Observations of genetic differentiation between the fall armyworm host straines

Authors: Nagoshi, Rodney

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2022
Publication Date: 11/11/2022
Citation: Nagoshi, R.N. 2022. Observations of genetic differentiation between the fall armyworm host strains. PLOS ONE. 17(11):e0277510. https://doi.org/10.1371/journal.pone.0277510.
DOI: https://doi.org/10.1371/journal.pone.0277510

Interpretive Summary: The threat of invasive species is increasing with the expansion of global trade and habitat disruption. A recent example is the invasion of fall armyworm, a noctuid moth native to the Americas, into most of the Eastern Hemisphere where it is projected to cause significant economic losses. The species had been subdivided into two populations that differ in their plant host specificity, however recent genomic studies questioned the validity of these host strains, which could have a significant impact on fall armyworm monitoring and mitigation protocols. From a study conducted by a scientist at USDA/ARS/Center for Medical, Agricultural and Veterinary Entomology, Gainesville, FL, results demonstrated significant genetic differentiation between the host strains as well as providing evidence that they experience substantially different selection pressures despite their overlapping geographical distributions. The data confirm that host strains are a fundamental characteristic of the species that need to be considered when developing monitoring and mitigation strategies. Awareness of strain is especially relevant for the Eastern Hemisphere where only the corn strain has been detected in significant numbers. Monitoring for outbreaks of the rice strain, a new invasive, could provide an important early warning of additional crop types at risk of fall armyworm infestations in Africa and Asia with significant consequences to global food security.

Technical Abstract: The threat of invasive species is increasing with the expansion of global trade and habitat disruption. A recent example is the invasion of fall armyworm (FAW), a noctuid moth native to the Americas, into most of the Eastern Hemisphere where it is projected to cause significant economic losses. The species had been subdivided into two populations that differ in their plant host specificity, however recent genomic studies have questioned the validity of these host strains, which could have a significant impact on FAW monitoring and mitigation protocols. Here is described a phylogenetic definition of the host strains that made possible the quantification of their genetic differences while also demonstrating that they are experiencing significantly different selection pressures. The results support the traditional view of these populations being at an intermediate stage of sympatric speciation driven by differential host use while also describing a new approach to investigate the evolution of this important global pest