ARS | Publication request: Artificial selection for developmental rates in fall armyworm (Lepidoptera: Noctuidae) and its implications on the design of feeding studies

Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 9, 2010
Publication Date: January 25, 2011
Citation: Nagoshi, R.N. 2011. Artificial selection for developmental rates in fall armyworm (Lepidoptera: Noctuidae) and its implications on the design of feeding studies. Annals of the Entomological Society of America. 104(1):88-94.

Interpretive Summary: Feeding studies are a convenient and frequently used method for assessing the susceptibility of pest insects to specific chemicals, plant hosts, or other treatments. Typically, the test populations are derived from laboratory-reared colonies and the mean developmental parameters and mortality rates calculated and compared for various diets or supplements. Variations of this strategy have been used to survey a variety of agriculturally important plant types for their ability to host the Noctuid pest fall armyworm, Spodoptera frugiperda (J. E. Smith), an important agricultural pest of the western hemisphere. A common assumption is that the test groups used are sufficiently representative of wild populations that the results can be generalized, i.e., repeated by different laboratories and used to accurately predict behavior in the field. Scientists at the USDA, ARS, Center for Medical, Agricultural and Veterinary Entomlogy, Gainesville, Florida, demonstrate that fall armyworm development is subject to substantial genetic variability, making it unlikely that of test results using inbred laboratory colonies are true for all world populations. The design and evaluation of feeding studies for fall armyworm need to take genetic variability into account.

Technical Abstract: Understanding of fall armyworm biology has frequently suffered from disagreements in the findings from different laboratories. One potential source of error is the assumption that laboratory colonies are sufficiently representative of wild populations that their biological parameters can be generalized. This is unlikely to be valid if the phenotype in question exhibits extensive genetic variation in the natural population, in which case laboratory lines can only be expected to contain a subset of the relevant genotypes. This study investigates whether this might be an issue of concern for experiments measuring larval developmental rate, a parameter frequently used to assess the relative resistance of different plant lines to fall armyworm herbivory. To estimate the genetic variation in this phenotype a simple selection experiment was performed to determine whether significantly different developmental rates could be isolated from inbred laboratory colonies. The results indicate a strong genetic component influences larval developmental. Therefore the average larval duration of the test population for a given treatment will depend on its genotypic composition that could vary significantly with different colonies. The implications of these findings on designing and evaluating feeding studies for fall armyworm are discussed.