Location: Crop Genetics and Breeding Research
2023 Annual Report
Objectives
1. Identify, develop, and release Southeast-adapted maize germplasm with reduced aflatoxin accumulation and resistance to key insect pests.
1A. Evaluate exotic maize germplasm from the Germplasm Enhancement of Maize (GEM) program, International Center for the Improvement of Maize and Wheat (CIMMYT), and the U.S. maize germplasm collection for reduced aflatoxin contamination.
1B. Screen for resistance to ear- and kernel-feeding insects in maize germplasm from the GEM, the CIMMYT, and the U.S. maize germplasm collection.
1C. Develop maize germplasm with reduced aflatoxin accumulation, increased resistance to insects, and enhanced agronomic performance in the southeastern Coastal Plain region.
2. Identify, develop, and release new sorghum germplasm with Southeast-adapted maturity genes and greater resistance to the sugarcane aphid, other key insects, and diseases.
2A. Evaluate sorghum lines from the U.S. germplasm collection for anthracnose resistance.
2B. Screen for foliar-feeding sugarcane aphid and fall armyworm and kernel-feeding sorghum midge resistance in sorghum lines from the U.S. germplasm collection.
2C. Develop sorghum germplasm with improved disease and insect resistance and high yield potential.
3. Develop molecular markers for reduced aflatoxin accumulation, and resistance to insects in maize and resistance to insects and foliar diseases in sorghum, and utilize molecular markers for gene identification and cultivar development.
3A. Develop molecular markers for reduced aflatoxin accumulation, and resistance to insects in maize, and utilize molecular markers for gene identification and cultivar development.
3B. Develop molecular markers for resistance to key insects and foliar diseases in sorghum, and utilize molecular markers for gene identification and cultivar improvement.
Approach
Objective 1: Exotic maize germplasm from the Germplasm Enhancement of Maize (GEM) Program, the International Maize and Wheat Improvement Center (CIMMYT), Mexico, and the U.S. maize germplasm collection will be screened for resistance to multiple insects and diseases, and reduced aflatoxin contamination under the southern climate. Equal priority will be given to the GEM and exotic germplasm, since the GEM germplasm will likely have better agronomic traits while the exotic germplasm may offer better resistance/tolerance to biotic and abiotic stress factors. Such a combination would allow us to develop new germplasm with good yield potential and resistant to multiple insects, diseases, and reduced mycotoxin contaminations. To effectively serve the seed industries, the screenings of maize insect pests will focus on key foliar-, ear- and kernel-feeding insects, in particular, fall armyworm, corn earworm and maize weevil. The genetic and biochemical bases for the biotic stress resistance in these newly identified germplasm lines will be further examined. New maize breeding crosses will be made by recombining germplasm with superior agronomic traits with the newly identified germplasm that confers multiple pest resistance and with reduced mycotoxin contamination. New maize germplasm will be developed by continuously screening and continuous self-pollination of the segregating populations. At the same time, maize recombinant inbred lines (RILs) will also be developed to identify DNA markers for multiple pest resistance.
Objective 2: A similar approach is utilized for the screening of sorghum germplasm for resistance to multiple biotic stress factors. Previously identified disease resistant and with agronomically-elite germplasm (with Ex-PVP program) in the U.S. germplasm collection will be screened for resistance to sugarcane aphid, fall armyworm, foliar anthracnose disease, and sorghum midge. The genetic and biochemical bases for insect and disease resistance will be examined. The roles of the secondary metabolites to biotic stress resistance in sorghum will also be examined. New sorghum breeding crosses will also be made using the newly identified sorghum germplasm lines that are resistant to multiple biotic stresses and with good yield potential. The breeding crosses will be continuously screened and selected, and self-pollinated to develop and release new sorghum germplasm lines (B lines, or maintainer lines). The best B lines will also be converted into A lines (or cytoplasmic-nuclear male sterile lines) to serve the seed industries. At the same time, sorghum RIL populations will be developed to identify DNA markers for multiple biotic stress resistance at vegetative and reproductive growth stages, respectively.
Objective 3: Development of molecular markers for reduced aflatoxin accumulation, and resistance to multiple pests in maize and sorghum will utilize the newly developed genetic resources (i.e., breeding crosses, RIL populations, and new germplasm lines) described in Objective 1 and Objective 2, respectively. The marker development will be performed by working closely with our collaborators and confirmed in multiple locations.
Progress Report
This is the final report for the project 6048-21220-018-000D which terminated in March 2023. Research activities have been continuously focused on the genetic improvement of maize and sorghum for yield related traits, resistance to Aspergillus flavus infection and aflatoxin accumulation, and damage caused by disease and insect pests.
