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.

GEM Breeding Crosses, Topcrosses, and Advanced Lines for Improving Drought tolerance, Grain Mold resistance, and Corn Earworm Resistance

Wenwei Xu

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

Objectives

The specific objectives of this project includes: (1) to conduct field trials for drought tolerance, CEW resistance, grain mold and yield of the topcrosses of the GEM lines with Holden’s (LH185, LH198, LH200, LH247, and LH283) and public tester lines; (2) to assay aflatoxin of 10 hybrids of the GEM lines; (3) To advance and characterize inbred lines from GEM breeding crosses; (4) to perform second-year field evaluation of 40 new GEM breeding crosses for drought tolerance, grain mold resistance, and CEW resistance; and (5) to characterize the 16 new recommended lines provided by the GEM Coordinator for drought, heat tolerance, and  resistance.  Most the data are being analyzed when this report is prepared.  This report provides a detailed information on 40 GEM breeding crosses in 2005 and combined analysis of the 2004 and 2005 data.

Materials and Methods

Objective 1: About 130 topcrosses of GEM lines were tested at three locations in the Texas High Plains (Lubbock, Halfway and Etter) and at four south Texas locations (College Station, Beeville, Corpus Christi, and Weslaco).  The Lubbock and Halfway sites has well-watered and drought-stressed treatments.  Data are being analyzed and results are not included in this report.

Data in 2004 and 2005 (only Weslaco site in south Texas available) show that lines from AR03056:N0902, SCROGP3:N2017, SCROPG3:N1411a, FS8A(T):N1801, DK888:N11 combine well with the used testers and produce high yielding hybrids.  For examples, cross (SCROPG3:N1411a-1) x B110 produced 274 bu/a at Dalhart in the north Texas panhandle in the 2004 Texas Corn Performance Test that used 36 entries (25 Bt, 16 non-Bt, and mostly commercial hybrids) and had an average yield of 272 bu/a.  The cross (SCROPG3:N1411a-1) x LH200 showed similar performance in 2004 tests and is in 2005 Texas State Corn Performance Test at Dalhart (north TX) and Prosper (central TX).  Use of LH200 would facilitate the line’s adoption along with biotech traits.  The official release proposal for the line from SCROPG3:N1411a will be submitted in the fall of 2005.

Objective 2: Ten topcrosses of GEM lines including (CUBA117:S15)-3-2 x LH185, (CUBA117:S15)-1A-1 x Tx205, C3S1B73-3-1 x Tx205, (AR03056:N0902)F9-1-1 x LH200, LH200 x (SCROGP3:N1411a)F9-1-2 were grown along with 15 hybrids in Lubbock, Halfway, Corpus Christi and Beeville for aflatoxin assays where the test plots were inoculated with A. flavus.  These hybrids were chosen for good performance in previous years.  Some hybrids are expected to have high yield and low aflatoxin in the southern U.S.  Grain samples and data are being analyzed.

Objective 3: About 300 F5-F8 lines were advanced, mostly from ANTIGO01:N16, ANTIGO03:N12, AR16026:N12, AR03056:N0902, BR52051:N04, CH05012:N12, CUBA164:S20, CUBA117:S15, DK888:N11, DKXL380:S08a, FS8A(T):N11a, and GUAT209:N1925.  The more advanced lines were also grown in replicated trials for characterizing their drought/heat tolerance, pest resistance, and overall agronomic traits.

Objective 4: Evaluation of 41 GEM breeding crosses for the second year in Lubbock under three regimes of water stress. The 41 GEM breeding crosses and three checks (Garst 8285 and Pioneer hybrids 34K77 and 3223) were grown under three water treatments in Lubbock in 2004 and 2005.  Planting date for 2005 was April 19.  Under each water treatment, a randomized complete block design with three replications was used.  Each plot was a 18 foot-long row with 40-inch row-spacing.  The stand was thinned to 22,646 plants/a.  Three water treatments (100% ET, 50% ET and V-10 drought stresses) were in the same field, and each received a total of 16.54, 5.1, and 7.35 acre-inch irrigation water during the season.  Total precipitation from planting to August 30 was about 10 inches.  The 50% ET irrigation provides a moderate-severe stress throughout the season.  In V-10 drought stress, irrigation was withheld 10 days before and after flowering to create a severe drought stress around the flowering time.  Plants in V-10 showed moderate to severe drought stress symptom around flowering time. 

