Location: Crop Genetics and Breeding Research2018 Annual Report
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.
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.
This project was established in March of 2018, thus no milestones have been completed yet. In 2018, a total of 197 new breeding crosses were made and advanced for maize germplasm development. Selections were made 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). A maize RIL population of 793 lines with low aflatoxin level, and a set of near-isogenic maize lines with fall armyworm resistance are being advanced in 2018. A series of segregating populations at varying stages (e.g., 497 F3, 302 F5 and 52 F6 populations) are being evaluated in 2018 with the goal of pyramiding aflatoxin, insect, and abiotic resistance in the improved genetic backgrounds for yield. Several advanced backcross corn populations are being developed using elite, but aflatoxin susceptible, lines as the recurrent parent. Some crosses have been made in the greenhouse between BC2F2 lines and a haploid inducer line in order to investigate the use of doubled haploids to accelerate the development of advanced-backcross RIL populations for genetic mapping. In addition, we are participating in the Georgia state variety trial for corn, and are evaluating 54 commercial corn hybrids for ear-feeding insect resistance, and will provide the information for growers to use for hybrid selection. In 2018, we are again 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. This year we have planted 512 hybrid plots at our location, and will record yield and other phenotypic data, which are shared with the G2F collaborators. In-field weather data is also being collected with a Watch Dog mini weather station. For sorghum research, a total of 37 commercial grain sorghum hybrids are being evaluated in 2018 for sugarcane aphid and other insect and bird damage, as part of the Georgia State Variety Trial to provide growers with needed information for hybrid selection in future. In 2018, a segregating population of 665 lines, derived from the breeding crosses made previously using aphid and fall armyworm resistant sorghum inbreds will be evaluated and advanced for sorghum germplasm development. Thirty-six sweet sorghum selections are currently at the F6 stage and will be screened for brix and other agronomic traits, as well as response to sugarcane aphid-feeding, in 2018. Additional sources of sugarcane aphid resistance have been identified, and these have been crossed with elite sweet sorghum lines in the greenhouse. Data collected in 2017 on a mapping population is currently being used in 2018 for QTL analysis to identify markers for sugarcane aphid resistance. A RIL mapping population (PI 602951 x SC112) has been planted for sugarcane aphid evaluation in the field.