Invasion of sorghum in the Americas by a new sugarcane aphid (Melanaphis sacchari) superclone

Authors: NIBOUCHE, SAMUEL - Cirad, France; COSTET, LAURENT - Cirad, France; HOLT, JOCELYN - Texas A&M University; JACOBSON, ALANA - University Of Arkansas; PEDARCIK, ADRIAN - Auburn University; SADEYEN, JOELLE - Cirad, France; Armstrong, John - Scott; PETERSON, GARY - Texas A&M Agricultural Experiment Station; MCLAREN, NEAL - University Of The Free State; MEDINA, RAUL - Texas A&M University

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/6/2018
Publication Date: 4/25/2018
Citation: Nibouche, S., Costet, L., Holt, J.R., Jacobson, A., Pedarcik, A., Sadeyen, J., Armstrong, J.S., Peterson, G.C., Mclaren, N., Medina, R.F. 2018. Invasion of sorghum in the Americas by a new sugarcane aphid (Melanaphis sacchari) superclone. PLoS One. 13(4): e0196124. https://doi.org.10.1371/journal.pone.0196124.
DOI: https://doi.org/10.1371/journal.pone.0196124

Interpretive Summary: We investigated whether the sugarcane aphid emergence in the United States on sorghum was due a new genotype that was invasive, or if it happened to be an actual biotype from previously known sources. We used microsatellite markers and COI sequencing to compare the genetic diversity of SCA populations collected in the U.S. following the 2013 sugarcane outbreak on sorghum (2013-2017) to older samples collected before the pest outbreak (during 2007-2009). Our results show that the SCA outbreak in the Americas and the Caribbean observed since 2013 belong to populations exhibiting low genetic diversity and consisting of a dominant clonal lineage, MLL-F, which colonizes Sorghum spp. and sugarcane. The comparison of MLL-F specimens collected post-2013 with specimens collected in Louisiana in 2007 revealed that both populations are genetically distinct, according to COI sequencing and microsatellite data analyses. Our result suggest that MLL-F is a new invasive genotype introduced into the Americas that has spread rapidly across sorghum growing regions in the U.S., Central America (Mexico and Honduras), and the Caribbean. The origin of this introduction is either Africa or Asia, with Asia being the most probable source.

Technical Abstract: In the United States (U.S.), the sugarcane aphid (SCA) Melanaphis sacchari (Zehnter) (Hemiptera: Aphididae) was introduced in the 1970s, however, at this time it was only considered a pest of sugarcane. In 2013, a massive outbreak of M. sacchari occurred on sorghum, resulting in significant economic damage to sorghum grown in North America to include the U.S., Mexico, and Puerto Rico. The aim of the present study was to determine whether the SCA pest emergence in American sorghum was due to the possible introduction of new genotypes, or due to the emergence of a new biotype from previously identified populations. To this end we used microsatellite markers and COI sequencing to compare the genetic diversity of SCA populations collected in the Americas after the 2013 SCA outbreak on sorghum (during 2013-2017) to older samples collected before the pest outbreak (during 2007-2009). Our results show that the SCA outbreak in the Americas and the Caribbean observed since 2013 belong to populations exhibiting low genetic diversity and consisting of a dominant clonal lineage, MLL-F, which colonizes Sorghum spp. and sugarcane. The comparison of MLL-F specimens collected post-2013 with specimens collected in Louisiana in 2007 revealed that both populations are genetically distinct, according to COI sequencing and microsatellite data analyses. Our result suggest that MLL-F is a new invasive genotype introduced into the Americas that has spread rapidly across sorghum growing regions in the U.S., Central America (Mexico and Honduras), and the Caribbean. The origin of this introduction is either Africa or Asia, with Asia being the most probable source.