In the field season of 2022, a total of 42 maize F1 accessions (new crosses made in 2021) were screened for fall armyworm resistance, and 85 accessions (F4 - F6) accessions were evaluated for fall armyworm and disease resistance and good agronomic traits (e.g., germination, flowering time, yield, and lodging) for germplasm development. New Germplasm Enhancement Maize (GEM) releases (17 inbred lines) were evaluated for fall armyworm and corn earworm resistance and reduced aflatoxin with 7 controls with insect and disease resistance/susceptibility. In addition, 24 maize inbred lines from GEM Program were evaluated for foliar-, ear-, and kernel-feeding insect resistance. A total of 17 maize selections (Material Transfer Research Agreement (MTRA)) and their parental inbred lines were evaluated for multiple insect resistance. A set of 190 inbred lines (e.g., Ex-PVP and exotic inbred lines with resistance to abiotic and biotic stresses) were screened for insect resistance, seed were increased, and/or new breeding crosses for new germplasm development. A set of 155 maize recombinant inbred lines (derived from NC358 x NC350) were evaluated for insect resistance and seed were increased. A set of 37 newly procured African maize germplasm lines (with drought and heat tolerance, and reduced aflatoxin) were screened for insect resistance, seed were increased, and breeding crosses were made for germplasm development. In our breeding nursery of 2022, ARS scientists at Tifton, Georgia, advanced 114 S5-S6 selections by selecting for superior agronomic traits with fall armyworm resistance, low aflatoxin accumulation, and superior agronomic traits. Approximately 500 additional selections in various stages of development (F1 – F6 and BC1) were advanced in 2022.
In 2022 a set of 192 hybrids was evaluated for yield and aflatoxin at Tifton, Georgia and Mississippi State, Mississippi by ARS scientists. The hybrids were produced by crossing six top ARS lines from Tifton and Mississippi with a set of 32 Ex-PVP inbred lines. Eight commercial checks were included in both experiments for comparison. Visual ear rot ratings were also recorded. Data are being analyzed and the experiment is being repeated in 2023.
ARS scientists at Tifton, Georgia, also work with other scientists from the Aflatoxin Mitigation Center of Excellence (AMCOE) project by continuously screening a set of accessions (derived from 4-way and 8-way crosses with low levels of aflatoxin accumulation from Texas A&M) for fall armyworm resistance and superior agronomic traits at Tifton, Georgia. To serve growers in the region, our team continuously participated in the Georgia State Corn Variety Trial to identify the best hybrids with insect resistance in 59 commercial corn hybrids. In addition, our team also conducted collaborative research in understanding Bt resistance in fall armyworm and corn earworm.
For sorghum research, sugarcane aphid (also known as sorghum aphid) outbreaks caused severe yield and economic losses which requires us to focus on providing growers with short- and long-term solutions for managing this invasive pest. In 2022, 22 grain, 12 silage, and 12 forage sorghum hybrids were evaluated and results were published in the Georgia State Variety Trial Annual Report, which provided growers with short-term solutions on aphid management by identifying the best sorghum hybrids in our region. For a long-term solution on managing the current sorghum aphid outbreak, ARS scientists at Tifton, Georgia, are continuously working on new germplasm screening and development with all types of sorghum (including grain, sweet, forage, silage and bioenergy sorghum). A total of 983 selected F5 sorghum accessions (from 2020 and 2021) derived from 10 breeding crosses made in 2015 with sugarcane aphid resistance were evaluated and advanced for germplasm development with insect and disease resistance. A set of newly procured 45 sorghum germplasm lines were evaluated for insect and disease resistance, and good agronomic performance, and seed were increased from the best performing lines. Thirteen new crosses were evaluated and advanced for new germplasm development.
In 2022, 439 mostly sweet sorghum selections were planted in the breeding nursery and 324 were advanced. Twenty F7 sweet sorghum lines were evaluated for sugarcane aphid response and other traits. Sugarcane aphid infestation was unusually light in 2022, but some inferior lines were discarded based on lodging and other traits.
In 2022, a set of 95 sweet sorghum lines were screened for anthracnose in the field to validate the results of marker assisted selection. These lines were in the BC3F3 generation, where the recurrent parent (Early Honey) was highly susceptible. Each backcross line carries one or two known markers for anthracnose resistance or susceptibility. The markers represent five loci derived from eight anthracnose resistant sorghum conversion (SC) lines. Some of the backcross lines with resistant markers were found to be resistant, but not all of the markers conferred resistance. Seed was increased for screening at additional locations in 2023.
