Germplasm Enhancement of Maize

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Javier Betrán
Mark Campbell
James Coors
Larry Darrah
Jim Hawk
Bruce Hibbard
Robert Lambert
Richard Pratt
Ken Russell
Margaret Smith
Paul Williams
Dennis West
Wenwei Xu

GEM - 2001 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.

 

Development of food-grade corn germplasm with superior grain quality and adaptation

Javier Betrán

Texas A&M University

General Objective:

To develop food-grade corn maize inbreds with superior grain quality and adaptation to the Southern USA .

Specific Objectives:

1.     To advance and select lines from GEM breeding crosses (50% temperate:50% exotic) that have demonstrated potential in testcross and per se performance evaluations in Texas.

2.     To evaluate testcross yield potential and adaptation of advanced GEM lines in Texas.

Activities and results during 2001:

We have conducted breeding and evaluation activities with two groups of GEM derived inbreds:

(1)  Lines derived from GEM breeding crosses in Texas: A total of 9 GEM 50% temperate:50% exotic breeding populations (CUBA173:S04, AR16021:S09, DKB830:S19, AR16021:S08a02, AR16026:S1704, AR16026:N1209, AR13026:N08c09, DREP150:N2011D, AR17026:N1019) were selected based on agronomic performance and adaptation in trial evaluations during 1998 (100 original initial GEM crosses at 5 locations) and 1999 (reevaluation of the best 19 crosses during 1998 at 3 locations), and on grain quality traits. Based on testcross performance and line per se evaluations during the last three years approximately 20 advanced lines from breeding crosses AR16021:S09, DKB830:S19, AR16021:S08a02, AR16026:S1704, AR16026:N1209 and AR17026:N1019 have been further selected  in our nursery at College Station Texas during 2001. We are currently making testcrosses of these lines in our winter nursery at Weslaco, TX that will be evaluated during year 2002 across Texas locations.

(2)  Advanced Inbreds derived from public S2 GEM-derived lines: Bulks of early generation GEM lines selected based on the results from 1998 testcross evaluations were provided by Dr. Major Goodman (NCSU) in 1999. Bulks of these lines derived from DK212T:S11, DKXL380:S11, TUXPENO CHIS775 N19, DK212T N11, DKXL370A N11, DKXL380 N11, and PE1 N16, DK888 N11 have been advanced and selected in our nurseries during the 1999 to 2001 seasons. Lines per se and their testcrosses have been evaluated during years 2000 and 2001. The results for the 2001 testcross evaluations at College Station and Weslaco, TX are presented in Table 1. The most promising inbreds for our conditions have been developed from GEM crosses DK212T N11 and DKXL380 N11.

Future Activities:

Advanced lines developed from selected breeding crosses will be characterized further for overall adaptation, agronomic performance and grain attributes at different environments of Texas including subtropical and temperate locations, Aspergillus flavus artificial inoculation and different water regimes (well-watered conditions vs. drought stress, rainfed vs. irrigated).

Justification of our work:

The profitability of corn growers in the Sourthern Plains is decreasing as a consequence of low levels of corn production due to drought conditions, low commodity prices, and aflatoxin contamination. Aflatoxin limits corn marketability and causes enormous health and economic losses. Aflatoxin in 1998 resulted in $85 to $100 million in losses to corn producers in Texas, Louisiana and Mississippi. Development of food-grade corn germplasm with superior grain quality and adaptation to Texas growing conditions will help to increase farmers corn industry to compete in external markets. New sources of stress resistance and value added traits could be found in GEM germplasm. Harder kernels and improved nutritional value would enhance the USA grain quality for export. The development of stress tolerant germplasm will increase yields and facilitate sustainable production strategies that preserve the environment and reduce the effects of environmental stresses.

Progress and significant accomplishments:

We have develop advanced inbreds lines from 50% exotic GEM breeding crosses which were selected based on agronomic performance, grain quality and adaptation in trial and nursery evaluations during years1998 to 2001. In general, GEM testcrosses appear to perform better in transitional areas between subtropical and temperate environments. In addition to our breeding activities we have contribute to evaluate GEM hybrids in Texas during these years.

We have characterized GEM germplasm for adaptation to the Southern Plains and identified breeding materials to incorporate in breeding programs to develop food corn. We have advanced and selected GEM derived lines considering grain quality attributes, less susceptibility to biotic stresses (e.g. aflatoxin) and tolerance to abiotic stresses (e.g. drought and high temperatures).

The initial phase of the development of early generation lines has been completed. We are now in the phase of characterizing more extensively the advanced lines for additional selection before release.

List of publications and presentations:

  • L.L.Darrah, D.R. West, R.L. Lundquist, B.E. Hibbard, A. Schaafsma, E.A. Lee, S. Mbuvi, C.G. Poneleit, F.J. Betran, W. Xu, J.K. Pataky, L.D. Maddux, B. Gordon, R.W. Elmore, D. Stenburg, Z. W. Wicks III, P. Beauzay, P. Thomison, D.M. Jordan, K.E. Ziegler, R. Henry, J.A. Deutsch, J.F. Strissel, and D.B. Fischer. White food corn 2000 performance tests. Special Report 535. ARS-USDA.

  • J.M. Ribaut, F.J. Betran, K. Dreher, K. Pixley, and David Hoisington. 2001. Marker-assisted selection in maize: strategies, examples and costs. In Plant & Animal Genome IX abstracts, San Diego, CA.
  • F.J. Betrán, Tom Isakeit, Gary Odvody. 2001. Aflatoxin resistance of maize germplasm in Texas A&M University. In 55th Annual Meeting of the Rio Grande Valley Horticulture Society, Weslaco, TX. January 23, 2001.
  • F.J. Betrán, Tom Isakeit, Gary Odvody. 2000. Aflatoxin resistance of maize germplasm in Texas. In Agronomy Abstracts. Minneapolis, MN.
  • M. Willcox, G. Davis, G. Windham, Paul Williams, Hamed Abbas, and F.J. Betran. 2000. Confirmation of QTL regions for aflatoxin resistance by evaluating tails of the Va35 x Mp313E mapping population in multiple environments. p 120 in proceedings of the Aflatoxin/Fumonisin Workshop 2000, October 25-27, 2000, Yosemite, CA .
  • P. Williams, G. Windham, M. Willcox, H. Abbas, F.J. Betran, D. White, S. Moore, R. Mascagni, K. Damann and N. Widstrom. 2000. Multilocation evaluation of single cross maize hybrids for aflatoxin contamination. p 158 in proceedings of the Aflatoxin/Fumonisin Workshop 2000, October 25-27, 2000, Yosemite, CA.
  • F.J. Betrán, L. Rooney, F. Fojt, D. Pietsch, L. Synatschk. 2000. Quality Protein Maize development in Texas. In Agronomy Abstracts. Minneapolis, MN.
  • S. Bhatnagar, F.J. Betrán, D. Transue, H. Cordova, G. Srinivasan. 2000. Evaluation of QPM subtropical/tropical hybrids in Texas. In Agronomy Abstracts. Minneapolis, MN.
  • F.J. Betrán, Tom Isakeit, Gary Odvody. 2000. Maize resistance to aflatoxin in Texas. p 150 in proceedings of the Aflatoxin/Fumonisin Workshop 2000, October 25-27, 2000, Yosemite, CA.
  • Pietsch D., L., Synatschk, L. Betran, F.J., Fojt III, F. 2000. 2000 Corn Performance Tests in Texas. Technical Report No. 2001-01. Tx.. Agr. Exp. Sta. College Station, Texas, 71pp.

