Research Project: Enhanced Resistance of Maize to Aspergillus flavus Infection, Aflatoxin Accumulation, and Insect Damage

Location: Corn Host Plant Resistance Research

2021 Annual Report

Objectives
1. Identify new sources of maize germplasm with resistance to Aspergillus (A.) flavus infection and aflatoxin accumulation. 1.A: Screen maize germplasm obtained from the GEM project, CIMMYT, and other sources for resistance to aflatoxin accumulation to identify new and potentially useful sources of resistance. 1.B: Determine optimal combinations of A. flavus and A. parasiticus isolates for screening maize germplasm for resistance to aflatoxin accumulation under different environmental conditions. 2. Identify new sources of maize germplasm with resistance to fall armyworm, southwestern corn borer, and corn earworm. 2.A: Screen maize germplasm from CIMMYT, the GEM project, and other sources for resistance to leaf feeding by fall armyworm and southwestern corn borer. 2.B: Screen maize germplasm for resistance to ear feeding by fall armyworm, southwestern corn borer, and corn earworm. 3. Develop and characterize genetic mapping populations, identify and elucidate functions of genes associated with resistance, and develop molecular markers for enhancing maize germplasm resistance to A. flavus/aflatoxin and insects. 3.A: Identify genetic loci associated with resistance to A. flavus infection and aflatoxin accumulation via analysis of linkage and association mapping and sequencing data. 3.B: Identify genetic loci associated with resistance to lepidopteran insect feeding via analysis of linkage and association mapping, pathway analysis, or sequencing data. 3.C: Identify genes and elucidate functions of genes associated with resistance to A. flavus/aflatoxin and insects. 4. Develop and release maize germplasm with resistance to Aspergillus flavus infection, aflatoxin accumulation, and insect damage. 4.A: Develop and release maize germplasm lines with resistance to A. flavus infection and aflatoxin accumulation using conventional breeding methods. 4.B: Develop and release lines with resistance to feeding by southwestern corn borer and fall armyworm using conventional breeding methods. 4.C: Develop lines with resistance to A. flavus infection, aflatoxin accumulation, and insects using molecular markers and release together with marker information.

Approach
Objective 1: Identify new sources of maize germplasm with resistance to Aspergillus (A.) flavus infection and aflatoxin accumulation. Screen maize germplasm obtained from the Germplasm Enhancement of Maize project (GEM) project, International Center for Maize and Wheat Improvement (CIMMYT), and other sources for resistance to aflatoxin accumulation to identify new and potentially useful sources of resistance. Determine optimal combinations of A. flavus and A. parasiticus isolates for screening maize germplasm for resistance to aflatoxin accumulation under different environmental conditions. Objective 2: Identify new sources of maize germplasm with resistance to fall armyworm, southwestern corn borer, and corn earworm. Screen maize germplasm from CIMMYT, the GEM project, and other sources for resistance to leaf feeding by fall armyworm and southwestern corn borer. Screen maize germplasm for resistance to ear feeding by fall armyworm, southwestern corn borer, and corn earworm. Objective 3: Develop and characterize genetic mapping populations, identify and elucidate functions of genes associated with resistance, and develop molecular markers for enhancing maize germplasm with resistance to flavus/aflatoxin and insects. Identify genetic loci associated with resistance to A. flavus infection and aflatoxin accumulation via analysis of linkage and association mapping and sequencing data. Identify genetic loci associated with resistance to lepidopteran insect feeding via analysis of linkage and association mapping, pathway analysis, or sequencing data. Identify genes and elucidate functions of genes associated with resistance to A. flavus/aflatoxin and insects. Objective 4: Develop and release maize germplasm with resistance to A. flavus infection, aflatoxin accumulation, and insect damage. Develop and release maize germplasm lines with resistance to A. flavus infection and aflatoxin accumulation using conventional breeding methods, and develop and release lines with resistance to feeding by southwestern corn borer and fall armyworm using conventional breeding methods. Develop lines with resistance to A. flavus infection, aflatoxin accumulation, and insects using molecular markers and release together with marker information.

