|Cooper, William - Rodney|
Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/21/2014
Publication Date: 6/1/2014
Citation: Puterka, G.J., Nicholson, S.J., Brown, M.J., Cooper, W.R., Peairs, F.B., Randolph, T.L. 2014. Characterization of eight Russian wheat aphid (Hemiptera: Aphididae) biotypes using two-category resistant-susceptible plant responses. Journal of Economic Entomology. 107(3):1274-1283. Interpretive Summary: Eight biotypes of the Russian wheat aphid (RWA) have been discovered in the United States since 2003. They can be identified by the distinct damage they cause to wheat carrying individual RWA resistance genes (genes Dn1 through 9). More efficient methods are needed to reduce the plant material needed to facilitate biotyping large numbers of RWA samples. The goal of this study was to evaluate the eight RWA biotypes on16 resistant and susceptible wheat characterize the damage caused by RWA feeding. Using a two category plant response of resistant (live) and susceptible (dead) for classifying percent leaf yellowing it was found that most RWA biotypes produced unique damage responses to the 16 plant entries except RWA3, RWA4, RWA5, and RWA7 which formed one group. Leaf roll and plant height was only moderately associated with leaf yellowing damage. This study determined that percent leaf yellow using only four resistance genes were needed to classify the RWA biotypes. This finding makes area-wide studies that process large numbers of aphid samples more feasible to conduct.
Technical Abstract: Eight biotypes of the Russian wheat aphid (RWA), Diuraphis noxia (Kurd.), were discovered in the United States since 2003. Biotypes are identified by the distinct feeding damage responses they produce on plants carrying different RWA resistance genes, Dn1 to Dn9. Efficient methods are needed to identify biotypic variation in RWA order conduct much needed regional studies on biotypic diversity. We evaluated all eight biotypes against 16 resistant and susceptible cereal entries to identify the minimum number of entries need to identify RWA biotypes. The distribution of chlorosis ratings followed a bimodal pattern indicating two categories of plant responses, resistant or susceptible. Plants carrying resistance genes Dn1 - 6 and Dn9 were either resistant (R) or susceptible (S), depending on RWA biotype. Correlations were significant between chlorosis ratings and leaf roll (r2 = 0.72), and chlorosis ratings and plant height (r2 = 0.48). Only four plant entries carrying the Dn3, Dn4, Dn6, and Dn9 resistance genes, plus use of appropriate susceptible (e.g. 'Yumar' wheat) lines, was needed to indentify the current biotypes by chlorosis damage ratings. RWA1, 2, 6, and 8 were identified as unique biotypes while RWA3, 4, 5, and 7 were grouped as similar using an R/S rating system. Much needed studies that address biotypic variation in RWA will be more feasible by limiting the number of plant entries to make identifications. Reducing the number of resistance genes needed to identify the current biotypes also provides valuable space to include other resistance sources to identify new biotypes.