  • Pietsch D., Rooney, L.W., Riley, E., Synatschk, L. Betran, F.J., Fojt III, F. 2000. 2000 Texas food corn performance tests. Technical Report No. 2001-03. Tx.. Agr. Exp. Sta. College Station, Texas, 27pp.

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Selection for maize inbreds with high-amylose starch using GEM germplasm

    Mark Campbell, Nyambura Nedegwa and Allison Carr

Truman State University

General objective: To identify modifying genes from GEM accessions that, together with the recessive amylose extender (ae) mutation, increase starch amylose content to 70% (amylomaize VII) or greater.

Specific Objectives:

1.  To continue selfing of materials derived from crosses between GEM accessions and the hybrid OH43 ae x H99 ae towards the development of inbred lines.

2.  To continue selection based on amylose levels of the starch determined in the laboratory using a standard starch iodine assay for development of amylomaize VII-types inbred lines.

Justification of the importance of the work

High amylose corn is grown because of its unique starch characteristics. Approximately 30,000-40,000 acres of high amylose corn is grown annually, mostly in east central Illinois and central Indiana. High amylose corn yields only about 60-80% of normal hybrids so all production is grown under contract and brings a premium price. Amylose corn is grown exclusively for wet milling to produce a starch that crystallizes quickly. The starch from high amylose corn is used in textiles, gum candies, biodegradable packaging materials and, adhesives for manufacturing corrugated cardboard. In addition, there is interest in high-amylose starch as a “nutraceutical” in order to increase dietary fiber and lower the glycemic index foods.

Breeding and research has been limited to a small number of private companies. Therefore, there are essentially no publicly available sources of amylomaize VII germplasm. Some of the disadvantages to this include 1) a general lack of breadth of the germplasm 2)  limited basic research regarding the inheritance and potential genetic variation that may exist and 3) limited access of amylomaize VII material to new processors. This is especially surprising since this material has been in existence for over 50 years and is not protected by any patent

The GEM project has played an integral role in our program. The material not only provides a seemingly unlimited array of genetic variation but is also a freely available source of superior germplasm for public and private breeders in the US. In addition, grant funds for germplasm enhancement using GEM materials has been important since public support for breeding and germplasm enhancement has been eroding in recent years.

Publication/Presentations

Campbell, M.R, H. Yeager, N. Abdubek, L.M. Pollak and, D.V. Glover. 2002. Comparison of Methods for Amylose Screening Among Amylose-Extender (ae) Maize Starches from Exotic Backgrounds. Cereal Chemistry. Accepted for publication.

Nurtay Abdubeck. Comparison of methods for amylose screening among ae maize starches with GEM and other plant introduction background. Annual meeting of the American Association of Cereal Chemistry. Kansas City, Missouri. November 2000.

Materials and Methods 

In 1997, 101 experimental GEM crosses were planted in a summer nursery and used as female plants in crosses with OH43ae x H99ae. The F1 generation was advanced in a winter breeding nursery in Puerto Rico and F2 plants grown in the summer of 1998 from kernels presumed to be homozygous the ae allele. Of these F2 plants Guat209:S13 x (Oh43ae x H99ae) displayed the highest amylose content and therefore was advanced ear to row to the F3 (1999), F4 (2000) and F5 (2001) generations while selecting for overall plant condition (free of folier or stalk diseases and minimal lodging ), ear quality (full ears and lack of kernel rot) and starch amylose content. For each of the generations of inbreeding, two ears from each ear-to-row family were analyzed according to a standard iodine binding method using purified starch. All evaluations were conducted as a single location near Kirksville, MO.  

Results

Many of the F4 families evaluated in 2000 showed relatively high-amylose levels compared to a check entry consisting of B73 ae (Table 1). Although the data summary indicates that lines derived from CUBA110:N1711c x (OH43ae x H99ae) were slightly higher in amylose (63.3%) compared to GUAT209:S13 x (H99ae x OH43ae) (61.0%) the GUAT lines had a large number (n=14) of families that exceeded 70%. In fact the maximum value for the GUAT families (78.6%) far exceeded that the maximum observed for CUBA (66.0%). We are currently conducting amylose testing for F5 materials harvested from the 2001 season and our preliminary results indicate that the high amylose levels are being inherited. A partial summary of these findings will be presented at the ASTA GEM cooperators meeting in Chicago in December 2001. 

In addition, F5 families showing high amylose levels were crossed on many GEM lines obtained from Dr. Linda Pollak (USDA, Ames, IA) having been previously selected for superior agronomic traits including yield. These materials will be advanced in a winter nursery and F2 plant evaluated in the summer of 2002. If the high-amylose phenotypes can be recovered in the F2’s the trait will be backcrossed into the GEM materials.

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Silage evaluation of topcrosses with advanced lines from GEM breeding crosses

James G. Coors

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, and we determined that a smaller, selected subset should be looked at in more detail. As a result of the second round of screening in 1996 we decided to develop S1 families from several advanced breeding populations for evaluation as inbreds. Several of our most promising advanced generation S5+ inbreds in 2001 trace back to this initial trial. 

In 1998, we also started to routinely evaluate elite GEM topcrosses involving high-grain yielding hybrids (< 120RM). These hybrids are chosen annually based on excellent grain yield in GEM evaluations conducted in previous years. We have chosen GEM topcross hybrids with good grain yield potential because many farmers do not decide until fall whether to harvest their corn for silage or grain. We believe that it is not only possible to identify dual-use (grain and silage) hybrids, but that dual-use hybrids are preferable to single-use hybrids because they provide farmers with management options at the time they need them. 

Activities in 2001: The purpose of our GEM research in 2001 was to estimate silage yield and nutritive value of the most productive GEM topcrosses. We conducted two trials involving GEM topcrosses. The first trial (GEMA, Table 1) included 10 topcrosses involving four GEM S3 bulks (three from CUBA164 and one from SCRO1) and one breeding cross (CUBA164:S1517). CUBA164 materials were crossed to LH185 and LH283, and the SCRO1 S3 bulk was crossed to LH198 and LH200. The particular breeding crosses selected for this evaluation had previously been shown to have silage potential based on UW trials conducted in 1999 and 2000.The GEMA also included three population crosses involving the Wisconsin Quality Synthetic (WQS), three testcrosses involving inbred lines derived from WQS (71712-B-1-1-3-1-B, 53090-1-1-6-1-2, 53090-1-1-6-1-9), and nine commercial hybrids.

The second trial (GEMB, Table 2) involved 23 GEM topcrosses and nine experimental and commercial hybrids. The GEM topcrosses involved inbreds derived from CHO5015, CHIS775, DKB844, DKXL212, DKXL370, and UR13085 crossed to LH198. These breeding crosses had previously been shown to have good grain yield potential in trials coordinated by GEM in 2000.

