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ARS Home » Southeast Area » Tifton, Georgia » Crop Genetics and Breeding Research » Research » Research Project #424772

Research Project: Genetic Improvement of Maize and Sorghum for Resistance to Biotic Stress

Location: Crop Genetics and Breeding Research

2014 Annual Report

1. Identify new sources of maize germplasm with resistance to aflatoxin and insects, and identify new sources of sorghum germplasm with improved insect resistance. 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 resistance to infection by Aspergillus flavus and aflatoxin contamination. 1B. Screen for resistance to ear- and kernel-feeding stink bugs, sap beetles, thrips and maize weevil in maize germplasm from the GEM, the CIMMYT, and the U.S. maize germplasm collection. 1C. Evaluate sorghum lines from the U.S. germplasm collection for anthracnose resistance. 1D. Screen for whorl-feeding fall armyworm and head-feeding sorghum midge resistance in sorghum lines from the U.S. germplasm collection. 2. Develop maize and sorghum germplasm adapted to the southeastern United States with enhanced resistance to diseases and insects. 2A. Develop maize germplasm with reduced aflatoxin accumulation, increased resistance to insects, and enhanced agronomic performance in the southern Coastal Plain region. 2B. Develop sorghum germplasm with improved disease and insect resistance and high yield potential.

Objective 1: Exotic maize germplasm from the Germplasm Enhancement of Maize (GEM) Program, the International Maize and Wheat Improvement Center (or CIMMYT), Mexico, and the U.S. maize germplasm collection will be screened for resistance to multiple insects and diseases, and reduced aflatoxin contamination. Equal priority will be given to the GEM and exotic germplasm, since the GEM germplasm will likely have better agronomic traits but the exotic germplasm may have better adaptation to the South. Such a combination has the potential that allows us to identify new germplasm resistant to multiple insects, diseases, and reduced mycotoxin contaminations. To effectively serve the seed industries, the screenings of maize insect pests will focus on ear- and kernel-feeding insects, in particular, stink bugs, sap beetles, thrips and maize weevil. The genetic and biochemical bases for the biotic stress resistance in these newly identified germplasm lines will be further examined. Three genetic studies (i.e., diallel analysis, xenia effect, and heterosis) will be used to elucidate the genetic mechanisms, whereas phytoalexins and other secondary metabolites of plants will be examined to elucidate biochemical and physiological bases of biotic stress resistance. A similar approach is utilized for the screening of sorghum germplasm for resistance to multiple biotic stress factors. Previously identified disease resistant and agronomically-elite germplasm in the U.S. germplasm collection will be screened for resistance to fall armyworm, foliar anthracnose disease, and sorghum midge. The genetic mechanisms of insect and disease resistance will be examined utilizing three genetic studies (i.e., North Carolina Design II, heterosis, and xenia effect). The contributions of the secondary metabolites to biotic stress resistance in sorghum will also be examined. Objective 2: New maize breeding crosses will be made by recombining germplasm with superior agronomic traits with the newly identified germplasm that confers multiple insect and disease 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, recombinant inbred lines (RILs) will also be developed to identify DNA markers for the newly-developed multiple pest-resistant maize germplasm lines. 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, recombinant inbred lines will also be developed and used to identify DNA markers for the newly-developed multiple biotic stress-resistant sorghum germplasm lines at both vegetative and reproductive growth stages.

Progress Report
Activities focused on the genetic improvement of corn and sorghum for yield related traits, resistance to Aspergillus flavus infection and aflatoxin accumulation, and damage caused by disease and insect pests. Temperate corn inbreds were evaluated for fall armyworm resistance. New elite Germplasm Enhancement of Maize (GEM) inbreds and hybrids selected from Iowa, North Carolina, and Texas programs were evaluated for resistance to whorl and ear feeding insects. In addition to 63 newly requested Ex-PVP and other maize germplasm lines from the National Genetic Resources Program, Germplasm Resources Information Network (GRIN), a total of 54 GEM inbreds and hybrids from Iowa, North Carolina, and Texas were evaluated for the foliar- and ear-feeding insects and aflatoxin resistance in 2014. A set of 48 intermated B73 and Mo17 (IBM) recombinant inbred lines (RIL) were evaluated for insect resistance in 2014. A total of 138 new experimental hybrids made in 2014 utilizing the parents of insect and disease resistance, and good agronomic traits were also evaluated for insect resistance and agronomic traits (e.g., lodging and yield potential). Ninety six new hybrids are being evaluated for yield and aflatoxin, and 91 segregating populations at varying stages were evaluated with the goal of pyramiding aflatoxin, insect, and abiotic resistance in improved genetic backgrounds. In addition, a set of 23 heat- and drought-tolerant maize germplasm from the GRIN has also been evaluated again for whorl-feeding fall armyworm resistance in the southern Coastal Plain region. Ten maize weevil resistant inbred lines were evaluated for whorl- and ear-feeding insect resistance. Final data collection for a set of two maize germplasm lines was conducted to support a release. For sorghum research, the effect of planting dates on sorghum midge and bird damage on 25 commercial hybrids is evaluated in 2014, which is a repeat of the experiment in 2013. A sorghum RIL mapping population was acquired from collaborators at Purdue University, and was screened in the field for disease resistance. This population will be screened again this year to verify data for publication. An additional 194 lines were acquired from GRIN this year and will be screened in the field. In collaborative research efforts with other teams in the region, we continued participation in a multiple state research project of Aflatoxin Mitigation Center of Excellence (AMCOE) in 2014 to examine the experimental hybrids for insect damage and aflatoxin accumulation; and participated in a team effort to differentiate plant defensive responses in a maize inbred line and its mutant in fungal infection and aflatoxin contamination in corn ears at pre-harvest. Working with other scientists at our location, a corn field day of the AMCOE states was successfully held at our location in Tifton, Georgia. Continuously participated in the South Eastern Regional Aflatoxin Test (SERAT) Program, and processed and analyzed approximately 500 grain samples for aflatoxin using the VICAM Aflatest procedure in 2013. Continuously participated in the SERAT aflatoxin and yield trials, as well as the State Variety Tests and examined the new corn and sorghum hybrids for insect resistance in 2014. This is a multi-location Genotype x Environment interaction study involving scientists from ARS and universities across the U.S. and Canada.


Review Publications
Chen, Y., Ruberson, J.R., Ni, X. 2014. Influence of host plant nitrogen fertilization on haemolymph protein profiles of herbivore Spodoptera exigua and development of its endoparasitoid Cotesia marginiventris. Biological Control. 70:9-16.