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Title: Absence of mitochondrial DNA sequence variation in Russian wheat aphid (Hemiptera: Aphididae) populations consistent with a single introduction into the United States

Author
item Shufran, Kevin
item KIRKMAN, LYNDIA - OKLAHOMA STATE UNIV
item Puterka, Gary

Submitted to: Journal of Kansas Entomological Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/6/2007
Publication Date: 11/1/2007
Citation: Shufran, K.A., Kirkman, L.R., Puterka, G.J. 2007. Absence of mitochondrial DNA sequence variation in Russian wheat aphid (Hemiptera: Aphididae) populations consistent with a single introduction into the United States. Journal of Kansas Entomological Society. 80(4):319-326.

Interpretive Summary: The Russian Wheat Aphid (RWA) was introduced into North America in Mexico during 1980 and by 1988 had spread north across the Western US into Southern Canada. Its rapid spread was due to its asexual method of reproduction in which females give birth to live females without having sex. South Africa has been suspected as the source of the introduction. RWA is the major insect pest of wheat and barley in the southern and central plains states. Resistant wheat was the primary management tactic until a biotype (a population able to survive on and injure resistant wheat) appeared in Colorado during 2003. The source of the biotype is unclear, that is whether it represents an introduction of a new asexual form from another country, or if it arose, evolved or mutated from populations already in the US. We were able to address this question by conducting DNA sequencing of RWA collected in the US from 1986 through 2006. Also included were specimens from Mexico and South Africa. Zero genetic variation was found in US populations over a 20 year period. No new genetic types were found. US populations were also genetically identical to those found in Mexico and South Africa. The data supports the hypothesis that RWA were only introduced one time in North America in 1980 and they originally came from South Africa. No new genetic RWA types were introduced into the US after 1980. The RWA biotype injuring resistant wheat most likely arose from the original population already found in the US.

Technical Abstract: Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), was introduced into North America in Mexico during 1980 and by 1988 had spread north across the Western US into Southern Canada. South Africa has been suspected as the source of the introduction. RWA is the major insect pest of wheat and barley in the southern and central plains states. Resistant wheat was the primary management tactic until a biotype (designated RWA2) appeared in Colorado during 2003. The source of the biotype is unclear, that is whether it represents a new introduction from another country or if it arose from the extant population in the US. We sequenced a 525 bp portion of the cytochrome oxidase subunit I gene in the mtDNA of RWA collected in the US from 1986 through 2006. Also included were specimens from Mexico and South Africa. No sequence variation was found in US populations over a 20 year period. US populations had mtDNA sequences which were identical to those found in Mexico and South Africa. No unique mtDNA haplotypes were found, suggesting that the biotype RWA2 did not represent a second introduction from a genetically distinct population from another country. The data are consistent with a single introduction from South Africa and no other introductions into the US have occurred since 1986.