Both trials were evaluated at two WI locations, Madison and Arlington, with three replications at each location. Planting dates were May 2 (Madison) and May 18 (Arlington). The trials were harvested on September 14 (GEMA, Madison), September 18 (GEMB, Madison), October 5 (GEMA, Arlington) and October 8 (GEMB, Arlington). Planting densities averaged 30,702 and 27,745 plants/acre and Madison and Arlington, respectively. Dry conditions prevailed until late July. Several violent rain and windstorms occurred later in the season and caused extensive root lodging. For example, over 8” of rain fell in one 12-hr period at the Madison location in early August and damaged the Madison plots. 

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 new MILK2000 equations (www.wisc.edu/dysci) developed 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.

In GEMA (Table1), GEM topcrosses yielded well for the most part, but forage quality tended to be lower than desired, at least relative to the high-quality checks. As a result, Milk/acre tended to be low to intermediate with the exception of Cuba164:S1517 X LH283, Cuba164:S2008a-280-1-B X LH283, and SCRO1:N1310-398-1-B X LH198. Additional inbreds are being developed from Cuba164:S1517 and SCRO1:N1310-398-1-B in the UW silage breeding nursery.

In GEMB (Table 2), there were a large number of productive topcrosses based on yield. Nine were equivalent to the highest yielding check hybrid, Pioneer brand 33A14. Quality was also excellent, in general, with 18 GEM topcrosses equivalent to Pioneer brand hybrids 33A14 and 35R58. Of particular note were four topcrosses: CH05015:N15-8-1-B X LH198 with excellent NDF, IVD, IVNDFD, and starch; CHIS775:N1912-321-1 X LH198 with excellent yield and high protein; DKXL212:N11a-481-1-1 X LH198 with excellent yield and low NDF; and finally DKXL370:N11a20-97-1 X LH198 with excellent yield, NDF, IVD, IVNDFD, CP, and starch. The relative maturities of these topcrosses are also appropriate for southern Wisconsin .

In our inbred breeding nursery, approximately 60 S5 families were derived from breeding crosses URZM13085:N0204, URZM13085:N0207, ARZM17026:N1013, ARZM17026:N1019, and SCRO1:N1310-398-1-B. Approximately 140 new S2 families were derived from CUBA164:S1517. We also developed approximately 75 S4 families from CUBA164:S15-184-1-B. Our silage nursery and our silage trials are available for review at http://uwsilagebreeding.agronomy.wisc.edu/.

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Evaluation of testcrosses of S3 lines extracted from ARO1150:N04 and selfing of UR13085:S1912 S1 selections in 2001

Larry Darrah

USDA-ARS, Columbia, MO

Objectives:  Evaluate testcrosses of S3 lines extracted from ARO1150:N04, and self 1999 and 2000 selections from testcrosses of UR13085:S1912 S1s.

Background:  Testcrosses of S3 lines extracted from ARO1150:N04 were produced in 2000 for evaluation in 2001. Crosses were attempted to three testers according to grain color: Missouri’s White Synthetic Tester (WST, all lines),  MoSCSSS(R19)C4 (yellow or yellow/white segregating lines), and Mo17 Elite Syn.(R20)C4 (yellow or yellow/white segregating lines).

UR13085:S1912 testcrosses were evaluated in 1999 and 2000 with one successful site each year. Few of the top-yielding entries were in common between years with 1999 having moisture stress and 2000 adequate moisture. Selected entries from each year were planted for selfing to S3 toward line development. A decision on recombination and further recurrent selection has not been made pending results from evaluation of testcrosses (to be made in 2002) of these S3 lines.

Results: No 2000 testcrosses of ARO1150:N04 S3 lines to Mo17 Elite Syn.(R20)C4 produced seed. One of five testcrosses attempted with MoSCSSS(R19)C4 and six of 17 crosses to Missouri’s White Synthetic Tester were likewise unsuccessful. Four testcrosses to MoSCSSS(R19)C4 and 11 to Missouri’s White Synthetic Tester were planted at three locations in 2001. Seed was not sufficient to grow all 15 entries at four locations. The evaluation planted at Novelty in northeast Missouri had significant rainfall immediately after planting and cold temperatures; only an estimated 60% stand resulted and the location was abandoned in its entirety. Yellow and white testcrosses were evaluated in separate experiments and were grouped with other testcrosses with the same endosperm color. Data from three-replication experiments grown at Columbia and Tipton, MO, were analyzed to obtain combined means.

Combined yield and agronomic data from Columbia and Tipton, MO, for ARO1150:N04 S3 line testcrosses grown in 2001. Data for ear height and days to flower were observed only at Columbia. No significant root or stalk lodging occurred in the white endosperm experiments.

 

Nursery activity:

Thirteen lines from ARO1150:N04 were planted for advancing from S4 to S5 in 2001:

  • ARO1150: NO4 S4‑003Y

  • ARO1150: NO4 S4‑046W

  • ARO1150: NO4 S4‑061Y/W

  • ARO1150: NO4 S4‑070W

  • ARO1150: NO4 S4‑081W

  • ARO1150: NO4 S4‑150W

  • ARO1150: NO4 S4‑198Y

  • ARO1150: NO4 S3‑222Y/W

  • ARO1150: NO4 S4‑229W/Smokey

  • ARO1150: NO4 S4‑234W

  • ARO1150: NO4 S4‑260W

  • ARO1150: NO4 S4‑271Y/W

  • ARO1150: NO4 S4‑285W

Ten lines from UR13085:S1912 were planted for selfing from S2 to S3 based on testcrosses to CarPop(E5)C5 grown in 1999 and 2000:

  • UR13085:S1912[CarPop(E5)C5 tester](99)S2‑02

  • UR13085:S1912[CarPop(E5)C5 tester](99)S2‑27

  • UR13085:S1912[CarPop(E5)C5 tester](99)S2‑46

  • UR13085:S1912[CarPop(E5)C5 tester](99)S2‑82

  • UR13085:S1912[CarPop(E5)C5 tester](99)S2‑83

  • UR13085:S1912[CarPop(E5)C5 tester](00)S2‑19

  • UR13085:S1912[CarPop(E5)C5 tester](00)S2‑56

  • UR13085:S1912[CarPop(E5)C5 tester](00)S2‑59

  • UR13085:S1912[CarPop(E5)C5 tester](00)S2‑76

  • UR13085:S1912[CarPop(E5)C5 tester](00)S2‑79

Ten lines from UR13085:S1912 were planted for selfing from S2 to S3 based on testcrosses to Mo17 Syn.(H14)C4 grown in 1999 and 2000:

  • UR13085:S1912[Mo17 Syn.(H14)C4](99)S2‑04  

  • UR13085:S1912[Mo17 Syn.(H14)C4](99)S2‑06  

  • UR13085:S1912[Mo17 Syn.(H14)C4](99)S2‑21  

  • UR13085:S1912[Mo17 Syn.(H14)C4](99)S2‑34  

  • UR13085:S1912[Mo17 Syn.(H14)C4](99)S2‑54  

  • UR13085:S1912[Mo17 Syn.(H14)C4](00)S2‑17  

  • UR13085:S1912[Mo17 Syn.(H14)C4](00)S2‑49  

  • UR13085:S1912[Mo17 Syn.(H14)C4](00)S2‑59  

  • UR13085:S1912[Mo17 Syn.(H14)C4](00)S2‑61  

  • UR13085:S1912[Mo17 Syn.(H14)C4](00)S2‑64

Importance:  We seek to expand the germplasm base of our project and identify new germplasm that crosses well with either our domestic (Stiff Stalk, Lancaster, and white) or exotic (CarPop) germplasm. Of particular interest to us would be a good combiner for CarPop because of its high quality, flint-type grain.

