Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 20, 2010
Publication Date: June 1, 2010
Citation: Meagher Jr, R.L., Nagoshi, R.N. 2010. Identification of fall armyworm (Lepidoptera:Noctuidae) host strains using male-derived spermatophores. Florida Entomologist. 93(2):191-197. Interpretive Summary: Fall armyworm is a migratory agricultural pest that attacks row and vegetable crops such as sweet corn, field corn, peanuts, sugarcane, turf and pasture grasses. Populations develop in southern Texas and southern Florida and move into the central and eastern United States every spring and summer. This species has two host strains that feed on either corn or sorghum (corn strain) or small grasses such as bermudagrass and rice (rice strain). Several ecological and behavioral studies have been conducted to investigate mating between corn and rice strain individuals, but these studies have used indirect techniques to measure this important biological characteristic. Scientists at the Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Florida, have developed a technique to directly measure interstrain mating in wild populations. This report describes a technique where females are dissected and the spermatophore (the packet of sperm and other materials transferred to the female by males during mating) is molecularly analyzed to identify the host strain of the mating males. Therefore, we will be able to determine from females collected in the field the host strain paternity of their progeny.
Technical Abstract: Laboratory experiments were designed to identify the host strain paternity of fall armyworm [Spodoptera frugiperda (J. E. Smith)] mated females. In no-choice tests, corn or rice strain females were placed in cages with males of the opposite strain. After 48 h, females were dissected and spermatophores were removed. Molecular markers in the COI gene were used to identify host strain identity from the spermatophores and results showed the host strain pattern of the mating males. In choice tests, females of either strain were placed in cages with males of both strains. After 48 or 96 h, spermatophores were dissected and were molecularly analyzed to identify the host strain of the mating males. Corn and rice strain females contained spermatophores from males of both strains, indicating that interstrain mating commonly occurs in the laboratory. The analysis of the spermatophores isolated from mated females provides a convenient means of identifying the strain of the mated male. This technique has the promise of being able to directly measure interstrain mating in wild populations.