In 2022, an MTRA was executed with a seed company to test the effects of sorghum aphid on forage sorghum quality. Three aphid-resistant lines from ARS, one susceptible public line, and four entries from the seed company were sampled three times during the growing season for forage quality. The experiment was laid out as a split-plot to compare sprayed (no aphids) and unsprayed (with aphids) treatments. Aphid infestation was light, but some minor differences between treatments in forage quality were noted for one susceptible entry from the seed company. The experiment is being repeated in 2023.
Five-Year Summary
Maize is an important grain, silage, and biofuel feedstock crop in the Southeastern Coastal Plains. However, biotic and abiotic factors in the southern states are conducive to aflatoxin accumulation in maize, which has caused billions of dollars of economic losses to the agricultural industry. Although reduced susceptibility to aflatoxin accumulation has been identified, the integration of this trait into commercial breeding programs is limited due to difficulty in selecting for the trait and poor agronomic performance in the most insect and disease resistant germplasm. This project has focused on identifying untapped sources of maize germplasm with resistance to major biotic and abiotic stresses, and incorporating resistance traits into agronomically elite lines that are adapted to the Southeastern U.S. ARS scientists at Tifton, Georgia have screened and identified new sources of biotic resistance in maize, and developed new maize germplasm resistant to Aspergillus flavus infection with reduced aflatoxin accumulation, as well as resistance to fall armyworm, corn earworm, and maize weevil. In particular, 18 new lines developed at Tifton were tested in various hybrid combinations for yield and aflatoxin over four years. Three lines (GT1203, GT1209, and GT1309) were found to have superior combining ability for yield or reduced aflatoxin. Some hybrids were competitive with commercial checks for yield and had lower aflatoxin.
ARS scientists at Tifton, Georgia have participated in two large collaborative maize research projects, Genomes to Fields (G2F) and Southeast Regional Aflatoxin Trial (SERAT), throughout the life of this project. Each year approximately 500 hybrid plots were grown at Tifton for the G2F project. Yield and other phenotypic data, as well as in-field weather data, were collected and shared with the G2F collaborators. The first eight years (2014-2021) of genotypic, phenotypic, and weather data from all G2F locations are now available to the public through DOI weblinks, as well as inbred ear images from the first two years. ARS scientists also participated in the SERAT. This project tests publicly-developed maize hybrids for yield and/or aflatoxin at multiple locations in Georgia, Texas, Mississippi, and North Carolina. Tifton served as a screening location for the trials each year, and hybrids developed by ARS scientists at Tifton were also entered into the trials.
Accomplishments
1. Demonstrated combining ability for yield and reduced aflatoxin in new maize lines. Aflatoxin contamination of maize grain presents risks to animal and human health and causes economic losses for growers, particularly in the southeastern United States. Development of hybrids with genetic resistance to aflatoxin contamination by the fungus Aspergillus flavus will help to minimize these risks. Two crossing experiments were conducted to evaluate yield, agronomic traits, and aflatoxin in maize hybrids. In Exp. 1, 18 aflatoxin-resistant (GT) lines developed by ARS scientists at Tifton, Georgia, were each crossed to 6 testers. In Exp. 2, 13 of the same lines were each crossed to 10 different testers. Each experiment was conducted for two years at Tifton, Georgia, and commercial check hybrids were included for comparison. Ears were inoculated with a strain of A. flavus that is known to produce high aflatoxin by the side-needle technique, and aflatoxin was quantified in the harvested grain. Among experimental lines, GT1209 and GT1309 had consistent positive general combining ability (GCA) for yield, which means hybrids of these lines tended to yield greater than average. Hybrids of GT1203 and GT1204 had consistently lower than average aflatoxin. Significant GCA effects, both positive and negative, for aflatoxin were also observed among testers in both experiments. Some experimental hybrids had yields that were comparable to commercial checks while also having lower aflatoxin, demonstrating that progress is being made in improvement of both traits in maize hybrids adapted to the Southern United States. GT1203, GT1209, and GT1309 are the top candidate lines for release.
Review Publications
Deng, Z., Zhang, Y., Gao, C., Shen, W., Wang, S., Ni, X., Liu, S., Li, X. 2022. A transposon-introduced G-quadruplex motif is selectively retained and constrained to downregulate CYP321A1. Insect Science. 29(6):1629-1642. https://doi.org/10.1111/1744-7917.13021.