Progress:  Random sets of lines from two GEM populations have been in various testcrosses and selected progeny identified for further development. Our testers have included Mo17 Synthetic(H14)C4, Mo17 Elite Syn.(R20)C4, CarPop(E5)C5, and Missouri’s White Synthetic Tester. The first two are yellow synthetics made up from various commercial versions of Mo17, and the third is a population originating with Everett Gerrish, formerly of Cargill Hybrid Seeds, which has a large component of tropical dent Tuxpeño. The broad-based White Synthetic Tester includes several strains, representing public and private germplasm with white endosperm.

Publications/presentations: None.

Accomplishments: What we have done is considered a “work in progress;” no singular accomplishment is identifiable.

Other: Dr. D. B. Willmot joined the Plant Genetics Research Unit at Columbia, MO, in March of 2001 in an ARS enhancement of maize germplasm effort. Relevant specific objectives include, but are not limited to: I) in cooperation with collaborators throughout the United States, evaluate and characterize maize germplasm accessions in the National Germplasm System, especially those for which there are few data on GRIN and/or MaizeDB, for genes conditioning adaptation, productivity, and host plant resistance to major pathogens and pests of maize; ii) employ up-to-date genetic/genomic technology (e.g., SSRs, SNPs) to detect allelic diversity in Zea and develop genetic markers closely associated with agriculturally important traits to facilitate their incorporation into adapted germplasm; incorporate the preceding characterization and evaluation data in GRIN and/or MaizeDB; and iii) together with cooperators throughout the United States, conduct one component of the GEM Project, which is genetically enhancing public maize germplasm by incorporating alleles from unadapted germplasm for productivity, quality, and resistance to biotic and abiotic stresses.  

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Inbred line development and hybrid evaluation in GEM breeding crosses

James A. Hawk and Tecle Weldekidan

University of Delaware

Objectives: 

  1. To develop inbred lines from DKXL212:N11a and other GEM breeding crosses adapted to the Mid-Atlantic and Corn Belt regions with good per se and testcross performance and resistance to abiotic and biotic factors.

  2. To identify lines from GEM breeding populations that have high levels of grain protein, starch, or oil content.

Materials and Methods:  The top fourteen DKXL212:N11a lines from the 2000 yield and per se performance results were testcrossed to LH198 and a proprietary B73 line. These hybrids including five commercial checks were planted across the Corn Belt with GEM cooperators at 18 locations with 25 reps (Tests 1121A &1121B). Eight lines were inoculated with European corn borer (ECB) at Newark, DE (4 reps) and evaluated for leaf-feeding resistance. We applied 30-50 larvae on five successive days at the mid-whorl stage and the plants were rated using Guthrie’s 1 to 9 scale where 1=no visible leaf injury or a small amount of pin or fine shot-hole type of injury on a few leaves and 9= most of the leaves with long lesions. The lines per se (one rep) and the LH198 testcross (three reps) were also evaluated for gray leaf spot in two-row plots by Erik L. Stromberg at Virginia Polytechnic Institute and State University. The plants were rated on a 0-5 scale where 0= no gray leaf spot lesions and 5= all leaves dry and dead. Twenty-five DKXL212:N11a lines were evaluated at GEM-USDA, Iowa State University for grain quality traits (protein, oil, and starch) using NIR whole grain analysis. 

Twenty-eight GEM breeding crosses with 25% or 50%  exotic germplasm (BR105, BR106, CUBA164, DK212T, DK888, and UR13085 accessions) were each planted in a block of 16 rows (20 feet long). The 28 populations were evaluated prior to flowering and 16 were self-pollinated based on maturity and plant height. Ears were selected based on plant height, ear placement, stalk and root strength, flowering, grain drydown, grain quality, disease, and insect resistance. 

Results:  Based on the testcross yield evaluations, none of the DKXL212:N11a entries out-yielded the check mean for either the LH198 or proprietary B73 testers.

Entries 4, 10, and 12 (DKXL212:N11a-365-1-1-2-1-1, DKXL212:N11a-338-1-1-1, and DKXL212:N11a-139-1-1, respectively) with the LH198 tester did not yield significantly different than the check mean but had significantly higher grain moisture percentage

(Table 1).   Standability was comparable to the check mean.  Entry 4 (DKXL212:N11a-365-1-1-2-1-1) with the proprietary B73 tester also did not yield significantly different  than the check mean, but had a significantly higher grain moisture percentage (Table 2).

Six of the DKXL212:N11a lines rated more resistant to gray leaf spot than Mo17 in an unreplicated per se evaluation (Table 3). Three of the eight lines rated intermediate for ECB leaf-feeding resistance (Table 4) including  DKXL212:N11a-365-1-1-2-1-1-1. Four lines had a relatively high protein percentage (>13%) compared to the mean of 11.7% and nine lines had a relatively high starch percentage (>70%) compared to the mean of 69.24% (Table 5).

Per se evaluations of 28 GEM breeding crosses (Table 6) provided 417 S1 ears from 12 of the 16 self-pollinated populations.  The ears selected from these populations have excellent grain texture, ear size, and other agronomic traits and will be further evaluated in 2002.

Conclusions and Future Outlook:

Based on the yield results of experiments 1121A and 1121B and per se evaluations, inbred lines DKXL212:N11a-365-1-1-2-1-1, DKXL212:N11a-338-1-1-1, and DKXL212:N11a-139-1-1 have potential in breeding programs for improving both agronomic and disease performance. Reducing husk coverage by an additional generation of recycling these lines with elite temperate germplasm could enhance both grain drydown and agronomic performance.  

Presentation/Publication: Weldekidan, T. and J.A. Hawk. 2001. Evaluation and breeding in GEM populations for agronomic performance and adaptation to the Mid-Atlantic and Corn-Belt. Proc. 56th N.E. Corn Improvement Conference (NEC29): 7-11.

Acknowledgements: We thank the following cooperators for their assistance in conducting these trials: USDA-GEM (Iowa State University), Monsanto, Holden Foundation Seeds, Inc., Pioneer Hi-Bred Int., Inc., AgReliant Genetics, Syngenta, Mycogen, and Illinois Foundation seeds, Inc.   