Objective 5: 16 lines from the GEM coordinator were tested in a replicated trial under full-irrigation and V-10 drought stress in Lubbock, TX Section 1 for details) for a second year to confirm the results in 2004.  drought stress  In 2004, the best lines included CUBA164:S2012-444-1-B-B, FS8B(T):N11a-110-1-B-B, DKXL370:N11a20-199-2-B-B-B, DKXL370:N11a20-234-2-B-B-B, and UR11003:S0302-937-1-B-B were better than others.  The best line was CUBA164:S2012-444-1-B-B, it had no leaf firing, low CEW damage, low grain mold, low percent of barren plants, good drought and stay green rating.  Plant height, stage green rating and other agronomic data were collected during the growing season.  The CEW feeding damages were measured on 10 ears.  The data from 2005 are being analyzed.

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Results and Discussion

The 2005 data for well-irrigated, 50% ET and V10 drought stress are presented in Tables 1 to 3 respectively.  Three crosses BR52051:N0417, CML323:N15, and GUAD05:N3215 did not have enough seeds and were not used in 2005.  Overall, the 2004 and 2005 results are similar.

CEW resistance and yield of 41 GEM breeding crosses under well irrigation in 2004 and 2005:  The average yield was 130 bu/a ranging from 75 (CHIS740:S14) to 183 bu/a (P3223).  The average yield of check hybrids P3223, P34K77, and Garst 8285 was 174 bu/a compared to 182 bu/a in 2004. UR13010:N0613, CML323:N15, AR17056:S19, UR11003:S17b, NS1:S08, UR13085:N0204, UR05071:S04, AR17056:S12, and AR16024:N1210 yielded 162 to 143 bu/a. The yields of top ten breeding crosses are statistically equal to the check means.  These crosses also have nice lloking plants with dark green leave, long ears and large kernels (Tables 1 and 4).  CHIS740:S14 had lowest yield because it was late and highly susceptible to high temperatures.  In 2004, the yield of several crosses was affected by the high green snap that occurred on June 18 when a storm with over 50 miles wind struck the field.  This was the only time we have had observed green snap damage in our location since 1998.

There was a significant difference among the entries in all other traits.  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 5.3 to 9.1 cm with a mean of 7.3 cm.  UR0571:S04 and GUTA209:N11c had CEW damage below test mean (7.3 cm).  Grain mold was not significant among entries but a few crosses had lower grain mold than others.  High grain mold is usually correlated high mycotoxin (aflatoxin and fumonisin) contamination.  Several crosses have long ears and large kernels (Table 4).

Yield and stay green of GEM breeding crosses under 50% ET and V-10 drought stresses: The average yield of 50% ET and V-10 stresses was 57.5 and 59.4 bu/a respectively.  The average yield of three checks was 107 and 105 bu/a under 50% ET and V-10 drought stress, a 40% yield reduction in comparison to the well-irrigated test.  Under this stress condition, one should consider the crosses with more ears per plant (less barren plants), better ear rating, lower stay green rating value, and low grain mold.  Stay green rating should be examined along with the maturity. . Most of the top yielding crosses tend to have these characters The best performing breeding crosses under 50% ET and V-10 stress include AR16026:N1210, AR13026:N08a04, BR52051:N0417, BR51721:N2012, CML323:N15 (one year data), UR13085:N0204, UR13010:N0613, and UR11003:S17b (Table 5).

Publications and Field Days

Field days:

GEM germplasm was showed and discussed in the field days on August 19 at Halfway, TX and on August 26 at Etter, TX.

Publications discussed GEM germplasm:

Wenwei Xu, Gary Odvody, W. Paul Williams, Patrick Porter, and Greg Cronholm. 2005 Introgression of tropical germplasm to reduce the damage of ear-feeding pests and develop products for organic corn production.  ASA-CSSA-SSSA Annual Meetings Abstract, Salt Lake City, UT, Nov. 6-10, 2005.

Xu, W. and Gary Odvody: 2005. Registration of maize germplasm lines Tx204 and Tx205. Crop Science (submitted).

Wenwei Xu, Jinfen Zhang, Gary Odvody, and W. Paul Williams. 2005. Corn hybrids with exotic germplasm and low-aflatoxin.  Abstract of 2005 Aflatoxin/Fumonisin Elimination and Fungal Genomics Workshops.  October 23-28, 2005, Raleigh, NC.

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Table 1. Days to pollen shedding (DTP), plant height (PHT, cm), ear height (EHT), husk rating (HUSK), root lodging (RTL) stay green rating (SG822), CEW ear penetration (CEW, cm), ear length (EL, cm), grain mold (%), and yield (YBU, bu/a) of GEM breeding crosses under well-irrigated condition in Lubbock, TX in 2005.