected plants based on stalk and root strength, plant height, ear placement, maturity, grain drydown, grain quality, and disease and European corn borer (ECB) resistance. Five hundred sixty-four S1 families, derived from fifteen Stiff Stalk and six non-Stiff Stalk GEM breeding crosses, were self-pollinated. S2 ears were harvested from selected S1 families based on agronomic, disease and insect evaluations. Yield tests were conducted on 152 Stiff Stalk and 189 non-Stiff Stalk lines crossed to LH185 and a Pioneer Stiff Stalk line, respectively, at two irrigated and one dryland locations in Delaware (two reps/location) and one location (one rep) at Ames, Iowa. The lines were also advanced and evaluated per se for agronomic performance.


The GEM breeding crosses recommended for line development are listed in Table 1. Two hundred forty-six S2 ears were selected from 164 of the 366 Stiff Stalk S1 families evaluated, and 131 S2 ears were selected from 88 of the 198 non-Stiff Stalk S1 families (Table 2). A higher percentage of selections were made from the following breeding crosses: CML325:S18, CUBA164:S2012, CUBA164:S2008a, DK212T:S0620, UR13061:S2221, UR13088:S0619, AR03056:N1625, DK212T:N11a10 and DK888:N11a18b.

Based on per se evaluations for plant height, ear placement, stalk and root strength, maturity, disease and ECB resistance, selections were made in 9 of the 10 new Stiff Stalk and 5 of the non-Stiff Stalk breeding crosses (Table 3). We were not able to pollinate the CML287:S18 breeding cross due to its extreme plant height and late flowering. Four hundred ninety-eight Stiff Stalk and 188 non-Stiff Stalk S1 ears were selected based on grain quality, grain texture, ear size, maturity, insect and disease resistance, and other agronomic traits. 

Yield test results are listed in Tables 4 - 11. Yield data are limited due to loss of two locations in Delaware from damage by Hurricane Isabel. The top 25-35% of S3 lines will be advanced. S2 and S3 lines from selected populations will be testcrossed in 2003-4 winter isolation blocks, and hybrid evaluations will be conducted Summer 2004. 

Acknowledgements: We thank the USDA-GEM Project at Iowa State for collaboration in conducting yield trials and Holden Foundation Seeds, Inc. and Pioneer Hi-Bred Int. Inc. for making testcross.

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A Report on: Identifying Resistance to Infection by Aspergillus flavus and Fusarium in GEM Breeding Crosses and Advanced Breeding Lines

Manjit S. Kang

Department of Agronomy and Environmental Management

Louisiana State University Agricultural Center

The GEM crosses (30) and advanced breeding lines (41) supplied by Dr. Michael Blanco, GEM Coordinator, were planted on 23 April 2003 at Ben Hur Plant Science Farm near Baton Rouge. The experimental design was a randomized complete block with two replications. Each two-row plot was 20 ft long with 40-inch row spacing. Ears of six randomly chosen plants were inoculated as follows:  Thirty days after mid-silk, the first row of each plot was inoculated with conidial suspension of Aspergillus flavus  and the second row was inoculated with Fusarium verticillioides. In late August, A. flavus-  and F. verticillioides-inoculated ears were harvested separately. Ears were shelled and seed has been stored in a freezer. Inoculated kernel samples will be analyzed for percent kernel infection. We expect analyses to be completed by the end of March 2004. Five samples with highest and five samples with lowest kernel infections will be assayed for aflatoxin and fuminosin concentrations.

We hope to be able to repeat the experiments in 2004.

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Optimization of Protein and Oil Value-Added Traits and Their Combination with Elite Ames and Southern Gem Lines

Rich Pratt

Ohio Agricultural Research and Development Center

The Ohio State University, Wooster, OH

BACKGROUND:  This is a new project.  High protein and high oil GEM lines, and their sister lines or other closely related lines with desirable agronomic performance, were identified by examination of existing data sets.  In total, 1 Set C; 7 Set E; 1 Set F; 6 Set G and 28 lines from the southern GEM (NC State) were selected.  Three lines displayed both high grain quality and high agronomic performance in previous tests.  

OBJECTIVE: The objective will be to verify the reported phenotypes of the selected lines and then to initiate selection within lines, and within newly generated populations for 1) a favorable balance of agronomic and grain quality traits and 2) extreme trait expression per se. 

APPROACH: All lines were planted in the field at two locations near Wooster, Ohio in replicate tests.  A split-application of nitrogen fertilizer was made to ensure adequate supply of N late in the season.  Controlled pollinations were made in the experimental plots.  High-trait lines were self-pollinated and crossed to other high-trait lines, and also to closely related GEM lines with superior agronomic performance.  Notes were made concerning agronomic traits and disease reactions.