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Evaluation of 25% exotic GEM breeding crosses for and western corn rootworm and European corn borer resistance

 Bruce E. Hibbard, Arnulfo Q. Antonio, and David B. Willmot

USDA-ARS, Columbia, Missouri

More hectares of crop land receive insecticide applications for the three species of Diabrotica corn rootworms than for any other agricultural pest in the United States. Losses and pesticide costs have been estimated at $1 billion each year. Since the emergence of the western corn rootworm, Diabrotica virgifera virgifera LeConte, as a pest 50 years ago, a variety of management tactics have been implemented, but many have failed. Resistance developed to cyclodiene insecticides more than 30 years ago (Ball and Weekman 1962) and more recently to organophosphate and carbamate insecticides (Meinke et al., 1998). The northern corn rootworm, Diabrotica barberi Smith & Lawrance adapted to crop rotation by extending their diapause an additional year (Krysan et al., 1986). Adults of the western corn rootworm have adapted to crop rotation by laying eggs in fields adjacent to corn (Zea mays L.), usually soybean (Glycine max L.), in addition to corn in parts of Illinois and Indiana where crop rotation has been prevalent (Levine and Oloumi-Sadeghi, 1996). These eggs overwinter and hatch in a rotated corn field the following spring.  There are currently no practical alternatives to insecticides where the above biotypes dominate or in continuous corn (Levine and Oloumi-Sadeghi, 1991). These problems, and possible implications of the Food Quality Protection Act of 1996 (Public Law 104-170), make additional strategies to manage these pests highly desirable. Development of alternative control strategies would be valuable environmentally and economically. Transgenic corn with strong resistance to western and northern corn rootworm larval feeding has been tested by several commercial seed companies, but acceptance of transgenic technology by countries that import grain is not assured. This project facilitates the development of native sources of resistance to the corn rootworm larval feeding. Previously, we have evaluated all of the original GEM accessions, all of the 50% exotic GEM breeding crosses, and half of the available 25% exotic GEM breeding crosses for resistance to western corn rootworm European corn borer larval feeding. At each step, those materials with rootworm resistance were evaluated again the following year and incorporated into our breeding program if resistance was also found the second year of evaluation. In 2001, we evaluated the second half of the 25% exotic GEM breeding crosses for both corn rootworm resistance and resistance to first and second generation European corn borer, Ostrinia nubilalis (Hübner), the other major insect pest of corn.

Materials and Methods

 

Corn rootworm trial.  For rootworm evaluations, cultivars were planted in a randomized complete block design with 12 kernels hand-planted in a 5 ft plot, each replicated three times. The Agronomy Research Center, approximately 9.6 km east of Columbia, MO was used for experiments. The field was planted to soybeans (Glycine max L.) the previous year and was treated with conventional herbicide and fertilizer regimes for Missouri growing conditions (atrazine @ 1.3 lb ai/acre and metolachlor @ 0.8 q ai/acre). All plots were mechanically infested with western corn rootworm eggs. Eggs were placed in 0.15% agar suspension and applied at a rate of 900 viable eggs (actual rate was 1,200) per ft of corn row using equipment modified after Sutter and Branson (1980). Eggs used in the experiment were supplied from the USDA-ARS Brookings, SD laboratory.  Plots were planted on April 25, infested on May 10, when seedlings were approximately at the two-leaf stage (Hibbard et al., 1999). On July 3, when maximum damage had occurred (when approximately two-thirds of the western corn rootworm larvae had pupated in infested border rows), plots were dug (Praiswater et al., 1997), and four roots from each plot (the average for which was considered one replication) were removed. Roots were washed and rated on July 3 and 5 using a linear scale (0 to 3) based upon the number of nodes pruned (Oleson, 1999). The data were analyzed with proc GLM in SAS followed by a Fisher’s Least Significant Difference numerical range test. 

 

European corn borer trials. For corn borer evaluations, cultivars were planted in a 7.6 m plot (center to center) with a 1.2 m alley using a Wintersteiger plot planter. Two locations were planted with one replication each for evaluating both leaf feeding resistance and stalk tunneling resistance. The locations were the University of Missouri Hinkson Valley Research Farm in the center of Columbia, Missouri and a private farm site near Tifton, Missouri. The fields were treated with conventional herbicide and fertilizer regimes for Missouri growing conditions (atrazine @ 1.3 lb ai/acre and metolachlor @ 0.8 q ai/acre). First and second generation ECB screening was conducted by infesting ~140 neonate larvae on the first six and last six plants 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 splitting the stalks with a linoleum knife and counting the number of tunnels and estimating the length of tunneling near the end of the growing season.

Results and Discussion

In corn rootworm evaluations, no statistically significant differences were observed with just three replications in one location between the 84 lines evaluated. One line, AR17056:N2025 (inventory number 980003) was only slightly more damaged than the insecticide control (Table 1). A total of 64 of the 84 lines were nominally less damaged than the resistant control used in this study, but the resistant control had more than one node of roots destroyed (it was a poor resistant control in this location this year). A total of 17 lines had a damage rating less than 0.7 and could be considered somewhat resistant. Only four lines were more damaged than the susceptible control. Elite, modern hybrids are somewhat tolerant to corn rootworm larval injury (Riedell and Evenson, 1993) and since 75% of this genes in the lines evaluated in 2001 were elite, some of the resistance found in these materials were likely contributed by the elite parent.

In European corn borer leaf feeding evaluations, all entries but two were less damaged than the susceptible check WF9´W182E. A total of 26 lines were less damaged than the resistant control, Mycogen 7250, for leaf feeding. In European corn borer stalk tunneling evaluations, 42 lines were less damaged than the resistant check Mycogen 7250. Exotic crosses UR13010:N0613, BVIR155:S2012, BR51501:N11a08d, and DK212T:N11a12 were particularly resistant to tunnel feeding by European corn borer larvae with only 1.27, 1.27, 1.52, and 1.78 cm of tunneling. Only six lines were more susceptible to tunnel feeding by European corn borer larvae than the susceptible check, WF9´W182E.

Overall, several lines appear to show promise for resistance to corn rootworm and/or European corn borer larval feeding. Lines with the greatest resistance will be evaluated again and incorporated into our breeding program.

References Cited

  • Ball, H.J. and G.T. Weekman. 1962. Insecticide resistance in the adult western corn rootworm in Nebraska. J. Econ. Entomol. 55: 439-441.

  • Hibbard, B.E., B.D. Barry,  L.L. Darrah, J.J. Jackson, L.D. Chandler, L.K. French, and J.A. Mihm. 1999. Controlled field infestations with western corn rootworm (Coleoptera: Chrysomelidae) eggs in Missouri: Effects of egg strains, infestation dates, and infestation levels on corn root damage. J. Kans. Entomol. 72: 214-221.

  • Krysan, J.L., D.E. Foster, T.F. Branson, K.R. Ostlie, and W.S. Cranshaw. 1986. Two years before the hatch: Rootworms adapt to crop rotation. Bull. Entomol. Soc. Am. 32: 250-253.

  • Levine E., and H. Oloumi-Sadeghi. 1991. Management of diabroticite rootworms in corn. Annu. Rev. Entomol. 36: 229-255.

  • Levine E., and H. Oloumi-Sadeghi. 1996. Western corn rootworm (Coleoptera: Chrysomelidae) larval injury to corn grown for seed production following soybeans grown for seed production.  J. Econ. Entomol. 89: 1010-1016.

  • Meinke, L.J., B.D. Siegfried, R.J. Wright, and L.D. Chandler. 1998. Adult susceptibility of Nebraska western corn rootworm (Coleoptera: Chrysomelidae) populations to selected insecticides. J. Econ. Entomol. 91: 594-600.

  • Praiswater, T.W., B.E. Hibbard, B.D. Barry, L.L. Darrah, and V.A. Smith. 1997. An implement for dislodging maize roots from soil for corn rootworm (Coleoptera: Chrysomelidae) damage evaluations. J. Kans. Entomol. Soc. 70: 335-338.

