Location: Crop Genetics and Breeding Research
2021 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
ARS scientists at Tifton, Georgia, 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. For maize breeding efforts, inbreds and hybrids from Germplasm Enhancement of Maize (GEM) program from North Carolina and Iowa, International Maize and Wheat Improvement Center (CIMMYT) and United States national germplasm center (GRIN database) were evaluated by ARS scientists at Tifton, Georgia, for resistance to whorl and ear feeding insects, and reduced aflatoxin accumulation. In addition, Ex-PVP and other maize germplasm lines (such as from the GEM program and collaborators) are being evaluated continuously by ARS scientists for foliar and ear-feeding insect resistance. New breeding crosses have been made continuously and advanced by ARS scientists for new maize germplasm development by screening for insect and disease resistance, low aflatoxin accumulation, heat and drought tolerance, and good agronomic traits (e.g., no lodging and good yield potential). In 2020, a total of 10 sets of breeding crosses at various stages (F1 to F6) and recombinant inbred lines (RIL) populations were advanced by ARS scientists for new germplasm development with insect resistance and reduced aflatoxin accumulation. Ninety-four new hybrid testcrosses were evaluated by ARS scientists in a four-replication randomized complete block design (RCBD) for both yield and aflatoxin in 2020. Also in 2020 another set of 115 new hybrids (new ARS lines x Ex-PVP testers) was also evaluated by ARS scientists at Tifton, Georgia for yield and aflatoxin in a four-replicate RCBD experiment. However, aflatoxin could not be evaluated by ARS scientists at Tifton, Georgia due to lab occupancy restrictions.
In multidisciplinary collaborative/cooperative research efforts in our region, ARS scientists at Tifton, Georgia, continue to participate in the South Eastern Regional Aflatoxin Trial (SERAT) with two separate trials for yield and aflatoxin accumulation, respectively. Six hybrids were entered by ARS scientists for the trial in 2020 and our location again served as a test location for yield and aflatoxin trials with 40 entries each. ARS scientists also work with other scientists from the Aflatoxin Mitigation Center of Excellence (AMCOE) project by screening a set of 52 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. In our breeding nursery of 2020, ARS scientists advanced 114 S5-S6 selections by selecting for superior agronomic traits with fall armyworm resistance, low aflatoxin accumulation, and superior agronomic traits. Approximately 486 additional selections in various stages of development (F1 – F6 and BC1) were advanced in 2020. In addition, a new set of 45 maize inbred lines from Africa with known early maturity, drought and low-nitrogen tolerance was also screened by ARS scientists for insect resistance and aflatoxin accumulation.
A minimum path set of 41 B73-teosinte introgression lines (ILs) was acquired from the Maize Genetics Stock Center by ARS scientists. Seed production on these lines was low in our environment, but enough seed for experiments was recovered by ARS scientists for all but one IL. The remaining 40 ILs and B73 were screened for aflatoxin in inoculated experiments over two seasons (RCBD, 4 reps/year). Two ILs had significantly lower aflatoxin than B73. Seed was increased for future experiments to screen for resistance to insects or other diseases.
ARS scientists at Tifton, Georgia, are participating in the Genomes to Fields (G2F) project. This is a multi-location G x E study involving scientists from ARS and universities from across the U.S. and Canada. Each year ARS scientists have planted approx. 500 hybrid plots at our location, and recorded yield and other phenotypic data, which are shared with the G2F collaborators. A WatchDog mini weather station is used to log in-field weather conditions, and these data are also shared with the G2F team. The first five years (2014-2018) of genotypic, phenotypic, and weather data from this project are now available to the public through DOI weblinks, as well as inbred ear images from the first two years. In 2019 and 2020, a collaborator from the University of Georgia collected samples from our G2F field for a microbiome screening experiment.
