Assessing levels of resistance to Spodoptera frugiperda in four experimental inbred lines of maize

Authors: Abel, Craig; Woolfolk, Sandra; Lopez, Miriam; FREI, URSULA - Iowa State University

Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/9/2024
Publication Date: 12/2/2024
Citation: Abel, C.A., Woolfolk, S.W., Lopez, M.D., Frei, U.K. 2024. Assessing levels of resistance to Spodoptera frugiperda in four experimental inbred lines of maize. Southwestern Entomologist. 49(4):1-7. https://doi.org/10.3958/059.049.0416.
DOI: https://doi.org/10.3958/059.049.0416

Interpretive Summary: The fall armyworm is an economically important pest of maize that is native to the Americas and is now an invasive pest in many countries across the continents of Africa, Asia, and Oceania. The pest has become resistant to the most common tactics used for its control, namely insecticides and genetically modified maize. Other tactics, such as cultural and mechanical control, are being integrated to help deal with the problem. These efforts can be enhanced by equipping maize plants with the ability to defend against pest injury. In this study, four experimental maize lines developed by USDA-ARS were tested for resistance to fall armyworm leaf feeding at locations in Iowa and Mississippi in 2023 and 2024. One experimental line, BS39:76-F3, tested resistant and was more resistant in Mississippi 2024 when compared to two highly resistant maize controls. This experimental line may be useful for breeders who are developing commercially available maize varieties that are resistant to fall armyworm. This study also noted two experimental lines varied widely in their ability to defend from fall armyworm injury and environment played a role in this variable response. Future studies designed to better understand this variability may yield information that will identify the underlying mechanisms of maize resistance to fall armyworm.

Technical Abstract: An economically important pest of maize (Zea mays L.), the fall armyworm, Spodopera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) injures ear, leaf, and tassel tissue, threatening the livelihood of producers. It is a recent invasive pest to countries in Africa, Asia, and Oceania and new control strategies are needed to reduce the damage that occurs. Integrated pest management systems are strengthened by breeding maize for multi-trait host plant resistance. The objective of this study was to evaluate four experimental lines that were derived from two maize genotypes that previously demonstrated variability in response to fall armyworm leaf injury. In 2023 and 2024, genotypes were grown in Iowa and Mississippi, infested with fall armyworm, and leaf injury recorded after 14 days. Experimental line BS39:76-F3 had lower scores than the source genotype, BS39, from which it was derived and was not different than the resistant checks at both locations in 2023 and had significantly lower scores in Mississippi 2024. BS39:76-F3 may provide useful levels of resistance for breeders that are improving maize for resistance to fall armyworm leaf feeding. Experimental lines GEMN-0095:0201-F4 and GEMN-0095:0202-F4 varied in their response to leaf injury with moderate to susceptible scores at both locations in 2023 and Mississippi 2024, and resistant scores (2.3 and 3.2) not different than the resistant checks, in Iowa 2024. Understanding the abiotic and biotic factors producing this variability in response could lead to identifying mechanisms conferring resistance in these, and possibly other, resistant maize genotypes.