  • Riedell, W.E. and P.D. Evenson. 1993. Rootworm Feeding Tolerance in Single-Cross Maize Hybrids From Different Eras.  Crop Science 33:951-955

  • Sutter, G.R. and T.F. Branson. 1980. A procedure for artificially infesting field plots with corn rootworm eggs. J. Econ. Entomol. 73: 135-137.  

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Corn lines from GEM germplasm with enhanced multiple disease resistance, grain yields, and starch content

R. J. Lambert

University of Illinois (retired)

Most present day commercial corn hybrids are improvements on two inbreds B73 (released in 1973) and Mo17 (released in the 1960's). Although this is a narrow genetic base corn breeders have been successful in improving these inbreds with enhanced pest resistance and increased plant density tolerance to produce improved hybrids. It is difficult to predict when this improvement will cease or decrease but based on the genetic inbreeding theory improvement cannot continue forever. Several breeding methods are available that will broaden the genetic base of commercial corn breeding materials so that enhancement will continue into the future. One way to broaden this genetic base is to utilize “new” genetic alleles found in exotic germplasm, unrelated to B73 or Mo17, for desirable agronomic traits. This requires first to evaluate exotic germplasm sources and then isolate in these sources genotypes with adapted genes for important agronomic traits and use these lines to enhance parents of commercial hybrids. The GEM project is designed to accomplish this goal.

This project has been selecting corn lines in two GEM populations Drep150 and BR5101 for the past 3.5 years. Selection has been for enhanced multiple disease resistance, improved starch content and grain yields based on testcross performance. Initially about 1,000 plants were evaluated for multiple disease resistance in each GEM population and about 100 S0 plants self pollinated in each population. These have been inoculated with multiple diseases and the most resistant plants selfed each generation. From 1998 to 2000 the number of lines has been reduced to about ten lines of Drep 150 and six lines of BR5101. Twenty-seven experimental crosses were grown in performance trials at 4 locations with two reps at each location in 2001. Fourteen of the crosses were among the Drep 150 x BR5101 lines, six crosses among Drep 150 lines and hi-starch testers (B84 and B73 types), four crosses were Drep 150 x ICA #43, and three crosses were BR5101 x ICA #45. The experiment also included three commercial check hybrids for a total of thirty hybrids. The three BR5101 x ICA #45 hybrids were also tested in 2000. The materials were grown at Clinton, Ivesdale, Monticello, and Urbana, IL. Mean grain yields at the four locations were Clinton, 106 Bu/ac; Ivesdale, 139 Bu/ac; Monticello, 132 Bu/ac; and Urbana, 139 Bu/ac.

The low average yields at Clinton were due to a lack of rainfall and poor distribution. Total rainfall for June and July was 4.25 inches at Clinton and 6.47 at Urbana, IL. About 50% of the rainfall during this period fell in the first 15 days of June at Clinton, but at Urbana 50% (2.05 inches) of the total fell during the first eight days of July which corresponded to the pollination period.

The grain yields for three crosses of BR5101 x ICB $45 that performed similar to the checks are presented in table 1.

Two of the three experimental hybrids produced yields similar to the check hybrids.  Stalk lodging for these hybrids was below the mean and varied from 2 to 8%. Grain moisture at harvest was also normal at each location (range 15% to 23%). Grain sample of these materials will be assayed for oil, protein, and starch values. Preliminary results are encouraging and continued inbreeding and selection plus tests for combining ability with elite inbreds needs to be done.  

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Introgression of grain quality traits from GEM germplasm into Corn Belt maize

 Richard Pratt

Ohio State University-Ohio Agricultural Research Development Center, Wooster

Selections of superior (top 10% for yield) S2 progenies from the GEM population FS8(A):S09 were made based on performance tests of approximately 200 testcrosses evaluated in multi-location trials during 1999. During the summer of 2000, controlled self-pollinations within selected S2 progenies were made to produce S3 progenies for characterization. Selected S2 progenies were testcrossed to two non-Stiff Stalk proprietary inbreds by a private cooperator during the winter season of 2000-01. Resultant testcross seed were distributed to cooperators, and planted during spring of 2001 in Ohio, Iowa, and Illinois (total of 9 replications at 7 locations). 

Yields in the Iowa tests were higher than those of the Illinois and Ohio tests. Three Illinois locations showed average yields and one was low-yielding due to inadequate moisture during the spring. The Ohio site experienced above average precipitation in the spring and virtually no precipitation in July. 

Progenies with top performance in 199 plots and 2001 plots are presented in tables 1-3. Line 362-1 by tester nSS1 was competitive in comparison with the mean value of the six commercial checks in the Iowa test. Its performance was below average in the Illinois and Ohio tests. Performance of the line 43-2 was essentially equal to that of the mean of the commercial checks in the Illinois and Ohio tests. It was below average in the Iowa tests. In general, the better experimental testcrosses displayed harvest moisture values lower than those of the checks, and stalk quality that was approximately the same.

Progeny were also selected for another experiment based on kernel protein composition values. High and low protein lines were testcrossed by low protein inbred B73 by the OSU project and by an elite high protein proprietary inbred by the ISU/ARS project. Testcrosses were planted in four-row plots in Iowa and Ohio. Grain samples will be analyzed during the winter of 2000-2001.

Publications: 

Pratt, R.C., P.E. Lipps, G. Bigirwa, and D.T. Kyetere. 2000. Germplasm enhancement through cooperative research and breeding using elite tropical and U.S. Corn Belt maize germplasm. Afr. Crop Science Jour. 8:345-353.  

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Selection for low concentration of grain phosphorus in GEM breeding crosses

W. Ken Russell

University of Nebraska-Lincoln

Long-term Objective:  Develop and release germplasm with significantly lower levels in the concentration of total phosphorus in the grain [P-Gr] compared to current elite germplasm.

Short-term Objectives:

i)   Initiate selection in the GEM breeding cross identified as having the greatest potential for development of inbreds with low [P-Gr];
ii)  Re-evaluate the best selections from 30 GEM breeding crosses for low [P-Gr] and also evaluate these entries for grain protein and seedling vigor.

Overview of Problem:

The concentration of phosphorus in the corn grain is of interest because in many commercial hybrids the level of phosphorus appears to exceed by a factor of two the dietary needs of yearling beef cattle. The excess phosphorus is excreted in the manure and becomes a potential pollutant that causes algae blooms in freshwater supplies. This problem is aggravated by the common practice in many large feedlots of supplementing the cattle diet with by-products of the wet-milling industry that contain even higher levels of phosphorus than whole corn.

Recently, considerable effort by the USDA and private companies has gone into the development of low-phytate corn. Achieving low levels of phytate is important because monogastric animals cannot digest this compound, and much of the phosphorus in normal corn is present as phytate. Low phytate corns hold the promise of eliminating the need to supplement the diet of these animals with phosphorus and also of reducing the level of phosphorus in the manure.

Cattle, however, are able to digest phytate. Because the concentration of total phosphorus is largely unchanged in the low phytate mutants, these specialty corns will not remedy the problem of too much phosphorus in the diet of corn-fed beef.

Prior Work:

This research effort commenced in 2000. The initial object was to screen a minimum of 30 breeding crosses to determine the best source(s) for development of low [P-Gr] germplasm. Another objective was to compare the level of [P-Gr] in these breeding crosses to that found in 100% Corn Belt germplasm. Twenty-five self-pollinations were made per breeding cross and in each of 3 Corn Belt F2s. A grain sample from each ear with good grain fill was finely ground and submitted for determination of percentage phosphorus content using X-ray analysis. At the time of last year's report, the results from these analyses had not been obtained.

