Occurrence of a New Russian Wheat Aphid Biotype in Colorado

Abstract

Russian wheat aphid [RWA, Diuraphis noxia (Mordvilko)] is a serious pest of wheat (Triticum aestivum L.) in the western USA Great Plains region. While variation in virulence among different RWA isolates has been reported elsewhere, no such variation has been documented among North American RWA isolates. Our objective was to confirm observations in spring 2003 suggesting that a new biotype of RWA was present in southeastern Colorado. The new biotype induced greater injury (leaf rolling and overall plant damage) than the original biotype in standard greenhouse seedling screening tests with a limited collection of resistant and susceptible cultivars. A second experiment with a broader collection of known RWA resistance sources identified only one accession, 94M370 (Dn7 gene), with resistance to the new biotype. Development of wheat cultivars with resistance to this new biotype will depend on rapid identification and deployment of new resistance sources.

Positive Correlation of Fitness with Group Size in Two Biotypes of Russian Wheat Aphid (Homoptera: Aphididae)

“…The reduced performance of RWA1 observed on both resistant cultivars is consistent with previous work (Haley et al 2004, Jyoti et al 2006. The juvenile survival of RWA1 was reduced on both resistant cultivars at 24ЊC, although only on Halt at 20ЊC, with the same pattern evident for both singles and groups.…”

“…Cultivars of wheat vary in their suitability as food for D. noxia (Ali et al 1985, Jyoti et al 2006 and various "biotypes" of D. noxia are recognized based on their ability to damage cultivars expressing particular genetic sources of resistance (Basky 2003, Haley et al 2004. For example, a series of commercial cultivars bred speciÞcally for resistance to D. noxia express a gene designated Dn4, and these cultivars have been widely planted in regions of the United States where D. noxia has persistently caused economic losses (Randolph et al 2003, CASS 2004, whereas other sources of resistance such as Dny have not been planted as widely.…”

Comparative gut transcriptome analysis reveals differences between virulent and avirulent Russian wheat aphids, Diuraphis noxia

“…This result suggests that RWA2 gut transcriptome diversity may be related to the increased survival of RWA2 known to occur on RWA1-resistant wheat plants containing the Dn4 resistance gene (Haley et al 2004;Weiland et al 2008;Lazzari et al 2009). …”

“…In response to D. noxia-related yield losses, numerous D. noxia-resistant varieties of barley and wheat have been developed and deployed, primarily in North America and South Africa (Mornhinweg et al 2006;Tolmay et al 2006). Nevertheless, virulent genotypes of D. noxia referred to as biotypes now exist that are unaffected by otherwise resistant plants (Basky, 2003;Haley et al 2004;Smith et al 2004;Dolatti et al 2005; Burd et al 2006;Malinga et al 2007;Tolmay et al 2006). Therefore, there is an urgent need to understand the relationship between molecular mechanisms of wheat defenses against D. noxia and corresponding D. noxia counter defenses.…”

“…Other than differential plant foliar damage (Burd et al 2006, Haley et al 2004 and related differences in the feeding behavior, growth and survival of different D. noxia biotypes (Khan et al 2009, Lazzari et al 2009), little is known about the ecological and genetic factors underlying the development of D. noxia biotypes. Therefore, we investigated alterations in the D. noxia gut transcriptome that may identify genes involved in D. noxia-wheat interactions.…”