Progress Report
Identify new sources of maize germplasm with resistance to Aspergillus (A.) flavus infection and aflatoxin accumulation. We evaluated 50 maize germplasm lines from the Germplasm Enhancement of Maize (GEM) project for resistance to aflatoxin accumulation in replicated field trials in 2020. A few of the new selections showed promise as a source of resistance to be used in our breeding program, and those selections have been incorporated into the breeding program. We are evaluating another 65 lines for resistance to aflatoxin in the 2021 trials. Based on the information gained from two bi-parental mapping populations, Mp715 x Va35 and Mp717 x Va35, evaluated for resistance to aflatoxin accumulation, we are selecting lines with molecular markers associated with resistance to aflatoxin accumulation. Our goal is to develop near-isogenic lines (NILs) that have good agronomic characteristics as well as resistance to aflatoxin. We are also evaluating the effects of quantitative trait loci (QTL) identified in these two populations using a series of lines as recurrent parents. We evaluated a group of NILs developed from the cross between Mp313E (resistant to aflatoxin accumulation) and Va35 (susceptible to aflatoxin accumulation) for resistance to aflatoxin accumulation. Identify new sources of maize germplasm with resistance to fall armyworm, southwestern corn borer, and corn earworm. We evaluated a diverse set of 300 germplasm lines for resistance to fall armyworm damage in replicated trials in 2019, 2020, 2021. We identified potentially promising sources of resistance in this group of lines. We also evaluated a group of segregating breeding lines for resistance to fall armyworm and southwestern corn borer in 2021. The best of these will be advanced and evaluated again next year. We initiated a study to determine the effect of plant age at the time of infestation with fall armyworm larvae on leaf damage and yield loss. Based on the results of a QTL mapping study of a bi-parental mapping population, Mp705 x Mp719, we are developing NILs for a QTL associated with fall armyworm resistance identified on Chromosome 9. Results of some of our previous studies indicate that the QTL is associated with juvenile-adult phase transition. Resistance is apparently associated with an earlier transition. Develop and characterize genetic mapping populations, identify and elucidate functions of genes associated with resistance, and develop molecular markers for enhancing maize germplasm with resistance to A. flavus/aflatoxin and insects. We concluded a 3-year Genome Wide Association Study (GWAS) for resistance to fall armyworm in 2021. This study will provide additional information on molecular markers that can be used in breeding for resistance. We initiated two new gene expression studies in 2021, one for resistance to fall armyworm and the other resistance to aflatoxin accumulation. For the fall armyworm study, we collected leaf tissue from fall armyworm infested and non-infested plants at different growth stages from resistant and susceptible corn germplasm lines. For the other investigation, ears were hand-pollinated and inoculated or not inoculated with A. flavus. Ears were harvested at 2, 3, 5, and 7 days after inoculation. The tissue will be used in proteomic, metabolomic, and other gene expression studies. Comparisons with be made between inoculated and non-inoculated ears. Develop and release maize germplasm with resistance to A. flavus infection, aflatoxin accumulation, and insect damage. We evaluated 80 advanced generation lines from our breeding program for resistance to aflatoxin accumulation in 2020, and 50 of those are being re-evaluated in 2021. In both 2020 and 2021 we evaluated 45 hybrids developed by collaborators in Texas, Georgia, and Mississippi for resistance to aflatoxin accumulation and for yield at five locations. Experimental hybrids developed at Mississippi State exhibited excellent levels of resistance to aflatoxin accumulation. We also evaluated 30 advanced generation breeding lines from our breeding program for resistance to fall armyworm and southwestern corn borer leaf feeding damage. We are increasing seed of the most recently developed lines in the breeding nursery so they can be further evaluated and released if they continue to perform well. These lines were included in the GWAS, and results of that study should indicate whether we have identified new genes for resistance. We are also conducting an experiment to evaluate the benefits of native fall armyworm resistance in reducing aflatoxin accumulation in the grain.