Yu, W., Head, G.P., Price, P., Brown, S., Cook, D., Ni, X., Reay-Jones, F., Dimase, M., Huang, F. 2022. Estimation of resistance allele frequencies to Cry1A.105 and Cry2Ab2 in the corn earworm (Lepidoptera: Noctuidae) with F2 isolines generated from a mass-mating method. Crop Protection. 161:106054. https://doi.org/10.1016/j.cropro.2022.106054.
Uyi, O., Lahiri, S., Ni, X., Buntin, D., Jacobson, A., Reay-Jones, F., Punnuri, S., Huseth, A.S., Toews, M.D. 2022. Host plant resistance, foliar insecticide application and natural enemies play a role in the management of Melanaphis sorghi (Hemiptera: Aphididae) in grain sorghum. Frontiers in Plant Science. 13:1006. https://doi.org/10.3389/fpls.2022.1006225.
Uyi, O., Reay-Jones, F.P., Ni, X., Buntin, D., Jacobson, A., Punnuri, S., Toews, M.D. 2022. Impact of planting date and insecticide application methods on Melanaphis sorghi (Hemiptera: Aphididae) infestation and forage sorghum yield. Insects. 13. Article 1038. https://doi.org/10.3390/insects13111038.
Uyi, O., Ni, X., Buntin, D., Jacobson, A., Reay-Jones, F.P., Punnuri, S., Toews, M.D. 2023. Management of Melanaphis sorghi (Hemiptera: Aphididae) in grain sorghum with early planting and in-furrow flupyradifurone application. Crop Protection. 164. Article 106148. https://doi.org/10.1016/j.cropro.2022.106148.
Deng, Z., Zhang, Y., Fang, L., Zhang, M., Wang, L., Ni, X., Li, X. 2023. Identification of the flavone-inducible counter-defense genes and their cis-elements in Helicoverpa armigera. Toxins. 15:365. https://doi.org/10.3390/toxins15060365.
Wen, Z., Conville, J., Matthews, P., Hootman, T., Himes, J., Wong, S., Huang, F., Ni, X., Chen, J., Bramlett, M. 2023. More than 10 years after commercialization, Vip3A-expressing MIR162 remains highly efficacious in controlling major Lepidopteran maize pests: laboratory resistance selection versus field reality. Pesticide Biochemistry and Physiology. 192:105385. https://doi.org/10.1016/j.pestbp.2023.105385.
Guo, X., Jia, B., Zhang, H., Ni, X., Zhuang, H., Lu, Y., Wang, W. 2023. Evaluation of Aspergillus flavus growth and detection of aflatoxin B1 content on maize agar culture medium using Vis/NIR hyperspectral imaging. Agriculture. 13. Article 237. https://doi.org/10.3390/agriculture13020237.
Banerjee, R., Placidi De Bortoli, C., Huang, F., Lamour, K., Meagher Jr, R.L., Buntin, G., Ni, X., Reay-Jones, F., Steward, S., Jurat-Fuentes, J. 2022. Large genomic deletion linked to field-evolved resistance to Cry1F corn in fall armyworm (Spodoptera frugiperda) from Florida. Scientific Reports. 12:13580. https://doi.org/10.1038/s41598-022-17603-3.
Kick, D.R., Wallace, J.G., Schnable, J.C., Kolkmann, J.M., Alaca, B., Beissinger, T.M., Edwards, J.W., Ertl, D., Flint-Garcia, S.A., Gage, J.L., Hirsch, C.N., Knoll, J.E., de Leon, N., Lima, D.C., Moreta, D., Singh, M.P., Thompson, A., Weldekidan, T., Washburn, J.D. 2023. Yield prediction through integration of genetic, environment, and management data through deep learning. G3, Genes/Genomes/Genetics. 13(4). Article jkad006. https://doi.org/10.1093/g3journal/jkad006.
Lima, D., Castro Aviles, A., Alpers, T., Mcfarlan, B., Kaeppler, S., Ertl, D., Romay, C., Gage, J., Holland, J.B., Beissinger, T., Bohn, M., Buckler, E., Edwards, J., Flint-Garcia, S., Hirsch, C., Hood, E., Hooker, D., Knoll, J., Kolkman, J., Liu, S., Mckay, J., Minyo, R., Moreta, D.E., Murray, S., Nelson, R., Schnable, J., Sekhon, R., Singh, M., Thomison, P., Thompson, A., Tuinstra, M., Wallace, J., Washburn, J.D., Weldekidan, T., Wisser, R., Xu, W. 2023. 2018-2019 field seasons of the maize genomes to fields (G2F) G x E project. BMC Genomic Data. 24:29. https://doi.org/10.1186/s12863-023-01129-2.
