Change in biotypic diversity of Russian wheat aphid (Hemiptera: Aphididae) populations in the United States

Authors: Puterka, Gary; GILES, KRISTOPHER - Oklahoma State University; BROWN, MICHAEL - Oklahoma State University; Nicholson, Scott; HAMMON, ROBERT - Colorado State University; PEAIRS, FRANK - Colorado State University; RANDOLPH, TERRI - Colorado State University; MICHAELS, GERALD - Texas Agrilife Research; BYNUM, EDSEL - Texas Agrilife Research; Springer, Timothy; Armstrong, John; Mornhinweg, Dolores - Do

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/14/2014
Publication Date: 4/1/2015
Publication URL: http://handle.nal.usda.gov/10113/61771
Citation: Puterka, G.J., Giles, K.L., Brown, M.J., Nicholson, S.J., Hammon, R.W., Peairs, F.B., Randolph, T.L., Michaels, G.J., Bynum, E.D., Springer, T.L., Armstrong, J.S., Mornhinweg, D.W. 2015. Change in biotypic diversity of Russian wheat aphid (Hemiptera: Aphididae) populations in the United States. Journal of Economic Entomology. 108(2):798-804.

Interpretive Summary: The Russian wheat aphid (RWA) is an important pest of wheat which has been managed by breeding wheat cultivars resistant to this pest in the United States. However, a new strain, also known as biotypes, of RWA called RWA2 developed which can over-came resistance now resistant cultivars are not affective. RWA2 became the prevalent biotype in wheat throughout the Great Plains Region by 2005. Currently, little is known about the number of biotypes in RWA population or what their capacity is overcome the new sources of resistance identified by wheat breeders. This study collected aphids across the Great Plains and Colorado Plateau Region in wheat fields commonly infested by the RWA and tested their ability to damage the former and new sources of resistance in wheat and barley. The objectives were to determine the diversity of RWA biotypes at a regional and local level by screening aphid collections against the sources of resistance in wheat. We found five primary RWA biotypes existed at the regional and local level and that numbers of individual biotypes varied. Biotype RWA6 was the most prominent biotype in the populations which is far less damaging to the resistance sources in wheat. We documented that the biotype composition shifted from highly virulent RWA2 to far less virulent RWA6. This study serves as an important base-line for RWA populations before new resistant wheat cultivars become available to wheat growers.

Technical Abstract: A key component of Russian wheat aphid (RWA), Diuraphis noxia (Kurdjumov), management has been through planting resistant wheat cultivars. A new biotype, RWA2, appeared in 2003 which caused widespread damage to wheat cultivars containing Dn4 gene. Biotypic diversity in RWA populations has not been addressed since 2005 when RWA2 dominated the biotype complex. Our objectives were to determine the biotypic diversity in the Central Great Plains and Colorado Plateau regions at the regional (2010, 2011, 2013) and local (2012) levels and presence of new RWA biotypes. Regional and within-field aphid collections were screened against RWA resistant wheat genotypes containing genes Dn3, Dn4, Dn6, Dn7, Dn9, CI2401; and resistant barley STARS 9301B. In 2010, all aphid collections from Texas were avirulent the Dn4 resistance gene in wheat. Regional results revealed Dn4 avirulent RWA6 was widespread (55-84%) in populations infesting wheat in both regions. Biotypes RWA1, 2, and 3/7 were equally represented with percentages <20% each while RWA8 was not detected or was rare. Combining percentages of RWA1, 6, and 8 across regions to estimate avirulence to Dn4 gene revealed high percentages for both 2011 (64-80%) and 2013 (69-90%). In contrast, 2012 local populations found biotype structure differed and biotype percentages varied up to >=2-fold between fields. No new biotypes were detected, therefore, Dn7, CI2401, STARS9301B remained resistant to all known RWA biotypes. This study documents a shift to Dn4 avirulent biotypes and serves as a valuable base-line for biotypic diversity in RWA populations prior to the deployment of new RWA-resistant wheat cultivars.