Submitted to: Annals of the Entomological Society of America
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/2/2009
Publication Date: 3/1/2010
Citation: Nagoshi, R.N. 2010. The fall armyworm Triose phosphate isomerase (Tpi) gene as a marker of strain identity and interstrain mating. Annals of the Entomological Society of America. 103(2):283-292. Interpretive Summary: The fall armyworm, Spodoptera frugiperda, is a major agricultural pest of corn, forage grasses, rice, cotton, and peanuts. Two strains of fall armyworm exist that have significant physiological and behavioral differences, including resistance to pesticides and preference to different plant hosts. Previous studies showed that hybrids between strains can be produced, but remarkably little is known about the frequency of such pairings or how the resulting hybrids differ in behavior from the parental strains. Such information is important for the effective control of this pest. To address this issue, a scientist at the Center for Medical, Agricultural and Veterinary Entomology (Gainesville, Florida) developed a molecular marker that facilitates the identification of strains and potential interstrain hybrids. This genetic marker was used in combination with other markers to confirm the results of past studies on hybrids and to demonstrate that what had previously been thought to be a seasonal aberration in strain-specific plant host preference was actually the result of increased interstrain hybridization. Studies of this type will make possible determining the economic impact of hybrids and the identification of the genetic factors determining plant host and mating partner choice that could be used to disrupt these important behaviors.
Technical Abstract: Fall armyworm is a significant agricultural pest in the United States, affecting most notably sweet corn and turfgrass. Two morphologically identical strains exist that differ physiologically and behaviorally, but are morphologically indistinguishable. Polymorphisms within the fall armyworm triose phosphate isomerase gene (Tpi; EC 188.8.131.52) were characterized and used to develop a PCR-based method for identifying fall armyworm strains. The Tpi markers were used in multi-locus analysis to estimate interstrain hybrid frequency and their distribution in populations from the U.S. and Brazil. The results were compared to previous studies using different marker combinations to test hypotheses about interstrain mating behavior and to explain earlier observations of unusual strain distribution patterns. The importance of understanding the frequency and consequences of interstrain hybridization to deciphering the mechanism of strain divergence and the distribution of fall armyworm subpopulations in different habitats is discussed.