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Submitted to: Insect Molecular Biology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/19/2003 Publication Date: 10/1/2003 Citation: Nagoshi, R.N., Meagher Jr, R.L. 2003. Fall armyworm FR sequences map to sex chromosomes and their distribution in the wild indicate limitations in interstrain mating. Insect Molecular Biology. 12(5):453-458. 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 but are morphologically identical. Remarkably little is known about whether and to what degree interstrain matings occur in the wild, how the resulting hybrids differ from the parental strains, and whether there are strain-specific differences in migration and overwintering behaviors, information that is essential for the effective control of this pest. In this manuscript, interstrain crosses were performed that genetically mapped a strain-specific genetic element (FR clusters) to the sex chromosomes. The FR sequence and a strain-specific mitochondrial marker were used to examine the distribution of different marker combinations in field-isolated specimens. A significant fraction of the wild population was found to carry a hybrid marker combination consistent with the frequent mating of rice strain females to corn strain males. In contrast, the marker configuration indicative of the reciprocal cross was not found, suggesting that interstrain mating occurs primarily in one direction. The results also demonstrate that FR clusters, previously shown to be present in all rice strain individuals isolated and tested in Georgia, are found in only a minority subset of the rice strain population from south Florida. Technical Abstract: The fall armyworm, Spodoptera frugiperda, consists of two host strains (rice and corn) that are morphologically indistinguishable, but differ in developmental, physiological, and behavioral characteristics. FR sequences are tandem-repeat genetic elements reportedly found only in the rice strain. Interstrain crosses were performed that genetically mapped FR clusters to the sex chromosomes. The FR sequence and a strainspecific mitochondrial marker were used to examine the distribution of different marker combinations in field-isolated specimens. A significant fraction of the wild population was found to carry a hybrid marker combination consistent with the frequent mating of rice strain females to corn strain males. In contrast, the marker configuration indicative of the reciprocal cross was not found, suggesting that interstrain mating occurs primarily in one direction. The results also demonstrate that FR clusters, previously shown to be present in all rice strain individuals isolated and tested in Georgia, are found in only a minority subset of the rice strain population from south Florida. |
