Location: Crop Genetics and Breeding Research2010 Annual Report
1a. Objectives (from AD-416)
The long-term objective of this project is to develop corn and pearl millet germplasm with reduced aflatoxin contamination and insect damage in order to increase the productivity and quality of grains produced in the southeastern United States. Over the next five years we will: 1) Identify new sources of germplasm with resistance to Aspergillus flavus/aflatoxin contamination, and to multiple ear-feeding insect damage; 2) Determine biochemical and physiological bases and associated key phenotypic traits conferring resistance/ susceptibility to chewing and piercing-sucking insects in corn and pearl millet germplasm; 3) Identify quantitative trait loci associated with reduced aflatoxin accumulation in corn; and 4) Develop maize germplasm with desirable agronomic traits and reduced aflatoxin accumulation and increased resistance to ear-feeding insects for use in the Coastal Plain region.
1b. Approach (from AD-416)
In comparison with molecular (gene to trait, or top-down) approach, a trait to gene (bottom-up) approach will be taken for this project. Diverse (exotic and temperate) germplasm will be screened under field conditions for resistance to aflatoxin and insect pests (i.e., corn earworm, fall armyworm, maize weevil, and stink bugs). Field-proven germplasm entries will be further evaluated for key unique phenotypic traits in relation to resistance mechanisms and underlying genetics using both conventional and molecular techniques. Following rigorous field and laboratory screenings, selected germplasm will be further examined for biochemical and physiological bases that confer resistance to multiple insect pests and aflatoxin. Insect resistance mechanisms in the selected corn and pearl millet germplasm will be categorized and the biochemical and physiological processes that confer certain insect resistance will be identified. Segregating populations with resistance to aflatoxin contamination and multiple insect damage will be developed. These new populations will serve as the sources of favorable alleles for ultimately developing aflatoxin- and insect-resistant corn inbred lines with elite agronomic traits, which will improve corn production under biotic and abiotic stresses in our region.
3. Progress Report
Activities focused on the genetic improvement of corn and pearl millet for yield-related traits, resistance to Aspergillus flavus and aflatoxins, and insect pests. Brazilian maize introductions were evaluated for resistance to lepidopteran pests. Temperate corn inbreds were evaluated for corn rootworm and fall armyworm resistance. New elite Germplasm Enhancement of Maize project (GEM) inbreds and hybrids selected from Iowa, North Carolina, and Texas programs were evaluated for resistance to whorl and ear feeding insects. The previously evaluated GEM inbreds and hybrids from Texas and Iowa are evaluated for the foliage feeding insects in 2010. Fall armyworm and southern rust-resistant inbreds from the FAWCC(C5) population were advanced. High maysin experimental hybrids were evaluated for resistance to feeding by ear insects (corn earworm, stinkbug, maize weevil) and fall armyworm, as well as for natural enemy attraction in whorl stage. Introduced Chinese inbreds were evaluated for resistance to ear feeding insects, and rust and smut. The co-occurrence of aflatoxin contamination and maize weevil and stinkbug distributions in fields of AgraTech 760RR was assessed. Inoculation methods to allow for more effective screening for Aspergillus flavus and aflatoxin contamination were assessed. Approximately 2500 grain samples were analyzed for aflatoxin using the Vicam procedure. Approximately 500 hybrids were evaluated in 3 environments with the goal of combining aflatoxin, insect, and drought resistance in improved genetic backgrounds. Forty selections were intermated to initiate 1200 phase 2 breeding populations evaluated for agronomic traits, drought tolerance, and tolerance to late-season pests and diseases.
Maas, A., Ni, X. 2009. Inheritance of chinch bug (Heteroptera: Blissidae) resistance in grain pearl millet. Journal of Semi-Arid Tropical (SAT) Agricultural Research 7. http://ejournal.icrisat.org/Volume7/Sorghum_Millets/PM703.pdf.
Ni, X., Wilson, J.P., Buntin, G. 2009. Differential responses of forage pearl millet genotypes to chinch bug (Heteroptera:Blissidae) feeding. Journal of Economic Entomology. 102:1960-1969.
Park, Y., Gobel, C., Ni, X., Feussner, I., Kolomiets, M.V. 2010. Comparative molecular and biochemical characterization of segmentally duplicated 9-lipoxygenase genes ZmLOX4 and ZmLOX5 of maize. Planta. 231:1425-1437.