Results from Current Year's Work:

The average of [P-Gr] across the 30 GEM breeding crosses ranged from a low of 0.21% in CHIS740:S1411a to a high of 0.42% in UR13061:S05 (Table 1). The average among all breeding crosses was 0.30%. The average of the three Corn Belt F2s was 0.31%.

Within most breeding crosses and F2s, the range of [P-Gr] values was large (Table 1). In 11 of the 30 GEM breeding crosses and in 2 of the 3 F2s, at least a two-fold difference existed between the lowest and highest value of [P-Gr]. In this screening an estimate of error was not available. However, in an adjacent experiment in which [P-Gr] was measured among S1 families based on seed from four bulked ears from each of two replications, the LSD was 0.08%.

2001, Exp. 1 - Based on the frequency of ears with a value of [P-Gr] less than 0.25%, CHIS740:S1411a and DK844:N11b17 were the two sources identified as being most worthy for more extensive sampling. In 2001, approximately 100 self-pollinations were made in each of these breeding crosses. These ears have been harvested and individually shelled. A grain sample from each ear has been ground and submitted for phosphorus analysis.

2001, Exp. 2 - 100 S1 families from the self-pollinated ears produced in 2000 with the lowest level of [P-Gr], regardless of the parental GEM breeding cross or Corn Belt F2, were grown in two replications, one 15-foot row per replication. Approximately two-thirds of these S1s were from breeding crosses of non-Stiff-Stalk parentage and the remainder from breeding crosses of Stiff-Stalk parentage. Also included in this experiment were four elite, inbred checks. Five sib pollinations, using different plants as males and females, were made per row. All ears per row were harvested and individually shelled, and then a balanced bulk was made. Each bulk has been ground and submitted for both phosphorus and protein analysis. Initially, seedling vigor scores also were to be taken. The reason was to test for a positive correlation between low [P-Gr] and poor seedling vigor. However, due to a poor seed bed the variation in emergence within rows was too great to allow for precise determination of seedling vigor on a per row basis.

Looking Ahead:

The material in Exp. 2 has been evaluated for two years. Based on both years' data, the best four to eight lines of Siff-Stalk background will be inter-mated to form one low [P-Gr] population and likewise on the non-Stiff-Stalk side to form a second low [P-Gr] population.

The most promising material from both Exp.'s 1 and 2 will continue to be self-pollinated and selected with the goal of developing one or more inbreds with a low level of [P-Gr].  

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 Anthracnose stalk rot resistance from exotic maize germplasm

Margaret Smith

Cornell University

Justification:

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 the U.S. Corn Belt. 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:

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, 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. This process was repeated with S5 ears in summer 2001, including yield tests at two New York locations.

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 S4 families grown in 2000 and for the S4 plants from which S5 ears were selected are shown in Table 1. Ears were saved from only the more resistant families and the best plants within these families. Plants with very limited stalk rot in the lowermost internode (injection site) were eliminated, as research has indicated that these represent partial escapes rather than truly resistant plants.   

Yield data based on S4 testcross performance also was considered in selecting which S4 families to maintain (see Table 2 for yield data on S4 testcrosses related to families that were selected for stalk rot resistance). Yield trial results were generally disappointing. This 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. The few hybrids with very high root lodging scores in the later maturity test each had one replication that was located in an extremely wet corner of one field, and all of the root lodging is from this bad corner of one field. Under normal field conditions root lodging is not expected to be a problem for these hybrids. Nonetheless, agronomic quality in general for these progenies is not what we had hoped based on previous years' testing. The most competitive testcross was from the progeny CH04030:S0906-15 crossed to the RD6501/RD6502 tester, which was comparable in yield, yield-moisture ratio, and stalk and root lodging to the commercial checks.

Disease resistance ratings on S5 progenies and data from the corresponding yield trials done in the current season have been collected, but remain to be converted, analyzed, and summarized. Field observations suggest that uniform resistance is being achieved and levels of resistance look good in the S5 families. Yield trials showed significant stalk lodging in one of the two locations, so should provide good selection pressure for standability.

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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Evaluation of maize germplasm for resistance to Aflatoxin and southwestern corn borer

 W. Paul Williams

USDA-ARS, Mississippi State, MS

Our goal is to identify maize germplasm with resistance to aflatoxin and southwestern corn borer for use in developing germplasm lines and populations that will be publically released. Aflatoxin contamination of corn grain is a chronic problem for corn production in the South and a sporadic problem in the Midwest. Growing corn hybrids with genetic resistance to aflatoxin is the most promising and most cost effective way to combat the problem. Although a few sources of resistance have been identified, resistant hybrids are not currently available commercially. We evaluated the Set A S3 bulk lines in 2001 for (1) aflatoxin accumulation following inoculation with an Aspergillus flavus spore suspension and (2) aflatoxin accumulation and ear damage from insect feeding following inoculation of ears with a fungal spore suspension and infestation with southwestern corn borer. Aflatoxin analyses are still in progress.  

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Breeding value-added maize lines with exotic germplasm

Dennis West

University of Tennessee

Objective: Develop new white-grain maize lines with desirable milling characteristics and competitive yield from GEM populations.

Justification:  Performance of white maize varieties lags behind that of yellow maize in the U.S. Incorporation of  genes from exotic germplasm and elite commercial germplasm into populations for selection has the potential to produce new white maize lines that exceed the performance of those currently available. 

Accomplishments:

 1)   Outstanding new lines from GEM accessions were identified from yield trials in 2001.
2)
     Crosses between 24 new GEM accessions and adapted germplasm were made to initiate new selection populations.

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 white-grain lines. Self-pollinate and select in segregating populations of  crosses between GEM and adapted lines.

Results: In 2001, 993 experimental hybrids were evaluated in 18 yield trials in Tennessee. These hybrids were crosses between GEM lines and adapted germplasm. As shown in table 1, several experimental hybrids were competitive with commercial check hybrids included in these trials. Entry 27 in experiment W69 yielded 50 bu/a more than the average of 5 check hybrids, and entry 6 in experiment W59 produced 30 bu/a more than the check average. The best lines from the GEM accessions will be selected for further testing and incorporation into value-added breeding for new white-grain lines. Inbreeding and selection was continued in populations resulting from crosses between GEM lines identified in previous trials, and 24 new GEM lines were crossed with adapted elite germplasm in 2001 to initiate additional populations for selection.

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Drought and heat tolerance and corn earworm resistance from exotic germplasm

 Wenwei Xu

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

General objectives: To develop corn inbreds with drought tolerance, heat tolerance, corn earworm (CEW) resistance, and good yield potential from GEM germplasm for the corn production in the Texas and southern United States.

Specific objectives: (1) to evaluate the GEM breeding crosses with 25 to 50% tropical germplasm for drought tolerance, CEW resistance, and yield performance; (2) to evaluate the released GEM lines for heat tolerance and CEW resistance; and (3) to continue selfing and selection of the lines derived from GEM crosses.