For sorghum research, sugarcane 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. ARS scientists have been participating in a five-year area-wide integrated pest management (IPM) project for sugarcane aphid management since 2016, in addition to participating in the State Variety Test every year. In 2020, 15 grain, 28 silage, and 15 forage sorghum hybrids were evaluated and published in the 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 outbreak, ARS scientists 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 296 mostly grain sorghum germplasm lines from the sorghum association panel (SAP) were screened for sugarcane aphid and anthracnose resistance in 2020. This SAP experiment was also used in developing a robot-based phenotyping platform in collaboration with Fort Valley State University and Iowa State University. Drone-based imagery was also captured several times throughout the summer in collaboration with ARS scientists from Tifton, Georgia.
A total of 11 breeding crosses were made in 2015 by ARS scientists at Tifton, Georgia using sorghum inbreds with aphid and fall armyworm resistance, and a total of 182 selected accessions from the previous year were continuously evaluated for sugarcane aphid resistance and advanced in 2020. In 2020, 506 sweet sorghum selections were evaluated for sugarcane aphid response. Infestation was heavy and many lines were discarded but some superior lines were advanced. Five new sugarcane aphid resistant sweet sorghum lines have been developed and are being prepared for release by ARS scientists. Seed was increased in 2020 and the lines were evaluated at Tifton, Georgia, Mississippi State, Mississippi, and Lubbock, Texas, by ARS collaborators. They were also tested at Fort Valley, Georgia. A larger seed increase has been planted by ARS scientists at Tifton, Georgia in 2021.
In order to map quantative trait loci (QTL) for sugarcane aphid resistance, in 2018 and 2019 ARS scientists at Tifton, Georgia, planted 104 RILs from the cross PI 602951 x SC112 in RCBD experiments in naturally infested fields in Tifton, Georgia. SC112 is highly resistant to sugarcane aphid. In cooperation with an ARS scientist at Mayaguez, Puerto Rico, a major QTL for aphid resistance was found on Chromosome 6. Markers linked to this QTL will be useful for breeding sugarcane aphid resistance into elite sorghum lines. An additional 125 lines were advanced to F5 from the cross SC173 x N98, which will be used for future mapping experiments.
Accomplishments
1. Use of unmanned aerial systems (UAS) to evaluate sugarcane aphid damage in sorghum. ARS scientists at Tifton, Georgia, suggests since 2013, the invasive sugarcane aphid has become a serious pest on all types of sorghum. Development of cultivars with genetic resistance to sugarcane aphid is one strategy to reduce losses caused by this pest. However, evaluating sugarcane aphid population, plant damage, and other traits in the field is labor-intensive, and visual ratings may be subjective. In collaboration with scientists from the University of Georgia, ARS scientists at Tifton, Georgia, utilized unmanned aerial systems (UAS) to evaluate sugarcane aphid damage. Ground measurements were also taken by ARS scientists at Tifton, Georgia. The study demonstrated that the normalized difference red edge (NDRE) index and canopy cover collected by the UAS were strongly correlated with ground-based damage ratings. These results demonstrated that the UAS can be used to quickly and accurately assess sugarcane aphid damage. Such tools could not only be used to accelerate the process of developing aphid resistant germplasm and cultivars, but also be used to evaluate the efficacy of other sugarcane aphid management strategies in sorghum production.
Review Publications
Deng, Z., Zhang, Y., Zhang, M., Huang, J., Ni, X., Li, X. 2020. Characterization of the first W-unique protein-coding gene for sex determination in Helicoverpa armigera. Frontiers in Genetics. 11:649. https://doi.org/10.3389/fgene.2020.00649.
Chu, X., Wang, W., Ni, X., Li, C., Li, Y. 2020. Classifying Maize Kernels Naturally Infected by Fungi Using Near-infrared Hyperspectral Hmaging. Infrared Physics and Technology. 105: Article 103242. https://doi.org/10.1016/j.infrared.2020.103242.
Lu, Y., Wang, W., Ni, X., Zhuang, H. 2020. Non-destructive discrimination of illicium verum from poisonous adulterant using vis/nir hyperspectral imaging combined with chemometrics. Infrared Physics and Technology. 111: Article 103509. https://doi.org/10.1016/j.infrared.2020.103509.