PRELIMINARY OBSERVATIONS: It was possible to obtain selfed ears in approximately 90% of the rows despite the fact many are late maturing and the season in Wooster was cool and wet.  Water-logged soil conditions were experienced at one location.  

DK888N11 materials displayed the following range of responses to natural infection by foliar pathogens:  GLS 0% to 5% PLAA; Stewarts Wilt 2% to 15% PLAA; Rust 0% to 15% PLAA; most rows did not show NCLB lesions.  The range of values for agronomic traits were as follows: plant height 1.25m to 2.25m; ear height .5m to 1.25m. In addition, 16 out of 31 rows displayed no lodging -  others ranged from 1 to 7 plants in the row lodged.   Most lines were not prolific   Six lines were more than 50% prolific.  XL380N11 and PE1N16 materials were similar to the DK888N11 lines with the noticeable difference that they were highly prolific.

A subset of these lines had been obtained for preliminary observation in 2002 and testcrosses were made with the following testers: B73, Mo17, GEMS:0002, (B102/B106), and (B91/B99).  The testcrosses were evaluated at one location in Wooster with two replications.  The plot was harvested on 11/21/03.  Overall means for each tester are presented below in table 1.

The highest yielding individual entry was B73 x DK888N11 F2S2  01RH700055 at 8.26Mg/ha with 34.3% moisture and 43% lodging. Stalk lodging was extremely high in the plot.  The mean value for the checks was 57% and for the experimental entries it was 78% with a range from 14% to 96%. 

ADDITIONAL WORK:  A population of one thousand GOQUEEN:N1612 plants was established.  Self pollinations have been performed on agronomically desirable plants to produce S1 progenies.  Progenies will be shared with Cornell for evaluation of anthracnose resistance.

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2003 Annual Report: United States Germplasm Enhancement of Maize Project

Margaret Smith

Department of Plant Breeding, Cornell University

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


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) Evaluate S5 and S6 lines derived from GEM populations and their testcross progeny for anthracnose stalk rot resistance in replicated plots.

2) Evaluate the testcross progeny (crossed to both public and Holden’s testers) for yield potential and agronomic quality in replicated yield trials at three New York locations.

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, S5 and S6 progenies were planted out ear-to-row for sib increase and testcrossing.  Twenty-seven lines and testcrosses of each to two testers (one public line cross and one Holden’s tester) were planted in two replications at Aurora NY in summer 2003 for stalk rot evaluation as described above.  Most of these testcrosses also had sufficient seed for yield evaluation at three New York locations.  Final yield plots have just been harvested and final stalk rot ratings are still being taken, so data analysis and interpretation from the 2003 season is yet to be done.

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.  Our funding during 2002 was minimal and focused only on generating testcross seed, so data from 2002 is limited.  Despite the funding constraints, we went ahead and evaluated a few of the more promising selections for stalk rot resistance and yield tested some of the best combinations from our 2001 yield tests.  Data from these evaluations is presented below.  In evaluating this data, it should be recognized that these represent only a very limited number of the selections being carried forward in this project. 

Table 1 shows means for anthracnose stalk rot ratings for several promising S5 families compared to standard checks.  The mean for the first internode (the injected internode) is presented separately from the mean of internodes two through eight, reflecting our interest in identifying plants that were clearly exposed to the pathogen (e.g., not escapes and thus showing relatively high disease in the injected internode) but in which spread up the stalk was minimal (e.g., low disease in internodes two through eight).  Two of these inbreds (FS8B(T):1802 15-255 and GOQUEEN:N1603 15-276) appear as resistant or more resistant than DE811ASR, and the latter is equivalent to our best breeding material (RD02LB1-2, which has not yet been released).  All have resistance better than NYLB31B.

Yield data was collected in 2002 on just a few crosses that had performed well in our 2001 tests.  Means for these two years are presented in Table 2.  Although the GEM testcrosses generally are not as high yielding and lodging resistant as the commercial checks, they are being evaluated on an older tester with poor standability (B73/CD1) precisely to highlight any differences in these traits arising from the new GEM lines.  Given the agronomic quality of the tester, some of the new GEM lines indeed look very promising. 

These lines along with many others are being tested currently on both the public line cross testers originally used in this work and on Holden’s testers, which should give us a more complete idea of their yield potential and agronomics. 

Data from 2003 for stalk rot evaluations and yield trials is still being collected and thus not available for inclusion in this report. 

Publications and Presentations:

“Rootworm Resistant Corn and Other New Pest Resistances in Field Crops”, presentation that included description of our GEM project research, given at four Annual Field Crop Dealer Meetings in New York, 21-24 October 2003. (Total audience about 300 people.)