Materials and methods: Sixty-seven GEM breeding crosses with 25 to 50% tropical germplasm and three check hybrids (B73xMo17 and Pioneer hybrids 34K77 and 3223) were grown under three water treatments in Lubbock, Texas. Each water treatment used a randomized complete block design with three replications. The plot size was 4.6 x 1 m2 single-row. Planting date was April 27. The three water treatments were well-watered block, pre-tassel drought stress, and post-tassel drought stress. In the growing season, the well-watered block received 11 acre-inch water (2 from May 29 to June 8, 4.2 from June 9 to July 9, and 4.8 from July 10 to August 10), pre-tassel drought stress received 7.4 acre-inch water (2 from May 29 to June 8, 0.6 on July 2, and 4.8 from July 10 to August 10), and post-tassel drought stress received 6.2 acre-inch water (2 from May 29 to June 8, 4.2 from June 9 to July 9, 0 from July 10 to August 10). The total rainfall from planting to maturity was 5.52 inches (3.99 in May, 0.26 in June, 0.74 in July, and 0.53 in August). Water was applied through a sub-surface drip irrigation system. Precipitation before planting (1.11 in. in January, 0.33 in. in February, 2.71 in. in March, and 0.28 in. in April) provided sufficient soil moisture for planting. The entire field was applied with 120 lb/a of nitrogen and 60 lb/a of phosphorous. The 40 GEM lines were evaluated in a separate field under well-irrigated condition.

Results:

Top performers under well-watered block: Plants under this water treatment experienced moderate drought stress during the season. The average yield was 72.6 bu/a. Top yielding entries include Pioneer hybrid 3223 (131.3 bu/a), FS8B(T):N11a08b (109.5 bu/a), FS8B(T):N11a08c (108.5 bu/a), DK888:N11a08b (105.5 bu/a), UR1001:N1708e (99.5 bu/a), Pioneer hybrid 34K77 (95.6 bu/a), and MBRC10:S17 (95.3 bu/a) (Table 1).

Top performers under post-tassel drought stress: Plants in this water treatment experience severe drought stress after the tassels emerged. Four entries yielded significantly higher than the mean of the entries: Pioneer hybrids 3223 (71.0 bu/a) and 34K77 (69.2 bu/a), DK888:N11a08a (59.3 bu/a), and FB8B(T):N11a08c (52.7 bu/a) (Table 1). The three testcrosses involving FS8B(T) yielded well under both post-tassel drought stress and well-watered condition. Stay green trait is often used as drought tolerance indicator. However, the entries with good stay green ratings had low yield (Table 1).

CEW resistance: The natural CEW infestation in the field was heavy. Ten ears from each plot were rated for the CEW feeding penetration. The average feeding was 7.9 cm. Four entries had the feedings below 6 cm:  BR105:N16 (5.2 cm), DK888:N11a08f (5.8 cm), GUAT209:S1308b (5.8 cm), and PASCO14:N24 (5.8 cm). BR105:16 had significantly lower CEW feeding than the average (Table 1).

Heat tolerance and CEW resistance of GEM A- and B-lines: A total of 40 GEM A- and B-lines and three checks were used in this study (Table 2). The test was planted on May 7. B73 is susceptible to CEW and heat stress. Pioneer hybrid 31B13 is a Bt-hybrid and has an above-average CEW resistance among the commercial hybrids. WQ-22 is a CEW resistant line developed by the TAES Corn Breeding program (not released). CML343 has shown a good CEW resistance in our previous trials. All entries, similar to B73, have a full-season maturity (Table 1). The average days to flowering were 71 (around July 18). Cuba117:S1520-562-1-B (69 days) was significantly earlier than the mean, while CML343 was significantly later than the all other entries.

All the 40 GEN lines were susceptible to heat stress. From mid-June to July, the plants experienced two heat waves (above 38°C). The 40 GEM lines had 3 to 64.3% of plants showing leaf firing, with an average of 30% (Table 2). CML343 and Pioneer hybrid 31B13 had good heat tolerance as indicated by the 0% leaf firing. Many lines showed severe tassel blasting. Plants with tassel blasting produce no or few viable pollens.  Seven GEM lines showed below-average leaf firing: AR16035:S19-84-1-B (2.6%), AR16035:S19-182-1-B (2.6%), AR16035:S19-190-1-B (10.0%), CUBA164:S2008a-326-1-B (9.1%), CUBA164:S2008a-448-1-B (6.1%), CUBA164:S2008a-469-1-B (1%), and CUBA164:S2008a-507-1-B (7.0%).

The 40 lines were from four breeding populations: AR16035:S19, CUBA117:S1520, CUBA164:S15, and CUBA164:S008a. The four populations showed different leaf firing: 28.8% for AR16035:S19, 40.3% for CUBA164:S15, 33.5% for CUBA164:S15, and 20.4% for CUBA164:S2008a. The 10 CUBA164:S2008a lines had fewer plants with leaf firing than the CUBA164:S15 lines, indicating that S2008a is more tolerant to heat stress. The leaf firing appears to be recessive and controlled by multiple genes (Xu, unpublished data). It is rarely detected in the F1 generation of most crosses. Selection must be made in the selfed progenies. The 1% to 42% leaf firing among CUBA164:S2008a lines and 3% to 56% leaf firing among AR16035:S19 lines showed that effective selection can be made for leaf firing in a segregating population. However, it would be difficult to identify heat tolerant lines from the populations such as CUBA117:S1520, CUBA164:S15. The poor seed setting made it difficult to measure the CEW resistance. It may be caused primarily by heat stress and further damage by the CEW feeding on the silks and kernels. The CEW data are note presented here.

Accomplishments from the GEM project

Identification of yield potential, drought tolerance and CEW resistance from GEM germplasm:  In last three years, a total of 140 GEM breeding crosses have been evaluated under different water treatments in Texas. Superior GEM breeding crosses have been identified for yield, drought tolerance and CEW resistance. Under moderate drought stress, ANTIGO01:S01, BR5150:S11a20, CUBA164:S20, CHRIS775:S19, DK844:S16, DK830:S19, FS8B(T):N11a08b, FS8B(T):N11a08c, DK888:N11a08b, UR1001:N1708e perform well. Under severe post-tassel drought stress, CML325:S18, CML287:S18, CML325:S11, DK212T:S06, DK212T:S0620, DK888:N11a08a, FB8B(T):N11a08c, and GUAT209:N1925 yielded well.  BR105:N16, BVIR103:S04, Cuba164:S20, CUBA117:S15, DKXL380:S08a, DK830:S19, DK888:N11a08f, GUAT209:N19, GUAT209:S1308b, and PASCO14:N24 show good CEW resistance. Inbred lines are being developed from these GEM germplasm.

Publications from the research using GEM germplasm

  • Xu, W.W., T.L. Archer, L.P. Bradford, and L.M. Pollak. 2000. Identification of drought tolerant and CEW resistant GEM germplasm. 2000 ASA-CSSA-SSSA Annual Meetings Abstract. p. 113, Minneapolis, MN, Nov. 5-9, 2000 .

  • Xu, W.W. S. Machado, L. Pollak, and T.L. Archer. 2001. Measuring drought responses of diverse corn genotypes with canopy temperature and reflectance. 2001 ASA-CSSA-SSSA Annual Meetings Abstract c01-xu111423-P in a CD-ROM. Charlotte, NC, Oct. 20-25, 2001.

 

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