Harris-Shultz, K.R., Ni, X. 2021. A sugarcane aphid (Hemiptera: Aphididae) 'Super-clone' remains on U.S. sorghum and johnsongrass ands feeds on giant miscanthus. Journal of Entomological Science. 56(1):43-52. https://doi.org/10.18474/0749-8004-56.1.43.
Rogers, A.R., Dunne, J.C., Romay, C., Bohn, M., Buckler IV, E.S., Ciampitti, I.C., Edwards, J.W., Ertl, D., Flint Garcia, S.A., Gore, M.A., Graham, C., Hirsch, C.N., Hood, E., Hooker, D.C., Knoll, J.E., Lee, E.C., Lorenz, A., Lynch, J.P., Mckay, J., Moose, S.P., Murray, S.C., Nelson, R., Rocheford, T., Schnable, J.C., Schnable, P.S., Sekhon, R., Singh, M., Smith, M., Springer, N., Thelen, K., Thomison, P., Thompson, A., Tuinstra, M., Wallace, J., Wisser, R.J., Xu, W., Gilmour, A., Kaeppler, S.M., Deleon, N., Holland, J.B. 2021. The importance of dominance and genotype-by-environment interactions on grain yield variation in a large-scale public cooperative maize experiment. Genes, Genomes, Genetics. https://doi.org/10.1093/g3journal/jkaa050.
Uchimiya, M., Knoll, J.E. 2020. Electroactivity of polyphenols in sweet sorghum (Sorghum bicolor (L.) Moench) cultivars. PLoS One. 15(7):e0234509. https://doi.org/10.1371/journal.pone.0234509.
Levinson, C.M., Marasigan, K.M., Chu, Y., Stalker, T.H., Holbrook Jr, C.C., Ni, X., Williams, W.P., Ozias-Akins, P. 2020. Resistance to fall armyworm (Lepidoptera: Noctuidae) feeding was identified in nascent allotetraploids cross-compatible to cultivated peanut (Arachis hypogaea). Peanut Science. 47:123-134. https://doi.org/10.3146/PS20-13.1.
Zhang, J., Maleski, J., Schwartz, B., Dunn, D., Mailhot, D., Ni, X., Harris-Shultz, K.R., Knoll, J.E., Toews, M. 2021. Assessing spatio-temporal patterns of sugarcane aphid (Hemiptera: Aphididae) infestations on silage sorghum yield using unmanned aerial systems (UAS). Crop Protection. 146: 105681. https://doi.org/10.1016/j.cropro.2021.105681.
Lahiri, S., Ni, X., Buntin, G., Punnuri, S., Jacobson, A., Reay-Jones, F.P., Toews, M.D. 2019. Combining host plant resistance and foliar insecticide application to manage Melanaphis sacchari (Hemiptera: Aphididae) in grain sorghum. International Journal of Pest Management. 67(1):10-19. https://doi.org/10.1080/09670874.2019.1660830.
Jarquin, D., De Leon, N., Romay, M., Bohn, M., Buckler IV, E.S., Ciampitti, I., Edwards, J.W., Ertl, D., Flint Garcia, S.A., Gore, M.A., Graham, C., Hirsch, C.N., Holland, J.B., Hooker, D., Kaeppler, S.M., Knoll, J.E., Lee, E.S., Lawrence-Dill, C.J., Lynch, J.P., Moose, S.P., Murray, S.C., Nelson, R., Rocheford, T., Schnable, J.C., Schnable, P.S., Smith, M., Springer, N., Thomison, P., Tuinstra, M., Wisser, R.J., Xu, W., Lorenz, A. 2021. Utility of climatic information via combining ability models to improve genomic prediction for yield within the genomes to fields maize project. Frontiers in Genetics. 11:592769. https://doi.org/10.3389/fgene.2020.592769.
