Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/21/2006
Publication Date: 12/1/2006
Citation: Puterka, G.J., Burd, J.D., Mornhinweg, D.W., Haley, S.D., Peairs, F.B. 2006. Response of resistant and susceptible barley to infestations of five Diuraphis noxia (Homoptera: Aphididae) biotypes. Journal of Economic Entomology. 99(6):2151-2155. Interpretive Summary: Five biotypes or strains of the Russian wheat aphid (RWA) have been recently been identified based on their ability to damage the nine RWA resistance genes in wheat, DN1-DN9. The damage responses on two primary sources of RWA resistance in Barley, STARS 9301B and STARS 9577B, and several susceptible barley cultivars to the new RWA biotypes was investigated. STARS 9301B showed resistance to all 5 RWA biotypes. STARS 9577B showed some variation in leaf damage by the biotypes but still remained resistant to moderately resistant. Most of the susceptible barley cultivars showed high levels of leaf damage except for Morex barley. Morex barley appeared to have a moderate level of resistance to some RWA biotypes. Based on our results the main sources of RWA resistance in barley are not threatened by the new RWA biotypes.
Technical Abstract: Since 2003, four new biotypes of the Russian wheat aphid (RWA2-RWA5) have been discovered that have the ability to damage the resistant wheat currently deployed in the field as well as many key sources of resistance in wheat to the original RWA population (RWA1). The RWA is also a significant pest of barley to the extent that growers in some regions no longer grow barley. The key germplasm sources in barley with resistance to RWA1 have not yet been evaluated against the newest biotypes. The objective of our study was to determine how biotypes RWA2-RWA5 affected the growth and leaf damage of RWA1 resistant (STARS 9301B, STARS 9577B, MR-015) and susceptible (Schuyler, Harrington and Morex) barley germplasm under controlled greenhouse conditions. RWA population levels were also monitored to determine how the resistant and susceptible barley germplasm affected the population growth of each biotype. STARS 9301B showed no variation in resistance to the RWA biotypes. Variations in leaf damage to STARS 9577B by the RWA biotypes occurred but chlorosis ratings were still well within the resistant category (chlorosis rating < or equal to 4.9). Variation in leaf chlorosis for MR-015 was significant but the damage rating still fell within a moderately resistant category. The greatest difference in leaf chlorosis occurred in the RWA susceptible Morex where RWA2 showed less virulence than the other biotypes. Only slight differences in leaf rolling and plant growth in response to RWA biotypes feeding was noted. The population levels of the RWA biotypes did not differ within barley entries (n=610-971) at the termination of the study (14d). From our research we conclude that the new RWA biotypes pose no threat to the key sources of resistance in barley (STARS 9301B and 9577B) and that STARS 9301B has broad resistance to the RWA biotypes we tested. In addition, our results suggest that certain RWA susceptible cultivars themselves, or as parents in resistance breeding programs, could offer an increased level of resistance, depending on the biotypic diversity of the region for which they are being developed.