Summary of Accomplishments:

The major accomplishment for this project to date is the development of advanced breeding lines (nearly finished inbreds) that are showing strong 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 better fraction of these resistant selections in terms of yield, maturity, and standability.

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Breeding Maize Lines with Exotic Germplasm

Dennis West

Plant Sciences Department

University of Tennessee, Knoxville

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

Justification:   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.  Diversification of the U.S. maize germplasm base may contribute decreased vulnerability to bio-terrorism.


 1)   Outstanding new lines from GEM accessions were identified from yield trials in 2003.
 2)      Crosses between GEM accessions and adapted germplasm were advanced by self-pollination and selection in 404 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.

Results:  In 2003, 859 experimental GEM hybrids were evaluated in 18 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 W31 yielded 40 bu/a more than the average of 6 check hybrids.  The best lines from these GEM accessions will be selected for further testing and incorporation into breeding for new value-added parental lines.  Inbreeding and selection was continued in populations resulting from crosses between GEM lines identified in previous trials.

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Molecular Breeding for Corn Rootworm Resistance in Maize

David Willmot and Bruce Hibbard

USDA-ARS, University of Missouri-Columbia


Corn rootworm (CRW) (Diabrotica spp.) damage and chemical control costs exceed $1 billion annually.  Environmental and health effects from the highly toxic and widely employed soil insecticides add to the cost.  Native plant resistance is needed to complement transgenic approaches to combating this highly mutable pest.  Moreover, marginal progress in past decades points to the need for exotic sources of resistance and molecular tools to dissect and deploy their mechanisms of resistance. 


To recombine favorable alleles for CRW resistance and agronomics into elite populations useful for:

(i)                 derivation of CRW resistant lines and
(ii)               quantitative trait loci (QTL) mapping studies.

Methods and Materials:

Results from previous replicated and multi-year CRW screening of GEM populations and accessions by our group from 1994 to the present and by Dr. Jon Tollefson at Iowa State University have been summarized.  Pedigrees were chosen that tested resistant repeatedly.  High yielding lines from those pedigrees were used to create synthetic populations.  Half sib families were screened for reaction to CRW in 2003 by artificial infestation with two replicates at each of two locations.  Plants were rated for pruning damage on a 0 to 3 scale ( and for relative root mass size.  Families were random mated within their pedigree. 


Rootworm screening and data summary was completed just before flowering.  Only families with damage below 0.4 nodes of roots were random mated.  Genetic gain was thereby increased.   Four pedigrees were selected for accelerated development including two Stiff Stalk and two non-Stiff Stalk pedigrees.  Based on the means of the half sib families, the selected pedigrees are more even resistant than anticipated compared to the check lines and hybrid. 

We plan to self pollinate these in the winter nursery and screen S1 lines next summer and random mate those with damage ratings below about 0.25 nodes of roots pruned.  We will narrow down to one Stiff Stalk and one non-Stiff Stalk pedigree to accelerate through cycle 3 and begin line selection for QTL mapping. 

In 2003, we completed an initial molecular marker study by selective genotyping of the most susceptible and resistant lines from two non-GEM populations that we developed.  Allelic frequencies of marker alleles contrasted significantly for 10 or 11 loci for each population.  Two of three insect resistance loci mapped by others co-segregated accordingly with our materials.  This study indicated that this complex trait can be dissected with molecular markers. 

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Drought Tolerance, Corn Earworm Resistance, Grain Mold and Yield Performance of the Breeding Crosses and Top Crosses from GEM Germplasm

Wenwei Xu

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


(1) To conduct a second year field evaluation of 71 GEM breeding crosses for drought tolerance, grain mold resistance, and CEW resistance; (2) to conduct second-year yield trials of the topcrosses of the inbred lines derived from GEM germplasm; (3) to continue inbred line development from selected GEM breeding crosses; and (4) to make topcrosses of the GEM inbred lines and advanced lines for 2004 trials.

Materials and Methods:

Objective 1: Seventy-one GEM breeding crosses and three checks (B73 x Mo17, Pioneer hybrids 34K77 and 3223) were grown under three water treatments in Lubbock in 2003.  Of the 71 crosses, 44 had 25% tropical background while 27 had 50% tropical background.  Seeds were planted on April 17.  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, and each received a total of 16.0, 12.3, and 8.0 acre-inch irrigation water during the season.  Total precipitation from planting to August 20 was 8.0 inches.  In Stress 1, limited irrigation was applied throughout the season.  In Stress 2, irrigation was withheld from June 24 to July 25 to create a severe drought stress around the flowering time.  In both Stresses 1 and 2, soil drought stress occurred when most genotypes were at tasseling stage.  Ten days after flowering, drought stress became severer.  Plants in Stress 2 experienced more severe drought stress than those in Stress 1.