Accomplishments

Review Publications
Stalker, T.H., Warburton, M.L., Harlan, J.R. 2021. Harlan’s Crops and Man: People, plants and their domestication. 3rd edition. Madison, WI: Crop Science Society of America. 320 p.
Williams, J.J., Henry, W.B., Smith, J.S., Buehring, N.W., Boykin, D.L. 2021. Aflatoxin accumulation in corn (Zea may L.) influenced by cultural production practices in the U.S. Mid-South. Crop Science. 61:729-738. https://doi.org/10.1002/csc2.20330.
Liu, N., Du, Y., Warburton, M.L., Xiao, Y., Yan, J. 2020. Phenotypic plasticity contributes to maize adaptation and heterosis. Molecular Biology and Evolution. 38(4):1262-1275. https://doi.org/10.1093/molbev/msaa283.
Oliveria, D.A., Tang, J.D., Warburton, M.L. 2021. Reference gene selection for RT-qPCR analysis in maize kernels inoculated with Aspergillus flavus. Toxins. 13(6):386. https://doi.org/10.3390/toxins13060386.
Rauf, S., Warburton, M.L., Naeem, A., Kainat, W. 2020. Validated markers for sunflower (Helianthus annuus L.) breeding. OCL - Oilseeds & fats, Crops and Lipids. 27. Article 47. https://doi.org/10.1051/ocl/2020042.
Gouda, A.C., Ndjiondjop, M.N., Djedatin, G., Warburton, M.L., Goungoulou, A., Kpeki, S.B., N'Diaye, A., Semagn, K. 2020. Comparisons of sampling methods for assessing intra and inter-accession genetic diversity in three rice species using genotyping by sequencing. Scientific Reports. 10:13995. https://doi.org/10.1038/s41598-020-70842-0.
Li, H., Thrash, A., Tang, J., He, L., Yan, J., Warburton, M.L. 2019. Leveraging GWAS data to identify metabolic pathways and pathway networks involved in maize lipid biosynthesis. Plant Journal. 98(5):853-863. https://doi.org/10.1111/tpj.14282.
Melotto, M., Brandl, M., Jacob, C., Jay-Russell, M.T., Micallef, S.A., Warburton, M.L., Van Deynze, A. 2020. Breeding crops for enhanced food safety. Frontiers in Plant Science. 11:428. https://doi.org/10.3389/fpls.2020.00428.
Jumaa, S.H., Sehgal, A., Kakar, N., Redoña, E.D., Chastain, D., Warburton, M.L., Reddy, K.R. 2020. Evaluation of rice genotypes for early- and mid-season vigor using morphological and physiological traits. Journal of the Mississippi Academy of Sciences. 64(3):319-345.
Coan, M.M., Pinto, R.J., Kuki, M.C., do Amaral Júnior, A.T., Figueiredo, S.T., Scapim, C.A., Warburton, M.L. 2019. Inheritance study for popping expansion in popcorn vs. flint corn genotypes. Agronomy Journal. 111(5):2174-2183. https://doi.org/10.2134/agronj2019.04.0295.
Jumaa, S.H., Kakar, N., Redona, E.D., Lone, A.A., Chastain, D., Gao, W., Warburton, M.L., Reddy, K. 2020. Assessing the early-season vigor of a diverse rice population by using morphophysiological traits. SABRAO J. of Breeding and Genetics. 52(3):248-270.
Li, H., Wang, M., Li, W., He, L., Zhou, Y., Zhu, J., Ronghui, C., Warburton, M.L., Yang, X., Yan, J. 2020. Genetic variants and underlying mechanism influencing variance heterogeneity in maize. Plant Journal. 103(3):1089–1102. https://doi.org/10.1111/tpj.14786.
Dadzie, M.A., Oppong, A., Ofori, K., Eleblu, J., Beatrice, E., Blay, E., Obeng-Bio, E., Appiah-Kubi, Z., Warburton, M.L. 2019. Distribution and genetic diversity among Aspergillus flavus isolates across three agro-ecologies essential for maize cultivation in Ghana. Plant Pathology. 68(8):1565–1576. https://doi.org/10.1111/ppa.13067.
Dadzie, M.A., Oppong, A., Ofori, K., Eleblu, J., Ifie, E.B., Blay, E., Obeng-Bio, E., Appiah-Kubi, Z., Warburton, M.L. 2019. Distribution of Aspergillus flavus and aflatoxin accumulation in stored maize grains across three agro-ecologies in Ghana. Food Control. 104:91-98. https://doi.org/10.1016/j.foodcont.2019.04.035.
Pingault, L., Varsani, S., Palmer, N.A., Ray, S., Williams, W.P., Luthe, D.S., Ali, J.G., Sarath, G., Louis, J. 2021. Transcriptomic and volatile signatures associated with maize defense against corn leaf aphid. Biomed Central (BMC) Plant Biology. 21:138. https://doi.org/10.1186/s12870-021-02910-0.
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.
Kakar, N., Bheemanahalli, R., Jumaa, S.H., Diaz Redoña, E., Warburton, M.L., Reddy, R.K. 2021. Assessment of agro-morphological, physiological and yield traits diversity among tropical rice. PeerJ. 9:e11752. https://doi.org/10.7717/peerj.11752.