Objective 2: Thirty-two top crosses of the inbred lines developed from GEM breeding crosses were evaluated in well-irrigated and limited-irrigation conditions in Texas.

Objective 3: Inbred lines from AR03056:N0902, AR01150:N0406, SCROGP3:N2017, SCROPG3:N1411a, FS8A(T):N1801, and other GEM breeding crosses were advanced and evaluated for drought and heat tolerance, corn earworm resistance, and other agronomic characters in three locations.

Objective 4: Top crosses were made between GEM inbred lines with Holden’s lines (LH185, LH198, LH200, LH247, and LH283) and public lines for 2004 field trial

Results and Discussion

CEW resistance, grain mold, and yield of GEM breeding crosses under well irrigation in 2002 and 2003: The CEW penetration, an indicator of CEW resistance and measured by larval penetration from ear tip toward the ear base over ten ears per replication, ranged from 4.4 to 10.4 cm with a mean of 6.8 cm. In 2003, the CEW pressure was moderate and lower than in 2002.  Over two years, DK888:N11a, DKXL380:N11a, BR51501:N11a, ANTIGO1:N16, CUBA84:D27, CML329:N18, SCROGP3:N411a, DK212T:N11a, BG07040:D27, and ANTIGO03:N12 had the lowest CEW penetration, while CH04030:N0306, GOQUEEN:N16, AR01150:N0406, AR17026:N1013, and SCRO1:N110 had the highest CEW damage.

The average percentage of molded kernels (mold) was 4.8% ranging from 2.7% to 8.8%. The molds in GOQUEEN:N16 were significantly higher than the average. Molds were highly correlated with CEW penetration (r = 0.70**). None of the 74 entries had molds significantly below the test mean.

The average yield was 110 bu/a ranging from 45.8 (CHIS462:N08a) to 168.5 bu/a (P3223).  Three check hybrids P3223, P34K77, and B73xMo17 were ranked as 1, 3, and 60 respectively. Top 10 yielding GEM breeding crosses were ANTIG03:N12, UR11002:N0308b, ANTIGO03:N1216, AR16026:N12, PRICGP:N1218, ANTIG01:N16, SCRO1:N13, CHIS775:N1920, AR03056:N0902, and CH05015:N1204.  Their yields were 132 to 148 bu/a.

Yield and stay green of GEM breeding crosses under Drought Stress 1 in 2003: The average yield was 41.6 bu/a ranging from 4.1 (CHIS462:N08a) to 112.3 bu/a (P3223).  Top 10 yielding breeding crosses include AR16026:N12, CML329:N18, AR03056:N0902, AR17056:N13, GUAD05:N06, BR51675:N0620, CHIS775:1920, BARBGP2:N08a18, ANTIGO03:12, and UR13085:N0215.  Their yield ranged from 83 to 59 bu/a.  The average stay green rating on August 12 was 3.0 with a range from 2.0 (PRICGP3:N12) to 4.0 (B73 x Mo17).  Most of the top yielding crosses had the stay green ratings below the test average.  The crosses with best stay green ratings did not yield well.

Yield and stay green of GEM breeding crosses under Drought Stress 2 in 2003: The average yield was 22 bu/a ranging from 3 (CUBA84:D27) to 47 bu/a (P3223).  A high percentage of plants were barren and died early.  Seed setting was poor.  The average number of ears per plant was 0.5.  The average stay green ratings on August 1 and 12 were 3.4 and 3.8.  Crosses with good yield and stay green ratings include ANTIGO03:N12, AR16026:N12, BARBGP2:N08a18, SCROP3:N1411a, UR11002:N0308b and UR13010:N06.

Yield performance of the top crosses from GEM inbred lines: The relative maturity of 32 top crosses ranged from 107 to 117 days.  Eleven top crosses produced 100% to 114% of the average yield (164 bu/a) of the four commercial checks under well-irrigated and limited-irrigation at Etter, Halfway, and Lubbock, TX.  Three top crosses  (AR01150:N0406)F8A2 x B110, (AR01150:N0406)F8A1 x B110, and (FS8A(T):N1801)F7-2 x B110 had an average yield of 187, 181, and 186 bu/a, which was 13-14% higher than the check average. They also had tall plants suitable for silage (Table 1). The hybrids made with (AR01150:N0406)F8A1, (AR01150:N0406)F8A2, (FS8A(T):N1801)F7-2, and SCROGP3:N1411a also performed well in 2002.  These lines are now uniform and have been characterized for their maturity, drought and heat tolerance, insect resistance, and other agronomic traits under different environments in 2002 and 2003.  Release proposals will be submitted to the Texas Agricultural Experiment Station by the end of 2003.


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